Faculty of Bioscience Engineering
Academic year 2013 - 2014
Primary sedimentation investigation using a physical-chemical analysis method.
Hélène Versluys Promotor: Prof. dr. ir. Ingmar Nopens Tutor: Ing. Youri Amerlinck
Master's dissertation submitted in fulfilment of the requirements for the degree of Master after Master in de Milieusanering en het Milieubeheer
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ACKNOWLEDGMENT It is impossible to thank everybody who has helped to establish this dissertation. For not only the material but also the mental support was invaluable. First of all I want to express my gratitude to my promoter Prof. Dr. ir. Ingmar Nopens for the research opportunity at BIOMATH. My gratitude also goes to my tutor Ing. Youri Amerlinck. He not only reviewed my work with a critical constructive eye, providing excellent advise but also took samples during good and harsh weather conditions. I also want to thank Tinne De Boeck and Giacomo Bellandi for the help and the guidance in the BIOMATH laboratory. I thank Ellen Vanassche for mental support and company during sampling and lab-work. I am grateful to the people of Aquafin and to the people of Waterboard the Dommel for their support in sample collection, procedure and information collection procedure. Also I want to thank the laboratory assistants from LABMET for the use of their equipment. This thesis would never have been possible without the unconditional support of my parents and family.
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LIST OF ABBREVATIONS AS Activated Sludge ASP Activated Sludge Process ASM Activated Sludge Model AST Activated Sludge Tank ATU Allylthiourea aPST after Primary Sedimentation Tank BOD Biological Oxygen Demand BOD5,inf BOD influent measured over a time period of 5 days BOD10 BOD measured over a time period of 10 days BODtot Total BOD bCOD biodegradable Chemical Oxygen Demand bPST before Primary Sedimentation Tank COD Chemical Oxygen Demand CODinf,tot Non-filtered total COD influent CODinf,sol COD influent after membrane filtration or flocculation CODeff,sol COD effluent after membrane filtration or flocculation CODVFA COD determined with gas chromatography or titration CSO Combined Sewer Overflows eff effluent GGA Glucose-Glutamic Acid GMP Good Modeling Practice IAWPRC International Association on Water Pollution Research and Control IAWQ International Association on Water Quality IWA International Water Association inf influent kBOD First order rate constant of the BOD versus time measurement NO3 nitrate NH4 ammonium NH4-Neff Ammonium nitrogen in the effluent NH4-Ninf Ammonium nitrogen in the influent N-Kjeff,sol Soluble Kjeldahl nitrogen in the effluent N-Kjinf,part Particulate Kjeldahl nitrogen in the influent N-Kjinf,sol Soluble Kjeldahl nitrogen in the influent N-Kjinf,tot Total Kjeldahl nitrogen in the influent PAO Phosphate Accumulating Organism PE Population Equivalent PO4-Peff Phosphate phosphor in the effluent PO4-Pinf Phosphate phosphor in the influent PSD Particle Size Distribution PST Primary Sedimentation Tank RAS Return Activated Sludge SA Fermentation products SF Fermentable, readily biodegradable organic substrates SI Inert soluble organic material SNH4 Soluble ammonium
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SPO4 Soluble phosphate SS Readily biodegradable material SST Secondary Sedimentation Tank STOWA Foundation for Applied Water Research TS Total Solids TSS Total Suspended Solids TKN Total Kjeldahl Nitrogen TN Total Nitrogen TNff Total Nitrogen in filtrated wastewater TP Total Phosphor TPeff,sol Soluble total phosphor in the effluent TPff Total Phosphor in filtrated wastewater TPinf,part Particulate total phosphor in the influent TPinf,sol Soluble total phosphor in the influent TPinf,tot Total phosphor in the influent XAUT Nitrifying organisms XH Heterotrophic organisms XI Inert particulate organic material XPAO Phosphate accumulating organisms XPHA Cell internal storage product of phosphorous accumulating organisms XS Slowly biodegradable substrates VFA Volatile Fatty Acid VSS Volatile Suspended Solids WFD Water Framework Directive WAS Waste Activated Sludge WWTP Wastewater Treatment Plant
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SUMMARY On the 20th of December 2000 the Water Framework Directive of the European Union was published and became valid. It aims to protect and enhance the quality and quantity of the aquatic ecosystem, the water stocks, lower the impact of droughts and use of water in a sustainable way. It was expected the goal could be reached before 2015. It now becomes obvious that the targets will not be met in Europe, due to the discharges of combined sewer overflows (CSO) and the effluents of wastewater treatment plants (WWTP). This study will focus on the primary sedimentation tank (PST) of the municipal wastewater treatment plants of Eindhoven and Roeselare. The PST is a part of the WWTP that is often neglected, although it is shown that these tanks change the ratio of biodegradable to non-biodegradable substances. The ultimate goal is to improve the existing mathematical model. For this a description of the system behaviour of the PST is needed. The study started by analysing different samples from before and after the PST and from the effluent of the WWTP. These analyses were done with a physical-chemical method proposed by STOWA (the Foundation for Applied Water Research). Once the characteristics of the wastewater were known the chemical oxygen demand (COD), nitrogen and phosphorous fractions were calculated and put in the model. The output of the model was than compared with the measured data. These fractions were also used to gain knowledge about the different processes going on in the PST. To know which particle sizes were in the wastewater, the particle size distribution was determined and different column tests were performed. The results for the WWTP of Roeselare revealed that when the WWTP receives high discharges, the PST is working properly. Which means that the total solids were reduced and that the nutrient concentrations were decreased. When the WWTP receives low discharges, the PST is not working properly. The total nitrogen concentrations and the COD concentrations are increasing after the PST. The increase in the COD concentrations can be linked to an increase in the particulate COD fraction, but the increase in the total nitrogen concentration can not be linked to an increase in ammonium or nitrate. Aquafin n.v. has seen the same problem in the COD, oxygen demand and biological oxygen demand (BOD). Also two column tests showed that the particle sizes are increasing after some time and that some particles started rising again. Until now it is unclear what is happening in the PST on days with low discharge rates. Different causes are summed up, such as a mistake in the analyses and the sampling, a plug flow in the PST, a washout of the PST, the presence of proteins,... It is therefore recommended that a further study is performed on the PST to reveal the cause of the problem. The results for the WWTP of Eindhoven were showing an increase of total phosphorous after the PST. This phenomena could be linked to the effluent of the sludge treatment plant of Mierlo. In this wastewater a high concentration of phosphorous is found and due to a technical problem in the WWTP the aluminium dosage was not working well leading to the increase in concentration. Other than this, the PST in Eindhoven is working properly.
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SAMENVATTING Op 20 december 2000 werd de Kaderrichtlijn Water van de Europese Unie gepubliceerd, vanaf deze dag was zij ook geldig. Het had als doel de aquatische ecosystemen en de watervoorraden te beschermen, de impact van droogtes te verminderen en het duurzaam gebruik van water te promoten. Deze doelen moesten verwezenlijkt zijn tegen 2015, maar het is duidelijk dat dit niet het geval zal zijn. Dit door de lozing van de gemengde riooloverlopen en door de effluentlozingen van de rioolwaterzuiveringsinstallaties op de natuurlijke waterlopen. De focus van deze studie is de primaire sedimentatie tank (PST) van de rioolwaterzuiveringsinstallaties (RWZI) in Eindhoven en Roeselare. De focus ligt op deze PST omdat deze vaak wordt vergeten in de studies, ook al is bewezen dat deze tank een belangrijke rol speelt in de ratioverandering van biodegradeerbaar en niet biodegradeerbaar materiaal. Het ultieme doel is het bestaande mathematische model van de RWZI van Eindhoven te verbeteren. Daarvoor is een systeembeschrijving van de PST nodig. De studie start met het analyseren van verschillende stalen voor en na de PST en van het effluent van de RWZI. Deze analyseresultaten zijn bekomen volgens de fysisch-chemische methode beschreven door STOWA (Stichting Toegepast Onderzoek Waterbeheer). Eenmaal de afvalwater karakteristieken gekend zijn, worden de chemische zuurstofvraag- (CZV), de stikstof- en de fosforfracties berekend. Deze fracties worden als input in het model gestoken en de output van het model wordt vergeleken met de analyseresultaten. De verschillende fracties zijn ook gebruikt om kennis te vergaren over de verschillende processen die een rol spelen in de PST. Om te achterhalen welke deeltjesgrootte in het afvalwater aanwezig zijn, is de deeltjesgrootte distributie bepaald en zijn verschillende kolomtesten uitgevoerd. De resultaten voor de RWZI van Roeselare toonden aan dat wanneer de RWZI grote debieten te verwerken had, de PST goed werkte. Dit betekent dat zowel de nutriënt concentraties als het aantal deeltjes verminderde na de PST. Wanneer de RWZI werkt met lage debieten, werkt de PST niet zoals het hoort. Na de PST wordt dan een verhoging van de CZV en een verhoging van de totale stikstof vastgesteld. De verhoging van de CZV kan gelinkt worden met een stijging in de deeltjes CZV. Maar de totale stikstof concentratie stijging, kan niet worden gelinkt met een stijging in nitraat of ammoniumconcentratie. Bij Aquafin n.v. hebben ze hetzelfde probleem ook vastgesteld in de CZV, de biologische zuurstofvraag en de zuurstofvraag. Uit de 2 kolomtesten is ook gebleken dat op bepaalde tijdstippen de deeltjesgrootte opnieuw toeneemt en dat deeltjes opnieuw beginnen te stijgen. Tot op vandaag is het onzeker wat er gebeurt in de PST op dagen met een laag debiet. Verschillende oorzaken zijn wel aangekaard zoals een fout in de analyses en staalname, de aanwezigheid van propstromen in de PST, een uitspoeling van de PST, de aanwezigheid van eiwitten,... Het is aangewezen dit verder te bestuderen, zodat de achterliggende processen kunnen gevonden worden en een bijsturing kan worden geformuleerd voor de RWZI van Roeselare.
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In de resultaten van de RWZI in Eindhoven is een stijging van de totale fosfor concentratie waargenomen. Deze stijging is ook te zien in een stijging van het fosfaatgehalte. De oorzaak van deze stijging kan gevonden worden in de verwerking van het effluent van de slibverwerking installatie van Mierlo. Dit afvalwater bevat hoge fosfaatconcentraties en door een technisch probleem bij de RWZI is de aluminium dosering verkeerd gelopen waardoor de fosfaat stijging is waar te nemen. Met uitzondering van dit probleem, werkt de PST van de RWZI van Eindhoven goed.
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TABLE OF CONTENT ACKNOWLEDGMENT ................................................................................................................. III LIST OF ABBREVATIONS .............................................................................................................. V SUMMARY ................................................................................................................................ VII SAMENVATTING ...................................................................................................................... VIII TABLE OF CONTENT ................................................................................................................... XI LIST OF FIGURES ...................................................................................................................... XIII LIST OF TABLES .........................................................................................................................XV 1. INTRODUCTION ................................................................................................................ 17 2. LITERATURE REVIEW ......................................................................................................... 19
2.1. Wastewater treatment plants ................................................................................... 19
2.1.1. Introduction ........................................................................................................ 19
2.1.2. Biological wastewater treatment plant .............................................................. 19
2.2. Primary sedimentation tank ...................................................................................... 20
2.3. Activated sludge model ............................................................................................. 21
2.3.1. Introduction ........................................................................................................ 21
2.3.2. The Activated Sludge Models ............................................................................. 21
2.3.3. Activated Sludge Model 2 and 2d ....................................................................... 22
2.3.4. Wastewater characterisation ............................................................................. 23
3. MATERIAL AND METHODS ............................................................................................... 29 3.1. Wastewater treatment plants ................................................................................... 29
3.1.1. Roeselare ............................................................................................................ 29
3.1.2. Eindhoven ........................................................................................................... 30
3.2. Sampling ..................................................................................................................... 31
3.3. Chemical analysis ....................................................................................................... 32
3.3.1. Introduction ........................................................................................................ 32
3.3.2. Parameter measurement ................................................................................... 32
3.3.3. Biochemical oxygen demand (BOD) ................................................................... 33
3.4. Suspended solids........................................................................................................ 35
3.4.1. Introduction ........................................................................................................ 35
3.4.2. Total suspended solids ....................................................................................... 35
3.4.3. Volatile suspended solids ................................................................................... 36
3.5. Particle size distribution ............................................................................................ 37
3.5.1. Introduction ........................................................................................................ 37
3.5.2. Settling column test for discrete settling ........................................................... 38
3.6. WEST Software Package ............................................................................................ 38
3.7. Quality laboratory analyses ....................................................................................... 39
3.7.1. Introduction ........................................................................................................ 39
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3.7.2. References for raw wastewater and primary effluent ...................................... 39
4. RESULTS AND DISCUSSION............................................................................................... 41 4.1. Introduction ............................................................................................................... 41
4.2. Wastewater characterisation .................................................................................... 42
4.2.1. Ratios according to Rieger et al. ........................................................................ 42
4.2.2. Ratios according to Henze et al. ........................................................................ 44
4.3. Influent fractionation ................................................................................................ 45
4.3.1. Carbon fractionation .......................................................................................... 45
4.3.2. Nitrogen fractionation ....................................................................................... 51
4.3.3. Phosphorous fractionation ................................................................................ 60
4.4. Removal efficiencies .................................................................................................. 68
4.5. Particle size distributions .......................................................................................... 69
4.5.1. Particle size distribution of the different samples ............................................. 69
4.5.2. Particle size distributions of the column tests ................................................... 71
4.6. General discussion ..................................................................................................... 74
4.6.1. Problems ............................................................................................................ 74
4.6.2. Wastewater treatment plant of Roeselare ........................................................ 76
4.6.3. Wastewater treatment plant of Eindhoven ....................................................... 77
5. CONCLUSION .................................................................................................................... 79 6. REFERENCES ..................................................................................................................... 80 7. APPENDIX ......................................................................................................................... 85
Appendix 1: Laboratory analyses ......................................................................................... 87
Appendix 2: Influent COD fractionation ............................................................................ 100
Appendix 3: Wastewater ratios ......................................................................................... 107
Appendix 3.1: Raw wastewater ratios for the WWTP of Roeselare compared with Rieger et al. (2013) .................................................................................................................... 107
Appendix 3.2: Primary effluent ratios for the WWTP of Roeselare compared with Rieger et al. (2013) .................................................................................................................... 108
Appendix 3.3: Raw wastewater ratios for the WWTP of Eindhoven compared with Rieger et al. (2013) ......................................................................................................... 110
Appendix 3.4: Primay effluent ratios for the WWTP of Eindhoven compared with Rieger et al. (2013) .................................................................................................................... 111
Appendix 4: Division of the wastewater ............................................................................ 112
Appendix 4.1: Raw wastewater division for the WWTP of Roeselare compared with Henze et al. (2001) ......................................................................................................... 112
Appendix 4.2: Raw wastewater division for the WWTP of Eindhoven compared with Henze et al. (2001) ......................................................................................................... 113
Appendix 5: Particle size distributions ............................................................................... 114
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LIST OF FIGURES Figure 1: Conventional biological wastewater treatment plant (Yetis and Tarlan, 2002) ....... 19
Figure 2: Influent COD fractions (STOWA, 1996) ..................................................................... 23
Figure 3: Nitrogen fractions (Nopens, 2010) ............................................................................ 26
Figure 4: Phosphorous fractions (STOWA, 1996) ..................................................................... 27
Figure 5: Schematic view of the treatment plant of Roeselare (Aquafin n.v., 1998)............... 29
Figure 6: Configuration of the activated sludge tank of the WWTP of Eindhoven (Amerlinck et al., 2013) ................................................................................................................................... 31
Figure 7: Fitted BOD-curve of before PST from 24-02-2014 .................................................... 39
Figure 8: Mean COD concentration for low discharge rate in the WWTP of Roeselare .......... 45
Figure 9: Mean COD concentration for high discharge rate in the WWTP of Roeselare ......... 46
Figure 10: Mean COD concentrations for the measurement campaign in the WWTP of Roeselare (12/03/2014) with low discharge rate..................................................................... 46
Figure 11: Mean COD concentration of the measurement campaign in the WWTP of Eindhoven (06/05/2014) .......................................................................................................... 47
Figure 12: Mean concentration for nitrogen compounds of the WWTP of Roeselare with low discharge rate ........................................................................................................................... 52
Figure 13: Mean concentration for nitrogen compounds of the WWTP of Roeselare with high discharge rate ........................................................................................................................... 53
Figure 14: Mean concentration for nitrogen compounds of the WWTP of Roeselare for the measurement campaign (12/03/2014) with low discharge rate ............................................. 54
Figure 15: Mean concentration for nitrogen compounds of the WWTP of Eindhoven for the measurement campaign (06/05/2014) .................................................................................... 54
Figure 16: Nitrogen fractions for the WWTP of Roeselare with high discharge rate .............. 56
Figure 17: Nitrogen fractions for the WWTP of Roeselare with low discharge rate................ 56
Figure 18: Nitrogen fractions for the WWTP of Roeselare of the measurement campaign (12/03/2014) with low discharge rate...................................................................................... 57
Figure 19: Nitrogen fractions for the WWTP of Eindhoven of the measurement campaign (06/05/2014) ............................................................................................................................ 57
Figure 20: Total Kjeldahl nitrogen (TKN) for different conversion factors for the WWTP of Roeselare with low discharge rates .......................................................................................... 58
Figure 21: Total Kjeldahl nitrogen (TKN) for different conversion factors for the WWTP of Roeselare with high discharge rate .......................................................................................... 59
Figure 22: Total Kjeldahl nitrogen (TKN) for different conversion factors for the WWTP of Roeselare for the measurement campaign (12/03/2014) with low discharge rate ............... 59
Figure 23: Total Kjeldahl nitrogen (TKN) for different conversion factors of the WWTP of Eindhoven of the measurement campaign (06/05/2014) ....................................................... 60
Figure 24: Phosphorous compounds for the WWTP of Roeselare with low discharge rate .... 61
Figure 25: Phosphorous compounds for the WWTP of Roeselare with high discharge rate ... 61
Figure 26: Phosphorous compounds for the WWTP of Roeselare for the measurement campaign (12/03/2014) ............................................................................................................ 62
Figure 27: Phosphorous compounds for the WWTP of Eindhoven for the measurement campaign (06/05/2014) ............................................................................................................ 62
Figure 28: Phosphorous fractions for the WWTP of Roeselare with high discharge rate ....... 64
Figure 29: Phosphorous fractions for the WWTP of Roeselare with low discharge rate ........ 64
Figure 30: Phosphorous fractions for the measurement campaign of the WWTP of Roeselare (12/03/2014) ............................................................................................................................ 65
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Figure 31: Phosphorous fractions for the measurement campaign of the WWTP of Eindhoven (06/05/2014) ............................................................................................................................ 65
Figure 32: Total phosphorous concentration for different conversion factors for the WWTP of Roeselare with high discharge rates ........................................................................................ 66
Figure 33: Total phosphorous concentration for different conversion factors for the WWTP of Roeselare with low discharge rates ......................................................................................... 66
Figure 34: Total phosphorous concentration for different conversion factors for the measurement campaign of the WWTP of Roeselare (12/03/2014) ........................................ 67
Figure 35: Total phosphorous concentration for different conversion factors for the measurement campaign of the WWTP of Eindhoven (06/05/2014) ...................................... 67
Figure 36: The different percentiles for the WWTP of Roeselare with a high discharge rate 69
Figure 37: The different percentiles for the WWTP of Roeselare with low discharge rate .... 70
Figure 38: The different percentiles for the WWTP of Roeselare of the measurement campaign (12/03/2014) ........................................................................................................... 70
Figure 39: Best fit between the results of the column test and a sample after the PST of Roeselare .................................................................................................................................. 71
Figure 40: Particle size distribution of the column test of the 5th of May after two hours ..... 72
Figure 41: The different percentiles for the two column tests performed on a sample before the PST of the WWTP of Roeselare (05/05/2014). (A) Top tap, (B) Center tap, (C) Base tap, (D) Top tap second column test, (E) Center tap second column test and (F) Base tap second column test .............................................................................................................................. 73
Figure 42: The different percentiles for the column test performed on a sample before the PST of the WWTP of Eindhoven (30/04/2014). (A) Top tap, (B) Center tap and (C) Base tap 74
Figure 43: Mean increase or decrease of the nitrogen compounds on low discharge days ... 76
Figure 44: Mean increase in concentration of total phosphorous and phosphate ................. 78
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LIST OF TABLES Table 1: Conversion factors for N (Roeleveld and van Loosdrecht, 2002) ............................... 26
Table 2: Conversion factors for phosphorous (Roeleveld and van Loosdrecht, 2002) ............ 27
Table 3: Test kits used for the chemical analysis ..................................................................... 32
Table 4: Volumes used for measuring range BOD .................................................................... 34
Table 5: Needed volumes for BOD tests................................................................................... 35
Table 6: Different mean ratios defined by Rieger et al. (2013) ................................................ 40
Table 7: Typical ratios for raw municipal wastewater according to Henze et al. (2008) ......... 40
Table 8: Sampling time and method, discharge rate, type of analyses and division of the samples for WWTP Roeselare .................................................................................................. 41
Table 9: Sampling time and method, type of analyses and problems for WWTP Eindhoven . 41
Table 10: Comparison of the divisions of the WWTP of Roeselare between high and low discharge rates ......................................................................................................................... 44
Table 11: Percentages of influent COD-fractions for the WWTP of Roeselare ........................ 48
Table 12: Reference values and range of values for the WWTP of Roeselare for raw wastewater and primary effluent ............................................................................................. 49
Table 13: Percentages of influent COD-fractions for the WWTP of Eindhoven ....................... 50
Table 14: Reference values and range of values for the WWTP of Eindhoven for raw wastewater and primary effluent ............................................................................................. 51
Table 15: Minimum and maximum nitrogen compound concentrations for the WWTP of Roeselare and Eindhoven ......................................................................................................... 52
Table 16: Different nitrogen conversion factors ...................................................................... 55
Table 17: Different conversion factors for phosphorous ......................................................... 63
Table 18: Reference removal efficiencies ................................................................................ 68
Table 19: Removal efficiencies of this study ............................................................................ 68
Table 20: BOD-COD ratios for the different samples ............................................................... 75
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1. INTRODUCTION On 22 December 2000 the Water Framework Directive (WFD) of the European Union (2000/60/EC) was published in the Official Journal and became valid from that day onward. The WFD aims to protect and enhance the quality and quantity of the aquatic ecosystem, the water stocks, lower the impact of droughts and use of water in a sustainable way. This will be done by controlling the polluting discharges by keeping them under environmental quality standards and emission limits. Also the principle ‘polluter pays’ is implemented, so that the costs of control and remediation can be recovered. Under these conditions, it is expected that the goal can be reached before 2015 (Kaika and Page, 2003). It now becomes obvious however, that the targets will not be met in Europe, this due the discharges of combined sewer overflows (CSO) and the effluents of wastewater treatment plants (WWTP) (Amerlinck et al., 2013). The European Directive is implemented in the Flemish decree on Integral Water Policy of 18th of July 2003. Within the Integral Water Policy, the first step is the organisation and planning of the integrated water management. To accomplish this, the water system is divided in different districts, regions and basins, each with their own policy plans. The second step of the policy is to provide information on properties, this by the means of the 'Watertoets' (CIW, 2014). This thesis will focus on one of the many polluters of the natural streams, the municipal wastewater treatment plants. Wastewater treatment is defined as the manipulation of water from various sources to remove or reduce pollutants in order to obtain a water quality that meets the standards specified by the regulator agency (EPA, 2008). To obtain a better water quality the ultimate goal is to improve the existing mathematical model that has been developed and calibrated for the WWTP Eindhoven (the Netherlands) with the purpose of cost-effective integrated water management to comply with the WFD (Kallisto, 2010). To make an improvement the focus will lie on the role of the primary sedimentation tank (PST) in the wastewater treatment. This part of the WWTP is often neglected, although it is shown in previous studies that these tanks change the ratio of biodegradable to unbiodegradable substances (Hassan, 2013). For the improvement of the mathematical model of the WWTP a description of the system behaviour of the PST is needed. For the process simulations the wastewater needs to be divided into different fractions. These fractions are obtained after a thorough wastewater characterisation. This characterisation is done for the influent and effluent of the PST and for the effluent of the WWTP. This will be done with a physical-chemical method (the STOWA method) (Roeleveld and van Loosdrecht, 2002). Once the characterisation is done, the different fractions are calculated. The calculation is done with formulas found in STOWA (1996) and in Roeleveld and van Loosdrecht (2002). Then these will be put in the model and the output will be compared with the measured data. The output of the model can then also be used to estimate the impact on the activated sludge system. And can give rise to new operating strategies.
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The aim is to achieve a better alignment between the model predictions and the actually measured values. The different chemical oxygen demand (COD), nitrogen and phosphorous fractions will be used to gain knowledge about the different processes going on in the PST. Variations in the influent fractions are expected due to variations in the influent flow rate. These variations are due to variable discharge amounts of substances, variations in the water consumption in households, infiltration (of groundwater and rainwater) and exfiltration (of the wastewater when there is a storm event, CSO) (Henze et al., 2008). The research for this study is done at Ghent University, Faculty of Bioscience Engineering, Department of Mathematical Modelling, Statistics and Bioinformatics, research unit BIOMATH. The starting point for the practical work is sample collection at the wastewater treatment plants of Roeselare and Eindhoven at the beginning of each week (Monday). The physical-chemical characterisation is done the two following days. After characterisation, the different influent fractions are calculated and are used in the Eindhoven model.
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2. LITERATURE REVIEW
2.1. Wastewater treatment plants
2.1.1. Introduction
Wastewater treatment plants are designed to speed up the natural purification process and to remove contaminants (organic pollution and nutrients) in wastewater. After these processes the clarified water can be discharged in the natural currents. A conventional WWTP uses physical and biological processes to remove the suspended and floating solids, the organic matter and the debris fragments. The alternative plants are classified into three categories: primary treatment (physical processes), secondary treatment (biological processes) and advanced treatment (combination of physical, biological and chemical processes) (Lee and Dar Lin, 1999).
2.1.2. Biological wastewater treatment plant
The wastewater in the plants of Roeselare and Eindhoven is treated in a biological manner. This means that microorganisms in the activated sludge purify the water and degrade organic materials. That is why these plants are called biological wastewater treatment plants. A biological WWTP mostly consist of three main units (Figure 1).
The first unit is the primary sedimentation tank (PST), in this tank the quantity of contaminated materials in the wastewater is reduced. The reduction is done by separating the settable solids from the raw wastewaters. Approximately 50 to 70 % of the suspended solid load and 30 to 50 % of the organic load is removed before the wastewater enters the second unit (STOWA (1999), Rössle and Pretorius (2001) and Ghangrekar and Kharagpur (2014)). This reduces the aeration cost of the activated sludge tank and allows the design of smaller bioreactors. The second unit - also called the activated sludge tank (AST) - contains the activated sludge. Activated sludge consists of bacteria, yeast, fungi, protozoa and rotifers. The basic principle is that the microorganisms grow by degrading substrates and that they clump the particles
Figure 1: Conventional biological wastewater treatment plant (Yetis and Tarlan, 2002)
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together (known as flocs). These flocs settle in the secondary settling tank, leaving a clear supernatant, free of organic material, biological nutrients, carbonaceous material and suspended solids (NESC, 2003). The use of activated sludge as a treatment process was developed in England in 1914. In the aeration tank the biological processes occur. The aeration source provides oxygen and mixes the liquid. In this tank nitrification takes place and when the aeration is stopped, denitrification will start. This results in lower nitrogen and phosphorous concentrations. The third unit is the secondary sedimentation tank (SST) also known as settling basin or clarifier. This tank allows the microorganisms and other solids to settle after the biological treatment by a decrease in flow velocity and under influence of gravity. The settled solids are partly reused in the aeration tank, called return activated sludge (RAS). For mass balance reasons, some settled solids need to be removed, called waste activated sludge (WAS). The clear water, the supernatant, is discharged in surface waters or can be reused (NESC, 2003).
