Quantitative Microbial Risk Assessment of Urban Wastewater Pertaining to Irrigation of Agricultural Products in Qom, Iran, in 2020

Abstract

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 3 pathogens-Escherichia coli, Vibrio cholerae, and E. coli O157 and carried out on 120 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 200 participants.  Results: Concentrations of E. coli, V. Cholerae, and E. coli O157:H7 in raw wastewater were determined to be 3.4 × 103 ± 500 cfu/100ml, 2.1 × 103 ± 100 cfu/100ml, and 312 cfu/100ml, respectively. Concentrations of E. coli, V. Cholerae, and E. coli O157:H7 in effluent were determined to be 2.1 × 103 ± 100 cfu/100ml, 0.8 × 103 ± 100 cfu/100ml, and 176 cfu/100ml, respectively. The conventional wastewater treatment system was effective in removing E. coli, V. Cholerae, and E. coli O157: H7 by 50%, 59%, and 43%, respectively. Crops irrigated with effluent contained 400 ± 250 cfu/100ml, 0.1 × 103 ± 0.019 cfu/100ml, and 52 cfu/100ml of E. coli, V. Cholerae, and E. coli O157:H7, respectively. According to the exposure scenarios, the total annual probability of infection in the studied population for E. coli, V. Cholerae, and E. coli O157:H7 was determined to be 8 × 10-2, 8 × 10-4, and 17 × 10-2, respectively. Conclusions: In irrigating agricultural crops with wastewater implementing wastewater safety plans (WWSP) is crucial.