The Study On Autotrophic Perchlorate Reduction By Sulfur Carbon Mixed Complex Three-dimensional Electrode Biofilm

In recent years, the discovery of perchlorate which can interfere with thefunction of the thyroid gland as well as its potential health impact at low-doseexposure in a large number of ground and surface water supplies has highly attractedthe attentions of people in worldwide. Because of its extreme low concentration andstrong resistance to most treatment technologies, perchlorate has become one of thebiggest challenges currently being faced by the drinking water industry.There are a lot of researches about different treatment technologies forperchlorate removal from drinking water.In this experiment， technology of sulfurcarbon mixed complex three-dimensional electrode biofilm which combines theelectrochemical reduction process and microbial method to study the efficiency ofperchlorate removal from drinking water，to optimum conditions of the trial operationparameters as well as the population changes of microbes. Facultative anaerobicmicrobe use of H₂and S as electron donor in anaerobic environment for reduction ofperchlorate in this system, with the degradation via the sequence: ClO₄^-�'ClO₃^-�'ClO₂^-�'Cl^-+O2.Transformation of perchlorate to chlorate is the rate-limiting step withcomplete conversion to chloride.In the experiment, four parallel reactors A, B, C, D are used to study the changesof influent perchlorate concentrations, HRT, electricity and HRT in the condition ofelectricity on the influence of perchlorate reduction,its results indicate:1. The potential of mixed microorganisms to reduce perchlorate was increasinglyimproved, removing300mg/L perchlorate from primitively seven days to three daysafter domestication.2. The effect of biofilm colonization for reactor A is not good because of someunreasonable experimental conditions, and after changing anaerobic sludge to aerobicsludge for other reactors, the effect of biofilm colonization has been greatly increased. 3. In the experiment, reactor A, B, C, D can almost maintain an appropriate pH,dissolved oxygen and ORP for microbial growth.4. Without electricity conditions, by changing concentration of inflow ClO₄^-for50μg/L、70μg/L、120μg/L and200μg/L，respectively. with HRT of18h in reactor A，the experimental results show that influent water concentration of ClO₄^-for70μg/L isthe best inflow concentration for its high perchlorate removal efficiency and goodeffluent quality; and through changing HRT at18h、12h、8h and4h respectively withinflow ClO₄^-concentration of50μg/L in reactor B, the experimental resultdemonstrate that8h is the best time for the results of its high perchlorate removalefficiency and good effluent quality.5.In the condition of electricity，by changing electricity for30mA、50mA and60mA respectively with inflow ClO₄^-concentration of10mg/L and HRT of12h inreactor C，the results show that60mA is the optimal electricity for its high perchlorateremoval efficiency and good effluent quality; and by changing HRT for、12h、8h and4h，respectively，with inflow ClO₄^-concentration of100mg/L and electricity of30mA,the results show that8h is the best HRT on considering the energy consumption andeffluent quality. In reactor D, Thauera phenylacetica，unidentified eubacterium cloneBSV87， Thermotogales str. SRI-15， Acidovorax sp. BSB421， bacteriumJN18_A7_F*，Levilinea saccharolytica，Desulfomicrobium escambiense microbialstrains existed during the whole reactor，bacterium JN18_A7_F*microbial strain isthe advantage bacterium in the botton of the reactor，Desulfomicrobium escambiensemicrobial strain is the advantage bacterium in the centrol and upper part of reactor D。6.The results above can show that sulfur carbon mixed complexthree-dimensional electrode biofilm technology can remove ClO₄^-from drinkingwater efficiently，which can be demonstrated by the increase of effluent Cl^-comparedwith influent Cl^-，because of the possible disproportionate reaction of sulfur granule inreactors, the concentration of SO₄^2-in effluent water is far more than theoretical valuewhich can influence the quality of effluent.