2.2. Primary sedimentation tank
A primary sedimentation tank can have a rectangular, circular or square configuration. In the further description, the attention will only go to circular tanks because both the WWTPs have circular primary sedimentation tanks. The most important process in these tanks is the sedimentation. In sedimentation there are four types of settling (EPA, 1997): - discrete settling is most seen with particles that hold a constant shape and size during the settling. This is mostly seen in liquors with solids concentrations from approximately 500 mg/l (WRAC, 2001). This is occurring in the sand trap. - flocculent settling is seen with particles that join together and are increasing in diameter and density, which ultimately lead to a higher settling ability. This type of settling is mostly seen in primary settling tanks. - hindered settling is seen in the activated sludge tanks, it consists of particles that form a blanket and settles and then consolidate as a mass - compression settling is a very slow type of sedimentation and this is only seen when a fresh particle blanket is pushing down another blanket. The purpose of the PST is to remove solids by settling and accumulate at the bottom of the tank by reducing the velocity of the incoming wastewater. The factors that are determining the efficiency of the tank are (EPA, 1997): - the type of solids present in the wastewater and this is depending on the type of wastewater that is entering the treatment plant - the hydraulic retention time, if this is too long the waste will start to degrade and form gas bubbles. These bubbles will rise and will hinder the settling - the design criteria based on the maximum flow. In most of the cases these are 2 hours for retention time, an overflow rate of 28.8 - 36 m³/m²/day and the weir overflow rate - sludge removal so that there is no chance of floating sludge - return liquors can contain solids which have different settling characteristics. The wastewater enters the tank in the center to obtain a radial flow pattern. Normally the inlet structure consists of a weir which is used to distribute the water uniformly. On the bottom of the tank the solids will be removed by scrapers and will be accumulated in a whole near the center where they will be removed by sludge pumps. On the top of the
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water surface skimmers will be placed to remove the grease and flotable material (Ghangrekar and Kharagpur, 2014).
2.3. Activated sludge model
2.3.1. Introduction
A biological nutrient removal system such as the Activated Sludge Process (ASP) is a complex system and it needs a large number of interacting compounds and biological reactions. These reactions need to be modelled as good as possible to obtain a good design and to develop and control the different systems (Melcer et al., 2003). Mathematical models can be used for system analysis or for system optimisation. The models for system analysis are used for new or poorly understood systems. Normally the basis of such studies is experimental analyses but due to the long run time the switch is made to mathematical models. For these the reality is described in a series of equations and then solved. The output is then the outcome of the experiment (Nopens, 2010). The models that are used for system optimisation are based on mathematical models that are working properly. Focus is now on the improvement of parameters in order to bring the model system more in line with reality (Nopens, 2010). For the modelling of the ASP the International Association on Water Pollution Research and Control (IAWPRC, now known as the International Water Association IWA) established a task group in 1982. Before that time a variety of models existed, most with a low level of accuracy due to limitations in computer power and only partial coverage of the complex reality (Henze et al., 2000). The task group goal was to create a platform that is useful for the development of simple models for nitrogen-removal ASP. The modelling was to cover four basic elements: process inputs, process models, process configuration and process operating conditions. The work resulted in a series of Activated Sludge Models (ASM) (Henze et al., 2000).
2.3.2. The Activated Sludge Models
The activated sludge models characterize the wastewater by fractions of carbon (expressed as COD), nitrogen and phosphorous (Melcer et al., 2003). In 1985 the first ASM (ASM1) was presented in Denmark, and was developed for municipal activated sludge wastewater treatment plants. The ASM1 describes the removal of organic carbon substances and nitrogen and the consumption of oxygen and nitrate as electron acceptors. Out of these descriptions a simulation of the activated sludge system behaviour is generated. The publication, presented a guideline for wastewater characterization, computer codes and a set of default values. The model served as the basis for further development and is used as a modelling tool for nitrification-denitrification processes. Also it has initiated further research in modelling wastewater characterisation (Henze et al., 2000). In ASM1, 8 fundamental processes of the activated sludge process are incorporated: aerobic and anoxic growth of heterotrophic biomass, death of heterotrophic biomass, aerobic growth of autotrophic biomass, decay of autotrophic biomass, ammonification of soluble organic nitrogen and hydrolysis of entrapped particulate organic matter and organic nitrogen (Nelson and Sidhu, 2009).
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ASM2 was published in 1995. This model is used for advanced wastewater treatment modelling. It is an adaptation of ASM1 that now includes nitrogen and biological phosphorous removal. But at the time of developing and publishing the role of denitrification in relation to biological phosphorous removal was uncertain and is not yet incorporated in ASM2 (Henze et al., 2000). In 1999 ASM2 was extented in ASM2d that does include the denitrifying phosphate accumulating organisms (PAOs). From 1998 the task group is developing the new model ASM3. Progress in understanding the ASP is at the basis of this adjustment. The models are generally accepted for three reasons. First, the modelers speak the same language when using the concepts, the nomenclature and the matrix notation. Second, the model has an organizing effect, which helps researchers to achieve more efficient experimental designs and treatment plant operators to understand and organize the available information. And last: the models provide a guidance tool for research. They demonstrate where extra research is needed and which aspect needs further detail focus (Henze et al., 2000). In what follows, only ASM2d will be described because this model is the basis for the Eindhoven model.
2.3.3. Activated Sludge Model 2 and 2d
ASM2 describes the biological phosphorus uptake in the activated sludge processes and it is a working tool for nutrient removal treatment plants. This model deals also with the removal of nitrogen and carbon. For this model the wastewater and biomass characterisation has to be more complex to explain the observed phenomena so that the model gives reliable predictions (Henze et al., 1995). The methods for the characterisation of the organic fractions have not been standardized. This is done to allow the development of easy and reliable characterisation techniques (Henze et al., 1995). In the model, the biomass is split into three fractions, the heterotrophs, the nitrifiers and the phosphate accumulating organisms. This leads to the following assumptions:
- that there is competition between heterotrophs and PAOs for the volatile fatty acids (VFA) under aerobic conditions;
- and that the PAOs do not possess denitrification capability (Henze et al., 1995). The extension of ASM2, ASM2d, is a mathematical model for the simulation of biological processes with COD, nitrogen and phosphorous removal in the activated sludge system. The model itself is used as a tool for research, process optimisation, teaching and design assistance (Henze et al., 1999). The main difference with ASM2 is the incorporation of two additional phosphate accumulating organisms processes: PAOs can use cell internal organic storage products for denitrification and they can also denitrify (Henze et al., 1999). Of course these models come with some assumptions and limitations (Henze et al., 1999): - the model is only valid for municipal wastewater - there is enough magnesium and potassium in the wastewater
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- there is no overflow of fermentation products to the aeration tank - the pH should be near neutral - the temperature is between 10 and 25 °C The ASM2d is the most accepted model for studying carbon, nitrogen and phosphorus removal. But due to the complicated calibration, the correctness of the model output can be questioned (Boontian, 2012).
2.3.4. Wastewater characterisation
2.3.4.1. Introduction
The wastewater characterisation varies from plant to plant and is one of the most important elements of the treatment process. It impacts the performance and available treatment capacity and influences greatly the model predictions (Henze et al., 2000). The wastewater characterisation is traditionally expressed in different classes of biodegradability in COD, nitrogen and phosphorus (Choubert et al., 2013). Also the total and volatile suspended solids (TSS and VSS) and the alkalinity can be determined (Hauduc et al., 2013). These different fractions can then be used to determine different aspects of the treatment process. E.g. the unbiodegradable particulate COD says something about the sludge production and the oxygen demand (Melcer et al., 2003). Or the ratios of BOD/COD, BOD/N or COD/N can provide information on the loading rate of the municipal wastewater (Henze et al., 2008).
2.3.4.2. Carbon fractionation
For the ASM2d model the organic matter is expressed in COD and this can be split into three groups (STOWA, 1996), as shown in Figure 2.
Figure 2: Influent COD fractions (STOWA, 1996)
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The total concentration of organic matter is expressed in the total chemical oxygen demand (CODtot) (STOWA, 1996):
(1) The COD fractions are divided into soluble (S) and particulate (X) components and a further division is made on the biodegradability (S for biodegradable or I for non-biodegradable). In this study, the different COD fractions are determined with physical-chemical methods. After the determination of the COD fractions, these can be used to find the different wastewater fractions for the ASM2d model. The following equations are used (Roeleveld and van Loosdrecht, 2002):
(2) (3)
(4) (5) (6) (7)
(8) (9)
(10)
(11)
The different abbreviations in the formulas stand for (Roeleveld and van Loosdrecht, 2002 and Henze et al., 1999): - CODinf,tot: non-filtered total COD influent - CODinf,sol: COD influent after membrane filtration or flocculation - CODeff,sol: COD effluent after membrane filtration or flocculation - CODVFA: COD determined with gas chromatography or titration - bCOD: biodegradable COD - BODtot: total BOD - kBOD: first order rate constant of the BOD versus time measurement - BOD5,inf: BOD influent measured over a time period of 5 days - SI: inert soluble organic material - SS: readily biodegradable material - SA: fermentation products - SF: fermentable, readily biodegradable organic substrates - XS: slowly biodegradable substrates - XI: inert particulate organic material - XH: heterotrophic organisms - XPHA: cell internal storage product of phosphorus accumulating organisms - XPAO: phosphate accumulating organisms - XAUT: nitrifying organisms (1) The readily biodegradable COD (SS) is determined after flocculation and filtration through a 0.45 µm filter by using a HACH-LANGE test kit. But through the filter both biodegradable and inert COD can pass.
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(2) The inert soluble organic fraction, SI, is determined on the effluent after flocculation and filtration through a 0.45 µm filter with a HACH-LANGE test kit. After determination of SI this amount is subtracted from the soluble influent COD to get the SS fraction (Roeleveld and van Loosdrecht, 2002). (3) The biodegradable COD (bCOD) can be found by taking the sum of the readily biodegradable soluble COD and the slowly biodegradable substrates (SS + XS). The slowly biodegradable substrates have a high molecular weight which means they need to undergo cell external hydrolysis before they are available for degradation (Henze et al., 1999). Determination of bCOD is based on the BOD10 (biological oxygen demand measured over a time period of 10 days) analysis. After this measurement the BODtot is calculated. (4) The particulate unbiodegradable COD (XI) is obtained by subtracting all organic fractions from the total COD of the influent (Roeleveld and van Loosdrecht, 2002). (5) The fermentation products (volatile fatty acids) or SA, are part of the biological processes. That is why this fraction is modelled separately from the other organic fractions. For simplicity it is assumed that SA is equal to acetate (Henze et al., 1999). (6) The fraction of the soluble COD that is directly available for biodegradation for heterotrophic organisms is called fermentable, readily biodegradable organic substrates, SF
(Henze et al., 1999). (7) The inert particulate organic material or XI, is the material that cannot be degraded and that is flocculated onto the activated sludge (Henze et al., 1999). (8) The biomass COD includes three groups: - XAUT are the nitrifying organisms responsible for nitrification. They oxidize ammonia into nitrate. - XHET or the heterotrophic organisms, they can grow aerobically and anoxically (denitrification) and active anaerobically (fermentation). They will hydrolyse the slowly biodegradable substrates and they can use all the other degradable organic substrates. - XPAO or the phosphate accumulating organisms represent the biomass of the poly-phosphate-accumulating organism but it does not include the cell internal storage. Therefore XPHA or the cell internal storage product of phosphorus accumulating organisms is included in the modelling. In reality this fraction is difficult to determine with physical-chemical methods (Henze et al., 1999).
2.3.4.3. Nitrogen fractionation
The nitrogen concentration that is available for oxidation determines the autotrophic oxygen demand and the denitrification capacity. (Roeleveld and van Loosdrecht, 2002). It is necessary to determine the nitrogen balance when there are strict effluent criteria. In the activated sludge models nitrogen (N) is divided into different fractions (Figure 3). (1) Total nitrogen is the sum of organic nitrogen, ammonia, nitrite and nitrate. This sum can also be written as the sum of the total Kjeldahl nitrogen (TKN), nitrate and nitrite (SNOx). (2) TKN is the sum of the ammonia nitrogen (SNH), organically bound N and of the active biomass N (XNB) (Nopens, 2010). The organic nitrogen can be further divided into soluble and particulate fractions and both can be further divided into biodegradable (SND and XND) and nonbiodegradable (SNI and XNI) fractions.
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In the ASM2d model fixed conversion factors for nitrogen (iN) of various COD fractions are assumed in the organic part of the nitrogen present in wastewater. These conversion factors are given in Table 1. These factors can be found by fitting the model on the measured nitrogen content of the sludge. But it can also be determined by the analysis of NH4-N and Kj-N from filtered and non-filtered samples (Roeleveld and van Loosdrecht, 2002).
Table 1: Conversion factors for N (Roeleveld and van Loosdrecht, 2002)
Conversion factors for N Unit Value
iNSI g N/g COD 0.01
iNSA g N/g COD 0
iNSF g N/g COD 0.03
iNXI g N/g COD 0.03
iNXS g N/g COD 0.04
The different factors are then used to calculate the different fractions of the Kjeldahl nitrogen. These fractions are calculated with the following equations:
(12) (13)
(14) (15)
(16)
With: - SNH4: soluble ammonium - NH4-Ninf: ammonium nitrogen in the influent - N-Kjinf,tot: total Kjeldahl nitrogen in the influent
Figure 3: Nitrogen fractions (Nopens, 2010)
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- N-Kjinf,sol: soluble Kjeldahl nitrogen in the influent - N-Kjeff,sol: soluble Kjeldahl nitrogen in the effluent - N-Kjinf,part: particulate Kjeldahl nitrogen in the influent - NH4-Neff: ammonium nitrogen in the effluent
2.3.4.4. Phosphorous fractionation
Phosphorous fractions are needed because it is an important nutrient for microorganisms (algae and bacteria) (Roeleveld and van Loosdrecht, 2002). In wastewater three forms are found, orthophosphate, polyphosphate and organic phosphate. The polyphosphate is hydrolysed to orthophosphate. And organic phosphate is mostly present in industrial wastewater and is neglected in domestic wastewater. For the characterisation the phosphorus content is called total phosphorous (TP). This can be further divided into soluble and particulate phosphorous (see Figure 4, STOWA, 1996). The orthophosphate is a soluble portion of the TP (Melcer et al., 2003).
Just as for nitrogen, there are phosphorus conversion factors. And these can also be found by fitting the model to the measured phosphorus content of the sludge. These factors are given in Table 2 (Roeleveld and van Loosdrecht, 2002).
Table 2: Conversion factors for phosphorous (Roeleveld and van Loosdrecht, 2002)
Conversion factors for P Unit Value
iPSI g P/g COD 0
iPSA g P/g COD 0
iPSF g P/g COD 0.01
iPXI g P/g COD 0.01
iPXS g P/g COD 0.01
And by using the different equations, the different phosphorous fractions can be calculated. (17)
(18) (19)
(20)
Figure 4: Phosphorous fractions (STOWA, 1996)
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(21)
With: - SPO4: soluble phosphate - PO4-Pinf: phosphate phosphor influent - TPinf,tot: total phosphor in the influent - TPinf,sol: soluble total phosphor in the influent - TPeff,sol: soluble total phosphor in the effluent - TPinf,part: particulate total phosphor in the influent - PO4-Peff: phosphate phosphor effluent
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3. MATERIAL AND METHODS
3.1. Wastewater treatment plants
3.1.1. Roeselare
The wastewater treatment plant of Roeselare is managed by Aquafin n.v. and operational since 1996 (Aquafin n.v., 1998). Aquafin n.v. is the company in charge of water remediation of the Flemish Region. It needs to design, implement, finance and exploit the municipal sewers, pumping stations and wastewater treatment plants since 1990. In fact it needs to help achieve the goals that are mentioned in the European Urban Wastewater Directive (collect and treat all the domestic wastewater by the end of 2005) and the European Water Framework Directive (good water quality for natural currents by 2015). The treatment of the wastewater already showed some result, as the water quality got better, fish migration is seen to the cleaner parts of the streams and by an increase in the selfcleaning properties of the waterways (Aquafin n.v., 2014). The treatment plant of Roeselare has a treatment capacity of 73,000 population equivalent (PE) and remediates biologically domestic (87 % of the total treated wastewater volume) and industrial wastewater (13 % of the total treated wastewater volume). After treatment, the wastewater is discharged in the river Mandel. In Figure 5 a schematic overview of the treatment plant is given.
The wastewater first goes through a mechanical treatment (1-5) to remove large, non biodegradable solids. This process consists of three parts, the first part of grids where big pieces of waste are trapped (1-2). The wastewater then passes to the second part, the aerated sand trap (3). This plant uses two aerated sand traps. This process removes the sand particles in order to protect the pumps from corrosion and damage. If there is a storm event or a long rain period the extra water is directed to four buffer tanks (4). The water stays there until the flow rate is decreased. If the rain period is too long, the water will be
Figure 5: Schematic view of the treatment plant of Roeselare (Aquafin n.v., 1998)
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discharged in the Mandel without treatment. This can be done due to the large dilution, in case of heavy rains, of the wastewater. The last part of the mechanical treatment is the primary sedimentation tank (5). Here, the primary sludge settles and the loading rate to the subsequent biological treatment step is reduced by 20 % (Aquafin n.v., 1998). Biological treatment (6-13) follows after the mechanical treatment. There are 5 stages to this part of the process. In the first part, the contact tank (6), the sludge settling characteristics are improved. The second part consists of 2 aeration tanks (the activated sludge tanks, 7), in these tanks oxygen is added by surface aerators. During this process, one of the tanks is aerated and nitrification occurs. Simultaneously, the aerators in the other tank are idle and denitrification takes place. The next phase is the secondary sedimentation tank (SST, 8). In this plant 4 such tanks are installed. Before the mixture of sludge and wastewater enters these tanks, it is divided in equal amounts in the splitter. After the sludge is settled and removed from the SST, it can go back to the biological treatment or it is taken out of the system (10). Before the sludge leaves the plant, it is dewatered and thickened (11, 12, 13) (Aquafin n.v., 1998).
3.1.2. Eindhoven
The wastewater treatment plant of Eindhoven is managed by the Waterboard De Dommel. It is the third largest WWTP of the Netherlands with a treatment capacity of 750,000 PE. The treated wastewater is discharged into the river Dommel. The plant consists of three parallel lines, in which biological treatment takes place and they are configured according to the UCT-principle. These lines can handle a maximum hydraulic load of 26,250 m³/h and consist of a primary settler, a biological tank and four secondary clarifiers. Extra wastewater (approximately 8,750 m³/h) can be treated mechanically and after passing a pre-settling rain buffer tank it can be discharged in the Dommel or it is treated in the biological tank when the load is again lower than 26,250 m³/h (Amerlinck et al., 2013). The activated sludge tanks are circular in construction and consist of 3 parts (see Figure 6) The inner ring is the selector or the anaerobic tank, then there is the denitrification tank (middle ring) and the outer ring is the nitrification tank. The nitrate poor sludge is pumped from the denitrifaction tank to the anaerobic tank. This is done for the benefit of the phosphate accumulating organisms (no disturbance of nitrate). A second transport of sludge to the denitrification tank comes from the nitrification tank where nitrate is formed (Claessen, 2010). For this treatment plant the modelling already started in the early 1990's. Since 2007 there is a cooperation for the modelling with the Ghent University (Department of Mathematical modelling, Statistics and Bioinformatics). The model development provides improvements so that increasingly complex problems can be addressed. The provided solutions come with an uncertainty because the models are a simplification of reality (Amerlinck et al., 2013).
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The latest adaptation of the model is made during the KALLISTO-project. The project started after renovation of the WWTP and dredging of the river Dommel, and was triggered by the observation that the river water was still greatly influenced by the WWTP effluent. Because the discharge rate of the WWTP is higher than the flow rate of the river Dommel. The influence of the effluent is seen in the depletion of dissolved oxygen (DO), in ammonia (NH4) peaks (toxic for aquatic organisms) and seasonal nutrient peaks (nitrate and phosphate) (Nopens et al., 2012). The aim of the project is the improvement of the water quality of the river Dommel. The improvement can be done by the implementation of real time monitoring, modelling and controlling of water flows and the construction of technical measures in the treatment plant. In this way storm water and wastewater flow can be controlled, steered and treated (Kallisto, 2010).
3.2. Sampling
Influent and effluent water from the PST and effluent water from the WWTP was collected from two WWTPs for experimental analysis in the BIOMATH laboratory. A total of six sampling days and one measurement campaign were carried out at the WWTP of Roeselare and one measurement campaign at the WWTP of Eindhoven. On the sampling days a combination of grab sampling and weekly sampling were used. This means that one sample is collected in a 10 l plastic container at a specific and fixed time of the week: in this case Monday morning 9:30. This type of sampling leads to a high variation in results but they are beneficial for design and modelling purposes (Henze et al., 2008). During the measurement campaigns time proportional samples were taken. These are samples taken at well defined time intervals and combined into one composite sample. This sampling method allows the study of small variations within the different wastewater components (Henze et al., 2008). In the case of the measurement campaign of the WWTP of
Figure 6: Configuration of the activated sludge tank of the WWTP of Eindhoven (Amerlinck et al., 2013)
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Roeselare one sample of 1 l represented 20 minutes and it contained samples of 100 ml that were taken each 2 minutes. Samples were taken before the PST, after the PST, from the effluent and the activated sludge. All samples were transferred to the BIOMATH laboratory, where the samples of the PST and of the effluent were kept in a cool (approximately 4 °C) and dark environment (refrigerator). The activated sludge samples were aerated.
3.3. Chemical analysis
3.3.1. Introduction
The chemical analyses are performed according to the STOWA method. Based on the analyses the composition of the influent of the PST and the effluent of the PST is deduced. The composition and the different fractions are important to get a good model of the activated sludge systems. If the fractions (and thus the composition) of the influent change then the activated sludge models need to create the corresponding output. A problem for influent characterisation is the absence of a standardized determination method (STOWA, 1996).
3.3.2. Parameter measurement
The different components to be analyzed and quantified were described in chapter 2.3.4. HACH LANGE kits are used to analytically separate the different components. These test kits contain the necessary reagents and come with precise instructions. Table 3 lists the test kits used during this project. The concentration of the different components is then determined in the spectrophotometer.
Table 3: Test kits used for the chemical analysis
Parameter LCK test kit number Measuring range
Total COD LCK 314 15 - 150 mg/l O2
LCK 514 100 - 2000 mg/l O2
COD flocculated and filtered LCK 614 50 - 300 mg/l O2
LCK 414 5 - 60 mg/l O2
Total phosphor LCK 350 2 - 20 mg/l PO4-P
LCK 348 0.5 - 5.0 mg/l PO4-P
Phosphor flocculated and filtered LCK 349 0.05 - 1.50 mg/l PO4-P
Phosphate LCK 350 2 - 20 mg/l PO4-P
LCK 348 0.5 - 5.0 mg/l PO4-P
Total nitrogen LCK 338 20 - 100 mg/l TNb
Nitrogen flocculated and filtered LCK 238 5 - 40 mg/l TNb
Ammonium LCK 303 2 - 47 mg/l NH4-N
Nitrate LCK 340 5 - 35 mg/l NO3-N
LCK 339 0.23 - 13.55 mg/l NO3-N
Some of the parameters in Table 3 are measured after flocculation and filtration. These two operations are done according to the standard method 417B (APHA, 1985). A sample volume of 100 ml is stirred and 1 ml of 10 g/l zinc sulphate solution is added. The sample is mixed vigorously for 1 minute, after which the pH is adjusted to 10.5. The pH adjustment is done by adding drops of 6 M sodium hydroxide solution. After the pH is reached, the stirring is
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stopped and the sample allowed to settle. Once a clear fluid is visible, the supernatant is withdrawn until a volume of 20 to 30 ml is collected. This volume is than passed through a 0.45 µm membrane filter, which is first washed with deionised water to remove any dust.
3.3.3. Biochemical oxygen demand (BOD)
3.3.3.1. Introduction
Determination of BOD is an empirical test to determine the relative oxygen requirements of wastewater, effluents and polluted waters. These tests are done according to the standardized laboratory procedures (5210) of the American Public Health Association (APHA). The BOD determination is most used for measuring waste load to treatment plants and for evaluating the BOD-removal efficiency of the treatment systems. The test measures the molecular oxygen utilized during a specified incubation period for the biochemical degradation of organic material and the oxygen used to oxidize inorganic material such as sulphides and ferrous iron. Normally it measures also the amount of oxygen used to oxidize the reduced forms of nitrogen. But in this study the oxidation of reduced forms of nitrogen is prevented by adding an inhibiting chemical (APHA, 1999).
3.3.3.2. Experimental set-up
For the determination of BOD of the influent before and after the PST and of the effluent, brown bottles closed with electronic stoppers (named OXITOP® manufactured by WTW) are used. In these bottles a well-defined volume of the sample is placed together with mineral solutions, a nitrification inhibitor and activated sludge from the wastewater treatment plant. The bacteria in the sludge will consume the biochemically degradable material during the incubation time. Due to the degrading, oxygen is consumed. This means that the oxygen concentration in the bottle will decrease and this causes a decrease in 'partial oxygen pressure'. The variation in the partial oxygen pressure is measured with the stopper and this variation is assumed to be equal to variation in the total pressure. The amount of oxygen that is consumed is displayed in mg/l and this is equal to the BOD. Due to the degradation carbon dioxide (CO2) is produced. This CO2 will lead to a pressure increase, but this can be avoided by adding NaOH-granules in the neck of the bottle. The bottles are placed on a magnetic stirrer and are stored in a dark place at a temperature of 20 °C. For repeatability these tests are done in duplicate. To check if the operational conditions are good, a BOD-test with glucose-glutamic acid solution (GGA) is used. The test is considered valid when the BOD-value is in the range of 198 30.5 mg/l (APHA, 1999).
3.3.3.3. Reagents
The necessary reagents are mineral solutions, inoculum and a nitrification inhibitor. In total 4 mineral solutions are required: - phosphate buffer solution: 0.85 g KH2PO4, 2.175 g K2H PO4, 3.340 g Na2HPO4 and 0.17 g NH4Cl dissolved into 100 ml of deionised water
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- magnesium sulphate solution: 2.25 g MgSO4.7H2O dissolved into 100 ml of deionised water - calcium chloride solution: 2.75 g CaCl2 dissolved into 100 ml of deionised water - iron chloride solution: 0.025 g FeCl3.6H2O dissolved into 100 ml of deionised water The inoculum is a specified volume of activated sludge from the wastewater treatment plant. The volume that is needed for the test is calculated as:
(22)
The nitrification inhibitor that is used is allythiourea (C4H8N2S or ATU), this ATU needs to be stored at 4 °C and is only stable for 2 weeks. After two weeks a new solution is made by adding 2.0 g allylthiourea to 1 l deionised water. The glucose-glutamic acid solution is made with glucose (C6H12O6) and glutamic acid (C5H9NO4) that is first dried in the oven at 103 to 105 °C for 2 hours. After the oven the substances are placed in the desiccator for 1 hour. Then 150 mg of each is added to 1 l of deionised water. To get a good result, the solution is made just before use.
3.3.3.4. Procedure
The analysis starts with determination of the wastewater COD and the TSS of the activated sludge. This allows to estimate the BOD value and the amount of activated sludge to be added. The estimation of the BOD is done using the following formula:
(23) From this estimation the correct volume of sample is selected from Table 4. The estimation is needed to assure that enough oxygen is available in the bottle and that no oxygen depletion occurs. Oxygen depletion obviously leads to erroneous measurements. If the added volume is too low, the measurements will be less accurate.
