Identifying your septic system
There are a variety of on-site systems used today: Septic tank/soil absorption (leach field) system, aeration (aerobic) system, and the mound system are the most common. Contacting your local Health Department for a copy of your septic system permit and soil evaluation sheet will indicate approximate location of the system and the size of the tank.
Septic Tank (leach field) System
A septic system consists of two main parts- a septic tank and a drain field. The septic tank is a watertight box, usually made of concrete or fiberglass, with an inlet and outlet pipe. Wastewater flows from the house to the septic tank through the sewer pipe. The septic tank treats the wastewater naturally by holding it in the tank long enough for solids and liquids to separate. The wastewater forms three layers: Solids lighter than water (such as grease or oil) float to the top forming a layer of scum. solids heavier than water settle at the bottom forming a layer of sludge. The middle layer is partially clarified wastewater. Bacteria in the wastewater work to break down the layers of scum and sludge. The layer of clarified liquid flows from the septic tank to the drain field or distribution device, which helps to uniformly distribute the wastewater into the drain field. A standard drain field (leach field) is a series of trenches or a bed lined with gravel and buried one to three feet below ground level. Perforated pipes or drain tiles run through the trenches to distribute the wastewater. The drain field treats the wastewater by allowing it to slowly trickle from the pipes out into the gravel and down through the soil.
Aeration (aerobic) System
Aeration systems are similar to septic systems in that they both use a natural process to treat wastewater. Unlike septic treatment, the aerobic treatment process requires oxygen. Aerobic treatment units use a mechanism to inject and circulate air inside the treatment tank. This mechanism requires electricity to operate. Aerobic systems treat wastewater in stages. Somtimes the wastewater receives pretreatment before it enters the aerobic unit and the treated wastewater leaving the unit requires additional treatment or disinfection before being returned to the environment. The process most aerobic systems use to treat wastewater is referred to as suspended growth. In the main aeration chamber, air is mixed with the wastewater. Air is forced into the aeration chamber by an air blower or a compressor. Aerobic bacteria is then formed to digest the solids in the wastewater. Unfortunately, the bacteria cannot digest all of the solids so they eventually settle out as sludge.
Other processes used by aeration systems are attached growth units and flow design. Attached growth units treat wastewater by taking a surface made of material bacteria can attach to, and then exposing that surface alternately to wastewater and air. Flow design uses different ways to control the flow of wastewater over a period of time.
Other processes used by aeration systems are attached growth units and flow design. Attached growth units treat wastewater by taking a surface made of material bacteria can attach to, and then exposing that surface alternately to wastewater and air. Flow design uses different ways to control the flow of wastewater over a period of time.
Mound System
Mound systems are necessary over traditional septic tank systems when there is slow or fast permeable soil, shallow soil cover over creviced or porous bedrock, or a high water table. Three components make up a mound system: a septic tank or pretreatment unit, a dosing or pump chamber, and the elevated mound. The septic tank works as explained above, leaving the wastewater to flow by gravity to the pump chamber. Once the wastewater rises to a certain level, the pump delivers a set amount to the mound. Once a sufficient amount of wastewater has been discharged, the level is lowered and the pump stops. The mound is a drainfield that is raised above the soil surface and is composed of sand fill. The wastewater is uniformly distributed throughout the bed and treatment occurs as it moves through the sand and returns to the natural soil.