Microbial aspects of wastewater reuse for irrigation

In many arid environments an alternative source of water is needed to meet the growing demands of the community, agriculture, and industry, thus wastewater reuse has become a viable option. Although the use of wastewater for agricultural irrigation has been practiced for centuries, recently a conservative approach in fully utilizing this source of water has been taken. The uncertainty of the health risks to an exposed population through wastewater irrigation practices due to the possible presence of enteric pathogenic organisms is one of the major disadvantages. Pathogenic bacteria, parasites, and viruses are all found in sewage and may survive treatment processes. Once in the environment, many are able to exist for prolonged periods of time and outbreaks associated with wastewater irrigation have been documented. Epidemiological evidence is scarce, however, much has been done to determine the fate of the pathogens in the environment. The incidence, survival, and inactivation of pathogens in environments associated with the wastewater aid in the understanding of the sudden occurrence of epidemics and potential routes of transmission. The scope of this review includes epidemiological studies on populations exposed to wastewater, the microbial survival on crops irrigated with wastewater, and the incidence of some of the pathogens in wastewaters. Because many areas are now utilizing wastewater for a variety of purposes from potable water to landscape irrigation, proposed regulations governing its use are discussed.