Table 4: Volumes used for measuring range BOD
Estimated BOD (mg/l) Volume sample (ml)
0 - 40 432
40 - 80 365
80 - 200 250
200 - 400 164
400 - 800 97
800 - 2000 43.5
2000 - 4000 22.7
The volume needed for the influent before and after the PST are in the range of 167 -250 ml and of the effluent in the range of 432 ml. For each of these volumes a special overflow flask is present. Before the samples are added to the bottles and the overflow flask, they are both rinsed with the sample. After rinsing, the correct volume is measured with the overflow flask and transferred to the bottle. The mineral solutions are added in amounts to represent only 1 % of the sample volume, the amounts that are needed are given in Table 5.
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To inhibit the nitrogenous oxygen demand, the nitrification inhibitor needs to be added to reach an end concentration of 10 mg/l. The volumes are also given in Table 5. After all this the activated sludge is added, this until an end concentration of 5 mg TSS/l is reached. This amount is calculated with equation (23).
Table 5: Needed volumes for BOD tests
Volume sample (ml) Mineral solutions (ml) ATU (ml)
432 1.08 2.16
365 0.9125 1.825
250 0.625 1.25
164 0.41 0.82
97 0.2425 0.485
43.5 0.10875 0.2175
22.7 0.05675 0.1135
The last step is to put the magnetic stirrer in the bottle and to put the rubber container on the top. This container is filled with 5 to 6 NaOH-pellets and then the OXITOP® is screwed on. This top is then started with the remote control. Date, number and name of the sample are written on the bottle.
3.4. Suspended solids
3.4.1. Introduction
The quantity of solids is determined because they are important in the control of biological and physical wastewater treatment processes and to assess the compliance with regulatory wastewater effluent limitations. The total solids (TS) are defined as the material residue left in the vessel after evaporation of the sample and drying in the oven at a well defined temperature. One of the most commonly used methods is the total suspended solids (TSS). These are the solids that are retained by a filter. The volatile suspended solids (VSS) are defined as the weight loss after ignition (APHA, 1999).
3.4.2. Total suspended solids
3.4.2.1. Principle
To determine the TSS a well mixed sample is filtered through a weighed glass-fibre filter and the residue retained on the filter is dried to a constant weight at 103 to 105 °C. The increase of weight of the filter represents the TSS (APHA, 1999).
3.4.2.2. Procedure
The glass-fibre filter is prepared in the Büchner filter, this apparatus creates a vacuum so that when the fibre is washed with distilled water the water runs through the filter. The washing is done three times, this to remove dust and other impurities in the filter. The filter is placed in an aluminium cup after washing and dried in the oven at 103 to 105 °C for 1 hour. Once out of the oven the filter and the cup are placed in a desiccator to balance the
36
temperature and the weight. This will happen for about 1 hour, after that the filter is weighed (APHA, 1999). To do the sample analysis, the filter is put back in the filter apparatus and suction starts. A well known volume of a well mixed sample is added to the filter. The suction stays on until all the water of the sample is drained through the filter. After this the sample is placed back in its aluminium cup and goes in the oven for approximately 1 hour at 103 to 105 °C. After that it is put back in the desiccator for 1 hour and the filter is then weighed. The following formula is used to obtain the mass of the total suspended solids:
(24)
This procedure is done in duplicate to check the repeatability (APHA, 1999).
3.4.2.3. Experimental set-up
In this thesis two types of filters are used, a glass-fibre filter and a paper filter. The glass-fibre filter is used to determine the TSS of the influent before and after the PST and the paper filter is used to determine the TSS of the activated sludge. Both filters are prepared in accordance with the procedure and are placed in the oven for 2 hours at 103 to 105 °C. After that they go in the desiccator for 1 hour and are weighed. In between coming out of the oven and weighing, cups and filter are never touched. This prevents fluids going back to the dried filter. Sample volume added to the filter is different for the influent and the activated sludge, because the activated sludge has more TSS than the influent. For the influent 100 ml sample is added on the glass-fibre filter and for the activated sludge 25 ml is added. The rest of the procedure is then followed, with the adjustment of the residence time in the oven to two hours.
3.4.3. Volatile suspended solids
3.4.3.1. Principle
A well-mixed sample is first evaporated in a weighed dish and dried in an oven at 103 to 105 °C. After heating the increase in weight of the dish is noted and then the residue is ignited at 550 °C. The remaining solids after the ignition represent the mass of fixed total solids and the weight loss due to ignition represents the mass of the volatile suspended solids. The determination of the fixed and the volatile suspended solids are useful as a control for the operations of a wastewater treatment plant because it offers an approximation of the amount of organic matter present in the solid fraction of the wastewater and activated sludge (APHA, 1999).
3.4.3.2. Procedure
A clean porcelain dish is heated for 1 hour at 103 to 105 °C and stored and cooled in the desiccator. After cooling the dish is weighed and used immediately. In the weighed dish a measured volume of a well-mixed sample is added. Then the sample goes back in the oven at 103 to 105 °C until the sample is completely dried.
37
Once dried the dish is put 1 hour in the desiccator to cool down and to balance the temperature. Then weigh the dried sample and put the sample in the muffle furnace at 550 °C. Normally 15 to 20 minutes of ignition is enough for one sample, but because more samples are added in the muffle furnace it takes longer. After the ignition the sample is air cooled until most of the heat is dissipated and then the sample is transferred to the desiccator. The dish is weighed after the temperature is balanced. The mass of the volatile suspended solids is calculated by the following equation:
(25)
The mass of the fixed suspended solids can be calculated as follows:
(26)
This procedure is done in duplicate to check the repeatability (APHA, 1999).
3.4.3.3. Experimental set-up
In this thesis the volatile suspended solids are determined as written in the procedure. This determination is done for the wastewater before and after the PST and for the activated sludge. In the experimental set up, each sample is measured two times and 25 ml of the well-mixed sample is added to a porcelain cup. Then the cups are put in the oven for approximately 2 to 3 days. Afterwards they spend one hour in the desiccator and are weighed. Then the six cups go in the muffle furnace for 2.5 to 3 hours at 550 °C. After the ignition, the cups are cooled in the desiccator for 1 hour and are weighed. The mass is then calculated according to equation 25.
3.5. Particle size distribution
3.5.1. Introduction
In the PST and the SST sedimentation is a crucial stage because it separates the suspended particles from the liquid by gravity. Sedimentation is one of the physical phenomena that is widely studied. The interest in the study started with the Law of Stokes (1851), this describes the velocity of sedimentation. In spite of all studies on the subject, it is still very difficult to simulate the settling in wastewater treatment plants (Martinez-Gonzalez et al., 2009). The particle size distribution is not only important for the simulation of the settling process, but it is also of importance for the introduction of new processes and for the application of technologies to use the wastewater in other sectors (e.g. agriculture). The advantages of settling organic matter are: maximizing the energy generation (anaerobic digestion), reduce the energy input for aeration in the biological process and lead to compacter biological reactors (Sophonsiri and Morgenroth, 2004).
38
3.5.2. Settling column test for discrete settling
3.5.2.1. Procedure
A settling column of approximately 9 l and an inner diameter of 150 mm is used as measuring device. At well defined heights 4 sampling holes are made, these are spread equally over the diameter. In total there are 16 sampling points. In each hole a sampling tube is placed that can be closed. This tube has an inner diameter of approximately 1 mm and needs to be as short as possible. With this set-up frequent sampling at different heights is possible. By switching between holes at one height several samples can be taken without hydraulic disturbance. Before adding the sample, the column is filled with water. This is to check for leaks and to clean the sampling tube from previous sample contamination. After this the sample is homogenised and is poured in the column until the sample is 4 cm above the highest sampling point. The sampling occurs at the top 3 sampling points and this at well defined times after the start (1 min, 2 min, 3 min, 5 min, 7 min, 10 min, 20 min, 30 min, 1 h, 2 h, 4 h, 6 h). Each sample is taken at a different point along the diameter of the column and is collected in a cuvette. The sample is analysed with the video channel and the laser channel of the Eye-Tech particle size analyser (Ankersmid, The Netherlands). The laser measurement works according to the laser obscuration time (LOT) technique. This means that a rotating laser beam scans individual particles in the sample zone and when a particle is encountered the laser beam is obstructed. This obstruction generates a signal detected by a photodiode. Because the laser beam rotates with a constant speed and the time of obstruction is measured the size of a particle can be calculated. Out of these measurements the volume percentage and the cumulative curve is calculated and leads to the particle size distribution. The video measurement uses dynamic image analysis to capture optimal particle images for processing. With this method the assumption of particle sphericity is not required. It groups the particles based on their size or shape and with the use of multiple parameters the particle size distribution can be calculated (Ankersmid, 2014).
3.6. WEST Software Package
To simulate the total BOD and to obtain the first order rate constant of the BOD versus time measurement WEST 2014 (MIKE by DHI) is used. The input data that is used are coming from the BOD5 and BOD10 tests. After changing the run time to 14,400 minutes or 7200 minutes the programme is started. The output of the calculation is represented in Figure 7, in this the bCOD (orange line) and the total BOD (blue line) are visible. The orange cubes represent the measured BOD5 or BOD10 values. The programme is using equations 9 and 10 to calculate the different BOD values.
39
3.7. Quality laboratory analyses
3.7.1. Introduction
The role of the analytical laboratory is to produce measurement-based information that is valid, defensible and has a known quality. In each measurement an error is introduced, this can be systematic or random. A random error will determine the precision of a measurement; this error needs to be as low as possible (APHA, 1999). The systematic error is a bias in the measurement. The source of the problem can be imperfect calibration, changes in the environment, error of the analyst,... (APHA, 1999).
3.7.2. References for raw wastewater and primary effluent
In Rieger et al. (2013) and Henze et al. (2008) different ratios are defined for raw wastewater and for primary effluent. These ratios can be used as reference values of the wastewater. If the values found are above these reference values, then there is the possibility that the wastewater has a huge contribution of industrial wastewater or that there is an error in the measurement or that there are anomalies. Rieger et al. (2013) have used questionnaires of GMP (the good modelling practice task group) to define different ratios for raw municipal wastewater, primary effluent and activated sludge. These ratios can be used for comparison (Table 6). Henze et al. (2008) divides the raw wastewater in different loading rates by using the different ratios (Table 7).
Figure 7: Fitted BOD-curve of before PST from 24-02-2014
40
Table 6: Different mean ratios defined by Rieger et al. (2013)
Ratio Unit Raw wastewater Primary effluent
Mean Min. Max. Mean Min. Max.
TN/CODtot gN/gCOD 0.095 0.050 0.150 0.134 0.050 0.360
NH4/TKN gN/gN 0.684 0.500 0.900 0.755 0.430 0.900
Ptot/CODtot gP/gCOD 0.016 0.007 0.025 0.023 0.010 0.060
PO4/Ptot gP/gP 0.603 0.390 0.800 0.741 0.500 0.900
CODtot/BOD5 gCOD/gBOD 2.06 1.410 3.000 1.874 0.500 3.000
CODff/CODtot gCOD/gCOD 0.343 0.120 0.750 0.449 0.150 0.750
TSS/CODtot gTSS/gVSS 0.503 0.350 0.700 0.38 0.180 0.560
CODpart/VSS gCOD/gVSS 1.69 1.300 3.000 1.718 1.400 3.500
VSS/TSS gVSS/gTSS 0.74 0.300 0.900 0.794 0.700 0.909
Table 7: Typical ratios for raw municipal wastewater according to Henze et al. (2008)
Ratio High pollution load Medium pollution
load Low pollution load
COD/BOD 2.5-3.5 2.0-2.5 1.5-2.0
COD/TN 12-16 8-12 6-8
COD/TP 45-60 35-45 20-35
BOD/TN 6-8 4-6 3-4
BOD/TP 20-30 15-20 10-15
COD/VSS 1.6-2.0 1.4-1.6 1.2-1.4
VSS/TSS 0.8-0.9 0.6-0.8 0.4-0.6
41
4. RESULTS AND DISCUSSION
4.1. Introduction
The wastewater treatment plant of Roeselare was visited 7 times, 6 times grab samples were taken and 1 time a more extensive measurement campaign was performed. Each time the discharge rate varied a lot and because of these variations it was decided to split the data into two sets, one with low discharge rate and one with high discharge rate. This division is visible in Table 8.
Table 8: Sampling time and method, discharge rate, type of analyses and division of the samples for WWTP Roeselare
Date Sample method Discharge rate
(m³/h) Analyses Division Comments
17/02/2014 Grab samples 1060 STOWA method High Only analyses
before the PST
24/02/2014 Grab samples 1900 STOWA method High
03/03/2014 Grab samples 2100 STOWA method High Not functioning
BOD device
12/03/2014 Measurement
campaign 800 STOWA method Low
No BOD duplicate due to lack of
space
24/03/2014 Grab samples 974 STOWA method High
07/04/2014 Grab samples 730 STOWA method Low
14/04/2014 Grab samples 680 STOWA method Low
05/05/2014 Grab samples 480 Column test Low No chemical
analyses
The wastewater treatment plant of Eindhoven was visited 1 time, but 2 measurement campaigns were performed (Table 9). Due to heavy rainfall, the first measurement campaign was cancelled because this decreased the retention time in the PST from 6 to 2 hours. This means that only samples of the first 2 hours were comparable. The second measurement campaign was performed correctly. Due to a technical problem (with one of the samplers) only seven samples were suitable for analyses. So for the WWTP of Eindhoven only 7 samples (from before the PST and after the PST) were analysed. On the first visit grab samples were taken before the PST and this sample was used for a test in the settling column.
Table 9: Sampling time and method, type of analyses and problems for WWTP Eindhoven
The results of all analyses are represented in Appendix 1. These are first used to calculate ratios and these ratios are then compared with mean municipal wastewater ratios as represented in Rieger et al. (2013) and with typical raw municipal wastewater ratios as found in Henze et al. (2008).
Date Sample method Analyses Comments
29/04/2014 Grab samples Column test
29/04/2014 Measurement
campaign STOWA method Sampling aborted
06/05/2014 Measurement
campaign STOWA method
Mechanical problem +
chemicals added
42
After this comparison the results are used to calculate the different fractions of carbon, nitrogen and phosphorous. The results are also used to look for trends and to calculate removal efficiencies. Grab sample results need to be interpreted cautiously because the retention time in the PST was not respected. This because all the samples were taken at the same moment without respecting the retention time of the PST (approximately 2 hours). The PSD (particle size distributions) of the samples and of the column test are examined.
4.2. Wastewater characterisation
4.2.1. Ratios according to Rieger et al.
The ratios for the wastewater of Roeselare and Eindhoven are represented in Appendix 3.
4.2.1.1. WWTP of Roeselare
For the WWTP of Roeselare 33 % of the mean ratios are below the reference ratios (Table 6) for raw wastewater: - VSS-TSS, TSS-CODtot and CODpart-VSS for the low discharge rate - NH4-TKN, TSS-CODtot and CODpart-VSS ratios for the high discharge rate For the primary effluent 56 % of the ratios are under the reference values (Table 6). The mean ratios are still within the range (minimum and maximum value) determined by Rieger et al. (2013). So the small contribution of industrial wastewater (13 %) does not have an influence on the municipal wastewater. On sampling days with a high discharge rate, the BOD5 concentrations are low (approximately 40 mg/l). These low concentrations are responsible for very high ratios of CODtot/BOD in the raw wastewater. This ratio exceeds the reference ratio by 153 % indicating that the wastewater with high discharge rate contains more slowly biodegradable organic material (Henze et al.,2008). On days with a low discharge rate the ratio exceeds the reference by 36 %. This indicates the raw wastewater contains an organic matter portion difficult to degrade. In the primary effluent the ratio exceeds the reference by 220 % for the high discharge rate and by 10 % for the low discharge rate. So after the primary sedimentation tank the slowly biodegradable organic matter is increased for the high discharge rate and decreased by 26 % for the low discharge rate. The mean value of the raw TN-CODtot ratio (0.134 g N/ g COD) by a high discharge rate is 41 % higher than the reference ratio (0.095 g N/ g COD). In the dry weather conditions this difference is approximately 30 % higher. In the samples this trend is also visible. For the primary effluent the ratio is 24 % higher for high discharge rates and 10 % higher for low discharge rates. The NH4-TKN ratios is 31 % lower than the reference for the high discharge rate raw wastewater and 34 % lower for the primary effluent. For the low discharge rates this ratio is 14 % higher for the raw wastewater and 14 % lower for the primary effluent. So when the discharge is high, there is dilution of the raw wastewater which leads to lower concentrations of ammonium and total Kjeldahl nitrogen.
43
The ratio TP-CODtot, is below the reference value for both the high and low discharge rates and for both the raw wastewater and the primary effluent. The ratio PO4-TP is for the raw wastewater 32 % (high discharge) and 34 % (low discharge) higher than the reference. For the primary effluent the ratio is 3 % higher for the high discharge rate and 7 % higher for the low discharge rate. The VSS-TSS ratio is 235 % higher than the reference value for the high discharge rates and 409 % higher for the low discharge rates. In the primary effluent this ratio is increased to 395 % for the high discharge rate and decreased to 359 % for the low discharge rates. So when the WWTP receives low discharges, the VSS and TSS concentrations are decreasing after the PST. On the high discharge days the particles are leaked out the PST, which leads to an increase in the VSS and TSS concentrations.
4.2.1.2. WWTP of Eindhoven
For the WWTP of Eindhoven 55 % of the ratios for the raw wastewater and 22 % for the primary effluent are below the reference ratio. The CODtot/BOD ratio is 41 % higher than the reference ratio for the raw wastewater and 27 % for the primary effluent. So in this case the raw wastewater contains more slowly biodegradable organic matter than the primary effluent. The CODsol/CODtot ratio is 6 % higher than the reference ratio for the primary effluent and 4 % lower in the raw wastewater. So after the PST there is more soluble COD in the wastewater. For the TN/CODtot ratio the difference with the reference is 4 % for the primary effluent. But for the raw wastewater the value is below the reference (20 %). The NH4-TKN ratios are 7 % and 13 % higher than the reference. So there is a slight increase in the concentration of the ammonium and the total Kjeldahl nitrogen. The TP-CODtot and the PO4-TP ratios are higher for the primary effluent and for the raw wastewater only the PO4-TP ratio is higher than the reference value, indicating that the concentration of total phosphorous and orthophosphate is higher after the PST. The ratio VSS-TSS is higher than the reference (117 % for the raw wastewater and 219 % for the primary effluent).
4.2.1.3. Comparison of the two plants
When the two PSTs are compared, some similarities and differences are found. Both plants lie in the ranges defined by Rieger et al. (2013). This means the wastewater has a domestic origin and the measurements and calculations have small errors. But the PST of the WWTP of Eindhoven is closer to the mean values presented by Rieger et al. (2013) than these of Roeselare. Both locations have high VSS-TSS ratios in the primary effluent, so both of them have more volatile suspended solids after the PST. Also the CODtot/BOD ratios are higher than the reference so, there is a part of slowly biodegradable organic matter in the wastewater.
44
But the low TSS - CODtot ratio indicates a decrease in the suspended solids after the PST. This is expected because the purpose of a PST is to remove the solids. The difference is found in the ratios with the nutrient concentrations in the primary effluent. For the PST of Roeselare the TN-CODtot ratio exceeds the reference, but in the PST of Eindhoven the ratio is around or below the reference value. So there may be a problem with the nitrogen fractions for the WWTP of Roeselare. But out of these ratios one can not be sure if this is the case because each WWTP has its own characteristics. And these characteristics depend on the influent characteristics of the WWTP. For Eindhoven the TP-CODtot and the PO4-TP for the primary effluent are relatively high, but for Roeselare these ratios are close to the reference. So in Eindhoven there may be a problem with the phosphorous fraction. This problem can be caused by the effluent of the sludge treatment plant in Mierlo. This effluent contains high nutrient concentrations and is cycled back to the WWTP of Eindhoven around noon.
4.2.2. Ratios according to Henze et al.
The divisions that are made on the basis of the ratios are found in Appendix 4. At the WWTP of Roeselare there is a difference between the high and low discharge rate (Table 10).
Table 10: Comparison of the divisions of the WWTP of Roeselare between high and low discharge rates
Ratio High discharge rate Low discharge rate
COD/BOD Higher than the ranges High pollution load
COD/TN Low pollution load Medium pollution load
COD/TP High pollution load Higher than the ranges
BOD/TN Lower than the ranges Low pollution load
BOD/TP Low pollution load High pollution load
COD/VSS Lower than the ranges Lower than the ranges
VSS/TSS Higher than the ranges Higher than the ranges
The wastewater has a substantial part of slowly biodegradable organic matter (high COD-BOD ratio). The high VSS-TSS ratio is an indicator that the wastewater will have a good digestion under anaerobic conditions. For both types there is also a high COD-TP ratio, a low COD-VSS and a low BOD-TN ratio. In the high discharge rate samples the COD-TN ratio is low. To facilitate a fast and efficient denitrification process a carbon source needs to be added to the wastewater (Henze et al., 2008). In the low discharge rate this is a medium pollution load. For the BOD-TP ratio the pollution load changes from low to high, because the concentration for BOD and TP is increased in the low discharge rate samples. For the WWTP of Eindhoven the COD-BOD ratio indicates a low pollution rate and more readily biodegradable organic matter in the wastewater than at the WWTP of Roeselare. The COD-TN ratio shows a low pollution rate. Here as well there is a need to add a carbon source to the water to enhance the denitrification process. The COD-TP ratio indicates a medium pollution load, just as well as the BOD-TP ratio. The BOD-TN ratio is lower than the ranges that are suggested by Henze et al. (2008). The COD-VSS ratio is a high pollution rate and the VSS-TSS ratio is higher than the ranges, so the wastewater is ideal for anaerobic digestion.
45
The conclusion is that both WWTPs have a different classification based on their pollution load. They have in common that their VSS-TSS ratios are above the ranges, from which can be deducted that the raw wastewater is ideal for anaerobic digestion. Both have low COD-TN ratios and need an additional carbon source. This additional carbon source is needed to assure a fast and efficient denitrification process. The difference is found in the phosphorous ratios, with a medium COD-TP and BOD-TP ratio for the WWTP of Eindhoven and a low to high BOD-TP ratio and a high COD-TP ratio for Roeselare. This indicates that in Eindhoven a higher phosphorous concentration is found than in Roeselare.
4.3. Influent fractionation
The different fractions will be given in mean concentrations. This is the average of the three measured concentrations for each compound.
4.3.1. Carbon fractionation
4.3.1.1. COD compounds
First the different COD compounds are represented in Figure 8, Figure 9, Figure 10 and Figure 11.
bPST: before primary sedimentation tank, aPST: after primary sedimentation tank, CODtot,inf: total COD-fraction of the influent, CODsol: soluble COD-fraction of the influent, CODpart: particulate COD-fraction of the influent
In Figure 8 the mean of total COD concentrations at low discharge rates are increased after the PST with approximately 45 mg COD/l.
0
50
100
150
200
250
300
bPST aPST bPST aPST bPST aPST
12/03 7/04 14/04
Mean
co
nc
en
trati
on
(m
g C
OD
/l)
Time (days) and sampling place
CODtot,inf
CODsol,inf
CODpart,inf
Figure 8: Mean COD concentration for low discharge rate in the WWTP of Roeselare
46
The increase of the mean total COD concentration is mostly due to the increase in the mean particulate COD concentration (approximately 40 mg/l) after the PST. But one must keep in mind these samples were taken around the same time (so without taking into account the retention time). So the increase of the particulate COD concentration can be caused by a higher content in the influent.
bPST: before primary sedimentation tank, aPST: after primary sedimentation tank, CODtot,inf: total COD-fraction of the influent, CODsol: soluble COD-fraction of the influent, CODpart: particulate COD-fraction of the influent In Figure 9 the mean of total COD concentrations at high discharge rates are decreased after the PST with approximately 25 mg COD/l.
bPST: before primary sedimentation tank, aPST: after primary sedimentation tank, CODtot,inf: total COD-fraction of the influent, CODsol: soluble COD-fraction of the influent, CODpart: particulate COD-fraction of the influent
0
50
100
150
200
250
300
bPST aPST bPST aPST bPST aPST bPST aPST
17/02 24/02 03/03 24/03
Mean
co
nc
en
trati
on
(m
g C
OD
/l)
Time (days) and sampling place
CODtot,inf
CODsol,inf
CODpart,inf
0
50
100
150
200
250
300
350
bPST aPST bPST aPST bPST aPST bPST aPST bPST aPST
09:55 - 10:55
12:05 - 13:05
10:55 - 11:55
13:05 - 14:05
11:55 - 12:55
14:05 - 15:05
12:55 - 13:55
15:05 -16:05
13:55 - 14:55
Mean
co
nc
en
trati
on
(m
g C
OD
/l)
Time (hours) and sampling place
CODtot,inf
CODsol,inf
CODpart,inf
Figure 9: Mean COD concentration for high discharge rate in the WWTP of Roeselare
Figure 10: Mean COD concentrations for the measurement campaign in the WWTP of Roeselare (12/03/2014) with low discharge rate
47
Figure 10 is a representation of the measurement campaign at the WWTP of Roeselare and shows that after the PST the mean of total COD is decreased with approximately 10 mg COD/l (standard deviation of 8 mg COD/l).
bPST: before primary sedimentation tank, aPST: after primary sedimentation tank, CODtot,inf: total COD-fraction of the influent, CODsol: soluble COD-fraction of the influent, CODpart: particulate COD-fraction of the influent
Figure 11 is a representation of the mean concentration of the different COD compounds of the measurement campaign at the WWTP of Eindhoven. In this the mean of total COD concentration after the PST is decreased with approximately 100 mg COD/l. The decrease of the mean of total COD concentration is due to a decrease in the mean particulate concentration. There is no similarity between the WWTP of Roeselare and Eindhoven. At the high discharge rates of the WWTP of Roeselare there is a decrease in the mean of total COD concentration but there is no direct link with a decrease in the mean concentration of the particulate nor soluble COD. At the WWTP of Eindhoven there is a direct link between the decrease in the mean of total COD concentration and the mean of particulate COD concentration. This can be linked to the settling of the particulate COD fraction in the PST.
4.3.1.2. COD fractions
4.3.1.2.1. WWTP of Roeselare In Table 11 the percentages of the influent COD fractions for the WWTP of Roeselare are listed (in Appendix 2, all the fractions are given). For the high discharge rates it is clear that the sum of the biodegradable fraction is lower than the sum of the non-biodegradable fraction and this both before and after the PST. For the low discharge rates the relation is
Figure 11: Mean COD concentration of the measurement campaign in the WWTP of Eindhoven (06/05/2014)
0
100
200
300
400
500
600
bPST aPST bPST aPST bPST aPST bPST aPST bPST aPST
08:00 - 08:30
16:00 - 16:30
08:30 - 09:00
16:30 - 17:00
09:00 - 09:30
17:00 - 17:30
09:30 - 10:00
17:30 - 18:00
10:00 - 10:30
18:00 - 18:30
Me
an c
on
cen
trat
ion
(m
g C
OD
/l)
Time (hours) and sampling place
CODtot,inf mg/l
CODsol,inf mg/l
CODpart,inf mg/l
48
not as clear, for the samples of the 12th of March, most of the sums of the biodegradable fractions are higher than the non-biodegradable fractions before the PST. But after the PST the sum of the biodegradable fraction is smaller than the sum of the non-biodegradable fraction. But this is not always true: for the 7th and the 14th of April the same trend is seen as for the high discharge rate.
