Normally, a septic tank is the minimal facility required for the disposal of waste water. This septic tank is subject to certain rules and regulations, regarding size, positioning and quality.
how a septic tank works
The functioning of a septic tank is based on an anaerobe sedimentation of the waste water, suspended solids settle on the bottom of the tank, floating substances create a layer on top of the waste water, the remaining water normally flows out to some kind of treatment facility, but unfortunately in many countries , still directly into the ground. It is highly recommended that the waste water from the septic tank is either put into a CWF or IPU for further purification.
In the previous century, when very few chemicals were used for household purposes, and the amount of waste water per capita/day was lower then 50 litres, a 2000 litres septic tank provided an adequate protection for the environment. However, nowadays, the amount of chemicals for cleaning, laundry, unclogging, disinfection etc. are a substantial risk to the environment, and even a 5000 litres septic tank, is not really adequate for a household of four, because of the high volume of waste water (150 -200 litres per capita/day). Many of the chemicals used have a negative impact on the bacteria in the septic tank, diminishing the functioning even further. The septic tank then becomes more of a holding tank.
Therefore it is highly recommended to apply a more effective way of treatment for your waste water, like a CWF or IPU.