1. 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

2. 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 – 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

3. BACKGROUND Cont’d Treatment Options
Anaerobic treatment + activated sludge
Anaerobic treatment + contact aeration
Activated sludge + chemical coagulation
Contact aeration + chemical coagulation.

4. 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
3070
3262.5
936.25
141.5

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

6. 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.

7. 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

8. 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

9. 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

10. 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
mg/l
Organic Loading Rate
(CODin x Q)/ V
1.314 kg COD/m3.d

11. 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

12. 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 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

13. Drawings

14. Drawings

15. Drawings

16. Drawings

17. Drawings

18. 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 mg/l to mg/l) with a HRT of 2.38days. The organic lading in the ABR was found to be 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 mg/l to 100 mg/l and the BOD from mg/l to 15.62mg/l.
System was found to have a 98.4% BOD reduction

19. 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.

20. 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.

21. 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,
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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