The biomass produced in activated sludge tanks and clarifying tanks is stabilized in the digestion tower and used to produce biogas. A thorough mixing of the sludge increases the gas yield and reduces its retention time in the reactor. In the process, the gas is withdrawn from the upper part of the digestion tower, compressed in the liquid ring compressor and reintroduced through the nozzles at the bottom.
WITTIG Rotary Vane Compressors are used in the processes that upgrade biogas (PSA, HPWS, membranes and others).
Digester gas compression
NASH liquid ring pumps draw the digester gas off the top of the digester and recirculate it to improve mixing and rate of reaction. The pump's operating liquid cools the digester gas by absorbing the heat of compression, thus providing an almost isothermal mode of operation. This has a positive effect on the service life of downstream valves, gas burners and motors, and it reduces maintenance costs. The cooling function of the operating liquid simultaneously acts as a flame arrester and reduces expenditures for explosion protection. The contaminated raw gas is also cleaned in the water ring as though in a gas scrubber and is partially dried. The gas is thus oxygenated and returned to the wastewater treatment process.
In this application, vacuum pumps are used to maintain a prime in cooling water systems. Maintaining a prime allows water circulating pumps to maintain design water flows with minimum power consumption. Single stage liquid ring pump packages, often supplied with priming valves, are ideal for this application because they prevent ingesting of water slugs into the pumps.
Wastewater Purification - Oxygenation of Activated Sludge Tanks
To reduce the space requirements and costs of wastewater treatment plants, a growing number of activated sludge tanks are being set up. The introduction of oxygen is extremely important for purifying wastewater. NASH compressors supply the pressure required for maximum oxygen yield.