Pathogens in Runoff Water Treated by a Sustainable Urban Drainage System in a Developing Country

Abstract

Sustainable Urban Drainage Systems (SUDS) are commonly used to control flooding in urban areas. These structures store and treat stormwater runoff. Several studies in high-income countries have reported the presence of pathogens in runoff water, but it is expected that runoff water in developing countries contains higher pathogen concentrations given their lack of resources to properly manage sewage; this could result in higher risks of infection for people interacting with SUDS. In this study, we investigated pathogen concentrations (i.e., Salmonella spp. and E. Coli O157) at the micropool of a SUDS train composed of a grassed swale followed by a dry extended detention basin in Bogotá (Colombia) during a 25-week period. We also estimated the risk of infection with the analyzed pathogens, given the high level of exposure to the detention structure. Additionally, we investigated if any of the physicochemical or meteorological variables were associated with pathogen concentrations at the site. We found that pathogen concentrations greatly exceeded concentrations reported for stormwater runoff in developed countries, namely 1562 CFU/mL, on average, for Salmonella spp. and 9160 CFU/mL, on average, for E. Coli O157. The risk of infection from Salmonella spp. and E. Coli O157 greatly exceeded risks previously reported for recreational waters and SUDS. Pathogen concentrations were associated with precipitation and the concentration of suspended solids in the runoff. Given our findings, it is recommended that SUDS in developing countries should consider potential higher pathogen concentrations in stormwater runoff to reduce exposure.