Sludge treatment and final disposal

In urban areas the main water polluting agents are sewage which is most often discharged directly into water bodies. Facing the intense degradation of water bodies the sewage from several Brazilian cities has been treated in Sewage Treatment Plants (STP) which operate in different technological systems. Some constituents of wastewater such as metals and helminth eggs when passing through the sewage treatment plant are concentrated in the sludge. Several organic (humic acids) and mineral (nitrogen and phosphorus) components confer fertilizing characteristics to the sludge; however other constituents are undesirable as: heavy metals organic pollutants and pathogenic microorganisms; for their health and environmental risk.