Synergistic treatment of acid mine drainage and urea wastewater based on urease-producing bacteria and sulfate-reducing bacteria: A strategy for waste resource utilization.

The acidic environment and lack of carbon sources in acid mine drainage (AMD) limit the effectiveness of sulfate-reducing bacteria (SRB) in its treatment. The use of urease-producing bacteria (UPB) to hydrolyze urea and drive SRB to treat AMD addresses these two key limitations. Based on the pollution characteristics of AMD from an abandoned sulfur iron mine in Southwest China, this study investigates the feasibility of the combined UPB-SRB treatment for simulated AMD, explores the synergistic mechanism, and evaluates the practical application of this synergy in the treatment of real AMD. The UPB-SRB combination outperforms the individual use of UPB or SRB. When UPB neutralized the pH of simulated AMD from 2 to 5, the highest cost-effectiveness was observed: the solution's pH increased to 7.2, with removal efficiencies for SO, Fe, Fe, and Mn reaching 89.18 %, 95.59 %, 95.81 %, and 88.2 %, respectively. The reaction products of the UPB-SRB synergy included FeOOH, FeO, FeS, Fe, and MnS. UPB utilized ammonia generated from urea hydrolysis to improve the acidic environment, while its metabolic by-products, including amino acids, organic acids, alcohols, and vitamin B, provided carbon and nitrogen sources for SRB. In the treatment of real AMD, the synergistic effect of UPB-SRB achieved removal efficiencies of 96.89 % for SO, 100 % for Fe, and 99.89 % for Mn, and raised the pH from 2 to 8. The treated AMD showed no bio-toxicity or potential risks and demonstrated agricultural reuse potential. By replacing traditional carbon/nitrogen sources with urea-containing wastewater, the combined use of UPB and SRB provides an efficient, safe, and cost-effective solution for AMD disposal, offering a novel approach to optimizing SRB-based AMD treatment and urea wastewater resource utilization.