The Study On Perchlorate Reduction Of Drinking Water By Membrane Electrolytic Hydrogen Autotrophy

Perchlorate is a highly diffused, persistend and toxic pollutant. It is primarilyused in the manufacturing of military products, fireworks and so on. The use ofperchlorate-contaminated water presumably interferes with iodine uptake andhormone production by human thyroid affecting the vital body functions.Conventional methods are difficult to remove perchlorate in water effectively. In thelast few years, electrolytic-biological method calls the attention. The novel combinedproton-exchange membrane electrolysis with autotrophic perchlorate reductionsystem was established in this sudy. In our experiments, membrane electrolytichydrogen autotrophic bioreactor was inoculated with hydrogen autotrophicinvestigated sludge, and the effect of various reaction parameters on perchloratebioremediation of reactor was studied. Inlarging reactor volume and introducingmembrane modules was for continuous study of bioreactor.Aerobic activated sludge and anaerobic digester sludge were both acclimated inanaerobic medium. The potentiality of microorganisms to reduce perchlorate wasincreasingly improved, removing300mg/L perchlorate in8days primitively to1daysafter domestication. Comparing two systems, the reduction rate of anaerobicacclimated system was a little faster in the early days. No intermediate products weredetected, pH was elevated in each period, and the protein content of sludge didn’tincrease considerably. The microbial morphology and community structures indifferent stages were studied by SEM and PCR-DGGE. Successional changes ofmicrobial morphology and community structures were found. Bacilli as the majorspecies involved and maintained a superior position in the whole operation, and astabilizatied community structure was formed at last for adapting the environment.The membrane electrolytic hydrogen autotrophic bioreactor was established toreduce perchlorate in water, and to test the impact on performance of bioreactor through changing domesticated sludge concentration, influent ClO₄^-concentration,applied current and distance of plates. The proton-exchange membrane was used fortransferring current and excluding the oxygen generated in the anode reactor. Asuitable concentration of acid added in anode cell could enhance the proton transportand keep the pH of cathode cell in an appropriate range. Under the performance ofdirect current, microorganism in cathode cell could utilize H2which was generated bycathode to reduce perchlorate. The batch mode study showed that the system wassuitable for perchlorate reduction. Under adequate current, the perchlorate reductionrate was affected by sludge concentration, and the kinetics of reduction processfollowed Zero-order kinetics model. But the rate wasn’t influenced by the influentClO₄^-concentration, applied current （≥20mA）and distance of plates.Continuous study of membrane electrolytic hydrogen autotrophic MBR showedthat the established reactor could operate efficiently in operating process. When theapplied current was fixed, the effluent ClO₄^-concentration raised slightly with thedecrease of the hydraulic retention time, while the ClO₄^-removal rate decreased.When the HRT kept in a certain value, the effluent ClO₄^-concentration reduced whenthe applied current became larger. No intermediate products were detected, and pHwas slightly elevated during operating period.