Treatment Performance And Key Factors Of Simultaneous Desulfurization And Denitrification Process

In this study, a laboratory-scale anaerobic fixed-bed bio-reactor was used to investigate the treatment performance and key factors of simultaneous de-sulfurization and de-nitrification process. Activated sludge was domesticated directionally to cultivate autotrophic sulfur-oxidizing/denitrifying bacterium, which are capable to oxidize sulfide to elemental sulfur when nitrate was adopted as electron acceptor under anaerobic or anoxic conditions and accumulate elemental sulfur extracellularly. Acetate was also added to incubate heterotrophic denitrificans. Thus, autotrophs and heterotrophs coexisted in the ecosystem, and cooperated to remove sulfide, nitrate and acetate simultaneously with elemental sulfur accumulation.The feasibility of simultaneous desulfurization and denitrification under mixotrophic condition was investigated via continuous-flow tests. Then key factors of the process, including pH value and sulfide/nitrate (S/N) ratio, were discussed. Under the optimum pH value and S/N ratio conditions, the volume loading rates were elevated until the treatment performance declined. The experimental results suggest:①The simultaneous removal of sulfide, nitrate and acetate as well as elemental sulfur accumulation could be achieved under mixotrophic condition. It was shown that the toxicity of sulfide had little inhibition on the functional microorganisms in this system.②The relation between autotrophic sulfur-oxidizing/denitrifying bacteria and heterotrophic denitrifiers was symbiotic. The heterotrophs could accelerate the autotrophic denitrification by utilizing its intermediate products, namely nitrite, which also ensured the accumulation of elemental sulfur.③Lower alkalescent pH condition was favorable to the SDD process. The theoretical S0 production rate was much lower under higher pH conditions.④S/N ratio had a remarkable influence on the treatment performance. The optimum S/N ratio to acquire the best efficiencies of both sulfide removal and elemental sulfur accumulation was supposed to be 5/6.⑤Complete sulfide removal and a theoretical elemental sulfur production rate of 2.4 kgS/m3d were achieved at a volume loading rate of 2.4 kgS2-/m3d. At higher loading rates, the efficiency deteriorated sharply. Based on these results, the...