Phosphorus recovery from sewage sludge

In recent years, new phosphorus recovery technologies have been developed to decrease the cost of sludge disposal and to recovery of phosphorus in content of sewage sludge as useful product. Phosphorus can be recovered from sewage sludge, wastewaters, and concentrated process waters. This research has utilized knowledge of phosphorus recovery as struvite from synthetic solutions and P-rich liquid which extracted from sludge, parameters affecting phosphorus recovery process like temperature, pH, pumice amount, and the applicability of pumice stone at struvite precipitation. Experimental results were evaluated by using Box-Wilson Experimental Design and Box-Behnken Experimental Design. It was detected that nitric acids is significantly efficient on phosphorus release by using acids at experimental results which were evaluated by using Box-Wilson Experimental Design. Box-Benhken Experimental Design was used to determine effects of base concentration, mixing time and temperature on phosphorus release with base. It was observed that sodium hydroxide (NaOH) has efficiency than potassium hydroxide (KOH) on phosphorus release. Temperature and base concentration on phosphorus release is the principal effect. However, mixing time slightly affected. Box-Benhken Experimental Design was used to determine effects of pH, pumice amount and temperature on PO4-P, NH4-N, Mg removals in the model reactor. According to experimental results, temperature and pH in model reactor are the most important parameters on phosphorus, ammonium and magnesium removal. The amount of pumice slightly affected phosphorus, ammonium, and magnesium removal. Good phosphorus removal could be achieved by pumice stone as crystal seeding. It was observed that struvite crystals were precipitated on pumice stone. It was observed that phosphate and ammonium precipitated significantly as struvite and calcium phosphate compounds on pumice stone and concentrations of heavy metals like cadmium, chromium, and nickel showed exchange with time, but copper concentration increased during reaction times at studies of struvite precipitation with P-rich liquid in model reactor. Keywords: Phosphorus recovery, pumice stone, sewage sludge, struvite