Hygienic Evaluation of Reclaimed Water Used to Irrigate Food Crops—A Case Study

Abstract

The study was designed to test the continued validity of a field pilot project (completed in 1987) that had found irrigation of food crops with tertiary-treated reclaimed municipal wastewater to be safe. It was also designed to determine whether or not pathogenic microorganisms of concern to food safety, such as E. coli 0157:H7, Cyclospora, enteric viruses and Salmonella were present in disinfected tertiary recycled water. Sampling of the tertiary water was conducted at intervals over a period of three months. In addition, at the same time, samples were taken from the raw incoming wastewater, from secondary effluent, and from a control source, local well water. The results from samples of recycled water are comparable to similar tests at other well-operated, tertiary recycled water treatment plants and compare well with sources of drinking water supply. Other parasites, of lesser concern to food safety than to drinking water safety, were either absent or were detected at extremely low concentrations of empty, non-viable cysts. The Tertiary Water Food Safety Study did not detect any Salmonella, Cyclospora and E. coli 0157:H7 in any of the samples of tertiary recycled water from the Monterey Country Water Recycling Projects (MCWRP).