Quantitative Microbial Risk Assessment of Urban Wastewater Pertaining to Irrigation of Agricultural Products in Qom, Iran, in ۲۰۲۰

Introduction: The present study aims to evaluate adverse health effects caused by the use of wastewater for the irrigation of fields in Qom province, Iran. Materials and Methods: An environmental monitoring program was designed for ۳ pathogens-Escherichia coli, Vibrio cholerae, and E. coli O۱۵۷ and carried out on ۱۲۰ samples from raw wastewater, effluent, and irrigated products with wastewater. In the next phase, exposure assessment and microbial risk assessment were performed using a questionnaire and interviewing ۲۰۰ participants.  Results: Concentrations of E. coli, V. Cholerae, and E. coli O۱۵۷:H۷ in raw wastewater were determined to be ۳.۴ × ۱۰۳ ± ۵۰۰ cfu/۱۰۰ml, ۲.۱ × ۱۰۳ ± ۱۰۰ cfu/۱۰۰ml, and ۳۱۲ cfu/۱۰۰ml, respectively. Concentrations of E. coli, V. Cholerae, and E. coli O۱۵۷:H۷ in effluent were determined to be ۲.۱ × ۱۰۳ ± ۱۰۰ cfu/۱۰۰ml, ۰.۸ × ۱۰۳ ± ۱۰۰ cfu/۱۰۰ml, and ۱۷۶ cfu/۱۰۰ml, respectively. The conventional wastewater treatment system was effective in removing E. coli, V. Cholerae, and E. coli O۱۵۷: H۷ by ۵۰%, ۵۹%, and ۴۳%, respectively. Crops irrigated with effluent contained ۴۰۰ ± ۲۵۰ cfu/۱۰۰ml, ۰.۱ × ۱۰۳ ± ۰.۰۱۹ cfu/۱۰۰ml, and ۵۲ cfu/۱۰۰ml of E. coli, V. Cholerae, and E. coli O۱۵۷:H۷, respectively. According to the exposure scenarios, the total annual probability of infection in the studied population for E. coli, V. Cholerae, and E. coli O۱۵۷:H۷ was determined to be ۸ × ۱۰-۲, ۸ × ۱۰-۴, and ۱۷ × ۱۰-۲, respectively. Conclusions: In irrigating agricultural crops with wastewater implementing wastewater safety plans (WWSP) is crucial.

Keywords:

Wastewater , Vibrio Cholerae , Escherichia Coli O۱۵۷ , Qom City , Crops , Agricultural.