The volume of sludge produced is influenced by how the unit is used (size, frequent overloads, type of waste water, routine maintenance). Each unit is different.
We estimate that an installation of 0.5l/day/p.e. will produce 182.5 litres per p.e. of sludge per year in the first year. The reality seems to be closer to 0.3l/p.e./year.
The volume of sludge produced will reduce over the first few years. Normally after the 4th or 5th year, the residual volume is reduced by 40%.
When emptying, the cleaner must leave a few centimetres of sludge at the bottom of the tank as the bacteria that break down the sludge are specific and take a long time to develop.