As wastewater treatment plants become larger and more sophisticated, so do the demands for handling large amounts of sludge – a complex and expensive operation. Pumps have to handle high solids concentrations and are expected to provide continuous operation, high reliability and energy efficiency. Xylem has the proven experience and equipment to meet these demands.

Secondary sludge pumping is part of the wastewater treatment process. It includes return activated sludge (RAS), which is continuously pumped back into the secondary biological treatment tank as part of the treatment process, and waste activated sludge (WAS), which is excess settled sludge that is pumped to the sludge handling process. 

Dewatering is typically the last step before disposal of sludge from secondary treatment and external sources. Sludge volume decreases by removing the water content, thus creating a thicker and more manageable mass. Dewatering may also reduce handling costs and minimize leachates and odors at landfills. 

After dewatering, the dry solids content is significantly higher. This may cause high head loss in transporting the sludge for disposal or further treatment. Thickened sludge needs to be pumped downstream, directly to disposal or sludge storage.