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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