Study On Functions Of Electron Donors In Microbial Treatment Of Vanadium Precipitation Wastewater

Vanadium is a strategic metal and has been widely used in industries due to its superior physicochemical characteristics.The increasing global demand for vanadium promotes intensive mining and smelting activities.However,high amounts of precipitating vanadium wastewater would be produced during the production process,including V?V?and NH₄⁺-N,etc.Over-exposure to vanadium can induce carcinogenic and toxic effects including damage to respiratory and circulatory systems.And if ammonia nitrogen is discharged directly into water without treatment,it is easy to cause eutrophication of water body.The study of controlling groundwater pollution by applying the Bioremediation Technique has become a hot topic in recent years.Electron donors play a key role in the process of microbial remediation.In this study,an membrane bioreactor was developed,in which acetic acid was used as electron donor to remove V?V?and NH₄⁺-N simultaneously.Until the last stage,the removal rates of V?V?and NH₄⁺-N were 98.3±0.4%and 97.4±1.1%,respectively.By changing the experimental conditions such as hydraulic retention time and initial pollutant concentration,the results show that changing the conditions will influence the operating efficiency of the reactor.The microbial community and functional genus changes in the reactors at different stages were analyzed,and it was found that Exiguobacterium and Pseudoxanthomonas and other large amounts of bacteria related to denitrification and heavy metal reduction were enriched in the reactors.Subsequently,by using a continuous flow column reactor,the elemental sulfur as the sole electron donor was used to perform microbial remediation of V?V?and NH₄⁺-N in the precipitating vanadium wastewater.When the initial V?V?and NH₄⁺-N concentrations were 10 mg/L,the removal rate of V?V?is 99.2±0.8%,and NH₄⁺-N is completely removed.The experiment results show that the increase of the initial V?V?concentration could influence the removal efficiencies of V?V?and NH₄⁺-N.At the same time,the microbial community also underwent major changes.Pseudomonas,Thiobacillus and other related bacteria that could use sulfur and their compounds to grow and can perform V?V?reduction enriched.In addition,some other heavy metal reducing and autotrophic denitrification bacteria were found to be enriched in the reactor,such as Sulphurialea and Alishewanella.Finally,ferrous sulfide as the sole electron donor was used to conduct simultaneously microbial reduction of V?V?and nitrogen removal by using a continuous flow column reactor.When the initial concentration of vanadium and NH₄⁺-N is 10 mg/L,the removal rates of vanadium and NH₄⁺-N are as high as 99.5±0.5 and 88.8±1.8%,respectively.However,when vanadium concentration reached100 mg/L,the removal efficiency of NH₄⁺-N and total nitrogen decreased to 80.2±0.9%and 80.0±0.3%,respectively.During the reaction process,Pseudomonas and Thiobacillus and other bacteria related to vanadium reduction and nitrification and denitrification were enriched.Anammox bacteria,such as SM1A02 and Candidatus_Kuenenia,emerges in the third stage,indicating that anammox occurs in the reactor.