Table 11: Percentages of influent COD-fractions for the WWTP of Roeselare
n.a.: not available, n.d.: not defined, bPST: before primary sedimentation tank, aPST: after primary sedimentation tank
Date Place Discharge
rate (m³/h)
SS (%) XS (%) Sum of
biodegradable fraction (%)
SI (%) XI (%) Sum of
particulate fraction (%)
17/02/2014 bPST 1060
(high)
56.32 -35.81 n.d. 7.86 71.63 79.49
aPST n.a n.a n.a. n.a. n.a. n.a.
24/02/2014 bPST 1900
(high)
46.93 -11.75 n.d. 10.24 54.58 64.82
aPST 8.55 13.60 22.14 11.11 62.92 74.03
3/03/2014 bPST 2100
(high)
6.33 n.a 6.33 26.85 n.a 26.85
aPST 14.08 n.a 14.08 44.90 n.a 44.90
12/03/2014 bPST
800 (low)
21.98 30.87 52.85 9.77 37.37 47.15
aPST 17.54 24.64 42.18 8.72 49.10 57.82
12/03/2014 bPST 24.02 34.17 58.18 7.26 34.56 41.82
aPST 16.31 21.31 37.62 7.51 54.87 62.38
12/03/2014 bPST 28.55 43.55 72.10 6.98 20.92 27.90
aPST 19.26 23.09 42.36 7.19 50.45 57.64
12/03/2014 bPST 37.41 6.74 44.15 6.95 48.90 55.85
aPST 21.50 22.61 44.11 6.82 49.07 55.89
12/03/2014 bPST 37.68 35.10 72.78 6.62 20.61 27.22
aPST n.a n.a n.a. n.a. n.a. n.a.
24/03/2014 bPST 974
(high)
17.84 12.44 30.28 8.29 61.43 69.72
aPST 10.34 15.96 26.30 10.97 62.73 73.70
7/04/2014 bPST 730
(low)
14.17 26.14 40.32 13.16 46.52 59.68
aPST 15.53 18.61 34.14 10.99 54.87 65.86
14/04/2014 bPST 680
(low)
15.25 23.91 39.16 11.47 49.37 60.84
aPST 15.91 26.46 42.37 9.24 48.39 57.63
The percentages are also compared with percentages found in the literature (for countries in the European Union, Table 12, Henze et al. (1987, 1995 and 1999), Roeleveld and van Loosdrecht (2002) and Pasztor et al. (2009)).
49
Table 12: Reference values and range of values for the WWTP of Roeselare for raw wastewater and primary effluent
Raw wastewater
Country Denmark Hungary The
Netherlands Belgium
High
discharge rate
Low discharge
rate
SS (%) 38.64 21.94 25.71 6.33 - 56.32
14.17 - 37.68
XS (%) 43.18 49.76 28.98 (-35.81) -
17.84 6.74 - 43.55
SI (%) 6.82 4.62 5.67 7.86 - 26.85
6.82 - 13.16
XI (%) 11.36 23.72 39.65 54.58 - 71.63
20.61 - 54.87
Reference Henze et al., 1995
Pasztor et al., 2009
Roeleveld and van
Loosdrecht, 2002
This study
Primary effluent
Country Denmark Denmark Denmark Hungary Switzerland Belgium
High discharge
rate Low discharge
rate
SS (%) 24.27 42.31 30.77 28.57 31.82 8.55 - 14.08 15.53 - 21.50
XS (%) 48.54 36.54 48.08 42.86 45.45 13.60 - 15.96 18.61 - 24.64
SI (%) 7.77 11.54 11.54 8.57 11.36 11.11 - 44.90 6.82 - 10.99
XI (%) 19.42 9.62 9.62 20.00 11.36 62.73 - 62.92 48.39 - 54.87
Reference Henze et al., 1987
Henze et al., 1995
Henze et al., 1999
Henze et al., 1987
Henze et al., 1987
This study
For the high discharge rates (Table 12), the negative percentages for the slowly biodegradable COD-fraction (XS) in the raw wastewater (bPST) are a bit strange. According to the literature the range should be 28.98 - 49.76 % while we obtained values in the range of -35.81 % to 17.84 %. The range for the readily biodegradable COD-fraction (SS) for the raw wastewater in this study is 6.33 - 56.32 %. This is larger than the range found in the literature (21.94 - 38.64 %). For the soluble (SI) and particulate non-biodegradable (XI) COD-fraction the ranges in this study are 7.86 - 26.85 % and 54.58 - 71.63 %. The literature mentions ranges 4.62 - 6.82 % and 11.36 - 39.65. So it is obvious that all the ranges for the raw wastewater at a high discharge rate are larger than the ranges found in the literature. In the literature the ranges are always defined under normal conditions and taking into account that each WWTP has its own characteristic raw wastewater, differences must be expected. But this case indicates that the ranges need to be enlarged and take higher discharge rates into account. The low discharge rates (Table 12) are larger than these found in literature. For the biodegradable fraction the lower boundary is different and for the non-biodegradable fraction the upper boundary differs. For the primary effluent (Table 12) the ranges in this study for the high discharge rates are smaller for the biodegradable fractions and higher for the non-biodegradable fraction. In the
50
low discharge rates the ranges for the biodegradable fractions are lower and for the soluble non-biodegradable fraction the range is comparable. For the non-biodegradable fraction the range is larger than the literature ranges. These findings are showing the increase of the XI fraction and the settling of particles after the PST. In the high discharge rate samples the SS fraction is greater than the XS fraction before the PST, after the PST the relationship is vice versa. The SI fraction is before and after the PST smaller than the XI fraction. For the low discharge rate samples the same relation is seen before and after the PST, the XS fraction is greater than the SS fraction and the XI fraction is greater than the SI fraction. In the literature it is seen that XS > SS and SI < XI before and after the PST. So for the low discharge rates the same trend is observed, but for the high discharge rate this is inversed for the raw wastewater. This can be due to the presence of more organic material like dust, leave remnants,... If the fractions are ranked from high to small the following trends are seen for: - high discharge rate: XI > SS > XS > SI - low discharge rate: XI > XS > SS > SI
The last observation for this WWTP is that the biodegradable fractions are decreased after the PST, but the unbiodegradable fractions are increased.
4.3.1.2.2. WWTP of Eindhoven
In Table 13 the COD-fractions of the WWTP of Eindhoven are shown.
Table 13: Percentages of influent COD-fractions for the WWTP of Eindhoven
n.d.: not defined, bPST: before primary sedimentation tank, aPST: after primary sedimentation tank
Sample number
Place SS (%) XS (%) Sum of
biodegradable fraction (%)
SI (%) XI (%) Sum of
particulate fraction (%)
Sample 1 bPST 27.71 0.57 28.28 4.74 66.98 71.72
aPST 46.06 17.72 63.78 4.16 32.06 36.22
Sample 2 bPST 27.85 22.24 50.09 4.39 45.51 49.91
aPST 36.62 4.55 41.17 5.25 53.59 58.83
Sample 3 bPST 77.48 -17.98 n.d. 5.15 35.35 40.50
aPST 40.66 -33.56 n.d. 5.88 87.02 92.90
Sample 4 bPST 29.14 35.79 64.93 5.25 29.82 35.07
aPST 44.96 14.26 59.22 6.27 34.51 40.78
Sample 5 bPST 28.33 31.58 59.91 4.48 35.61 40.09
aPST 42.10 -37.12 n.d. 6.35 88.67 95.02
The range for the different fractions before the PST (raw wastewater) and the primary effluent are given in Table 14. Before the PST the ranges are in the vicinity of the ranges found in the literature. After the PST the ranges for the non-biodegradable fractions are larger and in close vicinity for the biodegradable fractions. Another observation is that almost all fraction percentages increase after the PST.
51
In the Eindhoven treatment plant the fractions are ranked as follows, SS > XS and XI > SI for both raw wastewater and primary effluent. So for the non-biodegradable fractions the same trend is seen as in the literature but for the biodegradable fractions the trend is inverse. When all the fractions are ranked from high to small, the following trend is observed for both raw wastewater and primary effluent: XI > SS > XS > SI.
Table 14: Reference values and range of values for the WWTP of Eindhoven for raw wastewater and primary effluent
Raw wastewater
Country Denmark Hungary The
Netherlands The Netherlands
SS (%) 38.64 21.94 25.71 27.71 - 77.48
XS (%) 43.18 49.76 28.98 (-17.98) - 35.79
SI (%) 6.82 4.62 5.67 4.48 - 5.25
XI (%) 11.36 23.72 39.65 29.82 - 66.99
Reference Henze et al., 1995
Pasztor et al., 2009
Roeleveld and van
Loosdrecht, 2002
This study
Primary effluent
Country Denmark Denmark Denmark Hungary Switzerland The
Netherlands
SS (%) 24.27 42.31 30.77 28.57 31.82 36.62 - 46.06
XS (%) 48.54 36.54 48.08 42.86 45.45 (-37.12) - 17.72
SI (%) 7.77 11.54 11.54 8.57 11.36 4.16 - 6.35
XI (%) 19.42 9.62 9.62 20.00 11.36 32.06 - 88.67
Reference Henze et al., 1987
Henze et al., 1995
Henze et al., 1999
Henze et al., 1987
Henze et al., 1987
This study
4.3.1.2.3. Comparison of the two WWTP
In conclusion the ranking for the WWTP of Eindhoven is the same as the ranking for the WWTP of Roeselare for a high discharge rate. The ranges found in the literature are too small according to this study. Also the increase after the PST of the non-biodegradable fractions is observed in both WWTPs, but the total COD concentration is decreasing in the WWTP of Roeselare with high discharge rates and in the WWTP of Eindhoven. So in this case the increase is due to the settling of the biodegradable fraction. But with low discharge rates in the WWTP of Roeselare, the total COD concentration is increasing after the PST which will lead to a higher aeration need in the activated sludge tank.
4.3.2. Nitrogen fractionation
4.3.2.1. Nitrogen compounds
The nitrogen fractions will be discussed on basis of the analyses itself. Then the different fractions are calculated on the basis of different conversion factors found in the literature and finally they will be discussed on basis of the removal efficiencies.
52
The minimum and maximum concentrations of the different nitrogen compounds for both WWTPs are represented in Table 15. This table shows the WWTP of Eindhoven has the highest nitrogen compounds concentration. For the WWTP of Roeselare the nitrogen compounds have the lowest concentrations when the discharge rate is high.
Table 15: Minimum and maximum nitrogen compound concentrations for the WWTP of Roeselare and Eindhoven
TN: total nitrogen, TNff: total nitrogen after flocculation and filtration, NO3: nitrate, NH4: ammonium, TKN: total Kjeldahl nitrogen
WWTP Roeselare Roeselare Eindhoven
Place bPST aPST bPST aPST bPST aPST
Discharge rate
High Low High
TN (mg N/l)
Mean 21.04 16.04 29.93 37.05 53.01 55.83
Min. 9.15 7.60 26.93 32.47 45.33 48.17
Max. 26.13 20.87 32.93 42.83 61.67 60.43
TNff (mg N/l)
Mean 16.20 14.07 29.35 27.14 36.85 45.91
Min. 7.19 6.97 19.70 22.70 30.93 44.80
Max. 23.10 18.77 36.73 30.43 43.83 46.70
NO3 (mg N/l)
Mean 4.07 2.22 0.90 0.95 0.80 0.51
Min. 1.85 1.74 0.42 0.38 0.58 0.49
Max. 9.07 2.90 1.22 1.28 1.64 0.53
NH4 (mg N/l)
Mean 6.66 7.11 22.5 23.29 41.96 47.04
Min. 0.22 2.43 19.40 20.33 38.77 45.20
Max. 13.27 9.94 25.17 26.50 47.00 48.73
TKN (mg N/l)
Mean 17.95 13.83 29.03 36.10 52.20 55.32
Min. 6.92 5.59 25.96 31.19 44.76 47.64
Max. 24.28 19.13 31.95 41.65 61.05 59.93
The mean concentration of different nitrogen compounds are shown in Figure 12, Figure 13,
Figure 14 and Figure 15. These figures are divided in high and low discharge rates and in grab sampling and measurement campaigns.
TN: total nitrogen, TNff: total nitrogen after flocculation and filtration, NO3: nitrate, NH4: ammonium, TKN: total Kjeldahl nitrogen, bPST: before primary sedimentation tank, aPST: after primary sedimentation tank
Figure 12: Mean concentration for nitrogen compounds of the WWTP of Roeselare with low discharge rate
0
5
10
15
20
25
30
35
40
45
bPST aPST bPST aPST bPST aPST
12/03 7/04 14/04
Mean
co
nc
en
trati
on
(m
g/l
)
Time (days) and sampling place
TN
TNff
NO3
NH4
TKN
53
In Figure 12 the total nitrogen concentration after the PST is in average 5 mg N/l higher than before the PST. There is almost no difference in the mean nitrate concentration before and after the PST. For the samples taken on the 7th and 14th of April there is a similar increase in the mean ammonium concentration. This increase can be coming from the process called ammonification.
TN: total nitrogen, TNff: total nitrogen after flocculation and filtration, NO3: nitrate, NH4: ammonium, TKN: total Kjeldahl nitrogen, bPST: before primary sedimentation tank, aPST: after primary sedimentation tank In Figure 13 the high discharge rate days are given and in this figure the total nitrogen after the PST is almost 5 mg N/l lower than before the PST. A decrease in ammonium concentration after the PST is visible, this with 2 to 3 mg N/l. The nitrate concentration remains constant. Out of this figure it is also visible that on days with high discharge rates the nitrogen concentrations differ from day to day. When the highest discharge rate is measured (3th of March) the concentrations are at their lowest point, while when the lowest high discharge rate is measured (24th of March) the concentrations are high. This difference can be due to the dilution rate. In Figure 14 the measurement campaign in the WWTP of Roeselare is represented and shows the same trend as Figure 12. The total mean nitrogen concentration is increasing after the PST from 5 mg N/l to a maximum of 15 mg N/l, without a clear increase of the mean ammonium and nitrate concentration. The increase was also seen in the COD fractions, so in the PST there must be some process or a mass that adds to these fractions. During the measurement campaign there was a decrease in the total mean COD concentration after the PST. And an increase in the total nitrogen concentration, so this is not analogue to what was seen on days with a low discharge rate.
-5
0
5
10
15
20
25
30
35
bPST aPST bPST aPST bPST aPST bPST aPST
17/02 24/02 03/03 24/03
Mean
co
nc
en
trati
on
(m
g N
/l)
Time (days) and sampling place
TN
TNff
NO3
NH4
TKN
Figure 13: Mean concentration for nitrogen compounds of the WWTP of Roeselare with high discharge rate
54
In the mean total Kjeldahl nitrogen concentration the biggest contribution is from the mean ammonium concentration. This indicates that the wastewater only has a small organic nitrogen fraction.
TN: total nitrogen, TNff: total nitrogen after flocculation and filtration, NO3: nitrate, NH4: ammonium, TKN: total Kjeldahl nitrogen, bPST: before primary sedimentation tank, aPST: after primary sedimentation tank
Figure 15 is a representation of the measurement campaign in the WWTP of Eindhoven. It also shows an increase in the total mean nitrogen concentration after the PST, but in this case due to an increase in the mean ammonium concentration after the PST. Which points out that ammonification can play a role in the PST.
0
5
10
15
20
25
30
35
40
45
50
bPST aPST bPST aPST bPST aPST bPST aPST bPST
09:55 - 10:55
12:05 - 13:05
10:55 - 11:55
13:05 - 14:05
11:55 - 12:55
14:05 - 15:05
12:55 - 13:55
15:05 -16:05
13:55 - 14:55
Mean
co
nc
en
trati
on
(m
g N
/l)
Time (hours) and sampling place
TN
TNff
NO3
NH4
TKN
Figure 14: Mean concentration for nitrogen compounds of the WWTP of Roeselare for the measurement campaign (12/03/2014) with low discharge rate
Figure 15: Mean concentration for nitrogen compounds of the WWTP of Eindhoven for the measurement campaign (06/05/2014)
0
10
20
30
40
50
60
70
bPST aPST bPST aPST bPST aPST bPST aPST bPST aPST
08:00 - 08:30
16:00 - 16:30
08:30 - 09:00
16:30 - 17:00
09:00 - 09:30
17:00 - 17:30
09:30 - 10:00
17:30 - 18:00
10:00 - 10:30
18:00 - 18:30
Mean
co
nc
en
trati
on
(m
g N
/l)
Time (hours) and sampling place
TN
TNff
NO3
NH4
TKN
TN: total nitrogen, TNff: total nitrogen after flocculation and filtration, NO3: nitrate, NH4: ammonium, TKN: total Kjeldahl nitrogen, bPST: before primary sedimentation tank, aPST: after primary sedimentation tank
55
Both WWTPs thus show an increase in the mean TN concentration after the PST. But only for the WWTP of Eindhoven the increase can be linked to an increase in the mean ammonium concentration, indicating ammonification can play a role. For the WWTP of Roeselare the increase of the mean TN concentration is not seen as an increase of the mean ammonium nor nitrate concentration (for the measurement campaign). The mean TKN concentration is determined by the mean ammonium concentration for both wastewater treatment plants. The prevailing trend in both wastewater treatment plants is: TN ≥ TKN > TNff This trend is also seen in the studies of Orhon et al. (1997), Rieger et al. (2013) and Fall et al. (2011).
4.3.2.2. Nitrogen fractions
For the calculation of the different nitrogen fractions, different conversion factors are used. These conversion factors are found in the following literature: Hassan (2013), Henze et al. (1999), Roeleveld and van Loosdrecht (2002) and STOWA (1996) (Table 16). And these factors are used to compare the different concentrations of the total Kjeldahl nitrogen. For the comparison of the fractions the conversion factors found in Hasan (2013) for the wastewater treatment plant of Eindhoven are used (second column in Table 16).
Table 16: Different nitrogen conversion factors
Conversion factor (g N/ g COD)
Hassan (Eindhoven,
2013)
Roeleveld and van
Loosdrecht (2002)
Hasan (Canada,
2013)
Henze et al. (1999)
Stowa (1996)
iNSI 0.033 0.01 0.06 0.01 0.015
iNSA 0.00 0.00 0.00 0.00 0.00
iNSF 0.03 0.03 0.4 0.03 0.035
iNXI 0.02 0.03 0.05 0.02 0.0075
iNXS 0.04 0.04 0.06 0.04 0.035
Comparison of the nitrogen fractions
In Figure 16, Figure 17, Figure 18 and Figure 19 the different fractionations of nitrogen are represented for the WWTP of Roeselare for high and low discharge rates, for the measurement campaign and for the measurement campaign of the WWTP of Eindhoven. The trend in the high discharge rate figure (Figure 16) is, iNXI*XI > iNXS*XS > iNSF*SF > iNSI*SI. In the low discharge rate figures (Figure 17 and Figure 18) distinction between before and after the PST is needed. Before the PST the trend is iNXS*XS > iNXI*XI > iNSI*SI > iNSF*SF and after the PST it is iNXI*XI > iNXS*XS > iNSI*SI > iNSF*SF. For the WWTP of Eindhoven the trend is iNXI*XI > iNXS*XS > iNSF*SF > iNSI*SI.
So here again the WWTP of Eindhoven has the same trend as the WWTP of Roeselare on high discharge days (just as seen in the COD fractions). But the concentrations for the WWTP of Eindhoven are double in comparison with the WWTP of Roeselare.
56
-0,50
0,00
0,50
1,00
1,50
2,00
2,50
3,00
3,50
4,00
4,50
bPST aPST bPST aPST bPST aPST bPST aPST
17/02 24/02 03/03 24/03
Mean
co
nc
en
trati
on
(m
g N
/l)
Time (days) and sampling place
iNSI*SI
iNSA*SA
iNSF*SF
iNXI*XI
iNXS*XS
0,00
1,00
2,00
3,00
4,00
5,00
bPST aPST bPST aPST bPST aPST
12/03 7/04 14/04
Mean
co
nc
en
trati
on
(m
g N
/l)
Time (days) and sampling place
iNSI*SI
iNSA*SA
iNSF*SF
iNXI*XI
iNXS*XS
Figure 17: Nitrogen fractions for the WWTP of Roeselare with low discharge rate
Figure 16: Nitrogen fractions for the WWTP of Roeselare with high discharge rate
57
0,00
1,00
2,00
3,00
4,00
5,00
6,00
bPST aPST bPST aPST bPST aPST bPST aPST bPST aPST
09:55 - 10:55
12:05 - 13:05
10:55 - 11:55
13:05 - 14:05
11:55 - 12:55
14:05 - 15:05
12:55 - 13:55
15:05 -16:05
13:55 - 14:55
Mean
co
nc
en
trati
on
(m
g N
/l)
Time (hours) and sampling place
iNSI*SI
iNSA*SA
iNSF*SF
iNXI*XI
iNXS*XS
-2,00
-1,00
0,00
1,00
2,00
3,00
4,00
5,00
6,00
7,00
8,00
9,00
bPST aPST bPST aPST bPST aPST bPST aPST bPST aPST
08:00 - 08:30
16:00 - 16:30
08:30 - 09:00
16:30 -17:00
09:00 - 09:30
17:00 - 17:30
09:30 - 10:00
17:30 -18:00
10:00 - 10:30
18:00 - 18:30
Mean
co
nc
en
trati
on
(m
g N
/l)
Time (hours) and sampling place
iNSI*SI
iNSA*SA
iNSF*SF
iNXI*XI
iNXS*XS
Figure 19: Nitrogen fractions for the WWTP of Eindhoven of the measurement campaign (06/05/2014)
Figure 18: Nitrogen fractions for the WWTP of Roeselare of the measurement campaign (12/03/2014) with low discharge rate
58
Comparison of the calculated and measured total Kjeldahl nitrogen The different conversion factors that are used to obtain the different TKN concentrations are given in Table 16. The different mean concentrations of the TKN are given in Figure 20, Figure 21, Figure 22 and Figure 23. The different figures reveal that the conversion factors from Hasan (2013) are too high and that the TKN concentrations are approximately 50 % higher than the measured TKN. These conversion factors are the ones that are used in a model for a WWTP in Canada. The 50 % variation is due to the differences in wastewater characteristics. These characteristics determine the different fractions and thus alter the conversion factors. The wastewater characteristics are different due to the different climate, the population density and the socio-economic factors. For the high discharge rates all the conversion factors are too low and this leads to a 30 % decrease in the TKN. The low discharge rates and the measurement campaign of the WWTP of Roeselare and the WWTP of Eindhoven show a good relation with the different conversion factors. But the best conversion factors are these produced by the model of the WWTP of Eindhoven (TKN Eindhoven). The conversion factors found in STOWA show a similar trend as these of Eindhoven, since the conversion factors of the model of Eindhoven are based on the conversion factors formulated by STOWA.
-10
0
10
20
30
40
50
60
bPST aPST bPST aPST bPST aPST
12/03 7/04 14/04
Mean
co
nc
en
trati
on
(m
g N
/l)
Time (days) and sampling place
TKN measured
TKN Eindhoven
TKN Roeleveld and Van Loosdrecht
TKN Hasan
TKN Henze et al.
TKN STOWA
Figure 20: Total Kjeldahl nitrogen (TKN) for different conversion factors for the WWTP of Roeselare with low discharge rates
59
-10
0
10
20
30
40
50
bPST aPST bPST aPST bPST aPST bPST aPST
17/02 24/02 03/03 24/03
Mean
co
nc
en
trati
on
(m
g N
/l)
Time (days) and sampling place
TKN measured
TKN Eindhoven
TKN Roeleveld and Van Loosdrecht TKN Hasan
TKN Henze et al.
TKN STOWA
-10
0
10
20
30
40
50
60
70
bPST aPST bPST aPST bPST aPST bPST aPST bPST aPST
09:55 - 10:55
12:05 - 13:05
10:55 - 11:55
13:05 - 14:05
11:55 - 12:55
14:05 - 15:05
12:55 - 13:55
15:05 -16:05
13:55 - 14:55
Mean
co
nc
en
trati
on
(m
g N
/l)
Time (hours) and sampling place
TKN measured
TKN Eindhoven
TKN Roeleveld and Van Loosdrecht TKN Hasan
TKN Henze et al.
TKN STOWA
Figure 21: Total Kjeldahl nitrogen (TKN) for different conversion factors for the WWTP of Roeselare with high discharge rate
Figure 22: Total Kjeldahl nitrogen (TKN) for different conversion factors for the WWTP of Roeselare for the measurement campaign (12/03/2014) with low discharge rate
60
4.3.3. Phosphorous fractionation
4.3.3.1. Phosphorous compounds
The experimental results of the different phosphorous compounds are shown in Figure 24, Figure 25, Figure 26 and Figure 27. The first thing that catches the eye is the very low concentrations for the flocculated and filtered samples. These low concentrations are due to the use of ZnSO4 (solubility product of 35.7), after adding this solution Zn3(PO4)2 (solubility product of 9 * 10-33) is formed. This substance will precipitate and in the supernatant the concentration of phosphorous will decrease. The next thing that is visible, is that for the WWTP of Roeselare on all the days the total phosphorous and the phosphate concentrations are decreased after the PST. So for the removal of phosphorous the PST is working perfect. In the WWTP of Eindhoven there is an increase in the concentrations for the total phosphorous and the phosphate after the PST. This is linked to intake of the Mierlo sludge treatment plant effluent.
0
20
40
60
80
100
120
140
bPST aPST bPST aPST bPST aPST bPST aPST bPST aPST
08:00 - 08:30
16:00 - 16:30
08:30 - 09:00
16:30 -17:00
09:00 - 09:30
17:00 - 17:30
09:30 - 10:00
17:30 -18:00
10:00 - 10:30
18:00 - 18:30
Mean
co
nc
en
trati
on
(m
g N
/l)
Time (hours) and sampling place
TKN measured
TKN Eindhoven
TKN Roeleveld and Van Loosdrecht
TKN Hasan
TKN Henze et al.
TKN STOWA
Figure 23: Total Kjeldahl nitrogen (TKN) for different conversion factors of the WWTP of Eindhoven of the measurement campaign (06/05/2014)
61
-1
0
1
2
3
4
5
bPST aPST bPST aPST bPST aPST
12/03 7/04 14/04
Mean
co
nc
en
trati
on
(m
g P
/l)
Time (days) and sampling place
TP
TPff
PO4
Figure 25: Phosphorous compounds for the WWTP of Roeselare with high discharge rate
-1
0
1
2
3
4
5
6
7
bPST aPST bPST aPST bPST aPST bPST aPST
17/02 24/02 03/03 24/03
Mean
co
nc
en
trati
on
(m
g P
/l)
Time (days) and sampling place
TP
TPff
PO4
Figure 24: Phosphorous compounds for the WWTP of Roeselare with low discharge rate
TP: total phosphorous, TPff: total phosphorous after flocculation and filtration, PO4: phosphate, bPST: before primary sedimentation tank, aPST: after primary sedimentation tank
TP: total phosphorous, TPff: total phosphorous after flocculation and filtration, PO4: phosphate, bPST: before primary sedimentation tank, aPST: after primary sedimentation tank
62
-1
0
1
2
3
4
5
bPST aPST bPST aPST bPST aPST bPST aPST bPST aPST
09:55 - 10:55
12:05 - 13:05
10:55 - 11:55
13:05 - 14:05
11:55 - 12:55
14:05 - 15:05
12:55 - 13:55
15:05 -16:05
13:55 - 14:55
Mean
co
nc
en
trati
on
(m
g P
/l)
Time (hours) and sampling place
TP
TPff
PO4
0
2
4
6
8
10
12
bPST aPST bPST aPST bPST aPST bPST aPST bPST aPST
08:00 - 08:30
16:00 - 16:30
08:30 - 09:00
16:30 -17:00
09:00 - 09:30
17:00 - 17:30
09:30 - 10:00
17:30 -18:00
10:00 - 10:30
18:00 - 18:30
Mean
co
nc
en
trati
on
(m
g P
/l)
Time (hours) and sampling place
TP
TPff
PO4
TP: total phosphorous, TPff: total phosphorous after flocculation and filtration, PO4: phosphate, bPST: before primary sedimentation tank, aPST: after primary sedimentation tank
TP: total phosphorous, TPff: total phosphorous after flocculation and filtration, PO4: phosphate, bPST: before primary sedimentation tank, aPST: after primary sedimentation tank
Figure 26: Phosphorous compounds for the WWTP of Roeselare for the measurement campaign (12/03/2014)
Figure 27: Phosphorous compounds for the WWTP of Eindhoven for the measurement campaign (06/05/2014)
63
4.3.3.2. Phosphorous fractionation
Comparison of the phosphorous fractions
For the calculation of the different phosphorous fractions, two sets of conversion factors are used (Roeleveld and van Loosdrecht (2002) and STOWA (1996)). The factors found in Henze et al. (1999) are not used because these factors are the same as found in the article of Roeleveld and van Loosdrecht (2002) (Table 17).
