Copper and zinc removal from anaerobic digestates via Sporosarcina pasteurii induced precipitation: Effect of volatile fatty acids on process performance

Microbial induced carbonate precipitation (MICP) shows great potential for metals recovery from secondary sources, which is vital for circular economy. This study explores the feasibility of using Sporosarcina pasteurii for MICP to recover copper (Cu) and zinc (Zn) from acidogenic anaerobic digestates at laboratory scale. Pre-cultured S. pasteurii was inoculated into solutions containing 20 g L−1 of urea and varying concentrations of Cu and Zn (0–25 mg L−1). The system was maintained at 30 °C with continuous agitation for seven days to assess Cu and Zn removal at initial pH values of 5, 6 and 7. The influence of volatile fatty acids (VFAs) on urea hydrolysis and Cu and Zn removal via S. pasteurii-induced MICP was evaluated by adding 3 g COD L−1 of acetic and propionic acids to metal solutions. Results showed that S. pasteurii enhanced Cu and Zn removal, with yields varying from 22% to 100% depending on the initial pH. In the presence of VFAs, Cu and Zn removal was significantly reduced (p