A Comparative Microbial Composition Assessment of Stormwater, Urban Runoff and Wastewater

The goal of this study was to compare two methods for assessment of fecal indicator bacteria (FIB) in urban runoff (n = 96), stormwater (n = 8), and wastewater (n = 16). We quantified the densities and reductions of E. coli and Enterococcus, in raw stormwater, treated urban off from the Santa Monica Urban Runoff Recycling Facility (SMURRF) and wastewater from the Eastern Municipal Water District’s (EMWD) Moreno Valley water reclamation facility. We compared the overall FIB recovery efficiency by two varieties of USEPA-approved, culture-based laboratory methods in each type of water. The two types of methods were the IDEXX Quanti-Tray technique and the USEPA membrane filtration methods 1603 and 1600. All results showed the expected reduction of FIB densities across treatment processes. Among the raw influent water, the FIB in urban runoff had the lowest FIB density, followed by the stormwater, with the highest densities in the wastewater. We used the Wilcoxon signed rank test to compare recovery efficiency of the membrane methods versus the IDEXX methods. The IDEXX methods detected significantly higher levels in the raw stormwater, and in all treatment stages of tertiary-treated wastewater and of urban runoff, except in the raw urban runoff, where the USEPA method 1603 detected a higher density