ABSTRACT:

Wastewater treatment plants significantly reduce the microbe levels in water. However, the remaining microbes may regrow in the nutrient-rich wastewater effluent.
Therefore, using this reclaimed effluent as a secondary water source can potentially contaminate crops. For this study, an agricultural field was irrigated using reclaimed wastewater from the Hyrum Wastewater Treatment Plant. The water was tested before and after irrigation to determine the microbial load applied to the crops. Then, daily plant samples were collected to determine both the initial microbial contamination level and the die-off after the irrigation event. All samples were tested on IDEXX’s Colilert and Enterolert trays. These trays contain large and small wells that each give positive/negative results. The different sized wells act like different dilutions to help quantify bacteria concentrations. Positive wells are counted and an IDEXX table used to convert the well counts into MPN counts for coliforms, E. coli, and Enterococcus, all found in high levels in wastewater influent. Test results demonstrated microbial regrowth in the reclaimed wastewater system. Additionally, the reclaimed water contaminated the irrigated plants and the contamination level was reduced significantly in the first 48 hours after wastewater application.