In the anaerobic digesters another group of bacteria begin to digest and dissolve the solids to their basic components. This process uses bacteria which do not need atmospheric oxygen to survive, so therefore, no air is bubbled into the tanks. In fact, air mixed with the gasses may be explosive, so we strive to keep all air out.
The anaerobic digesters produce a stable sludge which is readily dewatered. The process is also a source of methane gas, which is used as a fuel source for heating the digesters, heating several buildings, and fueling the engine generator to produce electricity. The digester is kept at an optimum temperature of between 90 - 95 degrees F. About 50,000 cubic feet of methane gas are produced per day.
The Engine Generator
The engine generator runs on digester or natural gas. The generator supplies electrical power to essential pieces of treatment plant equipment.
In the event of a complete power outage, important equipment will be powered by the engine generator. Waste heat is used to help heat surrounding buildings.