Sulfate-reducing suspension and biofilm reactors for acidic sulfate and metal containing wastewaters

摘要

Sulfate-reducing suspension and biofilm processes were studied for treatment of synthetic wastewater containing sulfate, zinc and iron. With lactate supplemented upflow anaerobic sludge blanket (UASB) and fluidized bed reactors (FBR) the following precipitation rates were obtained: 300-400 mg/l*d for Zn and 80 mg/l*d for Fe with hydraulic retention time of 16 h. The alkalinity produced in the process neutralized the pH from 2,5-3. The highest achieved sulfate reduction rate was 2000-2500 mg/l*d. In terms of sulfate reduction, hydrogen sulfide production and effluent alkalinity, the start-up of the FBR with the 10 % fluidization rate was superior to the FBRs with 20-30 % fluidization rates. With increased loading rates, high recycling rate became an advantage. After process failure caused by overloading, the sulfate reduction recovered within two weeks. Metal precipitates in the reactors were predominantly FeS_2, ZnS and FeS.