Glossary: Household Wastewater Treatment

These terms may help you make more accurate assessments when completing the Household Wastewater Treatment Fact/Worksheet. They may also help clarify some of the terms used.

Aerobic treatment device: An aerated tank which produces an effluent similar to that of an intermittent sand filter.

Cesspool: Covered excavation in the ground that receives sewage directly from a building’s sewer system. It is designed to retain organic matter and solids and permit liquid to seep into soil cavities. Cesspools are prohibited in Idaho and are a high risk for ground-water contamination
(See seepage pit).

Clear water infiltration: Entry of water that does not need treatment — such as rainfall or tile drainage through direct plumbing, unsealed joints, access ports, and cracks — into a wastewater treatment system. Clear water infiltration can overload your septic system resulting in system failure.

Design capacity: Maximum volume of liquid a particular wastewater treatment system is designed to handle. For systems that include subsurface sewage disposal, capacity is affected by system maintenance and the soil’s ability to accept and treat sewage effluent. If you don’t know the design capacity of your system, use 200 gallons per day for a two bedroom home, add 50 gallons per day for each bedroom over two, as a minimum estimate when you fill out the worksheet. Check with your local public health district, because it may use a higher estimate.

Effluent: Liquid discharged from a septic tank or other treatment process.

Holding tank: An approved watertight receptacle for the collection and holding of wastewater.

Scum: Floatable solids, such as grease and fat.

Seepage pit (dry well): Underground receptacle constructed to permit disposal of septic tank effluent, treated wastes, or clear wastes by soil absorption through its bottom and walls.

Septage: Settled, partially decomposed solids resulting from wastewater treatment in a septic tank.

Septic tank: A watertight, pretreatment receptacle receiving sewage, designed and constructed to permit separation of settleable and floating solids from the liquid, and detention and anaerobic digestion of the organic matter, prior to discharge of the liquid.

Soil absorption: Use of soil contact in treating effluent to minimize its contamination potential. Can be done through use of a conventional drain field (trenches or beds), or alternative treatment systems (mounds or sand filters).