Protecting Public Health
Since 1854 when John Snow identified wastewater contamination of the Broad Street pump as the cause of a cholera outbreak in London, preventing pollution of drinking water sources has been a fundamental tenet of public health protection. The subsequent development of sewerage systems to remove and treat wastewater and the provision of reticulated water supplies delivering filtered and chlorinated water has greatly reduced the incidence of infectious diseases in society. The provision of reticulated water and sewerage systems in cities in the late 19th century and early 20th century reduced the incidence of infectious diseases by a factor of ten and halved the death rate.
Untreated wastewater typically contains a variety of biological and chemical constituents that may be hazardous to human health and harmful to the environment. The aim of wastewater treatment is to remove harmful constituents down to levels which allow the treated water to be safely discharged to the environment or to be recycled for beneficial uses.
Depending on the level of treatment, recycled water may contain residual levels of micro-organisms such as bacteria, viruses or protozoa which pose infection if ingested. It may also contain residual levels of chemicals which could be harmful to health if ingested in large quantities.
Water recycling systems need to be designed to ensure that use of recycled water is such that operators or the public are not exposed to significant risk of infectious disease through contact with or ingestion of recycled water.
In most countries, the authorities have now developed regulations or guidelines for recycled water systems. When recycled water is treated and applied to a beneficial use as prescribed, the risk of infection is negligible.