Table 17: Different conversion factors for phosphorous
Conversion factors (g P/g
COD)
Roeleveld and van Loosdrecht
(2002)
Henze et al. (1999)
Stowa (1996)
iPSI 0.00 0.00 0.0045
iPSA 0.00 0.00 0.00
iPSF 0.01 0.01 0.0125
iPXI 0.01 0.01 0.0075
iPXS 0.01 0.01 0.0125
To compare the different fractions the conversion factors for Roeleveld and van Loosdrecht (2002) are used, the results are presented in Figure 28, Figure 29, Figure 30 and Figure 31. The trend that is seen in the high discharge rates for the WWTP of Roeselare and the WWTP of Eindhoven is: iPXI*XI > iPSF*SF > iPXS*XS The trend in the low discharge rates in the WWTP of Roeselare is: iPXI*XI > iPXS*XS > iPSF*SF The same trend is seen in the COD and nitrogen fractions.
Comparison of calculated and the measured total phosphorous concentration
The different conversion factors that are used to obtain the different TP concentrations are shown in Table 17. The mean concentrations of the TP are given in Figure 32, Figure 33, Figure 34 and Figure 35. The different figures reveal that none of the conversion factors are good for modelling the phosphorous compounds. The conversion factors overrate the total phosphorous concentrations.
64
-0,5
0
0,5
1
1,5
2
2,5
bPST aPST bPST aPST bPST aPST bPST aPST
17/02 24/02 03/03 24/03
Mean
co
nc
en
trati
on
(m
g P
/l)
Time (days) and sampling place
iPSI*SI
iPSF*SF
iPSA*SA
iPXI*XI
iPXS*XS
Figure 29: Phosphorous fractions for the WWTP of Roeselare with low discharge rate
-0,2
0
0,2
0,4
0,6
0,8
1
1,2
1,4
1,6
bPST aPST bPST aPST bPST aPST
12/03 7/04 14/04
Mean
co
nc
en
trati
on
(m
g P
/l)
Time (days) and sampling place
iPSI*SI
iPSF*SF
iPSA*SA
iPXI*XI
iPXS*XS
Figure 28: Phosphorous fractions for the WWTP of Roeselare with high discharge rate
65
Figure 30: Phosphorous fractions for the measurement campaign of the WWTP of Roeselare (12/03/2014)
0
0,2
0,4
0,6
0,8
1
1,2
1,4
1,6
1,8
bPST aPST bPST aPST bPST aPST bPST aPST bPST aPST
09:55 - 10:55
12:05 - 13:05
10:55 - 11:55
13:05 - 14:05
11:55 - 12:55
14:05 - 15:05
12:55 - 13:55
15:05 -16:05
13:55 - 14:55
Mean
co
nc
en
trati
on
(m
g P
/l)
Time (hours) and sampling place
iPSI*SI
iPSF*SF
iPSA*SA
iPXI*XI
iPXS*XS
-0,5
0
0,5
1
1,5
2
2,5
3
3,5
4
4,5
bPST aPST bPST aPST bPST aPST bPST aPST bPST aPST
08:00 - 08:30
16:00 - 16:30
08:30 - 09:00
16:30 -17:00
09:00 - 09:30
17:00 - 17:30
09:30 - 10:00
17:30 -18:00
10:00 - 10:30
18:00 - 18:30
Mean
Co
nc
en
trati
on
(m
g p
/l)
Time (hours) and sampling place
iPSI*SI
iPSF*SF
iPSA*SA
iPXI*XI
iPXS*XS
Figure 31: Phosphorous fractions for the measurement campaign of the WWTP of Eindhoven (06/05/2014)
66
-1
0
1
2
3
4
5
6
7
8
bPST aPST bPST aPST bPST aPST bPST aPST
17/02 24/02 03/03 24/03
Mean
co
nc
en
trati
on
(m
g P
/l)
Time (days) and sampling place
TP measured
TP Henze et al.
TP STOWA
Figure 32: Total phosphorous concentration for different conversion factors for the WWTP of Roeselare with high discharge rates
0
1
2
3
4
5
6
7
bPST aPST bPST aPST bPST aPST
12/03 7/04 14/04
Mean
co
nc
en
trati
on
(m
g P
/l)
Time (days) and sampling place
TP measured
TP Henze et al.
TP STOWA
Figure 33: Total phosphorous concentration for different conversion factors for the WWTP of Roeselare with low discharge rates
67
-1
0
1
2
3
4
5
6
7
8
bPST aPST bPST aPST bPST aPST bPST aPST bPST aPST
09:55 - 10:55
12:05 - 13:05
10:55 - 11:55
13:05 - 14:05
11:55 - 12:55
14:05 - 15:05
12:55 - 13:55
15:05 -16:05
13:55 - 14:55
Mean
co
nc
en
trati
on
(m
g P
/l)
Time (hours) and sampling place
TP measured
TP Henze et al.
TP STOWA
Figure 35: Total phosphorous concentration for different conversion factors for the measurement campaign of the WWTP of Eindhoven (06/05/2014)
0
2
4
6
8
10
12
14
16
bPST aPST bPST aPST bPST aPST bPST aPST bPST aPST
08:00 - 08:30
16:00 - 16:30
08:30 - 09:00
16:30 -17:00
09:00 - 09:30
17:00 - 17:30
09:30 - 10:00
17:30 -18:00
10:00 - 10:30
18:00 - 18:30
Me
an c
on
cen
trat
ion
(m
g P
/l)
Time (hours) and sampling place
TP measured
TP Henze et al.
TP STOWA
Figure 34: Total phosphorous concentration for different conversion factors for the measurement campaign of the WWTP of Roeselare (12/03/2014)
68
4.4. Removal efficiencies
To see how good the PST is working under the different conditions, the removal efficiencies were calculated (Table 19) and compared with removal efficiencies found in the literature (Table 18, EPA (1999), STOWA (1999), Rössle and Pretorius (2001) and Ghangrekar and Kharagpur (2014)).
Table 18: Reference removal efficiencies
Element Removal efficiency (%) Reference
TSS 50 - 70 Rössle and Pretorius (2001) and Ghangrekar and
Kharagpur (2014)
COD 30 - 50 Rössle and Pretorius (2001) and STOWA (1999)
TKN 15 - 25 Rössle and Pretorius (2001)
TP 15 - 25 Rössle and Pretorius (2001)
NO3- 50 - 75 EPA (1999)
BOD5 50 - 70 Ghangrekar and Kharagpur (2014)
Table 19: Removal efficiencies of this study
Date Discharge
rate COD (%) BOD (%) TSS (%) TKN (%) TP (%) NO3 (%)
WWTP of Roeselare
17/02/2014
High
24/02/2014 7.82 37.07 45.26 21.39 17.67 7.64
3/03/2014 40.20
32.08 19.17 20.26 9.73
24/03/2014 24.36 2.11 36.60 21.21 41.42 6.29
12/03/2014
Low
-12.14 33.07 25.53 -15.46 4.81 -4.64
12/03/2014 3.26 40.07 32.72 -12.39 12.12 -19.48
12/03/2014 2.89 13.79 33.33 -44.69 13.53 -27.23
12/03/2014 -1.92 83.00 27.04 -48.25 20.45 -3.81
7/04/2014 -19.81 -8.36 17.09 -24.47 -16.55 3.53
14/04/2014 -24.17 -43.33 16.67 -15.94 -17.10 28.83
WWTP of Eindhoven
06/05/2014
High
24.04 -70.34 33.33 12.20 -34.19 8.44
06/05/2014 16.22 25.86 31.52 -16.96 -39.25 9.60
06/05/2014 12.39 100.00 32.72 -18.68 -31.17 70.02
06/05/2014 16.28 27.35 36.68 -12.68 -21.39 18.10
06/05/2014 29.43 100.00 35.15 1.84 -4.83 18.27
69
After comparing the removal efficiencies the following conclusions can be made: - for the removal of TSS, COD and BOD5 both WWTPs are scoring lower than the removals seen in the literature - the removal of TP in the WWTP of Roeselare with high discharge rate is in range with the removal efficiency found in the literature - the removal of TP, TKN and NO3- are lower in the WWTP of Eindhoven and Roeselare with low discharge rate than these found in the literature - the efficiency of the removal of TKN and NO3- for the WWTP of Roeselare with high discharge rate are lower than these in the literature These lower removal efficiencies can be also the reason why the ranges for the different COD-fractions need to be larger. But it is also remarkable that for the nitrogen compounds negative removal efficiencies are found at the WWTP of Roeselare with a low discharge rate. Out of this one can conclude that the nitrogen concentration after the PST is higher than before the PST. In the removal efficiencies of Eindhoven one can also see negative values, but this time it is for the phosphorous components. So here the conclusion is that there is a higher phosphorous concentration after the PST than before.
4.5. Particle size distributions
The particle size distributions are done for all the samples with the laser technique. To compare these distributions the D10, D50 and D90 are compared with each other. For the column tests these percentiles are used as well, but the comparison is made between the different taps. The PSD curves of the different taps are then compared with the PSD curve of a sample taken after the PST. Just to see which tap at which hour corresponds bests with the PSD curve from the sample after the PST.
4.5.1. Particle size distribution of the different samples
Figure 36: The different percentiles for the WWTP of Roeselare with a high discharge rate
0
50
100
150
200
250
300
350
400
bPST aPST bPST aPST bPST aPST
24/02/2014 24/02/2014 3/03/2014 3/03/2014 24/03/2014 24/03/2014
Par
ticl
e d
iam
ete
r (µ
m)
Time (days) and sampling place
D90
D50
D10
70
In the different figures it is seen that for the low discharge rate (Figure 37) the particle size is decreasing after the PST, which was expected. But for the high discharge rate (Figure 36) the particle size is increasing after the PST. This can be due to the higher velocity speed through the PST, which leads to re-suspension from the settled solids. On Figure 38 one can see the decreasing particle diameter after the PST. But at noon an increase in the particle diameter is seen after the PST, probably because the discharge rate of the WWTP is increasing.
Figure 38: The different percentiles for the WWTP of Roeselare of the measurement campaign (12/03/2014)
Figure 37: The different percentiles for the WWTP of Roeselare with low discharge rate
0
50
100
150
200
250
300
350
400
bPST aPST bPST aPST bPST aPST bPST aPST
12/03/2014 12/03/2014 7/04/2014 7/04/2014 14/04/2014 14/04/2014 5/05/2014 5/05/2014
Par
ticl
e d
iam
ete
r (µ
m)
Time (days) and sampling place
D90
D50
D10
0
50
100
150
200
250
300
350
400
bPST aPST bPST aPST bPST aPST bPST aPST bPST aPST
9:55-11:37 10:55-12:37 11:55-13:37 12:55-14:37 13:55-15:37
Par
ticl
e d
iam
ete
r (µ
m)
Hydraulic retention time (hours) and sampling place
D90
D50
D10
71
4.5.2. Particle size distributions of the column tests
The particle size distributions from the column test are showing some similarities with the particle size distributions after the PST. But the best fit is found with the particle size distribution of the top tap after 6 hours (Figure 39, rest of the distributions are found in Appendix 5). One small remark needs to be made this is that the column test is a static test, while the PST is a dynamic system which can vary over time. The problem that is found is that the hydraulic retention time of the PST is 2 hours and 50 minutes on the 5th of May. So this means that the column test needs double of the time. To check if this conclusion is correct, the result of the column test after 2 hours is shown in Figure 40. It shows the particle diameter is still too big to find a resemblance with the particle diameters after the PST.
0
10
20
30
40
50
60
70
80
90
100
0
2
4
6
8
10
12
14
16
18
20
0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300
Particle diameter (µm)
Cu
mu
lati
ve p
erc
en
tage
(%
)
Vo
lum
e p
erc
en
tage
(%
)
Top tap after 6 h
aPST
Top tap after 6 h
aPST
Figure 39: Best fit between the results of the column test and a sample after the PST of Roeselare
72
The different percentiles of the column tests are presented in Figure 41. It was expected that a descending curve would be visible. But in these different figures there are several peaks that are indicating greater particle diameters. The peaks are found after 3 minutes, 7 minutes and 2 hours of the start of the column test. During the column test it was observed that some particles were rising instead of going down in the column. So the peaks are due to the rising particles and maybe due to the coalescence of the particles. For the WWTP of Eindhoven a column test was also performed, the results are presented in Figure 42. In these a decreasing trend is visible, but there are also some peaks after 7 minutes and 1 hour of the start of the test. In this test there was no observation of rising particles, so these must be due to the coalescence of the different particles.
0
10
20
30
40
50
60
70
80
90
100
0
2
4
6
8
10
12
14
16
18
20
0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300
Particle diameter (µm)
Cu
mu
lati
ve p
erc
en
tage
(%
)
Vo
lum
e p
erc
en
tage
(%
)
Figure 40: Particle size distribution of the column test of the 5th of May after two hours
73
Figure 41: The different percentiles for the two column tests performed on a sample before the PST of the WWTP of Roeselare (05/05/2014). (A) Top tap, (B) Center tap, (C) Base tap, (D) Top tap second column test, (E) Center tap second column test and (F) Base tap second column test
(A) (B)
(C) (D)
(E) (F)
74
4.6. General discussion
4.6.1. Problems
4.6.1.1. Phosphorous analyses
For the phosphorous analyses there is a problem with the filtration and flocculation of the wastewater. The problem lies in the high solubility of the used coagulant zinc sulphate that will stay in solution while zinc phosphate precipitates (lower solubility product). This phosphate is needed to determine the soluble total phosphate concentration, but due to the precipitation the determination is impossible (the obtained concentration is lower than it is in reality). It would be better to use zinc hydroxide or another substance as coagulant as suggested by Roeleveld and van Loosdrecht (2002) and STOWA (1996). The solubility product of this Zn(OH)2 is 3.0*10-17 and the solubility product of Zn3(PO4 )2 is 9.0*10-33. The solubility is still higher than this for zinc phosphate, (but lower than zinc sulphate solubility and could therefore potentially give a better result).
(A) (B)
(C)
Figure 42: The different percentiles for the column test performed on a sample before the PST of the WWTP of Eindhoven (30/04/2014). (A) Top tap, (B) Center tap and (C) Base tap
75
4.6.1.2. First analyses
For the 17th of February there are only measurements from before the PST, this because these are the first measurements performed in the lab. And were seen as a test case, but for the completeness of the study they are listed as results.
4.6.1.3. Technical problem
On the 3rd of March there are no BOD results due to a technical problem. An attempt to recover the results was not successful. With all analyses done a pattern in the BOD5-COD ratios was looked for (Table 20). The 3rd of May is a day with a high discharge rate, so only the ratios of the 17th of February, 24th of February and the 24th of March are considered. The influent ratios range from 0.14 to 0.24 and for the effluent the ratio is 0.17. So it is possible to estimate the BOD5 from the effluent, but for the influent the ratios are spread out too much to allow a good estimation.
Table 20: BOD-COD ratios for the different samples
Date
BOD5/COD BOD5/COD
influent effluent
17/02/2014 Measured 0.141791045 n.a.
Mean 0.141791045 n.a.
24/02/2014
Measured 0.221465969 0.159748428
Measured 0.259195402 0.186163522
Mean 0.240330685 0.172955975
3/03/2014 Measured n.a. n.a.
Mean n.a. n.a.
12/03/2014
Measured 09:55 - 10:55 12:05 - 13:05
0.319806763 0.308571429
Mean 0.319806763 0.308571429
Measured 10:55 - 11:55 13:05 - 14:05
0.379699248 0.252238806
Mean 0.379699248 0.252238806
Measured 11:55 - 12:55 14:05 - 15:05
0.478571429 0.296309963
Mean 0.478571429 0.296309963
Measured 12:55 - 13:55 14:05 - 15:05
0.373188406 0.314893617
Mean 0.373188406 0.314893617
Measured 13:55 - 14:55
0.496575342 n.a.
Mean 0.496575342 n.a.
24/03/2014
Measured 0.201530612 0.184827586
Measured 0.210824742 0.149006623
Mean 0.206177677 0.166917104
7/04/2014 Measured 0.269856459 0.169879518
76
Measured 0.306930693 0.349593496
Mean 0.288393576 0.259736507
14/04/2014
Measured 0.258974359 0.339920949
Measured 0.258715596 0.266993464
Mean 0.258844978 0.303457206
4.6.2. Wastewater treatment plant of Roeselare
In the wastewater treatment plant of Roeselare there is a problem in the nitrogen mass balance of the PST on days with a low discharge rate. It is seen that the total nitrogen concentration is increasing after the PST, but this without a clear increase in the nitrate and ammonium concentration (Figure 43). After consultation with the people of the process technology of Aquafin n.v. it was clear that this was not the first time that something abnormal was seen. In their studies they have seen some rarities in the oxygen demand, COD and BOD concentrations. And also they do not know what is happening in the PST to get these results. At high discharge rates the PST is working good.
The increase in the total mean nitrogen concentration in the last two days is accompanied by a lower and equal increase in the ammonium concentration. But the nitrate concentration stays the same before and after the PST. Normally it is expected that the nitrogen compounds would decrease after the PST, but none of them is seen (Rössle and Pretorius (2001)). A number of possible causes come to mind: 1) septic incorporation in the PST, because it is seen that the ammonium concentration is also rising. But after consultation with the responsible people at Aquafin n.v. this seems unlikely because this is done in the raw wastewater. So the increase should be visible before the PST and that is not what is happening here. 2) a mix up in the samples came to mind because the total nitrogen after flocculation and filtration was showing a decrease in concentration. But the samples were always carefully
-11
-9
-7
-5
-3
-1
1
3
5
7
9
11
13
15
12/03/2014 19/03/2014 26/03/2014 2/04/2014 9/04/2014
Mean
on
cen
trati
on
(m
g N
/l)
Time (days)
TN
TNFF
NO3
NH4
TKN
Figure 43: Mean increase or decrease of the nitrogen compounds on low discharge days
77
labelled and analysed, so a mix up is very unlikely too. But for the last two samples also there is an increase seen, so this cause is nullified. 3) grab sampling versus time proportional sampling. With grab sampling one takes the sample before the PST and after the PST within the same time interval. So in these samples the hydraulic retention time is not taken into account. So when a nitrogen peak has passed before the PST one can see this peak concentration after the PST, but not anymore before the PST. Time proportional samples take into account the hydraulic retention time by using a time shift. This will show the peak flow passing through the PST. But in this case the total nitrogen concentration after the PST is higher than before the PST even for both the sampling types. So this cause could be true if the increase was not seen in the measurement campaign, but as it is seen this cause is also nullified. 4) with grab sampling the risk to churn up the sediment is high, which can lead to higher sediments in the samples and thus a higher concentration. But this reason is nullified because the different samples were taken in the overflow, where almost no sediment is found. 5) a washout of the PST 6) after the PST the floating and heavy particles are settled and only the suspended solids are still in the wastewater. When there is a high discharge rate the dilution is much bigger and the concentrations are lower. Also the hydraulic retention time is smaller which leads to a higher velocity through the PST, which can lead to plug flows. At low discharge rates the chance to get plug flows are much lower. At low discharge rates, the retention time is much higher and there is more time for mixing the wastewater. In this case a slow settling will take place (such as in the column test) and the concentration will stay higher than expected. 7) another possibility is the behaviour of proteins. When the dilution is high, the concentration of these molecules is low and they do not interact. But with a lower dilution rate (at low discharge rates) these concentrations are higher and the proteins can start forming bounds which leads to a greater particle diameter. These greater particle diameters are seen in the percentile curves of the column tests. But the presence can also be derived out of the increase of slowly biodegradable matter (Lodish et al., 2000). It can be seen that a further study is needed to know what the problem is with the PST at low discharge rates.
4.6.3. Wastewater treatment plant of Eindhoven
In the wastewater treatment plant of Eindhoven a mass balance problem with phosphorous is visible. After the PST the total phosphorous and phosphate concentration is higher than before the PST. The increase goes from 0.5 to 3 mg P/l for TP and for PO4
3- it goes from 1.5 to 3.5 mg P/l (Figure 44).
78
After consultation with the people of the Waterschap De Dommel, it was clear that these results were not a mistake. There are three causes for this increase. The first one is that the ingoing flow was lower than the outgoing flow of the PST to insure a long enough retention time. These two facts will cause a lower hydraulic retention time in the PST and will lead to a lower settling rate. The second cause is the rain that started during the measurement campaign. Because of the sudden higher incoming flow more nutrients were coming in. The third cause is the effluent of the sludge treatment in Mierlo. The sludge of the treatment plant in Eindhoven is not processed in the plant because of the close vicinity of residential areas. In Mierlo (7 kilometers from the plant) the sludge is treated in a closed system preventing odor problems for the surrounding environment. The effluent of the sludge treatment comes back to the treatment plant between 12 and 14 o'clock. This influent has a high phosphorous concentration. Normally this is prevented by the dosing of aluminum, but due to an incorrect influent measurement the aluminum dosing was incorrect. At the sand trap there is again a measurement of the phosphorous concentration. There the aluminum is dosed until a phosphorous concentration of 4.5 to 5 mg P/l is obtained. But further research is conducted to see if the aluminum dosage was right.
-0,5
0
0,5
1
1,5
2
2,5
3
3,5
4
Sample 1 Sample 2 Sample 3 Sample 4 Sample 5
Mean
co
nc
en
trati
on
(m
g P
/l)
Increase TP
Increase PO4
Figure 44: Mean increase in concentration of total phosphorous and phosphate
79
5. CONCLUSION Out of the comparison with the references of Rieger et al. (2013) it is concluded that the WWTP of Eindhoven and Roeselare are treating domestic wastewater. And that the WWTP of Roeselare does not experience an influence of the industrial wastewater. The effect of variations in the discharge rate is visible in the WWTP of Roeselare. When there is a high discharge rate (e.g. in a rain period) the primary sedimentation tank is working good (reduction of all the measured compounds). But when the discharge rate is low (e.g. in a drought period), the primary sedimentation tank is working opposite to what is expected. The nitrogen concentration is higher after the PST than before and the COD concentration is increasing as well. For the low discharge rate in the WWTP of Roeselare two column tests were performed as well. And in these it was visible that there is also a problem in the particle settling (rising of the particles, higher particle diameters after some time). Until now it is still unclear what the cause is. Further study is necessary to discover the different dynamics that influence the nitrogen mass balance and the settling problem. Also a study of the relationship between underflow and concentration is needed, to see if the same phenomena is occuring. In the WWTP of Eindhoven the effect of the primary sedimentation tank is more visible. But on the day of the sampling there was a problem with the aluminum dosage, so there was a mass balance problem visible. But the COD, BOD and nitrogen concentrations were decreasing so it is clear that the PST of this treatment plant is working properly. Out of the fractionation of the wastewater of the treatment plant of Roeselare with a low discharge rate, it is clear that there is more unbiodegradable material after the PST than before the PST. In the different fractionations the same trend is seen and that is the following, for the WWTP of Roeselare for high discharge rates: XI > SS > XS > SI and for low discharge rates: XI > XS > SS > SI. And for the WWTP of Eindhoven XI > SS > XS > SI. So in the WWTP of Roeselare at high discharges and in the WWTP of Eindhoven the percentage of SS is higher than the percentage of XS which will lead to a higher aeration need in the activated sludge process. The nitrogen conversion factors applied in the model of Eindhoven gives the best fit. The total Kjeldahl nitrogen was calculated and measured and it is clear that this consists mostly of ammonium. This indicates the biodegradability of the wastewater. The phosphorous fraction results are not in line with expected reality due to the use of the coagulant zinc sulphate. It is therefore advised to use zinc hydroxide as suggested by STOWA (1996) and by Roeleveld and van Loosdrecht (2002). Out of the removal efficiencies it is clear that the PST of the WWTP of Roeselare is not working well and that the PST of Eindhoven has some problems with the phosphorous concentrations.
