Wastewater refers to water that has been contaminated as a result of human interaction. Wastewater can include sewage and stormwater, which are treated to reduce adverse health impacts. Treated effluent is typically discharged to receiving waters or reclaimed for reuse. Wastewater influences the energy-water-food-nexus through its energy demands for treatment and pumping; land requirements for conveyance infrastructure; impacts of effluent and biosolids on receiving water quality, land and ecosystems; and opportunities to generate energy from biogas.

Stormwater is critical to the nexus because of factors such as development density, deforestation, fertilizer and pesticide use. These factors impact the quantity and quality of stormwater and raw water sources, creating the need to use more energy-intensive treatment technologies to bring water to potable levels. These factors also affect the health of ecosystems and associated goods and services they provide.