Information > Frequently Asked Questions > What are the potential risks associated with recycled water?
The risks associated with recycled water must be minimised to acceptable levels before recycled water can be used in any specific situation (i.e. the water must be fit for purpose). In most cases, these environmental and health risks can be managed through the level of wastewater treatment or by the carefully managed use of recycled water. However, in some cases these risks are too costly to manage and the reuse scheme may not be economically viable. Individual state/territory environment and/or health related authorities are generally responsible for ensuring the water recycled is fit for the intended use.
All of these risks outlined below are manageable if guidelines and appropriate risk management principles are followed.
Key potential health risks
Microbial pathogens in wastewater from sewage effluent are the major concern for human health when recycling water. The major groups of pathogens are:
- Bacteria (e.g. Escherichia coli, Salmonella spp)
- Viruses (e.g. Enteroviruses, Rotavirus, Hepatitis A)
- Protozoa (e.g. Giardia Lamblia, Cryptosporidium parvum)
- Helminths (e.g. Taenia spp (Tapeworm), Ancylostoma spp (Hookworm))
Not all infections make you sick. To become infected by a pathogen you must be exposed to a sufficient number of pathogens. If recycled water is fit for the intended purpose, exposure will be low and infection unlikely as it is related to the concentrations of pathogens in the recycled water and the amount of water ingested.
Key potential environmental risks
Some of the common environmental risks from recycled water include:
Salinity
A chronic problem which needs to be managed in all irrigation systems. Can result in reduced plant growth and plant damage and can impact on freshwater plants and invertebrates in natural ecosystems if discharged directly with little dilution. Most common salts are sodium chloride
Sodicity
Excess sodium in recycled water can cause soil dispersion/swelling, reducing water infi ltration on heavier textured soils. This can be difficult to remedy.
Sodium
Can be toxic to some plants if it accumulates in soils from ongoing irrigation. More important as a omponent of salinity and sodicity.
Chloride
Can be toxic to plants if sprayed directly on leaves, and if it accumulates in soils from ongoing irrigation, but is usually more important as a component of salinity.
Nitrogen
Mostly of benefit to cultivated plants, but can cause eutrophication (excessive nutrient levels) in land and aquatic ecosystems.
Phosphorus
Mostly of benefit to cultivated plants, but can cause eutrophication (excessive nutrient levels) in land and aquatic ecosystems.
Chlorine residuals
By-products of disinfection processes may be harmful to aquatic or marine ecosystems if discharged directly with little dilution.
Hydraulic loading
Too much water applied to land can result in excess groundwater recharge, water logging and secondary salinity.
Boron
Plant toxicity may arise in some plants in some soils if it accumulates from ongoing irrigation.
Surfactants
Some organic and inorganic surface active agents from detergents can remain in recycled water and be harmful to some aquatic organisms.
Other risks which require monitoring
A broad range of chemicals have been identified as having the potential to alter normal endocrine function in animals, i.e. endocrine disrupting chemicals (EDCs). At this stage, there is no evidence that environmental exposure to low levels of potential EDCs (potentially present in recycled water) affects human health because of the relatively low exposure.
However, ongoing monitoring is required to ensure good risk management. Pharmaceutical chemicals and their metabolites, potentially found in recycled water, raise similar issues to EDCs (above). Health impacts from pharmaceuticals should also be minimal because of the relatively low exposure. However, ongoing monitoring is required to ensure good risk management.
