The Study On Biological Perchlorate Reduction Of Drinking Water By Combined Process Of Sulfur Autotrophic And Electrochemical 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, biological method calls the attention. This study analysises thesuccession of microbial community structure changes and the dominant bacteria ofthe species are determined by DNA sequencing. Study on removing perchlorate fromdrinking water by a sulfur autotrophic bioreactor. Two aspects are discussed,including influent ClO₄^-concentration and empty bed contact time. The optimaloperating conditions and design parameters are gained by analyzing the changes ofthe parameters in the operating process. Study on the performance of sulfurautotrophic and electrochemical hydrogen autotrophic reactor collaborative removeperchlorate from drinking water.There is no ClO3-and ClO2-accumulation in the process of inoculating culture,ClO₄^-can completely transform to Cl^-. There is disproportionation of S⁰in thereduction of ClO₄^-, but SO₄^2-mainly produced by S⁰oxidation. The production of H+causes solution pH low to6.6to7.0, but still remains at the appropriate perchloratereducing bacteria metabolism range. At the beginning of culture, the concentration ofanaerobic sludge protein decreases, microorganism quantity reduces. At the middle ofculture, inorganic autotrophic anaerobic bacteria into the growth period, the numberof bacteria and protein concentration increase. At the end of culture, the increase ofsludge protein concentration reduces, the performance of reduction becomes stable. Observe microbial forms with scanning electron microscope, the results show thatduring the entire culture, bacilli and cocci are the major species. Using PCR-DGGEand clone technique to analysis the structure changes of microbial population in theculture period. Comparative profile of DGGE bands and the phylogenetic tree showthat during the culture the microbial diversity is well and complex changes are takenplace in the communities. α, β, γ, δ-Proteobacteria, Bacteroidia, Actinobacteria andClostridia are the main bacteria in the system. And the dominant member in thereactor is Proteobacteria. At the beginning of culture, the superior strains areSulfurospirillum sp. EK7、Sulfurospirillum cavolei、Marinobacter taiwanensis、Desulfocapsa thiozymogenes and Pandoraea sp. PVC（14d）6. At the middle of culture,Marinobacter taiwanensis is the superior strain, appears new strain--Jonquetellaanthropi. At the end of culture, strains Marinobacter taiwanensis、Methyloversatilis sp.cd-1and Desulfomicrobium norvegicum disappear; arsenate-reducing bacterium NP4and Methyloversatilis universalis become the superior strains.Fix the empty bed contract time, study the performance of the sulfur autotrophicbioreactor by changing the influent ClO₄^-concentration. The results show that theeffluent ClO₄^-concentration rises with the increase of influent ClO₄^-concentration,while the ClO₄^-removal efficiency decreases. The effluent ClO₄^-concentration meetsthe U.S. Environmental Protection Agency standards requires18μg/L. The influentpH is in the range of6.9to7.3, reduction reaction produce H+reduces effluent pH tothe range of6.5to7.2, meets the perchlorate reduction bacteria metabolism condition.At the whole operation stage, effluent DO is in the range of0.4to0.7mg/L, effluentORP is in the range of-280to-180mV, meets the anaerobic condition of ClO₄^-reduction. The concentration of effluent Cl^-is in the range of1.9to2.2mg/L, meetsthe sanitary standard for drinking water （GB5749-2006）.Fix the influent ClO₄^-concentration, study the performance of the sulfurautotrophic bioreactor by changing the empty bed contract time. The results show thatthe effluent ClO₄^-concentration rises with the decrease of empty bed contract time,while the ClO₄^-removal efficiency decreases. The influent pH is in the range of6.5to7.7, effluent pH is in the range of6.7to7.16, meets the perchlorate reduction bacteria metabolism condition. Effluent DO and ORP reduce with the decrease of empty bedcontract time. The concentration of effluent Cl^-reduces with the decrease of emptybed contract time, meets the sanitary standard for drinking water.Study the performance of the sulfur autotrophic and electrochemical hydrogenautotrophy. In the condition of influent ClO₄^-concentration is1100μg/L、currentintensity is50mA and the empty bed contract time are12h and8h, effluent ClO₄^-concentration are in the range of1.3to2.1μg/L and2.3to3.5μg/L, respectively. Theeffluent ClO₄^-concentration rises with the decrease of empty bed contract time, whilethe ClO₄^-removal efficiency decreases, but the removal efficiency of reactor is higherthan99%. Effluent SO₄^2-concentration is lower than120mg/L, meets the standard fordrinking water. The effluent SO₄^2-concentration rises with the decrease of empty bedcontract time. The influent pH is in the range of6.5to7.7, sulfur autotrophic pH is inthe range of6.7to7.1, electrochemical hydrogen autotrophic pH is in the range of7.8to8.2, meet the pH condition of reduction. Effluent DO and ORP are in the range of0.3to0.38mg/L and-280to-253mV, respectively. Under the empty bed contract timeof12h and8h, the concentration of effluent Cl^-are in the range of2.2to2.65mg/Land2.13to2.58mg/L, descend with the decrease of empty bed contract time.