Effect of UV Irradiation and Chlorination on E. coli Enumeration and Phylotype in WWTP Effluent.

Waste-water treatment plants (WWTPs) have been implicated as a source of bacterial contamination in streams and rivers across the country.  Carter Creek in College Station is on the 303(d) list of impaired waters for bacterial contamination.  There are two WWTPs located along Carter Creek that release treated waste-water effluent into the creek, one employs UV irradiation and the other chlorination.  Escherichia coli (E. coli) is an indicator organism used for water quality, and can be classified into various phylotypes (A, B1, B2, C, D, E, F, and clades I-V).  Phylotypes B2 and D are considered pathogenic.  Phylotyping E. coli isolates involves screening for the genes chuA, yjaA, arpA, and DNA fragment TspE4.C2.  Sampling completed in 2015 from before and after disinfection (UV or chlorination), including enumerating E. coli using EPA Method 1603, and phylotyping will provide evidence of E. coli survival or perishment in each disinfection process.  Conclusions will provide recommendations for WWTPs to reduce E. coli abundance and pathogenic E. coli occurrence.