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DESIGN OF A BIOLOGICAL SLAUGHTERHOUSE WASTEWATER TREATMENT SYSTEM (USING AN ANAEROBIC BAFFLE REACTOR – CONSTRUCTED WETLAND SYSTEM) < CASE STUDY OF KISERIAN SLAUGHTERHOUSE>
Mwangi Simon ThukuF21/2492/2009Supervisors : Mr. Orodi Odhiambo Eng. D. A. Mutuli
UNIVERSITY OF NAIROBI ENVIRONMENTAL & BIOSYSTEMS ENGINEERING
BACKGROUNDApproximated slaughterhouse waste content and NEMA standards for disposal into the environment
Waste Content Slaughterhouse (approx.)
NEMA Disposal Standards
BOD 5days at 20 oC 1000 – 4000 mg/L 30 mg/l
COD 2000 – 10000 mg/L 50 mg/l
Oil and grease High Nil
Total Suspended Solids 200 – 1500 mg/L 30 mg/l
Total Nitrogen 100mg/l
Johns et al., 1995; Manjunath et al., 2000, NEMA
BACKGROUND Cont’d
Treatment Options
Anaerobic treatment + activated sludge
Anaerobic treatment + contact aeration
Activated sludge + chemical coagulation
Contact aeration + chemical coagulation.
PROBLEM STATEMENT• This waste water flows to R.
Kiserian and eventually gets to Kiserian Dam.
• This causes eutrophication and anoxia in the water bodies.
• Waste from slaughterhouses also leads to air and soil pollution
Parameter pH TSS, mg/l TDS, mg/l COD, mg/l BOD5mg/l NH4+N (N)mg/l
Content 7.75 2315.25 3070 3262.5 936.25 141.5
Pre- treated Wastewater getting into the streams
• Kiserian is a settlement in Kajiado county
• Habitants are mainly pastoralist community
• Warm and Temperate climate.
• Rainfall =833mm
• Temperature = 17.8
Site Analysis
OBJECTIVESOverall objective To design a biological slaughterhouse wastewater treatment systemSpecific Objectivesi.To analyze the amount and the content of wastewater ii.To establish pertinent parameters for design of a biological slaughterhouse waste water treatment system.iii.To use the parameters from (ii) to size the baffle reactor and the constructed wetland.
STATEMENT OF THE SCOPE
Survey work Carrying out tests Determination of System Design Parameters Making detailed engineering drawings
Literature reviewTreatment Process ( primary, secondary and tertiary treatment)Why anaerobic?Anaerobic Baffle reactor (improved septic tank)Constructed Wetland
Methodology
Soil and waste water sampling
Laboratory tests (soil & waste
water)
Survey
ABR volume determination Result analysis
Determining the efficiency of
ABR
Structural design of the
ABR
Designing the wetland
Theoretical Framework
Chemical oxygen demand,
Biochemical Oxygen Demand, BOD5,mg/L =
Design Criteria for an
Anaerobic baffle reactor
Hydraulic Retention time, HRT >24 hours at maximum sludge depth and scum accumulation
Sludge Accumulation Rate, SAR Depending on TSS removal rate and waste water flow
Sludge and Scum Accumulation Volume
Sludge Accumulation Rate multiplied by flow rate
Desludging interval >1 year
Number of upflow chamber, N >2
Maximum upflow velocity, v 1.4 – 2m/h Sasse (1998), Wanasen (2003), Foxon et al., (2004) etc
ResultsParameter (ABR)m Formula Results
Flow rate, Q (200 x C) + ( 100 x S)
14.5m3/day
Length of upflow chamber, Lc =< half depth 1m
Maximum Peak Upflow Velocity, Vp
Q/t 2.4167m3/h
Area of upflow chamber, Au Vp/v 1.343m2
Width of the chamber, Cw Cw/Lc 1.343m2 ≈2m
Actual upflow velocity, Va Vp/(Lc x Cw) 1.208 m/h
Actual working volume, V Cw x d x (Lc+ Ld)N 30 m3
Hydraulic Retention Time, HRT V/Q 2 days
BOD removal BODeff = BODin e- Kt
x T 135.18 mg/l
Organic Loading Rate (CODin x Q)/ V 1.314 kg COD/m3.d
Results Cont’d
Parameter Value Results
BOD5 removal, percent 80 to 90% 93.625mg/l
COD removal , mass 1.6 x BOD5, removal 1348.2mg/l
Biogas production 0.5m3/kg COD removed 9.77 m3
Methane production 0.35m3/kg COD removed 6.84m3
Leslie C.P. et al, 1999
Results Cont’dParameter (CW) Formulae
Water Budget Qe = Qi + (P – ET) As
Surface Area of the system, As As = (Qave(ln Co – ln Ce))/Kt x d x n
Aspect Ratio between 2:1 to 3:1 (Mitsch et.al 2007)
Retention Time ,t (Lwyn)/Q (Crites et.al, 2006)
Bed Slope 0.5% to 1% Qi =
14.5m3/d
As =
126.22 m2
Length = 2 x 9 = 16 m
width = 7.94 m
y = 0.7 m
t = 1.85 days
dh = 0.01 x 15 = 0.15m
slope is taken to be 1.5
Drawings
Drawings
Drawings
Drawings
Drawings
Conclusion• Objectives of the design project were met.