80
6. REFERENCES AMERLINCK, Y., FLAMELING, T., MAERE, T., WEIJERS, S., NOPENS, I., 2013, Practical application of dynamic process models for wastewater treatment plant optimization: work in progress, Water Environment Federation (WEF), Alexandria, VA, USA ANKERSMID, 2014, Brochure: Eyetech. Particle size analysis, Dynamic image analysis, Concentration measurement. Beyond particle size. APHA, AWWA, WPCF (Joint Publication),1985, Standard methods for the examination of water and wastewater.13th edition, American Public Health Association, Washington DC APHA, 1999, Standard methods for the examination of water and wastewater. 20th edition.: American Public Health Association, Washington DC AQUAFIN n.v., 1998, Rioolwaterzuiveringsinstallatie Roeselare, Aquafin n.v., Aartselaar AQUAFIN n.v., 2014 , Werken aan zuiver water, Luc Bossyns, Aartselaar BOONTIAN, N, 2012, A calibration approach towards reducing ASM2d parameter subsets in phosphorus removal processes, Academy of Science, Engineering and Technology, Volume 6, number 4: 814 - 820 CLAESSEN, V., 2010, Optimalisatie procesregeling rwzi Eindhoven draag bij aan MJA- doelstelling Waterschap De Dommel, Neerslag, Volume III: 27 - 31 CHOUBERT, J.M., RIEGER, L., SHAW, A., COPP, J., SPERANDIO, M., SORENSEN, K., RÖNNER- HOLM, S., MORGENROTH, E., MELCER, H., GILLOT, S., 2013, Rethinking wastewater characterisation methods for activated sludge systems-a position paper, Water Science and Technology, Volume 67, Number 11: 2363 - 2371 CIW, 2014, Integrated water Policy of Flanders, Coordinatiecommissie Integraal Waterbeleid, Aalst EPA, 1999, Wastewater treatment manuals: primary, secondary and tertiary treatment, Environmental Protection Agency, Wexford, Ireland EPA, 2008, Wastewater management, Environmental Protection Agency, Wexford, Ireland FALL, C., FLORES, N.A., ESPINOZA, M.A., VAZQUEZ, G., LOAIZA-NAVIA, J., VAN LOOSDRECHT, M.C.M., HOOIJMANS, C.M., 2011, Divergence between respirometry and physicochemical methods in the fractionation of the chemical oxygen demand in municipal wastewater, Water Environment Research, Volume 83, Number 2: 162 - 172
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GHANGREKAR, M.M., KHARAGPUR,I.T., 2014, Module 16: Primary sedimentation tank, Lecture notes wastewater management, Indian institute of Technology Kharagpur HAUDUC, H., RIEGER, L., OCHMEN, A., VAN LOOSDRECHT, M.CM., COMEAU, Y., HEDUIT, A., VANROLLEGHEM, P.A., GILLOT, S., 2013, Critical review of activated sludge modelling: state of process knowledge, modelling concepts, and limitations, Biotechnology and Bioengineering, Volume 110, Number 1: 24 - 46 HASSAN, N., 2013, Experimental and model-based analysis of primary sedimentation for wastewater treatment plants, Master dissertation, University of Ghent HENZE, M., GRADY, C.P.L., GUJER, W., MARIAS, G.v.R., MATSUO, T., 1987, Activated sludge model no. 1, IWA Publishing, London, United Kingdom HENZE, M., GUJER, W., MINO, T., MATSUO, T., WENTZEL, M.C., MARAIS, G.v.R, 1995, Wastewater and biomass characterization for the activated sludge model no. 2: biological phosphorus removal, Water Science and Technology, Volume 31, Number 2: 13 - 23 HENZE, M., GUJER, W., MINO, T., MATSUO, T., WENTZEL, M.C., MARAIS, G.v.R, VAN LOOSDRECHT, M.C.M.,1999, Activated sludge model no. 2D, ASM2D, Water Science and Technology, Volume 39, Number 1: 165 - 182 HENZE, M., GUJER, W., MINO, T., VAN LOOSDRECHT, M., 2000, Activated sludge models ASM1, ASM2, ASM2d and ASM3, IWA Publishing, London, United Kingdom HENZE, M., VAN LOOSDRECHT, M.C.M., EKAMA, G.A., BRDJANOVIC, D., 2008 , Biological wastewater treatment: principles modelling and design, IWA Publishing, London, United Kingdom KAIKA, M., PAGE, B., 2003, The EU water framework directive: part 1. European Policy- making and the changing topography of lobbying, Wiley InterScience KALLISTO, 2010, Brochure: Kallisto samen slim schoon. Een integrale, duurzame en innovatieve aanpak in de afvalwaterketen en het watersysteem. LEE, C.C., DAR LIN, S., 1999, Handbook of environmental engineering calculations, McGraw-Hill Companies, New York LODISH, H., BERK, A., ZIPURSKY, S.L., MATSUDAIRA, P., BALTIMORE, D., DARNELL, J., 2000, Molecular cell biology, 4th edition, W.H. Freeman & Company, New York
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MARTINEZ-GONZALEZ, G., LORIA-MOLINA, H., TABOADA-LOPEZ, D., RAMIREZ- RODRIGUEZ, F., NAVARETTE-BOLANOS, J.L., JIMENEZ-ISLAS, H., 2009, Approximate method for designing a primary settling tank for wastewater treatment, Industrial & Engineering Chemistry Research, Volume 48, Issue 16: 7842-7846 MELCER, H., DOLD,P.L., JONES,R.M., BYE,C.M., TAKACS, I., STENSEL, H.D., WILSON, A.W., SUN, P., BURY, S., 2003, Methods for wastewater characterization in activated sludge modelling, Water Environment Research Foundation (WERF), Alexandria, VA, USA NELSON, M.I., SIDHU, H.S., 2009, Analysis of the activated sludge model (number 1), Applied Mathematics Letters, Volume 22, Issue 5: 629-635 NESC, 2003, Explaining the Activated Sludge Process, Pipeline, Volume 14 (2): 1-7 NOPENS, I., 2010. Modelling and control of wastewater treatment plant: 2010-2011 (Course notes of 1st/2nd Master Bio-science engineering). Department of Applied Mathematics,Biometrics and Process Control Research unit BIOMATH, Gent University. NOPENS, I., VAN NIEUWENHUIJZEN, A., FLAMELING, T., LANGEVELD, J., 2012, Geavanceerde dynamische modellering rwzi Eindhoven voor een schonere Dommel, H20, Volume 11: 31 - 33 PASZTOR, I., THURY, P., PULAI, J., 2009, Chemical oxygen demand fractions of municipal wastewater for modeling of wastewater treatment, International Journal of Environmental Science and Technology, Volume 6, Issue 1: 51 - 56 RIEGER, L., GILLOT, S., LANGERGRABER, G., OHTSUKI, T., SHAW, A., TAKACS, I., WINKLER, S., 2013, Guidelines for using activated sludge models. Scientific and Technical Report No. 22, IWA Publishing, London, United Kingdom ROELEVELD, P.J., VAN LOOSDRECHT, M.C.M., 2002, Experience with guidelines for wastewater characterisation in The Netherlands, Water Science and Technology, Volume 45, Number 6: 77 -87 ROSSLE, W.H., PRETORIUS, W.A., 2001, A review of characterisation requirements for in-line prefermenters. Paper 2: Process characterisation., Water SA, Volume 27, Number 3: 413 - 422 SOPHONSIRI, C., MORGENROTH, E., 2004, Chemical composition associated with different particle size fractions in municipal, industrial and agricultural wastewaters, Chemosphere, Volume 55, Issue 5: 691 - 703 STOWA, 1996, Methoden voor influentkarakterisering. Inventarisatie en richtlijnen, STOWA, Zoetermeer, Nederland
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STOWA, 1999, Influentkarakterisering van ruw en voorbehandeld afvalwater. De invloed van voorbezinking en voorprecipitatie, STOWA, Zoetermeer, Nederland WRAC, WESTERN REGIONAL AQUACULTURE CENTER, 2001, Settling basin design, WRAC publication n° 106 YETIS, U., TARLAN, E., 2002, Improvement of primary settling performance with activated sludge, Environmental Technology, Volume 23, Issue 4: 363 - 372
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7. APPENDIX
86
Appendix 1: Laboratory analyses
Roeselare 17/02/2014 Roeselare 24/02/2014 Roeselare 03/03/2014
V PST m³ 1365 1365 1365
HRT h 1.288 0.718 0.65
Q m³/h 1060 1900 2100
Analysed Mean Analysed Mean Analysed Mean
Bef
ore
pri
mar
y se
dim
enta
tio
n t
ank
CODtot mg/l 268 n.a. n.a. 268 191 174 172 179 52.2 53.9 52.1 52.7
CODff mg/l 172 n.a. n.a. 172 101 104 102 102 18.8 17.3 16.4 17.5
BOD10 mg/l 46.5 53.5 n.a. 50 50.7 53.5 n.a. 52.10 n.a. n.a. n.a. n.a.
BOD5 mg/l 38 42.3 n.a. 40.15 42.3 45.1 n.a. 43.70 n.a. n.a. n.a. n.a.
kBOD mg/l 0.28213651 0.41027701 n.a. 0.34620676 0.33716651 0.34418138 n.a. 0.34 n.a. n.a. n.a. n.a.
BODtot mg/l 46.71589 51.512602 n.a. 49.114246 52.633328 54.411477 n.a. 53.52 n.a. n.a. n.a. n.a.
TPtot mg/l 5.48 n.a. n.a. 5.48 2.28 2.36 2.32 2.32 1.01 1.07 0.941 1.007
TPff mg/l 0.044 n.a. n.a. 0.044 0.072 0.072 0.075 0.073 0.067 0.062 0.062 0.064
PO4 mg/l 4.62 n.a. n.a. 4.62 1.74 1.74 1.71 1.73 0.724 0.911 0.695 0.777
TNtot mg/l 24.4 n.a. n.a. 24.4 25.2 24.2 24 24.47 10.4 8.11 8.93 9.15
TNff mg/l 18.5 n.a. n.a. 18.5 19.5 12.9 15.7 16.03 7.31 7.02 7.23 7.19
TSS g/l 0.104 0.109 n.a. 0.1065 0.081 0.056 n.a. 0.068 0.022 0.031 n.a. 0.027
VSS g/l 0.196 0.236 n.a. 0.216 0.140 0.184 n.a. 0.162 0.112 0.088 n.a. 0.100
NH4 mg/l 9.07 n.a. n.a. 9.07 10.7 9.98 11.4 10.69 2.42 2.49 2.55 2.49
NO3 mg/l 5.11 n.a. n.a. 5.11 3.16 3.15 3.12 3.14 2.32 2.19 2.17 2.23
pH
7.89 n.a. n.a. 7.89 7.90 7.91 7.93 7.91 7.58 7.6 7.59 7.59
Kj-N mg/l 19.29 n.a. n.a. 19.29 22.04 21.05 20.88 21.32 8.08 5.92 6.76 6.92
bCOD mg/l 54.9598706 60.6030612 n.a. 57.7814658 61.92156235 64.01350235 n.a. 62.96753235 n.a. n.a. n.a. n.a.
AS TSS g/l 4.06 4.12 3.88 4.02 3.212 3.392 3.488 3.364 3.112 3.112 2.896 3.040
VSS g/l 2.28 2.28 n.a. 2.28 2.164 2.028 n.a. 2.096 1.900 1.892 n.a. 1.896
Effl
uen
t W
WTP
CODtot mg/l n.a. n.a. n.a. n.a. 31.8 22.4 22.8 25. 7 32.2 30.7 29.4 30.8
CODff mg/l 23.4 n.a. n.a. 23.4 20.3 20.9 19.9 20.4 15.2 16.3 15.7 15.7
BOD5 mg/l 3.1 n.a. n.a. 3.1 21.9 n.a. n.a. 21.9 n.a. n.a. n.a. n.a.
BOD10 mg/l 6.2 n.a. n.a. 6.2 11.5 n.a. n.a. 11.5 n.a. n.a. n.a. n.a.
kBOD mg/l 0.28599358 n.a. n.a. 0.28599358 0.27595306 n.a. n.a. 0.27595306 n.a. n.a. n.a. n.a.
BODtot mg/l 9.0114031 n.a. n.a. 9.0114031 12.378722 n.a. n.a. 12.378722 n.a. n.a. n.a. n.a.
Roeselare 17/02/2014 Roeselare 24/02/2014 Roeselare 03/03/2014
Analysed Mean Analysed Mean Analysed Mean
Aft
er p
rim
ary
sed
imen
tati
on
tan
k
CODtot mg/l n.a. n.a. n.a. n.a. 159 159 177 165.00 32 31.4 31.2 31.53333333
CODff mg/l n.a. n.a. n.a. n.a. 32.8 32.7 31.8 32.43 21.5 16.2 18.1 18.6
BOD5 mg/l n.a. n.a. n.a. n.a. 25.4 29.6 n.a. 27.50 5.44 5.338 5.304 5.360666667
BOD10 mg/l n.a. n.a. n.a. n.a. 29.6 35.2 n.a. 32.40 9.928 9.74185 9.6798 9.783216667
kBOD mg/l n.a. n.a. n.a. n.a. 0.40492 0.38136887 n.a. 0.39 n.a. n.a. n.a. n.a.
BODtot mg/l n.a. n.a. n.a. n.a. 28.449576 33.847847 n.a. 31.15 n.a. n.a. n.a. n.a.
TPtot mg/l n.a. n.a. n.a. n.a. 1.91 1.81 2.01 1.91 0.796 0.819 0.794 0.803
TPff mg/l n.a. n.a. n.a. n.a. 0.053 <0.050 <0.050 0.053 <0.050 <0.050 <0.050 <0.050
PO4 mg/l n.a. n.a. n.a. n.a. 1.5 1.4 1.53 1.48 0.607 0.618 0.612 0.612
TNtot mg/l n.a. n.a. n.a. n.a. 20.3 19.7 19 19.67 7.66 7.66 7.49 7.60
TNff mg/l n.a. n.a. n.a. n.a. 16.6 16.3 16.5 16.47 5.65 6.56 8.71 6.97
TSS g/l n.a. n.a. n.a. n.a. 0.044 0.031 n.a. 0.04 0.018 0.018
0.018
VSS g/l n.a. n.a. n.a. n.a. 0.14 0.132 n.a. 0.14 0.1 0.104
0.102
NH4 mg/l n.a. n.a. n.a. n.a. 8.81 8.63 9.46 8.97 2.46 2.38 2.44 2.43
NO3 mg/l n.a. n.a. n.a. n.a. 2.8 3 2.91 2.90 2.06 1.97 2 2.01
pH
n.a. n.a. n.a. n.a. 7.78 7.81 7.79 7.79 7.66 7.62 7.59 7.62
Kj-N mg/l n.a. n.a. n.a. n.a. 17.5 16.7 16.09 16.76 5.60 5.69 5.49 5.59
bCOD mg/l n.a. n.a. n.a. n.a. 33.47008941 39.82099647 n.a. 36.64554294 n.a. n.a. n.a. n.a.
Roeselare 12/03/2014
V PST m³ 1365 1365 1365
HRT h 1.706 1.706 1.706
Q m³/h 800 800 800
Sampling time 09:55 - 10:55 10:55 - 11:55 11:55 -12:55
Analysed Mean Analysed Mean Analysed Mean
Bef
ore
pri
mar
y se
dim
enta
tio
n t
ank
CODtot mg/l 207 191 195 198 266 258 274 266 280 273 277 277
CODff mg/l 67.8 61.1 59.4 62.8 89.8 81.9 77.9 83.2 102 99.2 93.7 98.3
BOD10 mg/l 83.1 n.a. n.a. 83.1 131 n.a. n.a. 131 170 n.a. n.a. 170
BOD5 mg/l 66.2 n.a. n.a. 66.2 101 n.a. n.a. 101 134 n.a. n.a. 134
kBOD mg/l 0.2771766 n.a. n.a. 0.2771766 0.31954866 n.a. n.a. 0.31954866 0.34138363 n.a. n.a. 0.34138363
BODtot mg/l 88.800876 n.a. n.a. 88.800876 131.54913 n.a. n.a. 131.54913 169.54387 n.a. n.a. 169.54387
TPtot mg/l 3.05 3.09 3.00 3.05 3.88 3.51 3.67 3.69 4.42 4.51 4.52 4.48
TPff mg/l <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 0.051 0.051 0.053 0.052 0.055 0.053
PO4 mg/l 2.34 2.36 2.46 2.39 2.96 2.98 2.88 2.94 3.81 3.49 3.59 3.63
TNtot mg/l 27.1 29.3 28.3 28.2 32.6 29.6 30.4 30.87 28.8 26.7 25.3 26.93
TNff mg/l 23.7 25 28.5 25.7 35.6 39.1 26.2 33.633 47.4 35.5 27.3 36.73
TSS g/l 0.091 0.097 n.a. 0.094 0.117 0.1 n.a. 0.1085 0.136 0.083 n.a. 0.1095
VSS g/l 0.232 0.208 n.a. 0.22 0.252 0.208 n.a. 0.23 0.228 0.248 n.a. 0.238
NH4 mg/l 19.5 19.2 19.5 19.4 22.6 21.5 21.5 21.87 24.6 23.2 23.6 23.8
NO3 mg/l 1.25 1.14 1.27 1.22 1.16 1.09 0.897 1.049 1.06 0.946 0.91 0.972
pH
7.93 8.03 8.05 8.00 8.17 8.19 8.13 8.16 8.07 7.99 7.96 8.01
Kj-N mg/l 25.85 28.16 27.03 27.01 31.44 28.51 29.50 29.81 27.74 25.75 24.39 25.96
bCOD mg/l 104.471619 n.a. n.a. 104.471619 154.763682 n.a. n.a. 154.763682 199.463377 n.a. n.a. 199.46337
AS TSS g/l 3.324 3.296 3.332 3.317 3.324 3.296 3.332 3.317 3.324 3.296 3.332 3.317
VSS g/l 1.848 1.868 n.a. 1.858 1.848 1.868 n.a. 1.858 1.848 1.868 n.a. 1.858
Effl
uen
t W
WTP
CODtot mg/l 34.2 28.9 28.0 30.4 34.2 28.9 28 30.4 34.2 28.9 28 30.4
CODff mg/l 24.9 20.3 19.2 21.5 24.9 20.3 19.2 21.5 24.9 20.3 19.2 21.5
BOD5 mg/l 6.5 n.a. n.a. 6.5 6.5 n.a. n.a. 6.5 6.5 n.a. n.a. 6.5
BOD10 mg/l 9.5 n.a. n.a. 9.5 9.5 n.a. n.a. 9.5 9.5 n.a. n.a. 9.5
kBOD mg/l 0.28599358 n.a. n.a. 0.28599358 0.28599358 n.a. n.a. 0.28599358 0.28599358 n.a. n.a. 0.28599358
BODtot mg/l 9.0114031 n.a. n.a. 9.0114031 9.0114031 n.a. n.a. 9.0114031 9.0114031 n.a. n.a. 9.0114031
Roeselare 12/03/2014
Sampling time 12:05 - 13:05 13:05 - 14:05 14:05 - 15:05
Analysed Mean Analysed Mean Analysed Mean
Aft
er p
rim
ary
sed
imen
tati
on
tan
k
CODtot mg/l 210 215 240 222 268 244 260 257 271 270 265 269
CODff mg/l 60.2 58.0 56.4 58.2 60.3 64.2 59.4 61.3 74.5 69.0 69.7 71.1
BOD5 mg/l 64.8 n.a. n.a. 64.8 67.6 n.a. n.a. 67.6 80.3 n.a. n.a. 80.3
BOD10 mg/l 80.3 n.a. n.a. 80.3 83.1 n.a. n.a. 83.1 97.2 n.a. n.a. 97.2
kBOD mg/l 0.37223007 n.a. n.a. 0.37223007 0.37914963 n.a. n.a. 0.37914963 0.37249599 n.a. n.a. 0.37249599
BODtot mg/l 79.48314 n.a. n.a. 79.48314 82.295806 n.a. n.a. 82.295806 96.725217 n.a. n.a. 96.725217
TPtot mg/l 3.06 2.88 2.76 2.90 3.32 3.34 3.06 3.24 3.99 3.81 3.83 3.88
TPff mg/l <0.050 <0.050 <0.050 <0.050 <0.050 <0.050 <0.050 <0.050 0.098 0.092 0.095 0.095
PO4 mg/l 2.29 2.1 2.17 2.19 2.69 2.64 2.67 2.67 3.26 3.27 3.09 3.21
TNtot mg/l 32.2 32.7 32.5 32.5 33.8 35.7 34.8 34.8 38.6 39 38.8 38.8
TNff mg/l 23.5 27.6 24.9 25.3 24.1 26.8 27.6 26.2 29.2 28.9 27.7 28.6
TSS g/l 0.07 0.07 n.a. 0.07 0.073 0.073 n.a. 0.073 0.075 0.071 n.a. 0.073
VSS g/l 0.164 0.28 n.a. 0.222 0.172 0.248 n.a. 0.21 0.228 0.24 n.a. 0.234
NH4 mg/l 20.3 20.2 20.5 20.3 21.7 20.1 20.7 20.8 24.3 23.2 23.1 23.5
NO3 mg/l 1.31 1.32 1.2 1.28 1.35 1.32 1.09 1.25 1.31 1.22 1.18 1.24
pH
8.01 7.99 7.98 7.99 8.15 8.09 8.11 8.12 8.15 8.13 8.14 8.14
Kj-N mg/l 30.89 31.38 31.30 31.19 32.45 34.38 33.71 33.51 37.29 37.78 37.62 37.56
bCOD mg/l 93.5095765 n.a. n.a. 93.5095765 96.8185953 n.a. n.a. 96.8185953 113.794373 n.a. n.a. 113.794373
Roeselare 12/03/2014 Roeselare 24/03/2014
V PST m³ 1365 1365 1365
HRT h 1.706 1.706 1.401
Q m³/h 800 800 974
Sampling time 12:55 - 13:55 13:55 - 14:55
Analysed Mean Analysed Mean Analysed Mean
Bef
ore
pri
mar
y se
dim
enta
tio
n t
ank
CODtot mg/l 276 285 273 278 290 292 294 292 196 194 197 196
CODff mg/l 130 120 120 123 133 129 126 129 54.2 49.5 49.7 51.1
BOD10 mg/l 100 n.a. n.a. 100 180 n.a. n.a. 180 50.7 50.7 n.a. 50.7
BOD5 mg/l 103 n.a. n.a. 103 145 n.a. n.a. 145 39.5 40.9 n.a. 40.2
kBOD mg/l 0.72918315 n.a. n.a. 0.72918315 0.35345561 n.a. n.a. 0.35345561 0.34677925 0.35027402 n.a. 0.348526635
BODtot mg/l 104.32964 n.a. n.a. 104.32964 180.6319 n.a. n.a. 180.6319 50.464975 50.247185 n.a. 50.35608
TPtot mg/l 4.89 4.69 4.70 4.76 3.86 3.93 4.07 3.95 3.04 3.09 3.02 3.05
TPff mg/l 0.058 0.056 0.054 0.056 0.079 0.077 0.079 0.078 <0.05 <0.05 <0.05 <0.05
PO4 mg/l 4.54 4.36 4.09 4.33 3.32 3.28 3.27 3.29 2.57 2.5 2.59 2.55
TNtot mg/l 22.8 26.2 38.7 29.2 24.7 32.7 41.4 32.9 26.8 27.2 24.4 26.1
TNff mg/l 29.3 33 34.7 32.3 34.6 29.7 30.1 31.5 23.8 22.8 22.7 23.1
TSS g/l 0.082 0.114 n.a. 0.098 0.132 0.11 n.a. 0.121 0.097 0.097 n.a. 0.097
VSS g/l 0.976 0.252 n.a. 0.614 0.22 0.236 n.a. 0.228 0.156 0.184 n.a. 0.17
NH4 mg/l 25.3 24.9 25.3 25.2 24.7 24.2 24.3 24.4 13.5 13.1 13.2 13.3
NO3 mg/l 1.27 1.13 1.01 1.14 1.01 0.958 0.979 0.982 1.87 1.85 1.84 1.85
pH
8.07 7.96 7.93 7.99 8.04 8.04 7.97 8.02 8.17 8.16 8.16 8.16
Kj-N mg/l 21.53 25.07 37.69 28.10 23.69 31.74 40.42 31.95 24.93 25.35 22.56 24.28
bCOD mg/l 122.740753 n.a. n.a. 122.740753 212.508118 n.a. n.a. 212.508118 59.3705588 59.1143353 n.a. 59.2424471
AS TSS g/l 3.324 3.296 3.332 3.317 3.324 3.296 3.332 3.317 3.296 3.548 3.552 3.465
VSS g/l 1.848 1.868 n.a. 1.858 1.848 1.868 n.a. 1.858 2.124 2.128 n.a. 2.126
Effl
uen
t W
WTP
CODtot mg/l 34.2 28.9 28.0 30.4 34.2 28.9 28.0 30.4 36.7 38.2 36.0 37.0
CODff mg/l 24.9 20.3 19.2 21.5 24.9 20.3 19.2 21.5 21.3 15.9 16.9 18.0
BOD5 mg/l 6.5 n.a. n.a. 6.5 6.5 n.a. n.a. 6.5 3.4 4.5 n.a. 3.95
BOD10 mg/l 9.5 n.a. n.a. 9.5 9.5 n.a. n.a. 9.5 5.1 7.6 n.a. 6.35
kBOD mg/l 0.28599358 n.a. n.a. 0.28599358 0.28599358 n.a. n.a. 0.28599358 0.28714233 0.28713045 n.a. 0.28713639
BODtot mg/l 9.0114031 n.a. n.a. 9.0114031 9.0114031 n.a. n.a. 9.0114031 8.3401842 8.3349306 n.a. 8.3375574
Roeselare 12/03/2014 Roeselare 24/03/2014 Roeselare 07/04/2014
Sampling time 14:05 - 15:05
Analysed Mean Analysed Mean Analysed Mean
Aft
er p
rim
ary
sed
imen
tati
on
tan
k
CODtot mg/l 282 289 279 283 145 151 148 148 249 246 243 246
CODff mg/l 82.3 82.8 75.6 80.2 34.1 31.9 28.6 31.5 69.7 63.0 63.0 65.2
BOD5 mg/l 88.8 n.a. n.a. 88.8 26.8 22.5 n.a. 24.6 42.3 86.0 n.a. 64.1
BOD10 mg/l 108 n.a. n.a. 108 32.4 28.2 n.a. 30.3 28.2 101 n.a. 64.6
kBOD mg/l 0.39044451 n.a. n.a. 0.39044451 0.26409196 0.33862602 n.a. 0.30135899 2.3541205 0.38187479 n.a. 1.367997645
BODtot mg/l 106.23481 n.a. n.a. 106.23481 38.506376 27.67615 n.a. 33.091263 38.994213 103.7957 n.a. 71.3949565
TPtot mg/l 3.99 3.72 3.65 3.79 1.78 1.74 1.84 1.79 3.77 3.9 3.67 3.78
TPff mg/l 0.058 0.054 0.055 0.056 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05
PO4 mg/l 3.41 3.17 3.08 3.22 1.33 1.35 1.35 1.34 2.88 2.80 2.79 2.82
TNtot mg/l 39.3 47.6 41.6 42.8 20.8 20.1 21.7 20.9 40.1 37.3 39.5 39.0
TNff mg/l 30.4 27.8 30.6 29.6 18.2 19.8 18.3 18.8 30.7 32.3 28.3 30.4
TSS g/l 0.073 0.070 n.a. 0.071 0.047 0.076 n.a. 0.061 0.051 0.046 n.a. 0.048
VSS g/l 0.212 0.22 n.a. 0.216 0.172 0.136 n.a. 0.154 0.232 0.244 n.a. 0.238
NH4 mg/l 23.7 22.6 21.9 22.7 10.5 9.23 10.1 9.9 26.1 25.5 25.9 25.8
NO3 mg/l 1.21 1.3 1.03 1.18 1.81 1.71 1.69 1.74 0.414 0.375 0.412 0.400
pH
8.16 8.14 8.12 8.14 8.02 8.03 8.05 8.03 7.82 7.85 7.84 7.84
Kj-N mg/l 38.09 46.3 40.57 41.65 18.99 18.39 20.01 19.13 39.686 36.925 39.088 38.566
bCOD mg/l 124.982129 n.a. n.a. 124.982129 45.3016188 32.5601765 n.a. 38.9308977 45.8755447 122.112588 n.a. 83.9940665
Roeselare 07/04/2014 Roeselare 14/04/2014
V PST m³ 1365 1365
HRT h 1.870 2.007
Q m³/h 730 680
Analysed Mean Analysed Mean
Bef
ore
pri
mar
y se
dim
enta
tio
n t
ank
CODtot mg/l 209 202 205 205 234 218 210 221
CODff mg/l 62.6 56.0 49.8 56.1 59.6 60.5 56.8 59.0
BOD10 mg/l 69.0 70.5 n.a. 69.7 71.9 69.0 n.a. 70.4
BOD5 mg/l 56.4 62.0 n.a. 59.2 60.6 56.4 n.a. 58.5
kBOD mg/l 0.35904437 0.37199433 n.a. 0.36551935 0.33194649 0.32485457 n.a. 0.32840053
BODtot mg/l 70.714304 70.018794 n.a. 70.366549 75.434986 71.467552 n.a. 73.451269
TPtot mg/l 3.29 3.24 3.20 3.24 3.65 3.61 3.50 3.59
TPff mg/l <0.05 <0.05 <0.05 <0.05 0.071 0.059 0.061 0.064
PO4 mg/l 2.44 2.52 2.49 2.48 2.84 2.76 2.71 2.77
TNtot mg/l 31.5 31.1 31.6 31.4 32.1 30.2 27.5 29.9
TNff mg/l 26.3 24 27.3 25.9 21.8 21.5 21.2 21.5
TSS g/l 0.059 0.058 n.a. 0.058 0.048 0.042 n.a. 0.045
VSS g/l 0.252 0.204 n.a. 0.228 0.504 0.188 n.a. 0.346
NH4 mg/l 21.5 21.1 21.4 21.3 21.6 21.4 21.4 21.5
NO3 mg/l 0.415 0.413 0.417 0.415 0.534 0.53 0.535 0.533
pH
7.97 7.96 7.96 7.96 8.11 8.1 8.08 8.10
Kj-N mg/l 31.085 30.687 31.183 30.985 31.566 29.670 26.965 29.400
bCOD mg/l 83.1932988 82.3750518 n.a. 82.7841753 88.7470424 84.0794729 n.a. 86.4132577
AS TSS g/l 3.688 3.556 3.580 3.608 4.380 4.356 4.264 4.333
VSS g/l 2.258 2.124 n.a. 2.191 3.144 2.992 n.a. 3.068
Effl
uen
t W
WTP
CODtot mg/l 38.1 35.8 34.8 36.2 32.9 29.7 29.0 30.5
CODff mg/l 32.2 28.9 29.0 30.0 29.8 26.0 28.6 28.1
BOD5 mg/l 4.8 2.0 n.a. 3.4 4.5 3.1 n.a. 3.8
BOD10 mg/l 7.6 3.9 n.a. 5.7 7.6 5.6 n.a. 6.6
kBOD mg/l 0.28715175 0.2873025 n.a. 0.28722713 0.2871981 0.28725971 n.a. 0.28722891
BODtot mg/l 8.3237956 8.3059109 n.a. 8.31485325 8.3210078 8.3190474 n.a. 8.3200276
Roeselare 14/04/2014
Analysed Mean
Aft
er p
rim
ary
sed
imen
tati
on
tan
k
CODtot mg/l 253 306 263 274
CODff mg/l 68.5 70.7 67.5 68.9
BOD5 mg/l 86.0 81.7 n.a. 83.8
BOD10 mg/l 103 95.8 n.a. 99.4
kBOD mg/l 0.4174338 0.41341729 n.a. 0.415425545
BODtot mg/l 101.83377 95.517398 n.a. 98.675584
TPtot mg/l 4.3 4.17 4.13 4.20
TPff mg/l 0.174 0.182 0.201 0.186
PO4 mg/l 3.23 3.14 3.17 3.18
TNtot mg/l 34.8 33.6 35.0 34.5
TNff mg/l 22.5 21.8 23.8 22.7
TSS g/l 0.040 0.035 n.a. 0.038
VSS g/l 0.180 0.172 n.a. 0.176
NH4 mg/l 26.8 26.1 26.6 26.5
NO3 mg/l 0.419 0.382 0.337 0.379
pH
7.95 7.93 7.93 7.94
Kj-N mg/l 34.381 33.218 34.663 34.087
bCOD mg/l 119.8044353 112.3734094 n.a. 116.0889224
Eindhoven 06/05/2014
V PST m³ 8759 8759 8759
HRT h 7.638 7.046 5.304
Q m³/h 1146.756 1243.107 1651.503
Sampling time 08:00 - 08:30 08:30 - 09:00 09:00 - 09:30
Analysed Mean Analysed Mean Analysed Mean
Bef
ore
pri
mar
y se
dim
enta
tio
n t
ank
CODtot mg/l 499 503 508 503 595 528 505 543 482 456 450 463
CODff mg/l 175 160 155 163 173 177 175 175 149 143 145 146
BOD10 mg/l 19.7 n.a. n.a. 19.7 228 n.a. n.a. 228 253 259 n.a. 256
BOD5 mg/l 118 n.a. n.a. 118 203 n.a. n.a. 203 214 222 n.a. 218
kBOD mg/l 1.7093218 n.a. n.a. 1.7093218 6.1739227 n.a. n.a. 6.1739227 0.52236195 0.50350554 n.a. 0.512933745
BODtot mg/l 121.00868 n.a. n.a. 121.00868 231.06411 n.a. n.a. 231.06411 229.89449 238.07895 n.a. 233.98672
TPtot mg/l 8.31 8.00 7.91 8.07 7.74 7.59 7.65 7.66 8.46 7.42 7.83 7.90
TPff mg/l 0.345 0.316 0.324 0.328 0.672 0.676 0.678 0.675 0.387 0.37 0.361 0.373
PO4 mg/l 6.28 6.15 6.08 6.17 6.11 6.14 6.25 6.17 6.18 5.97 5.88 6.01
TNtot mg/l 51.7 56.3 56.5 54.8 38.9 46.5 50.6 45.3 56.0 53.3 42.0 50.4
TNff mg/l 22.3 36.8 35.6 31.6 28.3 32.8 31.7 30.9 36.6 37.8 38.5 37.6
TSS g/l 0.139 0.143 n.a. 0.141 0.132 0.144 n.a. 0.138 0.143 0.129 n.a. 0.136
VSS g/l 0.276 0.232 n.a. 0.254 0.288 0.264 n.a. 0.276 0.300 0.224 n.a. 0.262
NH4 mg/l 40.6 40.9 41.6 41.0 44.0 42.2 39.5 41.9 39.4 38.8 38.1 38.8
NO3 mg/l 0.520 0.614 0.595 0.576 0.603 0.575 0.552 0.577 0.553 2.190 2.170 1.638
pH
7.49 7.47 7.45 7.47 7.44 7.48 7.48 7.47 7.63 7.64 7.65 7.64
Kj-N mg/l 51.180 55.686 55.905 54.257 38.297 45.925 50.048 44.757 55.447 51.11 39.83 48.80
bCOD mg/l 142.363153 n.a. n.a. 142.363153 271.840129 n.a. n.a. 271.840129 270.464106 280.092882 n.a. 275.278494
AS TSS g/l 4.252 4.436 4.316 4.335 4.252 4.436 4.316 4.335 4.252 4.436 4.316 4.335
VSS g/l n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a.
