Biofilms as sources of fecal bacteria contamination in the stormwater drainage system in Singapore

Abstract

A study was performed to examine a possible source of fecal bacteria contamination originating from within the stormwater drainage system in Singapore. The extent of fecal bacteria presence in storm drain biofilms was evaluated as a pathway for fecal bacteria contamination. In the research, biofilms were evaluated as reservoirs for fecal indicator bacteria (FIB), FIB concentrations were measured over time within biofilms and stormwater, and relationships between FIB in biofilms and FIB in stormwater were examined. The concentrations of three bacterial groups (total coliform, Escherichia coli, and enterococci) were used as indicators of fecal bacteria contamination. In the Singaporean districts of Choa Chu Kang and Toa Payoh, five locations within the storm drains were monitored once per week each between January 8, 2013 and January 22, 2013. Well-developed biofilms were observed and measured using concrete coupons in the storm drains at Choa Chu Kang Crescent, Verde View, Lorong 6 Toa Payoh, and two points at Lorong 8 Toa Payoh. An initial biofilm growth condition was observed for secondary research at Nanyang Technological University. The biofilms in the storm drains were observed to be reservoirs for FIB due to measured concentrations of each fecal indicator. The measured FIB concentrations fluctuated over time in the biofilms and the overlying storm drainage waters due to natural processes within the biofilms and the storm drain environments. Greater fluctuations in FIB concentrations in biofilms than in storm drainage waters indicate that the stormwater is more stable and has additional sources of FIB contributing to the contamination. FIB detachment from biofilms is a potential pathway for fecal bacteria contamination of stormwater.