Conventional septic systems can treat and dispose of waste. The septic tank acts as the treatment unit for waste and is usually a buried concrete tank where waste from the house collects. The bacteriological activity in the septic tank liquefies 65% to 70% of the solids.

Primary Treatment

The liquid waste, or effluent, flows from the septic tank to the distribution box, where it is evenly sent out to the drain or leaching fields before finally dissipating into the soil. The remaining solids collect on the tank's bottom in the form of sludge (septage), while the greases or buoyant materials float to the top of the tank in the form of scum. This separation process is known as primary treatment.

Baffles & Tanks

Among the most important components of the septic tank are the baffles. The inlet baffle forces wastewater down into the tank. The outlet baffle prevents the scum layer from moving into the drain field. In addition, a double compartment tank will give added protection against solids moving into the drain field. Septic tanks also have inspection ports for checking the depth of sludge and scum layers and a manhole for cleaning the tank. A typical tank size is 1,000 gallons.

Secondary Treatment

Partially treated effluent from the septic tank then flows into a distribution box that divides the flow evenly into a series of underground perforated pipes. The perforated pipes ensure that the effluent is distributed over the entire drain field. In the drain field, the effluent receives further treatment through various biological processes that remove most of the remaining impurities (germs and chemicals) before the effluent returns to the groundwater system. This purification process is known as secondary treatment.

Drain Field

The drain field (also known as the leach field, nitrification field, and soil absorption field) disposes of the effluent by distributing it over a large area of soil. This process filters out many of the bacteria and viruses and treats the effluent before it enters the groundwater, while still allowing the soil to retain certain nutrients such as phosphorus and some forms of nitrogen.

Parts of the septic system:

Concrete or steel tank (1000 to 1500 gallons is normal)

With maintenance, a concrete tank will typically last 40 to 50 years.

Steel tanks typically last approximately 20 years.

The tank has inlet and outlet pipes with baffles to separate scum/grease from the effluent that goes into the leaching fields.

Leaching fields

Stone beds with perforated pipe (most cases).

Sand mounds are only needed if the soil does not "perk" adequately.

Distribution box

This box is used to distribute the effluent evenly to the leaching fields. 

Maintenance:

A septic tank should be pumped out every 24 to 36 months (for an average family of four).

 It is recommended that garbage disposals are not used when a septic system or cesspool is present because it may     overload the bacteriological farm (depletes bacteria activity).

If a system becomes clogged because no one pumped it out, you can have the system treated with hydrogen peroxide to help break up the solids. There are varying levels of success with this process. Adding yeast to a septic tank to help the bacteria activity is a myth. Human waste will produce ample amounts of anaerobiotic bacteria.

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