Pollutants are removed from the wastewater effluent by physical, chemical and biological processes in the soil zone around the bed or trench. For adequate pollutant removal to occur, site conditions must be such that these processes can occur to the extent needed for a given loading rate. Pretreatment units and pumping system components and controls must be adequately maintained for pressure dosed effluent distribution systems to continue functioning properly. This technology is highly reliable as long as the system is adequately maintained and a reliable source of power is available. Other types of pretreatment units and processes will require maintenance of some type.
Pumps require either periodic maintenance or repair, or replacement.
Electrical and mechanical components which make up the pump control and alarm system may also need occasional repair or replacement. Maintaining the over the drainfield contributes to better performance of the soil disposal system. Improperly sited, designed or constructed systems can contaminate ground or surface water. Failing systems can result in odors, ponded effluent, and present risks to public health. This would be about 0.051 KWH of energy per day.