Quantitative microbial risk assessment for crops irrigated with wastewater from the WWTP of Ilha Solteira (SP)

Abstract

This work has quantitatively evaluated the microbial risk by consumption of crops irrigated with raw affluent and treated effluent from the wastewater treatment plant (WWTP) of Ilha Solteira-SP. It was estimated the risk of infection for virus, bacteria and protozoa due ingestion of raw lettuce, cabbage and tomato irrigated by sprinkling. The number of pathogens was estimated with the most probable number of fecal coliforms found at a previous monitoring carried in the WWTP. Using models reported by the literature, the volume of wastewater remaining in the products and the decay of microorganisms were estimated, and dose-response models were applied for each microorganism. The medians and the 95^th percentile of the risks of infection by the ingestion of lettuce and cabbage irrigated with raw or treated wastewater were higher than the limits set by the WHO for all pathogens, while for tomato, in both cases, the risk of infection by Cryptosporidium was below the limit; for tomato cultivated with treated effluent, the median of the risk of infection by Campylobacter was lower than the limits set by the WHO. The post treatment of the effluent for inactivation of pathogens would reduce the risks of infection and would allow the irrigation of the analyzed cultures.