Much of the wastewater generated by homes, industries, and businesses must be treated before it is released back into the environment. This is because it contains nutrients and other substances that can be harmful to the environment and human health, as well as to aquatic fauna and flora. These nutrients can cause oxygen depletion in water bodies, beach closures and contamination of drinking water. However, if the nutrients are recovered, they can often be put to beneficial use.

For instance, biorefineries use wastewater as a source of raw materials, generating products of value from waste nutrients and simultaneously producing clean water for reuse or discharge. Nutrients such as nitrogen and phosphorus can be converted into environmentally friendly fertilisers, and used for ecological restoration and agricultural purposes. Biosolids from wastewater can be used as fuel for heating, replacing fossil fuels and reducing the amount of biosolids sent to landfill.

Local governments have an important role to play in providing pipes, water management and treatment infrastructure to ensure that water is safely handled. They can also play a role in monitoring privately run facilities to ensure compliance with environmental performance standards. Finally, cities can connect stakeholders to match supply and demand for non-potable water, energy and nutrients recovered from wastewater.