• slaughterhouse wastewater was observed to have high content of waste. •The BOD5 removal efficiency for the ABR was found to be 90% (i.e. from 936.25mg/l to 93.625mg/l) with a HRT of 2.38days. The organic lading in the ABR was found to be 1.314 kg COD/m3.d (should range between 1 – 3 kg COD/m3.d).
•The CW reduced the concentration of nitrates in the waste water from 141.5 mg/l to 100 mg/l and the BOD from 93.625mg/l to 15.62mg/l.
•System was found to have a 98.4% BOD reduction
Recommendations•The first compartment of the ABR should be modified and increased in size to trap as much solids as possible.
•The ABR should be made air tight and a system to improve/increase the pressure of the biogas in the reactor to allow gas collection otherwise the first compartment can be constructed in such a way that it has a gas holder and made airtight (shape of a fixed dome).
•A gradient should be created between the ABR and the CW so as to utilize gravity as the driving force.
•Wastewater monitoring/ testing should be done on a regular basis in order to ensure that the content of waste flowing to the stream conforms with the NEMA standards and as a way of monitoring the performance of the system.
References
• Muench, E. (2008): Overview of anaerobic treatment options for sustainable sanitation systems. In: BGR Symposium "Coupling Sustainable Sanitation and Groundwater Protection".
• Bachmann, A., Beard, VL. and McCarty, PL. (1985). Performance Characteristics of the Anaerobic Baffled Reactor. Water Research 19 (1): 99–106.
• Sergio S. Domingos (2011), Thesis on Vertical flow constructed wetlands for the treatment of inorganic industrial wastewater, Murdoch University WA, Australia.
• Morel A. and Diener S. (2006). Greywater Management in Low and Middle-Income Countries, Review of diff erent treatment systems for households or neighbourhoods. Swiss Federal Institute of Aquatic Science and Technology (Eawag). Dubendorf, Switzerland.
• Nijaguna B.T. (2002), Biogas Technology, New Age International (P) Limited, New Delhi.
References• Rustige H &Platzer Chr. (2000),Nutrient Removal in Subsurface Flow
Constructed Wetlands for Application in sensitive Regions in: Proceedings – 7th Int. Conf. On Wetland Systems for Water Pollution Control, Orlando, USA
• Leslie Grady .C, Glen .T, (1999), Biological Wastewater treatment, 2nd ed, Maral
Dekker ,Inc, New York • Foxon KM, Pillay S, Lalbahadur T, Rodda N, Holder F, Buckley CA (2004) The
anaerobic baffled reactor(ABR): An appropriate technology for on-site sanitation. Water South Africa 30, 44-50.
• Lawrence A.W. and McCarty p.L (1970): Unified basis for biological Treatment
Design and Operation. J. Sanit. Eng. Div., Am. Soc. CivEngrs. • Walter R.H., Shermah R.M. and Downing D.L. (1974): Reduction in Oxygen
demand of abattoir effluent by Precipitation with metal. J. Agric. Fd Chem
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