Perchlorate Reduction By Autotrophic Bacteria Using Elemental Sulfur

ClO4-has been recognized as a widespread persisted contaminant of surface and groundwater. It has been discovered in a large number of water resources recently. It interferes withthe function of the thyroid gland as well as its potential health impact at low-dose exposure.Varied degradation of perchlorate has been gained attention recently. Perchlorate degradationusing heterotrophic bacterium leads to series of byproducts, such as the possible release ofunoxidized organic substrate, subsequent stimulation of microbiological growth in waterdistribution system, and the by-products of water disinfection. In order to overcome thesedisadvantages of organic substrates, chemolithotrophic perchlorate reduction was investigatedby utilizing inorganic electron-donating substrates just as sulfur.The potential of autotrophic bacteria to treat perchlorate contaminated water using surfulas electron donor was investigated in this study. Factors such as perchlorate concentration,domesticated sludge concentration, S0concentration, culture medium proportion, intial pH,co-anions such as nitrate, chlorate, phosphate, dissolved oxygen and temperature affecting theremoval of perchlorate were studied. The removal of perchlorate was also conducted on theoptimal conditions. Results indicate:(1) The potential of mixed microorganisms to reduce perchlorate was increasingimproved, removing15mg/L perchlorate from primitively15d to6d.(2) The complete conversion from perchlorate to chloride was demonstrated at astoichiometric ratio1.0, and the intermediates for other chloric compounds were not found tobe accumulated in the solution.(3) The enrichment culture can effectively coupled the oxidation of elemental sulfur tosulfate with the reduction of perchlorate to chloride.(4)15mg/L perchlorate was completely reduced by0.64g/L of domesticated sludgeadded with270mg/L of sulfur under the conditions of30℃and initial pH7.0within15h.(5) Dissolved oxygen and co-anions such as nitrate, chlorate, phosphate in the systemwould restrain the reduction of perchlorate. And the order of restrain is: DO＞NO₃^-＞PO₄^3-＞ClO₃^-...