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Understanding Microbial Loads in Wastewater Treatment Works as Source Water for Water Reuse
Citation:
Ryu, H., Y. Addor, N. Brinkman, M. Ware, L. Boczek, J. HoelleSchwalbach, J. Mistry, S. Keely, AND E. Villegas. Understanding Microbial Loads in Wastewater Treatment Works as Source Water for Water Reuse. 20th International symposium on IWA-HRWM, Vienna, AUSTRIA, September 15 - 20, 2019.
Impact/Purpose:
Diminishing freshwater supplies and increasing municipal water demands in highly populated arid areas make water reuse a feasible economical alternative. New water resources are being actively explored to ensure sufficient availability of fresh water for the entire population. Reuse of treated municipal wastewater has the potential to relieve the ever-increasing demands of providing water for (non-)potable use. However, negative public perception and health concerns due to the uncertain microbial quality of reclaimed water limit its widespread use and applications. Thus, additional research is needed to further characterize the microbial pathogens of concern present in wastewater effluent and the risks associated with exposure to these contaminants. The objective of this study was to assess microbial quality of reclaimed water focusing on a suite of waterborne pathogens and microbial indicators. Treatability of microorganisms during different treatment trains was also investigated. Overall, this study will assist municipalities considering wastewater effluent as another source of drinking water important data on the prevalence, occurrence, and persistence of waterborne pathogens of concern. More importantly, the results from this study will aid in building a richer pathogens and microbial indicators occurrence databases that can be used towards revising reuse guidelines and disinfection practices for water reuse practices.
Description:
Wastewater samples from three participating utilities in the Southwestern United States (U.S.) were collected monthly between March 2015 and June 2016. Fecal indicator organisms like, male-specific coliphages, somatic coliphages, total coliforms, fecal coliforms, Escherichia coli, and aerobic endospores were measured as well as concentrations of Cryptosporidium, Giardia and infectious human adenovirus were monitored in raw and final treated effluents. All the tested microorganisms were analyzed using U. S. Environmental Protection Agency Methods or modified Methods. Results revealed that human adenovirus and Giardia cysts were detected in 98% (46/47) of influent samples, whereas 66% (31/47) of the samples were positive for Cryptosporidium oocysts. In treated effluent samples, the prevalence of infectious adenovirus markedly decreased to 60%. Averages of Log10 reduction of adenovirus between influent and effluent for all three utilities ranged from 3.52 to 4.13, whereas relatively lower Log10 reductions with a range from 1.28 to 3.04 were achieved for both protozoan parasites. Compared to bacterial indicators, a relatively high prevalence of bacteriophages were observed in influent samples. Log10 reduction of bacteriophages were greater than that of human adenovirus, suggesting that both bacteriophages analyzed could be considered conservative viral indicators of human adenovirus. The Log10 reduction of aerobic endospores ranged from 4.25 to 4.46 which are lower than bacteriophages, but greater than protozoan parasites. Similarly, endospores could be a potential candidate for a surrogate of protozoan parasites for microbial treatability tests.