Wastewater Treatment

In WEAP, a wastewater treatment plant accepts wastewater from demand sites and treats it to remove pollutants. The treated effluent can be reused directly by other demand sites (green transmission links) or routed to rivers, aquifers and other supplies (red return flow links). You may also model combined sewer overflow (CSO) of stormwater. To do this, use a catchment to model stormwater runoff, and route the catchment's runoff to the wastewater treatment plant. Enter a daily capacity for the plant. In timesteps where the combined runoff and wastewater inflow to the treatment plant exceeds its capacity, the excess will overflow, causing untreated wastewater mixed with stormwater to flow through the wastewater return flow links.

Daily Capacity

Enter the maximum daily processing capacity of the treatment plant, or leave blank for no capacity limitation. Flows exceeding this limit will not be treated, flowing untreated through the wastewater return flow links.


Enter the consumptive losses for the treatment plant--water that is lost to evaporation or treatment or otherwise unaccounted for. These amounts are lost from the system. Consumption is entered as a fraction of the treatment plant inflow.

Treatment can be specified by two different methods: removal rate or outflow concentration. For each constituent, specify either removal rate or outflow concentration, but not both.

Removal Rate

The removal rates will typically vary among wastewater treatment plants and among the different types of pollutants. Enter the % (by weight) of each pollutant that is removed by treatment.

Outflow Concentration

Enter the concentration of the constituent in the outflow.

Entered on: Data View, Branch: Water Quality \ Wastewater Treatment, Tabs: Daily Capacity, Consumption, <Constituent Name> Removal, <Constituent Name> Concentration