ITT's Place in the Cycle of Water - Water Solutions

The Cycle of Water: Wastewatersludge treatmentSludge is the by-product of wastewater treatment andis generated from:• Primary treatment – primary sludge.• Secondary treatment – includes the portion ofthe return activated sludge that is removed(wasted) so that the biological populationfunctions properly.• Tertiary treatment – secondary sludge (wasteactivated sludge) when biological nitrogen orphosphorus removal is applied or chemicalsludge when phosphorus is precipitated withinorganic chemicals.Biosolids are primarily organic, accumulated solidsseparated from wastewater that has been stabilized bytreatment and can be beneficially used. Sludge is theunstabilized solids separated from wastewater, a termnot interchangeable with biosolids. Sludge may alsobe formed from clean water processes and is typicallycomposed of minerals and chemicals from coagulation/flocculation.Sludge treatment is of vital interest to wastewatertreatment plant operators because this aspect of theprocess tends to consume up to 50% of a plant’soperating budget.Sludge treatment involves primarily thickening,stabilization and dewatering. Thickening is normallyperformed in gravity thickeners but can also beachieved or enhanced by different mechanical methodssuch as belt filter thickeners, drum thickeners orcentrifuges. Stabilization is most often achieved eitherby aeration (aerobic stabilization), anaerobic digestion(with biogas production) or lime stabilization.Dewatering follows stabilization and is achieved eitherby solar drying, belt filter presses, chamber filterpresses or centrifuges.Traditionally, sludge was disposed either to farmlandor to landfill, but methods of reusing sludge haveincluded land reclamation or agriculture, incorporatingit into construction materials and soil and soilimprovers. However, the wastewater industry is movingaway from the quickest and cheapest route for sludgedisposal to a more holistic concept to accommodatethe type of product that end users will purchase orthat might be more beneficial to the environment.In countries all over the world there are laws thatcontrol or limit the use and disposal of sludge as wellas the contents of pollutants in sludge. In addition,worldwide, the sludge volumes are increasing due tohigher output from secondary treatment facilities.CASE STORY:ITT's N-Pumps Provide Solutionfor Digested Sludge in GermanWastewater PlantA wastewater plant in Germany wasexperiencing continual pump stops dueto digested sludge containing rags andabrasive mineral sand. Replacing a screwpump with an N-pump from ITT’s Flygtbrand has resulted in a more reliablecirculation process and substantially loweroperating costs.ITT’s Place In The Cycle of Water: Everything But The Pipes