Effl
uen
t
WW
TP CODtot mg/l 40.5 35.2 n.a. 37.8 40.5 35.2 n.a. 37.8 40.5 35.2 n.a. 37.8
CODff mg/l 28.4 24.6 n.a. 26.5 28.4 24.6 n.a. 26.5 28.4 24.6 n.a. 26.5
Eindhoven 06/05/2014
Sampling time 15:00 - 15:30 15:30 - 16:00 16:00 - 16:30
Analysed Mean Analysed Mean Analysed Mean
Aft
er p
rim
ary
sed
imen
tati
on
tan
k
CODtot mg/l 440 388 388 405 377 380 382 380 383 383 381 382
CODff mg/l 182 187 181 183 188 184 186 185 194 192 190 192
BOD5 mg/l -5.6 n.a. n.a. -5.6 169 n.a. n.a. 169 205 197 n.a. 201
BOD10 mg/l -53.5 n.a. n.a. -53.50 138 n.a. n.a. 138 234 222 n.a. 228
kBOD mg/l 0.1518065 n.a. n.a. 0.1518065 0.9408378 n.a. n.a. 0.9408378 0.6460473 0.6470038 n.a. 0.6465256
BODtot mg/l 16.637156 n.a. n.a. 16.637156 169.86955 n.a. n.a. 169.86955 210.34478 204.1871 n.a. 207.26594
TPtot mg/l 9.93 10.4 10.7 10.3 10.5 10.2 10.5 10.4 11.4 10.7 10.4 10.8
TPff mg/l 0.329 0.334 0.336 0.333 0.293 0.278 0.291 0.287 0.397 0.388 0.393 0.393
PO4 mg/l 9.43 9.11 9.35 9.30 9.11 8.89 9.23 9.08 10.10 9.45 8.97 9.51
TNtot mg/l 55.2 52.7 56.4 54.8 71.7 52.5 33.9 52.7 43.2 56.5 44.8 48.2
TNff mg/l 37.4 38.7 38.7 38.3 33.1 40.3 39.9 37.8 47.2 44.8 48.1 46.7
TSS g/l 0.097 0.099 n.a. 0.098 0.09 0.09 n.a. 0.09 0.096 0.092 n.a. 0.094
VSS g/l 0.248 0.252 n.a. 0.250 0.224 0.208 n.a. 0.220 0.292 0.272 n.a. 0.282
NH4 mg/l 26.9 35.6 38.8 33.8 44.5 45.5 43.3 44.4 45.2 46 44.4 45.2
NO3 mg/l 0.483 0.580 0.494 0.519 0.498 0.532 0.503 0.511 0.503 0.567 0.513 0.528
pH
7.38 7.41 7.42 7.40 7.38 7.42 7.44 7.41 7.53 7.56 7.58 7.56
Kj-N mg/l 54.717 52.120 55.906 54.248 71.202 51.968 33.397 52.189 42.697 55.933 44.287 47.639
bCOD mg/l 19.573125 n.a. n.a. 19.573125 199.846529 n.a. n.a. 199.846529 247.464447 240.220118 n.a. 243.842282
Eindhoven 06/05/2014
V PST m³ 8759 8759 8759
HRT h 4.457 4.334 4.595
Q m³/h 1965.229 2021.167 1906.316
Sampling time 09:30 - 10:00 10:00 - 10:30 10:30 - 11:00
Analysed Mean Analysed Mean Analysed Mean
Bef
ore
pri
mar
y se
dim
enta
tio
n t
ank
CODtot mg/l 454 456 454 455 532 546 519 532 608 678 600 629
CODff mg/l 155 159 155 156 176 176 172 175 215 216 215 215
BOD10 mg/l 273 276 n.a. 275 n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a.
BOD5 mg/l 234 234 n.a. 234 240 250 n.a. 245 280 220 n.a. 250
kBOD mg/l 0.5006319 0.48342813 n.a. 0.49203002 0.43275616 0.38306659 n.a. 0.40791138 0.53488294 0.57786035 n.a. 0.55637165
BODtot mg/l 250.18534 251.70083 n.a. 250.943085 271.07065 293.5992 n.a. 282.334925 299.13208 226.7712 n.a. 262.95164
TPtot mg/l 9.34 8.56 8.38 8.76 9.57 9.37 9.23 9.39 10.2 9.85 9.71 9.92
TPff mg/l 0.397 0.392 0.393 0.394 0.599 0.588 0.586 0.051 0.668 0.655 0.655 0.659
PO4 mg/l 6.97 6.74 6.73 6.81 8.24 7.42 7.08 7.58 7.33 7.37 7.41 7.37
TNtot mg/l 56 54.4 47.9 52.8 59.9 67.6 57.5 61.7 61.8 61.2 59.3 60.8
TNff mg/l 40.4 41.2 39.3 40.3 46.5 44.0 41.0 43.8 41.4 43.7 44.4 43.2
TSS g/l 0.139 0.150 n.a. 0.145 0.163 0.167 n.a. 0.165 0.185 0.202 n.a. 0.1935
VSS g/l 0.316 0.268 n.a. 0.220 0.328 0.288 n.a. 0.230 0.364 0.32 n.a. 0.238
NH4 mg/l 42.4 38.2 42.7 41.1 49.6 47.4 44.0 47.0 45.8 46.4 43.8 45.3
NO3 mg/l 0.615 0.629 0.601 0.615 0.615 0.629 0.601 0.615 0.67 0.738 0.726 0.711
pH
7.69 7.70 7.69 7.69 7.32 7.3 7.33 7.32 7.07 7.07 7.12 7.09
Kj-N mg/l 55.385 53.771 47.299 52.152 59.285 66.971 56.899 61.052 61.13 60.462 58.574 60.055
bCOD mg/l 294.335694 296.1186234 n.a. 295.227159 318.906647 345.410823 n.a. 332.158735 351.920094 266.789647 n.a. 309.354871
AS TSS g/l 4.252 4.436 4.316 4.335 4.252 4.436 4.316 4.335 4.252 4.436 4.316 4.335
VSS g/l n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a.
Effl
uen
t
WW
TP CODtot mg/l 40.5 35.2 n.a. 37.85 40.5 35.2 n.a. 37.85 40.5 35.2 n.a. 37.85
CODff mg/l 28.4 24.6 n.a. 26.50 28.4 24.6 n.a. 26.50 28.4 24.6 n.a. 26.50
Eindhoven 06/05/2014
Sampling time 16:30 - 17:00 17:00 - 17:30 17:30 - 18:00
Analysed Mean Analysed Mean Analysed Mean
Aft
er p
rim
ary
sed
imen
tati
on
tan
k
CODtot mg/l 454 456 454 455 433 389 394 405 383 379 380 381
CODff mg/l 193 189 189 190 186 190 190 189 195 198 192 195
BOD5 mg/l 197 104 n.a. 150 0 160 n.a. 80 170 140 n.a. 155
BOD10 mg/l 225 28.1 n.a. 126.55 n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a.
kBOD mg/l 0.6103454 1.723504 n.a. 1.16692484 2.529031 0.5264310 n.a. 1.52773123 0.4402495 0.5304250 n.a. 0.4853373
BODtot mg/l 205.98796 112.22328 n.a. 159.10562 24.460154 176.00076 n.a. 100.230457 191.63059 159.48253 n.a. 175.55656
TPtot mg/l 10.8 10.7 10.5 10.7 10.9 10.0 10.2 10.4 11.2 10.5 10.2 10.6
TPff mg/l 0.460 0.456 0.446 0.454 0.462 0.447 0.447 0.452 0.377 0.367 0.361 0.368
PO4 mg/l 9.20 9.04 8.76 9.00 9.49 9.03 9.43 9.32 9.49 9.25 8.87 9.20
TNtot mg/l 52.9 68.6 37.1 52.9 60.3 58.4 56.5 58.4 61.2 57.8 58.8 59.3
TNff mg/l 44.8 45.9 46.7 45.8 43.0 48.4 46.8 46.1 46.2 44.1 48.3 46.2
TSS g/l 0.092 0.097 n.a. 0.094 0.091 0.092 n.a. 0.0915 0.091 0.092 n.a. 0.091
VSS g/l 0.252 0.220 n.a. 0.236 0.240 0.220 n.a. 0.230 0.248 0.248 n.a. 0.248
NH4 mg/l 47 45.8 47.6 46.8 46.6 48.4 45.8 46.9 49.6 49 47.6 48.7
NO3 mg/l 0.5 0.503 0.561 0.521 0.502 0.501 0.470 0.491 0.488 0.507 0.516 0.504
pH
7.57 7.58 7.58 7.58 7.32 7.30 7.30 7.31 7.31 7.27 7.28 7.29
Kj-N mg/l 52.400 68.097 36.539 52.345 59.798 57.899 56.030 57.909 60.712 57.293 58.284 58.763
bCOD mg/l 242.338777 132.027388 n.a. 187.183082 28.7766518 207.059718 n.a. 117.918185 225.447753 187.626506 n.a. 206.537129
Eindhoven 06/05/2014
V PST m³ 8759
HRT h 4.294
Q m³/h 2039.971
Sampling time 11:00 - 11:30 18:00 - 18:30
Analysed Mean Analysed Mean
Bef
ore
pri
mar
y se
dim
enta
tio
n t
ank
CODtot mg/l 411 409 400 407
Aft
er p
rim
ary
sed
imen
tati
on
tan
k
CODtot mg/l 376 380 371 376
CODff mg/l 220 216 209 215 CODff mg/l 182 182 182 182
BOD10 mg/l n.a. n.a. n.a. n.a. BOD5 mg/l 0 140 n.a. 70
BOD5 mg/l 360 300 n.a. 330 BOD10 mg/l n.a. n.a. n.a. n.a.
kBOD mg/l 0.5622078 0.46261147 n.a. 0.51240964 kBOD mg/l 0.14381995 0.40092948 n.a. 0.272374715
BODtot mg/l 384.3159 335.21603 n.a. 359.765965 BODtot mg/l 15.902383 163.92226 n.a. 89.9123215
TPtot mg/l 10.7 10.8 10.6 10.7 TPtot mg/l 10.4 9.82 9.31 9.84
TPff mg/l 0.374 0.370 0.370 0.371 TPff mg/l 0.26 0.261 0.258 0.260
PO4 mg/l 7.91 7.56 7.83 7.77 PO4 mg/l 9.31 9.1 8.87 9.09
TNtot mg/l 64.6 66.9 68.5 66. 7 TNtot mg/l 56.7 61 63.6 60.4
TNff mg/l 36.4 38.8 39.6 38.3 TNff mg/l 42.2 44.9 47.3 44.8
TSS g/l 0.23 0.284 n.a. 0.257 TSS g/l 0.106 0.108 n.a. 0.107
VSS g/l 0.42 0.404 n.a. 0.614 VSS g/l 0.204 0.212 n.a. 0.208
NH4 mg/l 47.2 44.2 44.0 45.1 NH4 mg/l 48.8 47.2 46.6 47.5
NO3 mg/l 0.727 0.65 0.685 0.687 NO3 mg/l 0.495 0.520 0.493 0.503
pH
7.04 6.97 6.96 6.99 pH
7.23 7.19 7.2 7.21
Kj-N mg/l 63.873 66.25 67.815 65.979 Kj-N mg/l 56.205 60.48 63.107 59.931
bCOD mg/l 452.136353 394.3718 n.a. 423.254077 bCOD mg/l 18.7086859 192.849718 n.a. 105.779202
AS TSS g/l 4.252 4.436 4.316 4.335
VSS g/l n.a. n.a. n.a. n.a.
Effl
uen
t
WW
TP CODtot mg/l 40.5 35.2 n.a. 37.85
CODff mg/l 28.4 24.6 n.a. 26.50
Appendix 2: Influent COD fractionation
Roeselare 17/02/2014 Roeselare 24/02/2014 Roeselare 03/03/2014
Calculated Mean Calculated Mean Calculated Mean
Bef
ore
pri
mar
y se
dim
enta
tio
n t
ank
SI mg/l 21.06 n.a. n.a. 21.06 18.27 18.81 17.91 18.33 13.68 14.67 14.13 14.16
SI % 7.86 n.a. n.a. 7.86 9.57 10.81 10.41 10.24 26.21 27.22 27.12 26.85
SS mg/l 150.94 n.a. n.a. 150.94 82.73 85.19 84.09 84.00 5.12 2.63 2.27 3.34
SS % 56.32 n.a. n.a. 56.32 43.31 48.96 48.89 46.93 9.81 4.88 4.36 6.33
SA mg/l 74.56 n.a. n.a. 74.56 40.87 42.08 41.54 41.50 2.53 1.30 1.12 1.65
SF mg/l 76.38 n.a. n.a. 76.38 41.86 43.11 42.55 42.51 2.59 1.33 1.15 1.69
XS mg/l -95.98 n.a. n.a. -95.98 -20.81 -21.18 n.a. -21.04 n.a. n.a. n.a. n.a.
XS % -35.81 n.a. n.a. -35.81 -10.89 -12.17 0 -11.75 n.a. n.a. n.a. n.a.
XI mg/l 191.98 n.a. n.a. 191.98 110.81 91.18 n.a. 97.70 n.a. n.a. n.a. n.a.
XI % 71.63 n.a. n.a. 71.63 58.01 52.40 0 54.58 n.a. n.a. n.a. n.a.
SNH4 mg/l 9.07 n.a. n.a. 9.07 10.7 9.98 11.4 10.69 2.42 2.49 2.55 2.49
SNO3 mg/l 5.11 n.a. n.a. 5.11 3.16 3.15 3.12 3.14 2.32 2.19 2.17 2.23
SPO4 mg/l 4.62 n.a. n.a. 4.62 1.74 1.74 1.71 1.73 0.72 0.91 0.70 0.78
Aft
er p
rim
ary
sed
imen
tati
on
tan
k
SI mg/l n.a. n.a. n.a. n.a. 18.27 18.81 17.91 18.33 13.68 14.67 14.13 14.16
SI % n.a. n.a. n.a. n.a. 11.49 11.83 10.12 11.11 42.75 46.72 45.29 44.90
SS mg/l n.a. n.a. n.a. n.a. 14.53 13.89 13.89 14.10 7.82 1.53 3.97 4.44
SS % n.a. n.a. n.a. n.a. 9.14 8.74 7.85 8.55 24.44 4.87 12.72 14.08
SA mg/l n.a. n.a. n.a. n.a. 7.18 6.86 6.86 6.97 3.86 0.76 1.96 2.19
SF mg/l n.a. n.a. n.a. n.a. 7.35 7.03 7.03 7.14 3.96 0.77 2.01 2.25
XS mg/l n.a. n.a. n.a. n.a. 18.94 25.93 n.a. 22.44 n.a. n.a. n.a. n.a.
XS % n.a. n.a. n.a. n.a. 11.91 16.31 n.a. 13.60 n.a. n.a. n.a. n.a.
XI mg/l n.a. n.a. n.a. n.a. 107.26 100.37 n.a. 103.81 n.a. n.a. n.a. n.a.
XI % n.a. n.a. n.a. n.a. 67.46 63.13 n.a. 62.92 n.a. n.a. n.a. n.a.
