Research Of Perchlorate Reduction In Water By Bacteria

Perchlorate （ClO₄^-） is a new kind of persistent pollutant which comes from both humanactivities and natural processes.ClO₄^-enters human body via foods and skin contact, whichwill inhibite the thyroid function of concentrating iodine so as to inadequate secretion ofthyroid hormone, in turn, suppressing the body’s metabolism and growth.So it should not be delayed that seeking an effective method to remove ClO₄^-from water.ClO₄^-is in a stable structure and soluble in water but not volatile in air, these features increasethe difficulty to treat ClO₄^-. Biological treatment is so inexpensive that became a commonmethod to remove ClO₄^-from water.Research of biological treatment is necessary.In our experiment, anaerobic biological method is a main way to remove ClO₄^-fromwater. We research to remove ClO₄^-by using S as inorganic electron donor and using someorganics as organic electron donor respectively.In order to find the best organic electron donor for removing ClO₄^-, ClO₄^-was reductionswere distinct with different carbon sources. Based on kinetics of biological perchloratereduction, the order of the maximum specific substrate removal rate is：q_max（pyruvate）>qmax（acetate）>q_max（lactate）>q_max（glucose）>q_max（starch）>q_max（ethanol）,and pyruvateis the best one for microbial degradation of perchlorate. Factors such as perchlorateconcentration, domesticated sludge concentration, initial pH, temperature and co-anions suchas nitrate, sulfate, and pHospHate affecting the removal of perchlorate were studied. At last,60mg/L perchlorate was completely reduced by2g/L of domesticated sludge under theconditions of35℃and initial pH7.5. The order of co-anions affect is NO₃^-＞PO₄^3-＞SO₄^2-.Study on removing perchlorate from drinking water by autotropHic anaerobic bioreactordesigned S as inorganic electron donor. Two aspects are discussed, including influent ClO₄^-concentration and hydraulic retention time.S particle and zeolite are arranged alternately in the bioreactor as filler. The influent pHis adjusted to7.3.After180days of cultivation and biological filming, the removing rate ofClO₄^-reaches94.4%.Fixing the hydraulic retention time at24h, the performance of the anaerobic bioreactorwas studied by changing the influent ClO₄^-concentration. The experiment showed that withthe increase of the influent ClO₄^-concentration,the load of biology faced rises, it leads todecrease of the effluent ClO₄^-concentration rises. However, removal rate rises. After a periodof time, the effluent concentration of ClO₄^-decreases little by little till it is stable. The effluent concentration of Cl-and SO₄^2-rise with the increase of the influent ClO₄^-concentration. ThepH is range of7.3to7.5.Fixing the influent ClO₄^-concentration at50mg/L, the performance of the anaerobicbioreactor was studied by changing the hydraulic retention time. Because of volume loadraised, the effluent concentration of ClO₄^-improves, then it reduces gradually up tostabilization. With the hydraulic retention time lessened, the effluent concentration of ClO₄^-increases, while effluent concentration of Cl-and SO₄^2-decreases ClO₄^-.At last the pH is7.3.