Types of Systems

Cesspool —

This is the simplest type of subsurface disposal system and is common for homes built prior to 1930. The system consists of a pit that has been constructed out of fieldstone or concrete block. Openings between the stones or blocks laid on their sides allow water to flow out of the pit.

Sewage enters the pit through the building sewer. The liquid level in the pit rises while water is added. The water level drops as water flows out of the cesspool and into the surrounding soil. Cesspools are normally quite deep, and the pressure from the water column within the pit forces water through the openings into the soil.

Septic Tank and Effluent Disposal System —

(Septic System)

This system uses a septic tank to receive the sewage from the house. The tank is typically constructed of concrete; however, older systems may have a steel tank. The septic tank has an inlet opening and outlet opening near the top of the tank. The liquid level does not vary as in a cesspool.

As sewage enters the tank an inlet baffle directs the inflow towards the bottom of the tank. Solids settle to the bottom of the tank and form a sludge layer. Grease, soap and other floatables rise to the surface and form a scum layer. An outlet baffle extends down into the clear liquid between the sludge and scum layers.

When sewage enters the tank, an equal volume of water is displaced. This water (septic tank effluent) flows up through the outlet baffle and out of the tank to a disposal system.

The disposal system may include a seepage pit, disposal bed or disposal trenches. The disposal system allows effluent to seep into the soil and away from the septic system. A seepage pit is constructed similar to a cesspool in that openings in a tank or stone lined pit allow effluent to flow out in to the soil. Disposal beds and disposal trenches use a distribution box or pressurized manifold to evenly proportion the effluent amongst perforated laterals that allow effluent to flow out of the system and into the surrounding soil.

Separate Gray Water System —

Some homes may have a separate disposal system to accommodate wastewater from clothes washers, sinks or hot tubs. Typically, gray water is discharged directly to seepage pits or dry wells; however, some gray water systems may have a septic tank installed also.

Advanced Systems —

Advanced technologies including peat moss treatment, aerated treatment and drip irrigation disposal have emerged as viable alternatives to mitigate failing septic systems on lots where site constraints can not be overcome by conventional methods. These new systems offer excellent treatment and may be appropriate solutions on some projects. Bayer-Risse Engineering, Inc. has designed and permitted numerous alternative systems in the central New Jersey area.

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