Microbial Indicator asaPerformance Evaluation Tool for STP: Case Study

Abstract

Mixed community of microorganismsiskeytosewage treatment and few of them may be used as an indicatororganism to evaluate the performance of sewage treatment plants(STPs). The aeration tank in the activated sludgeprocess (ASP) forms an artificial ecosystem consist of bacteria and protozoans.Protozoans and E.coli can be usedasareliable microbial indicator to evaluate the performance of sewage treatment plant.Inthepresent research theexisting performance of Sanjauli Maliana Sewage Treatment Plant had evaluated in terms of removal efficiencyof Total Suspended Solids (TSS), 5-day Biochemical Oxygen Demand (BOD5) and Chemical Oxygen Demand
(COD). The operational parameter of extended aeration ASP has been determined which showed lowfood/microorganism (F/M) and high mean cell residence time(MCRT) but still the Dissolved oxygen (DO) ofaeration tank was very low. In contrarytothat, microscopic analysis suggested high food/active microorganismratio and low MCRT that explained the low DO. The corrective measures were implemented successfully toelevate the performance of STP. The performance evaluation of sewage treatment had been done after 4 weeksand 6 weeks of successful implementation of corrective measures. The removal efficiency ofTSS, BOD5,andCODhad increased to 94%, 89%, 92% from 79%, 75% and 83% similarly the total coliform removal has increasedby 10 foldsafter six weeks of implementation of corrective measures.The relative density of ciliates had increasedsignificantlyandthe relative density of amoeba had decreased.An optimal dose of bleaching powder had beenevaluated which may ensure theoptimizedcomplete disinfection to reduce the risk of Hepatitis E Virus (HEV)epidemics as well as nostresstothe aquatic life. In developing countries like India, these findings may increasethe reliability and adaptability of microbial indicators to evaluate the performance of STP which is currently donepredominately by physicochemical parameters.