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Municipal and Industrial Permits

There are three methods for disposing of treated wastewater effluent: surface water discharge, subsurface discharge, and land application for beneficial use.

Federal, state, and local regulations prohibit the disposal of untreated wastewater into storm drains or surface waters. In some cases, a permitted facility may discharge treated wastewater into surface waters. DEQ’s Idaho Pollutant Discharge Elimination System (IPDES) Program sets requirements and issues permits for this type of discharge, including specifying pretreatment requirements and limits on what can be discharged to ensure that the discharge does not harm water quality or public health.

Subsurface discharge occurs on-site where wastewater is treated by discharging septic tank effluent underground where it leaches through a drainfield.

Treated wastewater can also be applied to land for irrigation. The small amount of pollutants remaining in the wastewater after treatment is absorbed by the crop or are assimilated into the soil structure. Depending on the contaminants, the water may require pretreatment before discharge to meet water quality standards. DEQ issues permits for facilities treating wastewater and sludge through this method.

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