UNIVERSITY OF NAIROBI ENVIRONMENTAL & BIOSYSTEMS ENGINEERING Design of a biological slaughterhouse wastewater treatment system (Using an anaerobic baffle reactor – constructed wetland system) < case study of Kiserian Slaughterhouse> Mwangi Simon Thuku F21/2492/2009 Supervisors : Mr. Orodi Odhiambo Eng. D. A. Mutuli

BACKGROUND Approximated 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 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 Pre- treated Wastewater getting into the streams 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

Site Analysis Kiserian is a settlement in Kajiado county Habitants are mainly pastoralist community Warm and Temperate climate. Rainfall =833mm Temperature = 17.8

To analyze the amount and the content of wastewater Objectives Overall objective To design a biological slaughterhouse wastewater treatment system Specific Objectives To analyze the amount and the content of wastewater To establish pertinent parameters for design of a biological slaughterhouse waste water treatment system. To use the parameters from (ii) to size the baffle reactor and the constructed wetland.

Statement of the scope Literature review Survey work Carrying out tests Determination of System Design Parameters Making detailed engineering drawings Literature review Treatment Process ( primary, secondary and tertiary treatment) Why anaerobic? Anaerobic Baffle reactor (improved septic tank) Constructed Wetland

Methodology Survey Soil and waste water sampling Laboratory tests (soil & waste water) Determining the efficiency of ABR ABR volume determination Result analysis Designing the wetland Structural design of the ABR

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

Results Parameter (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’d Parameter (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 y = 0.7 m 126.22 m2 As = t = 1.85 days width = 7.94 m dh = 0.01 x 15 = 0.15m Length = 2 x 9 = 16 m 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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