Simultaneous Removal Of Bromate And Perchlorate In Hydrogen-based Membrane Biofilm Reactor

Bromate?BrO₃^-?and perchlorate?ClO₄^-?are toxic inorganic pollutants,causing serious threat to human health.The traditional water treatment process is expensive and prone to secondary pollution.Hydrogen-based Membrane Biofilm Reactor?MBfR?combines hollow fiber membrane micropore aeration with biofilm process to treat oxidative pollutants in water.It has the characteristics of clean hydrogen,no subsequent pollution and low biological yield.It has been widely used in water pollution control of pollutants.In this study,a feasibility test of autohydrogenotrophic reduction for BrO₃^-and ClO₄^-has been conducted,in which some influence factors on reduction process were also systematically investigated.A study on MBfR for simultaneous removing BrO₃^-and ClO₄^-was conducted,including reactor removal performance and mechanism for BrO₃^-and ClO₄^-,influence factors.Meanwhile,enzymatic activity and dynamics of microbial community structure on the membrane surface was analyzed using modern molecular biology techniques,trying to dissect or explain autohydrogenotrophic bioreduction mechanisms of oxidized contaminants.Through this study to obtain some theoretical parameters as valuable supports for engineering application of MBfR technology.The feasibility test verified that bioreductions of BrO₃^-and ClO₄^-were feasible,and no accumulate intermediate products at the end of the reaction.The most suitable temperature for the simultaneous degradation of BrO₃^-and ClO₄^-by hydrogen-autotrophic denitrifying bacteria is 25³5°C,and the optimum pH is 7.0⁷.5.When nitrate,BrO₃^-and ClO₄^-coexisted,NO₃^--N will compete the electron donor as the first electron acceptor with BrO₃^-and ClO₄^-.When the electron donor is limited,it will inhibit the degradation of BrO₃^-and ClO₄^-.Hydrogen-autotrophic microorganisms can degrade BrO₃^-and ClO₄^-to a certain extent,the concentration is too high or too low will reduce the degradation of BrO₃^-and ClO₄^-.Microorganisms attached on the membrane surface of MBfR gradually enriched and matured during a domestication period of NO₃^--N.MBfR had a good degradation effect on BrO₃^-and ClO₄^-in water,the most suitable conditions for simultaneous degradation of BrO₃^-and ClO₄^-by MBfR:hydrogen partial pressure is 0.04 MPa,influent flow rate is 2 mL/min,reflux ratio is 7.5 and the optimum pH is 7.0⁸.0.In the same reaction system,the order of competitive advantage for electron donors is NO₃^--N>NO₂^--N>ClO₄^->BrO₃^-,With NO₃^--N or NO₂^--N as nitrogen source,both of them will have fierce competition for electron donors,and then inhibit the reduction of BrO₃^-and ClO₄^-,and their inhibitory effect on ClO₄^-is more obvious,and the inhibition of NO₃^--N is stronger than that of NO₂^--N.Function or role played by microorganism lived on the outer surface of membrane directly caused the removal of NO₃^--N?BrO₃^-and ClO₄^-from water in the MBfR.Some of the denitrifying enzymes have the effect of degrading BrO₃^-and ClO₄^-.Proteobacteria are the most dominant bacteria for simultaneous degradation of BrO₃^-and ClO₄^-,they are mainly composed of Betaproteobacteria,followed by Gammaproteobacteria and alphaproteobacteria.The dominant bacteria of simultaneous degradation of BrO₃^-and ClO₄^-include Thiothrix,Chlorobaculum,Sulfuritalea,Azospira and Methyloparacoccus.The increase of NO₃^--N inhibited the growth of Thiothrix and Chlorobaculum,while the growth of Sulfuritalea and Azospira was promoted.At the same time,a small amount of Nitrospira was enriched in the reactor when the NO₃^--N concentration is above 5 mg/L,indicating the production of a small amount of NO₂^--N by-products.