Phosphorus recovery from sanitary sewage by struvite precipitation
About 90% of the world's phosphate production is destined for agriculture (Reinhard et al., 2017; Li et al., 2018), being used as fertilizers, such as by-products such as superphosphates and ammonium phosphates. (Lee, JD -1999). According to the United States Geological Survey (USGS, 2010), agriculture uses approximately 100 million tons per year of phosphorus in the form of P2O5, extracted from mining. Research indicates that it will take 50 to 100 years for us to have a problem with phosphate reserves. Brazil's situation in terms of its phosphate reserves is 6 million tons per year, 3.2% of global production, being a major importer of this raw material. (Adolpho, Campos, Cordani- 2016). Faced with this situation, it shows the need to find new phosphorus recovery technologies to develop new ways of large-scale production. A promising attempt is the recovery of phosphorus, present in sewage in the form of struvite crystals. (Huang et al., 2018). Struvite has great advantages over other fertilizers found on the world market (BRIDGER; SALUTSK), such as: Non-occurrence of hypersaturation of nutrients in plants; Absorption of nutrients before storm runoff; It has lower metal contents than mineral fertilizers; The nutrients nitrogen, potassium and magnesium are placed together with the struvite in the soil; Reduction of eutrophication of surface water bodies. However, struvite is still not produced on a large scale, because it presents some difficulties such as: Obtaining purity, produced in sanitary sewage or wastewater; A high expense in the operation with the use of alkaline metals; Lack of economic incentives to obtain phosphorus. In this context, the objective of this study is to evaluate the recovery of phosphorus through struvite crystals through chemical precipitation from sanitary sewage of a full-scale activated sludge system optimized for the joint removal of nitrogen and phosphorus.