Department of
Environmental Quality

Wastewater is spent or used water, such as from households and businesses, that contains enough harmful material to damage the water's quality. Every building with running water generates some sort of wastewater. Wastewater may contain contaminants such as oil, dirt, human waste, and chemicals. Untreated wastewater can cause serious harm to the environment and threaten human health.

Proper management and disposal of wastewater is essential to protect public health and Idaho's surface and ground water resources. DEQ's Wastewater Program establishes standards for on-site wastewater systems (septic systems) and issues wastewater reuse permits limiting the amount of wastewater that may be land-applied for irrigation.

Wastewater Collection and Treatment Systems

Any structure or facility that generates wastewater must dispose of it through some sort of wastewater treatment and disposal system, either centralized or decentralized. Large-scale public sewer systems (municipal wastewater treatment plants) are centralized systems. Homes and other buildings that are not served by public sewer systems depend on decentralized "on-site" septic systems to treat and dispose of wastewater. Learn more.

On-Site Wastewater Systems (Septic Systems)

On-site systems use a septic tank and underground (subsurface) drainfield to treat wastewater on-site. Septic systems dispose of household sewage, or wastewater, generated from toilet use, bathing, laundry, and kitchen and cleaning activities. On-site systems are the most common wastewater treatment system used in rural areas: 36% of Idaho's homes, or about 210,000 residences, use on-site septic systems to treat their sewage. A properly designed, located, constructed, and maintained septic system is imperative to protecting human health and the environment. Learn more.

• Nutrient-Pathogen Evaluations
• Technical Guidance Manual for Individual and Subsurface Sewage Disposal Systems

Wastewater Disposal Options

Once wastewater has been treated, it is "disposed" of by re-introducing it to the environment. The three main methods of disposing of treated wastewater effluent are surface water discharge, subsurface discharge, and land application for beneficial use. Learn more.

National Pollutant Discharge Elimination System (NPDES)

Industrial, municipal, and other point sources of pollution that discharge wastewater directly to surface waters are required to obtain National Pollutant Discharge Elimination System (NPDES) permits. NPDES permits limit the amount of pollution that point sources may discharge into surface waters. The purpose of NPDES permits is to protect water quality and public health. In Idaho, the NPDES permit program is administered by EPA, which means EPA is responsible for issuing and enforcing all NPDES permits in Idaho. Learn more.

Aquaculture in Idaho

Aquaculture is the cultivating of freshwater fish, such as salmon and trout, under controlled conditions for commercial, conservation, and recreation uses. Idaho's aquaculture industry ranks as the third largest food-animal industry in the state and is the nation's largest commercial producer of rainbow trout. Aquaculture waste can have a negative impact on surface water and ground water. Good waste management and water stewardship are necessary to ensure the quality of water in receiving streams. Learn more.

Concentrated Animal Feeding Operations (CAFOs)

CAFOs are agricultural facilities that house and feed a large number of animals—typically cows, hogs, chickens, or turkeys—in a confined area for a length of time. Careful management of these facilities is necessary to protect public health and the environment from runoff carrying animal waste into nearby sources of water and from animal waste leaching into ground water. Several agencies share responsibility for regulating CAFOs in Idaho. Learn more.

Stormwater in Idaho

Stormwater is water from rain or melting snow that does not immediately soak into the ground. Stormwater runs off of land and hard surfaces such as streets, parking lots, and rooftops, and picks up pollutants, such as fertilizers, dirt, pesticides, and oil and grease. Eventually, stormwater soaks into the ground or discharges to surface water (usually through storm drains), bringing the pollutants with it. Federal, state, and local government agencies; business and industry; and individual land owners all share responsibility for stormwater management in Idaho. Learn more.