SNH4 mg/l n.a. n.a. n.a. n.a. 8.81 8.63 9.46 8.97 2.46 2.38 2.44 2.43
SNO3 mg/l n.a. n.a. n.a. n.a. 2.80 3.00 2.91 2.90 2.06 1.97 2.00 2.01
SPO4 mg/l n.a. n.a. n.a. n.a. 1.5 1.4 1.53 1.48 0.61 0.62 0.61 0.61
XAUT mg/l 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1
XPAO mg/l 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1
XH mg/l 0 0 0 0 0 0 0 0 0 0 0 0
XPHA mg/l 0 0 0 0 0 0 0 0 0 0 0 0
Roeselare 12/03/2014
Sampling time 09:55 - 10:55 10:55 - 11:55 11:55 - 12:55
Calculated Mean Calculated Mean Calculated Mean
Bef
ore
pri
mar
y se
dim
enta
tio
n t
ank
SI mg/l 22.41 18.27 17.28 19.32 22.41 18.27 17.28 19.32 22.41 18.27 17.28 19.32
SI % 10.83 9.57 8.86 9.77 8.42 7.08 6.31 7.26 8.00 6.69 6.24 6.98
SS mg/l 45.39 42.83 42.12 43.45 67.39 63.63 60.62 63.88 79.59 80.93 76.42 78.98
SS % 21.93 22.42 21.60 21.98 25.33 24.66 22.12 24.02 28.43 29.64 27.59 28.55
SA mg/l 22.42 21.16 20.81 21.46 33.29 31.43 29.95 31.56 39.32 39.98 37.75 39.02
SF mg/l 22.97 21.67 21.31 21.98 34.10 32.20 30.67 32.32 40.27 40.95 38.67 39.96
XS mg/l 59.08 n.a. n.a. 61.02 87.37 n.a. n.a. 90.88 119.87 n.a. n.a. 120.48
XS % 28.54 n.a. n.a. 30.87 32.85 n.a. n.a. 34.17 42.81 n.a. n.a. 43.55
XI mg/l 80.12 129.90 n.a. 73.88 88.83 176.10 n.a. 91.92 58.13 173.80 n.a. 57.88
XI % 38.70 68.01 0.00 37.37 33.39 68.26 0.00 34.56 20.76 63.66 0.00 20.92
SNH4 mg/l 19.50 19.20 19.50 19.40 22.60 21.50 21.50 21.87 24.60 23.20 23.60 23.80
SNO3 mg/l 1.25 1.14 1.27 1.22 1.16 1.09 0.90 1.05 1.06 0.95 0.91 0.97
SPO4 mg/l 2.34 2.36 2.46 2.39 2.96 2.98 2.88 2.94 3.81 3.49 3.59 3.63
Sampling time 12:05 - 13:05 13:05 - 14:05 14:05 - 15:05
Aft
er p
rim
ary
sed
imen
tati
on
tan
k
SI mg/l 22.41 18.27 17.28 19.32 22.41 18.27 17.28 19.32 22.41 18.27 17.28 19.32
SI % 10.67 8.50 7.20 8.72 8.36 7.49 6.65 7.51 8.27 6.77 6.52 7.19
SS mg/l 37.79 39.73 39.12 38.88 37.89 45.93 42.12 41.98 52.09 50.73 52.42 51.75
SS % 18.00 18.48 16.30 17.54 14.14 18.82 16.20 16.31 19.22 18.79 19.78 19.26
SA mg/l 18.67 19.63 19.33 19.21 18.72 22.69 20.81 20.74 25.73 25.06 25.90 25.56
SF mg/l 19.12 20.10 19.79 19.67 19.17 23.24 21.31 21.24 26.36 25.67 26.52 26.18
XS mg/l 55.72 -39.73 n.a. 54.63 58.93 -45.93 n.a. 54.84 61.70 -50.73 n.a. 62.05
XS % 26.53 -18.48 n.a. 24.64 21.99 -18.82 n.a. 21.31 22.77 -18.79 n.a. 23.09
XI mg/l 94.08 196.73 n.a. 108.84 148.77 225.73 n.a. 141.19 134.80 251.73 n.a. 135.55
XI % 44.80 91.50 0.00 49.10 55.51 92.51 0.00 54.87 49.74 93.23 0.00 50.45
SNH4 mg/l 20.30 20.20 20.50 20.33 21.70 20.10 20.70 20.83 24.30 23.20 23.10 23.53
SNO3 mg/l 1.31 1.32 1.20 1.28 1.35 1.32 1.09 1.25 1.31 1.22 1.18 1.24
SPO4 mg/l 2.29 2.10 2.17 2.19 2.69 2.64 2.67 2.67 3.26 3.27 3.09 3.21
XAUT mg/l 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1
XPAO mg/l 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1
XH mg/l 0 0 0 0 0 0 0 0 0 0 0 0
XPHA mg/l 0 0 0 0 0 0 0 0 0 0 0 0
Roeselare 12/03/2014 Roeselare 24/03/2014
Sampling time 12:55 - 13:55 13:55 - 14:55
Calculated Mean Calculated Mean Calculated Mean
Bef
ore
pri
mar
y se
dim
enta
tio
n t
ank
SI mg/l 22.41 18.27 17.28 19.32 22.41 18.27 17.28 19.32 19.17 14.31 15.21 16.23
SI % 8.12 6.41 6.33 6.95 7.73 6.26 5.88 6.62 9.78 7.38 7.72 8.29
SS mg/l 107.59 101.73 102.72 104.01 110.59 110.73 108.72 110.01 35.03 35.19 34.49 34.90
SS % 38.98 35.69 37.63 37.41 38.13 37.92 36.98 37.68 17.87 18.14 17.51 17.84
SA mg/l 53.15 50.25 50.74 51.38 54.63 54.70 53.71 54.35 17.30 17.38 17.04 17.24
SF mg/l 54.44 51.48 51.98 52.63 55.96 56.03 55.01 55.67 17.73 17.81 17.45 17.66
XS mg/l 15.15 n.a. n.a. 18.73 101.92 n.a. n.a. 102.49 24.34 23.92 n.a. 24.34
XS % 5.49 n.a. n.a. 6.74 35.14 n.a. n.a. 35.10 12.42 12.33 n.a. 12.44
XI mg/l 130.85 165.00 n.a. 135.94 55.08 163.00 n.a. 60.17 117.46 120.58 n.a. 120.19
XI % 47.41 57.89 n.a. 48.90 18.99 55.82 n.a. 20.61 59.93 62.15 n.a. 61.43
SNH4 mg/l 25.30 24.90 25.30 25.17 24.70 24.20 24.30 24.40 13.50 13.10 13.20 13.27
SNO3 mg/l 1.27 1.13 1.01 1.14 1.01 0.96 0.98 0.98 1.87 1.85 1.84 1.85
SPO4 mg/l 4.54 4.36 4.09 4.33 3.32 3.28 3.27 3.29 2.57 2.50 2.59 2.55
Sampling time 14:05 - 15:05
Aft
er p
rim
ary
sed
imen
tati
on
tan
k
SI mg/l 22.41 18.27 17.28 19.32 19.17 14.31 15.21 16.23
SI % 7.95 6.32 6.19 6.82 13.22 9.48 10.28 10.97
SS mg/l 59.89 64.53 58.32 60.91 14.93 17.59 13.39 15.30
SS % 21.24 22.33 20.90 21.50 10.30 11.65 9.05 10.34
SA mg/l 29.59 31.88 28.81 30.09 7.38 8.69 6.61 7.56
SF mg/l 30.30 32.65 29.51 30.82 7.55 8.90 6.78 7.74
XS mg/l 65.09 -64.53 n.a. 64.07 30.37 14.97 -13.39 23.63
XS % 23.08 -22.33 n.a. 22.61 20.95 9.91 -9.05 15.96
XI mg/l 134.61 270.73 n.a. 139.03 80.53 104.13 132.79 92.84
XI % 47.73 93.68 n.a. 49.07 55.54 68.96 89.72 62.73
SNH4 mg/l 23.70 22.60 21.90 22.73 10.50 9.23 10.10 9.94
SNO3 mg/l 1.21 1.30 1.03 1.18 1.81 1.71 1.69 1.74
SPO4 mg/l 3.41 3.17 3.08 3.22 1.33 1.35 1.35 1.34
XAUT mg/l 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1
XPAO mg/l 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1
XH mg/l 0 0 0 0 0 0 0 0
XPHA mg/l 0 0 0 0 0 0 0 0
Roeselare 07/04/2014 Roeselare 14/04/2014
Calculated Mean Calculated Mean
Bef
ore
pri
mar
y se
dim
enta
tio
n t
ank
SI mg/l 28.98 26.01 26.10 27.03 26.82 23.40 25.74 25.32
SI % 13.87 12.88 12.73 13.16 11.46 10.73 12.26 11.47
SS mg/l 33.62 29.99 23.70 29.10 32.78 37.10 31.06 33.65
SS % 16.09 14.85 11.56 14.17 14.01 17.02 14.79 15.25
SA mg/l 16.61 14.82 11.71 14.38 16.19 18.33 15.34 16.62
SF mg/l 17.01 15.17 11.99 14.73 16.59 18.77 15.72 17.03
XS mg/l 49.57 52.39 n.a. 53.68 55.97 46.98 n.a. 52.77
XS % 23.72 25.93 n.a. 26.14 23.92 21.55 n.a. 23.91
XI mg/l 96.83 93.61 n.a. 95.52 118.43 110.52 n.a. 108.93
XI % 46.33 46.34 n.a. 46.52 50.61 50.70 n.a. 49.37
SNH4 mg/l 21.50 21.10 21.40 21.33 21.60 21.40 21.40 21.47
SNO3 mg/l 0.42 0.41 0.42 0.42 0.53 0.53 0.54 0.53
SPO4 mg/l 2.44 2.52 2.49 2.48 2.84 2.76 2.71 2.77
Aft
er p
rim
ary
sed
imen
tati
on
tan
k
SI mg/l 28.98 26.01 26.10 27.03 26.82 23.40 25.74 25.32
SI % 11.64 10.57 10.74 10.99 10.60 7.65 9.79 9.24
SS mg/l 40.72 36.99 36.90 38.20 41.68 47.30 41.76 43.58
SS % 16.35 15.04 15.19 15.53 16.47 15.46 15.88 15.91
SA mg/l 20.12 18.27 18.23 18.87 20.59 23.37 20.63 21.53
SF mg/l 20.60 18.72 18.67 19.33 21.09 23.93 21.13 22.05
XS mg/l 5.16 85.12 -36.90 45.79 78.12 65.07 -41.76 72.51
XS % 2.07 34.60 -15.19 18.61 30.88 21.27 -15.88 26.46
XI mg/l 174.14 97.88 216.90 134.98 106.38 170.23 237.26 132.59
XI % 69.94 39.79 89.26 54.87 42.05 55.63 90.21 48.39
SNH4 mg/l 26.10 25.50 25.90 25.83 26.80 26.10 26.60 26.50
SNO3 mg/l 0.41 0.38 0.41 0.40 0.42 0.38 0.34 0.38
SPO4 mg/l 2.88 2.80 2.79 2.82 3.23 3.14 3.17 3.18
XAUT mg/l 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1
XPAO mg/l 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1
XH mg/l 0 0 0 0 0 0 0 0
XPHA mg/l 0 0 0 0 0 0 0 0
Eindhoven 06/05/2014
Sampling time 08:00 - 08:30 08:30 - 09:00 09:00 - 09:30
Calculated Mean Calculated Mean Calculated Mean
Bef
ore
pri
mar
y se
dim
enta
tio
n t
ank
SI mg/l 25.56 22.14 n.a. 23.85 25.56 22.14 n.a. 23.85 25.56 22.14 n.a. 23.85
SI % 5.12 4.40 n.a. 4.74 4.30 4.19 n.a. 4.39 5.30 4.86 n.a. 5.15
SS mg/l 149.44 137.86 155.00 139.48 147.44 154.86 175.00 151.15 357.44 360.86 381.00 358.48
SS % 29.95 27.41 30.51 27.71 24.78 29.33 34.65 27.85 74.16 79.14 84.67 77.48
SA mg/l 73.82 68.10 76.57 72.83 72.84 76.50 86.45 74.67 176.58 178.26 188.21 177.09
SF mg/l 75.62 69.76 78.43 74.60 74.60 78.36 88.55 76.48 180.86 182.60 192.79 181.39
XS mg/l -7.08 -137.86 n.a. 2.88 124.40 -154.86 n.a. 120.69 -86.98 -80.77 n.a. -83.20
XS % -1.42 -27.41 n.a. 0.57 20.91 -29.33 n.a. 22.24 -18.04 -17.71 n.a. -17.98
XI mg/l 331.08 480.86 n.a. 337.12 297.60 505.86 n.a. 246.98 185.98 153.77 n.a. 163.54
XI % 66.35 95.60 n.a. 66.98 50.02 95.81 n.a. 45.51 38.58 33.72 n.a. 35.35
SNH4 mg/l 40.60 40.90 41.60 41.03 44.00 42.20 39.50 41.90 39.40 38.80 38.10 38.77
SNO3 mg/l 0.52 0.61 0.60 0.58 0.60 0.58 0.55 0.58 0.55 2.19 2.17 1.64
SPO4 mg/l 6.28 6.15 6.08 6.17 6.11 6.14 6.25 6.17 6.18 5.97 5.88 6.01
Sampling time 15:00 - 15:30 15:30 - 16:00 16:00 - 16:30
Aft
er p
rim
ary
sed
imen
tati
on
tan
k
SI mg/l 25.56 22.14 n.a. 15.90 25.56 22.14 n.a. 15.90 25.56 22.14 n.a. 23.85
SI % 5.81 5.71 n.a. 3.92 6.78 5.83 n.a. 4.19 6.67 5.78 n.a. 6.24
SS mg/l 156.44 164.86 181.00 167.43 162.44 161.86 186.00 170.10 168.44 169.86 190.00 176.10
SS % 35.55 42.49 46.65 41.31 43.09 42.59 48.69 44.80 43.98 44.35 49.87 46.06
SA mg/l 77.28 81.44 89.41 82.71 80.25 79.96 91.88 84.03 83.21 83.91 93.86 86.99
SF mg/l 79.16 83.42 91.59 84.72 82.19 81.90 94.12 86.07 85.23 85.95 96.14 89.11
XS mg/l -136.87 -164.86 n.a. -150.86 37.41 -161.86 n.a. -62.23 79.02 70.36 -190.00 67.74
XS % -31.11 -42.49 n.a. -37.22 9.92 -42.59 n.a. -16.39 20.63 18.37 -49.87 17.72
XI mg/l 394.87 365.86 n.a. 380.36 151.59 357.86 n.a. 254.73 109.98 120.64 381.00 114.64
XI % 89.74 94.29 n.a. 93.84 40.21 94.17 n.a. 67.09 28.71 31.50 100.00 29.98
SNH4 mg/l 26.90 35.60 38.80 33.77 44.50 45.50 43.30 44.43 45.20 46.00 44.40 45.20
SNO3 mg/l 0.48 0.58 0.49 0.52 0.50 0.53 0.50 0.51 0.50 0.57 0.51 0.53
SPO4 mg/l 9.43 9.11 9.35 9.30 9.11 8.89 9.23 9.08 10.10 9.45 8.97 9.51
XAUT mg/l 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1
XPAO mg/l 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1
XH mg/l 0 0 0 0 0 0 0 0 0 0 0 0
XPHA mg/l 0 0 0 0 0 0 0 0 0 0 0 0
Eindhoven 06/05/2014
Sampling time 09:30 - 10:00 10:00 - 10:30 10:30 - 11:00
Calculated Mean Calculated Mean Calculated Mean
Bef
ore
pri
mar
y se
dim
enta
tio
n t
ank
SI mg/l 25.56 22.14 n.a. 23.85 25.56 22.14 0.00 23.85 25.56 22.14 n.a. 23.85
SI % 5.63 4.86 n.a. 5.25 4.80 4.05 0.00 4.48 4.20 3.27 n.a. 3.79
SS mg/l 129.44 136.86 155.00 132.48 150.44 153.86 172.00 150.82 189.44 193.86 215.00 191.48
SS % 28.51 30.01 34.14 29.14 28.28 28.18 33.14 28.33 31.16 28.59 35.83 30.46
SA mg/l 63.94 67.61 76.57 65.45 74.32 76.01 84.97 74.50 93.58 95.77 106.21 94.59
SF mg/l 65.50 69.25 78.43 67.04 76.12 77.85 87.03 76.31 95.86 98.09 108.79 96.89
XS mg/l 164.90 n.a. n.a. 162.74 168.47 191.55 n.a. 181.34 162.48 72.93 n.a. 117.87
XS % 36.32 n.a. n.a. 35.79 31.67 35.08 n.a. 34.07 26.72 10.76 n.a. 18.75
XI mg/l 134.10 297.00 n.a. 135.59 187.53 178.45 n.a. 176.32 230.52 389.07 n.a. 295.46
XI % 29.54 65.13 n.a. 29.82 35.25 32.68 n.a. 33.12 37.91 57.39 n.a. 47.00
SNH4 mg/l 42.40 38.20 42.70 41.10 49.60 47.40 44.00 47.00 45.80 46.40 43.80 45.33
SNO3 mg/l 0.62 0.63 0.60 0.62 0.62 0.63 0.60 0.62 0.67 0.74 0.73 0.71
SPO4 mg/l 6.97 6.74 6.73 6.81 8.24 7.42 7.08 7.58 7.33 7.37 7.41 7.37
Sampling time 16:30 - 17:00 17:00 - 17:30 17:30 - 18:00
Aft
er p
rim
ary
sed
imen
tati
on
tan
k
SI mg/l 25.56 22.14 n.a. 23.85 25.56 22.14 n.a. 23.85 25.56 22.14 n.a. 23.85
SI % 5.63 4.86 n.a. 5.25 5.90 5.69 n.a. 5.88 6.67 5.84 n.a. 6.27
SS mg/l 167.44 166.86 189.00 166.48 160.44 167.86 190.00 164.82 169.44 175.86 192.00 171.15
SS % 36.88 36.59 41.63 36.62 37.05 43.15 48.22 40.66 44.24 46.40 50.53 44.96
SA mg/l 82.72 82.43 93.37 82.24 79.26 82.92 93.86 81.42 83.70 86.87 94.85 84.55
SF mg/l 84.72 84.43 95.63 84.24 81.18 84.94 96.14 83.40 85.74 88.99 97.15 86.60
XS mg/l 74.90 -34.83 n.a. 20.70 -131.66 39.20 n.a. -46.90 56.01 11.77 n.a. 35.39
XS % 16.50 -7.64 n.a. 4.55 -30.41 10.08 n.a. -11.57 14.62 3.10 n.a. 9.30
XI mg/l 186.10 301.83 n.a. 243.63 378.66 159.80 n.a. 263.57 131.99 169.23 n.a. 150.28
XI % 40.99 66.19 n.a. 53.59 87.45 41.08 n.a. 65.02 34.46 44.65 n.a. 39.48
SNH4 mg/l 47.00 45.80 47.60 46.80 46.60 48.40 45.80 46.93 49.60 49.00 47.60 48.73
SNO3 mg/l 0.50 0.50 0.56 0.52 0.50 0.50 0.47 0.49 0.49 0.51 0.52 0.50
SPO4 mg/l 9.20 9.04 8.76 9.00 9.49 9.03 9.43 9.32 9.49 9.25 8.87 9.20
XAUT mg/l 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1
XPAO mg/l 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1
XH mg/l 0 0 0 0 0 0 0 0 0 0 0 0
XPHA mg/l 0 0 0 0 0 0 0 0 0 0 0 0
Eindhoven 06/05/2014
Sampling time 11:00 - 11:30
Calculated Mean
Bef
ore
pri
mar
y se
dim
enta
tio
n t
ank
SI mg/l 25.56 22.14 n.a. 23.85
SI % 6.22 5.41 n.a. 5.86
SS mg/l 194.44 193.86 209.00 191.15
SS % 47.31 47.40 52.25 47.00
SA mg/l 96.05 95.77 103.25 94.43
SF mg/l 98.39 98.09 105.75 96.72
XS mg/l 257.70 200.51 n.a. 232.10
XS % 62.70 49.02 n.a. 57.07
XI mg/l -66.70 -7.51 n.a. -40.44
XI % -16.23 -1.84 n.a. -9.94
SNH4 mg/l 47.20 44.20 44.00 45.13
SNO3 mg/l 0.73 0.65 0.69 0.69
SPO4 mg/l 7.91 7.56 7.83 7.77
Sampling time 18:00 - 18:30
Aft
er p
rim
ary
sed
imen
tati
on
tan
k
SI mg/l 25.56 22.14 n.a. 23.85
SI % 6.80 5.83 n.a. 6.35
SS mg/l 156.44 159.86 182.00 158.15
SS % 41.61 42.07 49.06 42.10
SA mg/l 77.28 78.97 89.91 78.13
SF mg/l -137.73 32.99 n.a. -52.37
XS mg/l -36.63 8.68 n.a. -13.94
XS % 331.73 165.01 n.a. 246.04
XI mg/l 88.23 43.42 n.a. 65.49
XI % 48.80 47.20 46.60 47.53
SNH4 mg/l 0.50 0.52 0.49 0.50
SNO3 mg/l 9.31 9.10 8.87 9.09
SPO4 mg/l -137.73 32.99 -52.37
XAUT mg/l 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1
XPAO mg/l 0.1 - 1 0.1 - 1 0.1 - 1 0.1 - 1
XH mg/l 0 0 0 0
XPHA mg/l 0 0 0 0
107
Appendix 3: Wastewater ratios
Appendix 3.1: Raw wastewater ratios for the WWTP of Roeselare compared with Rieger et al. (2013)
Hig
h d
isch
arge
rat
e
Date 17/02/2014 24/02/2014 3/03/2014 24/03/2014 Mean STD Mean Rieger et al.
Min. Rieger et al.
Max. Rieger et al.
TN/CODtot (g N/g COD)
0.091 0.137 0.173 0.134 0.134 0.034 0.095 0.050 0.150
NH4/TKN (g N/g N)
0.470 0.501 0.359 0.546 0.469 0.080 0.684 0.500 0.900
TP/CODtot (g P/g COD)
0.020 0.013 0.019 0.016 0.017 0.003 0.016 0.007 0.025
PO4/TP (g P/g P)
0.843 0.746 0.771 0.837 0.799 0.048 0.603 0.390 0.800
CODtot/BOD (g COD/g BOD)
6.67 4.10 n.a. 4.87 5.21 1.32 2.06 1.410 3.000
CODsol/CODtot
(g COD/g COD) 0.642 0.572 0.332 0.261 0.452 0.184 0.343 0.120 0.750
TSS/CODtot (g TSS/g COD)
0.000 0.000 0.001 0.000 0.000 0.000 0.503 0.350 0.700
CODpart/VSS (g COD/g VSS)
0.44 0.47 0.35 0.85 0.53 0.22 1.69 1.300 3.000
VSS/TSS (g VSS/g TSS)
2.03 2.36 3.77 1.75 2.48 0.90 0.74 0.300 0.900
Low
dis
char
ge r
ate
(m
eas
ure
me
nt
cam
pai
gn)
Date 12/03/2014 12/03/2014 12/03/2014 12/03/2014 12/03/2014 Mean STD Mean Rieger et al.
Min. Rieger et al.
Max. Rieger et al.
TN/CODtot (g N/g COD)
0.143 0.116 0.097 0.105 0.113 0.115 0.017 0.095 0.050 0.150
NH4/TKN (g N/g N)
0.718 0.733 0.917 0.896 0.764 0.806 0.094 0.684 0.500 0.900
TP/CODtot (g P/g COD)
0.015 0.014 0.016 0.017 0.014 0.015 0.002 0.016 0.007 0.025
PO4/TP (g P/g P)
0.783 0.797 0.810 0.910 0.832 0.826 0.050 0.603 0.390 0.800
CODtot/BOD (g COD/g BOD)
2.99 2.63 2.06 2.70 2.01 2.479 0.423 2.06 1.410 3.000
CODsol/CODtot
(g COD/g COD) 0.318 0.313 0.355 0.444 0.443 0.374 0.065 0.343 0.120 0.750
TSS/CODtot (g TSS/g COD)
0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.503 0.350 0.700
CODpart/VSS (g COD/g VSS)
0.61 0.79 0.75 0.25 0.71 0.625 0.219 1.69 1.300 3.000
VSS/TSS (g VSS/g TSS)
2.34 2.12 2.17 6.27 1.88 2.957 1.857 0.74 0.300 0.900
108
Low
dis
char
ge r
ate
Date 7/04/2014 14/04/2014 Mean STD
Rieger et al.
Min. Rieger et al.
Max. Rieger et al.
TN/CODtot (g N/g COD)
0,153 0,136 0,144 0,012 0,095 0.050 0.150
NH4/TKN (g N/g N)
0,689 0,732 0,710 0,031 0,684 0.500 0.900
TP/CODtot (g P/g COD)
0,016 0,016 0,016 0,000 0,016 0.007 0.025
PO4/TP (g P/g P)
0,766 0,772 0,769 0,005 0,603 0.390 0.800
CODtot/BOD (g COD/g BOD)
3,47 3,77 3,620 0,215 2,06 1.410 3.000
CODsol/CODtot
(g COD/g COD) 0,273 0,267 0,270 0,004 0,343 0.120 0.750
TSS/CODtot (g TSS/g COD)
0,000 0,000 0,000 0,000 0,503 0.350 0.700
CODpart/VSS (g COD/g VSS)
0,65 0,47 0,561 0,132 1,69 1.300 3.000
VSS/TSS (g VSS/g TSS)
3,90 7,69 5,793 2,681 0,74 0.300 0.900
Appendix 3.2: Primary effluent ratios for the WWTP of Roeselare compared with Rieger et al. (2013)
Hig
h d
isch
arge
rat
e
Date 17/02/2014 24/02/2014 3/03/2014 24/03/2014 Mean STD Mean Rieger et al.
Min. Rieger et al.
Max. Rieger et al.
TN/CODtot (g N/g COD)
n.a. 0.119 0.241 0.141 0.167 0.065 0.134 0.050 0.360
NH4/TKN (g N/g N)
n.a. 0.535 0.434 0.520 0.496 0.055 0.755 0.430 0.900
TP/CODtot (g P/g COD)
n.a. 0.012 0.025 0.012 0.016 0.008 0.023 0.010 0.060
PO4/TP (g P/g P)
n.a. 0.773 0.763 0.752 0.763 0.011 0.741 0.500 0.900
CODtot/BOD (g COD/g BOD)
n.a. 6.000 n.a. 6.004 6.002 0.003 1.874 0.500 3.000
CODsol/CODtot
(g COD/g COD) n.a. 0.197 0.590 0.213 0.333 0.222 0.449 0.150 0.750
TSS/CODtot (g TSS/g COD)
n.a. 0.00 0.00 0.00 0.00 0.00 0.38 0.180 0.560
CODpart/VSS (g COD/g VSS)
n.a. 0.975 0.127 0.756 0.619 0.440 1.718 1.400 3.500
VSS/TSS (g VSS/g TSS)
n.a. 3.627 5.667 2.504 3.932 1.603 0.794 0.700 0.909
109
Low
dis
char
ge r
ate
(m
eas
ure
me
nt
cam
pai
gn)
Date 12/03/2014 12/03/2014 12/03/2014 12/03/2014 Mean STD Mean Rieger et al.
Min. Rieger et al.
Max. Rieger et al.
TN/CODtot (g N/g COD)
0.146 0.135 0.144 0.151 0.144 0.007 0.134 0.050 0.360
NH4/TKN (g N/g N)
0.652 0.622 0.626 0.546 0.611 0.046 0.755 0.430 0.900
TP/CODtot (g P/g COD)
0.013 0.013 0.014 0.013 0.013 0.001 0.023 0.010 0.060
PO4/TP (g P/g P)
0.754 0.823 0.827 0.850 0.814 0.042 0.741 0.500 0.900
CODtot/BOD (g COD/g BOD)
3.421 3.807 3.346 3.191 3.441 0.262 1.874 0.500 3.000
CODsol/CODtot
(g COD/g COD) 0.263 0.238 0.265 0.283 0.262 0.018 0.449 0.150 0.750
TSS/CODtot (g TSS/g COD)
0.00 0.00 0.00 0.00 0.00 0.00 0.38 0.180 0.560
CODpart/VSS (g COD/g VSS)
0.736 0.933 0.844 0.940 0.864 0.095 1.718 1.400 3.500
VSS/TSS (g VSS/g TSS)
3.171 2.877 3.205 3.021 3.069 0.151 0.794 0.700 0.909
Low
dis
char
ge r
ate
Date 7/04/2014 14/04/2014 Mean STD Mean Rieger et al.
Min. Rieger et al.
Max. Rieger et al.
TN/CODtot (g N/g COD)
0.158 0.26 0.142 0.023 0.134 0.050 0.360
NH4/TKN (g N/g N)
0.670 0.777 0.724 0.076 0.755 0.430 0.900
TP/CODtot (g P/g COD)
0.015 0.015 0.015 0.000 0.023 0.010 0.060
PO4/TP (g P/g P)
0.747 0.757 0.752 0.007 0.741 0.500 0.900
CODtot/BOD (g COD/g BOD)
3.835 3.268 3.551 0.401 1.874 0.500 3.000
CODsol/CODtot
(g COD/g COD) 0.265 0.251 0.258 0.010 0.449 0.150 0.750
TSS/CODtot (g TSS/g COD)
0.00 0.00 0.00 0.00 0.38 0.180 0.560
CODpart/VSS (g COD/g VSS)
0.760 1.165 0.962 0.287 1.718 1.400 3.500
VSS/TSS (g VSS/g TSS)
4.907 4.693 4.800 0.151 0.794 0.700 0.909
110
Appendix 3.3: Raw wastewater ratios for the WWTP of Eindhoven compared with Rieger et al. (2013)
Date 05/05/2014
08:00 - 08:30
05/05/2014 08:30 - 09:00
05/05/2014 09:00 - 09:30
05/05/2014 09:30 - 10:00
05/05/2014 10:00 - 10:30
Mean STD Mean Rieger et al.
Min. Rieger et al.
Max. Rieger et al.
TN/CODtot (g N/g COD)
0.109 0.084 0.109 0.116 0.116 0.107 0.01 0.134 0.050 0.360
NH4/TKN (g N/g N)
0.756 0.936 0.794 0.788 0.770 0.809 0.07 0.755 0.430 0.900
TP/CODtot (g P/g COD)
0.016 0.014 0.017 0.019 0.018 0.017 0.00 0.023 0.010 0.060
PO4/TP (g P/g P)
0.764 0.805 0.760 0.778 0.807 0.783 0.02 0.741 0.500 0.900
CODtot/BOD (g COD/g BOD)
4.266 2.673 2.122 1.943 2.218 2.644 0.95 1.874 0.500 3.000
CODsol/CODtot
(g COD/g COD) 0.325 0.322 0.826 0.344 0.328 0.429 0.22 0.449 0.150 0.750
TSS/CODtot (g TSS/g COD)
0.00 0.00 0.00 0.00 0.00 0.000 0.00 0.38 0.180 0.560
CODpart/VSS (g COD/g VSS)
1.339 1.332 0.307 1.356 1.555 1.178 0.50 1.718 1.400 3.500
VSS/TSS (g VSS/g TSS)
1.801 2.000 1.926 1.522 1.394 1.729 0.26 0.794 0.700 0.909
111
Appendix 3.4: Primay effluent ratios for the WWTP of Eindhoven compared with Rieger et al. (2013)
Date 05/05/2014
16:00 - 16:30
05/05/2014 16:30 - 17:00
05/05/2014 17:00 - 17:30
05/05/2014 17:30 - 18:00
05/05/2014 18:00 - 18:30
Mean STD Mean Rieger et al.
Min. Rieger et al.
Max. Rieger et al.
TN/CODtot (g N/g COD)
0.126 0.116 0.144 0.156 0.161 0.141 0.019 0.134 0.050 0.360
NH4/TKN (g N/g N)
0.949 0.894 0.810 0.829 0.793 0.855 0.065 0.755 0.430 0.900
TP/CODtot (g P/g COD)
0.028 0.023 0.026 0.028 0.026 0.026 0.002 0.023 0.010 0.060
PO4/TP (g P/g P)
0.878 0.844 0.899 0.866 0.924 0.882 0.031 0.741 0.500 0.900
CODtot/BOD (g COD/g BOD)
1.902 3.021 n.a. 2.239 n.a. 2.387 0.574 1.874 0.500 3.000
CODsol/CODtot
(g COD/g COD) 0.502 0.419 0.465 0.512 0.484 0.477 0.037 0.449 0.15 0.75
TSS/CODtot (g TSS/g COD)
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.38 0.180 0.560
CODpart/VSS (g COD/g VSS)
0.675 1.120 0.942 0.749 0.931 0.883 0.176 1.718 1.400 3.500
VSS/TSS (g VSS/g TSS)
3.000 2.497 2.514 2.710 1.944 2.533 0.387 0.794 0.700 0.909
112
Appendix 4: Division of the wastewater
Appendix 4.1: Raw wastewater division for the WWTP of Roeselare compared with Henze et al. (2001)
Hig
h d
isch
arge
rat
e
Date COD/BOD COD/TN COD/TP BOD/TN BOD/TP COD/VSS VSS/TSS
17/02/2014 higher than
ranges medium high
lower than
ranges
lower than
ranges low
higher than
ranges
24/02/2014 higher than
ranges low
higher than
ranges
lower than
ranges medium
lower than ranges
higher than
ranges
3/03/2014 higher than
ranges
lower than
ranges high
lower than
ranges
lower than
ranges
lower than ranges
higher than
ranges
24/03/2014 higher than
ranges low
higher than
ranges
lower than
ranges low
lower than ranges
higher than
ranges
Low
dis
char
ge r
ate
Date COD/BOD COD/TN COD/TP BOD/TN BOD/TP COD/VSS VSS/TSS
12/03/2014
high low higher than
ranges
lower than
ranges high
lower than
ranges
higher than
ranges
12/03/2014 high medium higher than
ranges low high
lower than
ranges
higher than
ranges
12/03/2014 medium medium higher than
ranges medium high
lower than
ranges
higher than
ranges
12/03/2014 high medium high low high lower than
ranges
higher than
ranges
12/03/2014 medium medium higher than
ranges medium
higher than
ranges low
higher than
ranges
7/04/2014 high low higher than
ranges
lower than
ranges medium
lower than
ranges
higher than
ranges
14/04/2014 higher than
ranges low
higher than
ranges
lower than
ranges medium
lower than
ranges
higher than
ranges
113
Appendix 4.2: Raw wastewater division for the WWTP of Eindhoven compared with Henze et al. (2001)
Sample number
COD/BOD COD/TN COD/TP BOD/TN BOD/TP COD/VSS VSS/TSS
Sample 1 lower than
ranges low medium
lower than ranges
lower than ranges
high higher than
ranges
Sample 2 medium low medium low medium high higher than
ranges
Sample 3 low low medium medium medium low higher than
ranges
Sample 4 high medium medium lower than
ranges low high
higher than
ranges
Sample 5 n.a. low medium lower than
ranges lower than
ranges high
higher than
ranges
Sample 6 medium low medium lower than
ranges medium medium
higher than
ranges
Sample 7 n.a. lower than
ranges medium
lower than ranges
lower than ranges
high higher than
ranges
114
Appendix 5: Particle size distributions
115
116
117
118
