Performance Evaluation of Murang’a Sewage Treatment Plant

Abstract
This project investigates Murang’a Sewage treatment plant, a wastewater stabilization pond
treatment system with a design flow capacity of 1500m3 per day. The system comprises of the
following units in series: grit chamber, two anaerobic ponds in parallel, two primary facultative
ponds in parallel, two secondary facultative ponds and two maturation ponds in parallel. The
overall performance of the system was evaluated based on analysis of physical, chemical and
biological quality parameters.
To analyze these physical, chemical and biological parameters six samples were taken; sample 1
at the influent pipe (raw influent), Sample 2 effluent at the grit chamber (influent to anaerobic
pond), sample 3 anaerobic pond effluent (primary facultative pond influent), sample 4 effluent
from the primary facultative pond (influent to secondary maturation pond), sample 5 secondary
facultative pond effluent (influent to maturation pond) and sample 6 maturation pond effluent
(final treated effluent). The system is completely un-mechanized and has a total hydraulic
retention time of 28.5 days.
The parameters tested were; pH, temperature, BOD, COD TSS and total coliforms and the

reported overall removals for BOD, COD, TSS and total coliforms were; 95.7, 94.2, 85.5 and
98.3 respectively. On the other hand, characteristics of the final effluent from the treatment plant
were reported as 35, 58, 80 mg/L, 4000MPN/100ml, 240C and 7.5 for BOD5, COD, TSS, total
coliforms, temperature, and pH respectively. The mean final effluent concentrations of BOD5,
COD, total coliform and TSS indicated non-compliance with regulations for effluent discharge.

 

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