Assessment of Escherichia coli Contamination in Tap Water at Selected Railway Stations in Colombo District, Sri Lanka

Abstract

Background: In Sri Lanka, public water sources are widely used for drinking and washing purposes, yet concerns about their safety persist. This research highlights the importance of identification of Escherichia coli (E. coli) contamination in public water sources that will aid in the control of health risks. Regular monitoring of water sources for E. coli is crucial to ensure drinking water safety, where E. coli is one of the main pathogens causing a spectrum of diseases. This study focuses on assessing E coli contamination of public water sources at selected railway stations in the Colombo district, Sri Lanka. Objective: To determine the presence of E. coli in tap water available at railway stations in the Colombo district, Sri Lanka Methods: This cross-sectional study investigated the presence of E. coli in tap water from 30 railway stations. Water samples were collected in sterile amber-colour glass bottles and transported in ice boxes following established protocols. The membrane filtration method was performed under vacuum pressure utilizing a 100 mL sample volume. Then, membrane filters were placed on Eosin Methylene Blue (EMB) agar and incubated at 35 °C for 24 hours. E. coli was identified by their characteristic shiny, metallic, greenish-coloured colonies. Results: The findings revealed that 36.66% of the samples contained bacteria. Among the bacteria positive samples, one sample (3.33%) was found to be positive for E. coli, with a colony count of 7 CFU/100 mL. According to the Sri Lanka Standards Institute (SLSI) guideline for drinking water, the acceptable limit for E. coli is 0 CFU/100 mL. The remaining 33.33% of the positive samples contained other bacterial species. Positive bacterial samples included 3.33% Gram- positive cocci, 10% Gram-negative cocci, and 23.33% Gram-negative bacilli. Conclusions: The findings indicate bacterial presence in a considerable number of water samples. E. coli contamination was found in one of the tap water samples taken from a railway station.The presence of E. coli indicates faecal contamination. Although with one sample contamination, this may indicate a potential health risk to the public. Improved monitoring mechanisms, regular testing, public awareness and sanitation measures are essential to ensure safe drinking water and prevent the spread of waterborne diseases through public water resources