Sulphate-reducing fixed-bed bioreactors fed with different organic substrates for metal precipitation

摘要

Batch upflow fixed-bed sulphate-reducing bioreactors have been set up and monitored for the treatment of synthetic, acidic (pH 3.5) solutions containing divalent iron (100 mg/L) , zinc (100 mg/L), copper (100 mg/L) , nickel (100 mg/L) and sulphate (1800 mg/L) , using acetate, ethanol and lactate as sole electron donors at 60% excess over stoichiometry. The reactors were inoculated with an ethanol-grown microbial community, which was dominated by Desulfobacter postgatei, an acetate-utilizing species. This paper comparatively discusses the results obtained from the batch runs of the reactors in terms of sulphate reduction and organic substrate utilization, metal precipitation capacity as well as solids composition and formation mechanisms. Quantitative precipitation of the soluble metal ions has been achieved. XRD and SEM-EDS analyses showed poorly crystalline phases of marcasite, covellite and wurtzite as well as several mixed metal sulphides. The reduction of sulphate was approximately 95 % for the ethanol-and lactate-fed reactor whereas it was limited to about 80% in the acetate-fed reactor after 30 h of operation. TOC degradation and residual acetate content ( < 100 mg/L for the ethanol-and lactate-fed reactor) showed that the original microbial community sustained its acetate-oxidizing capacity. Acetate, ethanol and lactate are completely degraded and this is important for the overall efficiency of the process.