Effect Of Organic Matter And Nitrate On Perchlorate Reduction Of A Combined Process Of Sulfur-and Bioelectrochemical Hydrogen-autotrophy

In this research, the effect of organic matter and nitrate on perchlorate reduction of a combined process of Sulfur-and Bioelectrochemical Hydrogen-autotrophy was investigated. Besides, the effect of HRT on perchlorate reduction of the combined process of Sulfur-and Bioelectrochemical Hydrogen-autotrophy was also investigated. This process use S0 and H2 as electron donor, CO2 as carbon source, enriching and cultivating perchlorate-reducing bacteria when the influent CIO4- was 30mg/L, the produced when using S0 as electron donor in the process of degrading CIO4- can be consumed as H2, and this process can make a drop of pH in the effluent. The concentration of SO42- in the effluent can also be controlled by adjusting the HRT.The results showed that the perchlorate treatment efficiency reduced with the increase of NO3--N in the influent. The treatment efficiency of CIO4- decreased from99% to 50% with the NO3-N concentration in the influent increased from 0 mg/L to 50mg/L, while the NO3-N treatment efficiency reduced to 45%or less. The redox potential of nitrate was higher than perchlorate, so it can get the electron more easily. Because of the disproportionation of S0, the concentration of SO42- ir the effluent was much more higher than the theoretical value.The removal efficiency of CIO4- was more than 99% under the steady states when adding organic matter into the influent from Omg/L to 150mg/L. But the CIO4-removal efficiency reduced to 97% when the influent COD concentration was add to 300mg/L, while the effluent pH had a drop as well. Microorganism would like to choose organic matter as electron donor instead of S0, this may lead to the decrease of concentration of SO42- in the effluent. The effluent ORP kept decreasing with the increasing of COD concentration. The effluent had a strong pungent odor, it showed that the internal SRB had produced H2S.The removal efficiency of ClO4- kept a high level under the steady states when adding both organic matter and nitrate into the influent, while the concentration of SO42- in the effluent had a little raise. When the influent NO3--N was 50mg/L, the COD was 150mg/L, the removal efficiency of ClO4-decreased from 99% to 97% with the decrease of HRT from 6h to 4h, while the nitrate removal efficiency always kept above 99%.The ClO4- in sulfur segment effluent had a little raise with the decrease of HRT from 6h to 4h,to 2h, while the perchlorate removal efficiency was always maintained above 99%. The concentration of ClO4- improved a lot when the HRT was reduced to 1h, and the removal efficiency of ClO4- was less than 50%. The concentration of SO42- in effluent kept decreasing when reduced the HRT of the reactor, while the effluent pH and ORP would slightly increase.The reactor maintained a great anaerobic environment during the whole experiment. The molar ratio of the reduction of ClO4- and the increment of Cl- was closed to 1:1, and there was not the phenomenon of the accumulation of ClO3- and ClO2-. The pH was maintained at 7.3-8.35 in this research, and it can satisfy the normal metabolism conditions of perchlorate-reducing-bacteria.