Is it possible to install a WWTP in an old septic tank or cesspit?

Technically, it is possible but in practice it brings more complications than it seems at first glance. In most cases, neither the dimensions nor the material and construction of the original septic tank or cesspit are known. Then it is difficult to calculate the work associated with installing the WWTP in the existing tank. Therefore, we have found that the approach of installing the WWTP next to the existing cesspit or septic tank and then using it for the accumulation of treated water works well.