Water Engineering and Development Centre
Series: WELL Studies in Water, Sanitation and Environmental Health Task 068/1
Use of wastewater in agriculture is becoming more important due to increasing water scarcity in dry climate regions of the world. Standards for wastewater reuse in many countries have been influenced by the WHO (1989) Health Guidelines and the USEPA/USAID (1992) Guidelines. Since then, epidemiological studies have been carried out by London School of Hygiene and Tropical Medicine, with colleagues in Mexico and Indonesia, and microbiological studies of crops irrigated with treated wastewater have been carried out by Leeds University, with colleagues in Brazil and Portugal, to assess the validity of these guidelines. The WHO (1989) Guidelines for Wastewater Reuse in Agriculture and Aquaculture are reviewed in the light of these and other recent studies.
There are currently three main approaches for establishing microbiological quality guidelines and standards for treated wastewater reuse in agriculture which have different objectives as their outcome:
(i) the absence of faecal indicator organisms in the wastewater,
(ii) no measurable excess cases in the exposed population, and
(iii) a model generated estimated risk below a defined acceptable risk.
In this review we use approach II, using empirical epidemiological studies supplemented by microbiological studies on pathogen transmission, in conjunction with approach III, using model-based quantitative microbial risk assessment for selected pathogens in coming to our conclusions. Recommendations have also been made for the use of a disease control approach in the setting of country standards.