Struvite Recovery from Digested Sewage Sludge

Struvite recovery is an ideal way to simultaneously recover phosphate (Pi) and ammonia from digested sludge. A full-scale plant to recover struvite directly from digested sludge was implemented at Higashinada Wastewater Treatment Plant (WWTP) having the sewage treatment capacity of 241,500 m3/day in Kobe City. The struvite recovery plant has a capacity of treating digested sludge of 239 m3/day, which is equivalent to a quarter of digested sludge generated at the WWTP. On average, it can recover approximately 40 and 90% of total P and soluble Pi, respectively, from digested sludge. The struvite recovery could reduce the volume of dewatered sludge by 3.3% on average and prevent struvite-scaling problems in the sludge treatment process. Recovered struvite has been registered as a chemical fertilizer and distributed to the Kobe area through fertilizer companies.