Sewage treatment plants are primarily and in many cases, exclusively, designed for domestic family houses, not large houses where wastewater treatment systems are underloaded. These are, typically, larger, 4 bedroomed houses, with only 2 people living in them.
Almost all sewage treatment plants are only designed to go down to 50% of the size of the plant, meaning that a 6 person plant, needed for a 4 bedroom house, must be used by a minimum of 3 people. This is in order for the bacteria to receive enough 'food' from the sewage per day. They are only tested down to 50% for their EN Certificate, so there is no data available for them for lower percentages, and in many cases, they don't work.
We manufacture 3 different types, each one designed for different situations to cope with this problem.
A sewage treatment plant that is connected to a normal house lived in by full-time residents who are responsible for the plant, is the ideal situation for any sewage treatment system. It has a stable flow rate of sewage into the plant and the concentration of pollutants is relatively stable as well.