Abstract:
Greater Kurunegala Sewage Treatment Plant (GKSTP) plays a crucial role in safeguarding public health by removing contaminants from wastewater before
discharge. Escherichia coli (E. coli) is a prominent fecal contamination
indicator of water. Despite the substantial investments made by treatment
plants to remove pathogens from wastewater, the efficacy of this process is
questioned when the treated water is reintroduced into contaminated canals.
This study aimed to investigate whether the removal of microbes in a treatment
plant is effective when the treated water is put back into the same polluted
canal, assessing the feasibility of achieving significant pathogen removal
maintaining water quality standards. Composite water samples were collected
from 5 sampling sites along the canals downstream to GKSTP during the dry
(DS) and wet (WS) seasons for microbiological analysis using Membrane
Filtration Protocol. The E. coli of water was assessed for spatial and temporal
variations using an Analysis of Variances (ANOVA). E. coli count of water
along Kurunegala city canals exhibited notable spatial variation (p<0.05).
Based on the findings, the E. coli counts in 100mL of water during the WS
ranged from 482 to uncountable whereas in the DS it ranged from 216 to not
clear (contaminated with other bacteria). E. coli levels remain high during the
WS and this could be attributed to surface runoff from residential and
agricultural areas, discharges from unconnected pipes to sewage networks,
and due to intentional release of sewage during WS. Despite the presence of a
GKSTP, biological parameters such as E. coli count cannot be effectively
reduced unless all sewage pipes within the city are connected and treated. The
futility of treatment costs becomes evident as reintroducing treated water into
polluted canals leads to microbial recontamination, posing a significant risk to
water quality standards downstream, thereby jeopardizing the safety and well being of water users. It underscores the need for a comprehensive approach to
address persistent pollution sources and ensure effective water quality
management.
