Influence of Sewage Treatment Plant Effluent on the Presence of Culturable Pathogenic Bacteria in the Water Body

Abstract

The purpose of the sewage treatment process is to decrease the concentration of contaminants, including pathogens, before discharging into the receiving streams. And the standard operating procedure of STP in Malaysia is to discharge the treated wastewater with low nutrient and low organic materials into the streams but the bacterial content of the discharge and its risk to the stream’s natural microbial verity or health is unknown. However, studies reported that pathogens could escape sewage treatment plants (STPs) processes and showed health risk of streams impacted by STP effluent. On the other hand, majority of these studies relied on metagenomic strategy, without assessing changes to culturable bacteria. Isolation of living microbes provides realistic risk assessment compared to metagenome survey alone. Therefore, this study aims to determine the presence of culturable pathogenic bacteria from water impacted by STP effluent to establish justifiable public health risk. For that, the presence of bile resistant bacteria was determined from water taken from surface water receiving effluent from STP-1 (Kolej 9, UTM) in Malaysia. Enumeration and isolation of bacteria were done on MacConkey agar through membrane filtration method, followed by partial identification, using Triple Sugar Iron agar (TSI). The result showed that STP effluent changes the diversity, and abundance, of bile resistant bacteria (specifically Enterobacteriaceae family) of receiving streams. Most of the isolated bile resistant bacteria are opportunistic pathogens for human. Findings from this study provide a snapshot of the bigger picture of microbial changes in a stream impacted by STP effluent painted initially by metagenome studies. And shows that despite of treatment, some contaminants (microbes) remained and released into surface waters, which contribute to the water pollutions.