The Research On Perchlorate And Nitrate In Water By Combined Process Of Sulfur Autotrophic-electrochemical Hydrogen Autotrophic

Perchlorate and nitrate are contaminations that have been found in many surfaceand underground water. Perchlorate is a highly diffused, persistend and toxic pollutant.It is primarily used in the manufacturing of military products, fireworks and so on.The use of perchlorate-contaminated water presumably interferes with iodine uptake.Nitrate mainly come from domestic sewage, industrial wastewater discharge and alarge number of nitrogenous fertilizers in agricultural production. Nitrate itself is nottoxic, but once inside the body it will be reduced to nitrite, making it increasedtoxicity. Conventional methods are difficult to remove perchlorate in water effectively.In the last few years, autotrophic biological method calls the attention.The sulfur autotrophic-electrochemical hydrogen autotrophic combined processwas used for the research of perchlorate and nitrate, this process use S0and H2aselectron donor for the reduction of ClO4-and NO3--N.NO3--N was used as the first element acceptor, then changed ClO4-, the feasibilityof sulfur-autotrophic and hydrogen-autotrophic denitrifying bacteria to regradeperchlorate was researched. The performance of synchronous reduction of perchlorateand nitrate using the combined process was also researched in anoxic and aerobicconditions.In the absence of perchlorate-reducing bacteria and denitrifying bacteria, ClO4-and NO3--N cannot be degraded. Part bacteria which were cultivated when usingNO3--N as the sole element acceptor can also degrade ClO4-,Under anoxic condition when influent concentration of ClO4-and NO3--N were10mg/L and30mg/L respectively, the reactor could be operated efficiently at HRTranging from12h to1h, and current intensity was10mA, the hydrogen period effluentconcentration of ClO4-and NO3--N could both satisfy the standard. When HRT was reduced to0.5h, minimum current intensity was15mA, and then finial effluentconcentration of NO3--N can satisfy the standard. When current intensity was35mA,finial concentration of ClO4-was1.27mg/L, when current intensity was45mA, therewould appear a hydrogen inhibition phenomenon. Through PCR-DGGE research,predominant bacteria in the reactor were Uncultured Campylobacterales bacterium、perchlorate-reducing bacterium RC1、 Kineosphaera limosa NBRC100340、Thiomicrospira denitrificans and Ignavibacterium album (T).Under aerobic condition, when influent concentration of ClO4-and NO3--N was10mg/L and30mg/L, respectively, the reactor can be operated efficiently at HRTranging from3h to1h, and current intensity was10mA, finial effluent concentrationof ClO4-and NO3--N can both satisfy the standard. When HRT was reduced to0.5h,minimum current intensity was15mA, and then the finial effluent concentration ofNO3--N can satisfy the standard. When current intensity was35mA, finialconcentration of ClO4-was2.02mg/L, when current intensity was45mA, there wouldappear a hydrogen inhibition phenomenon. Through PCR-DGGE research,predominant bacteria in the reactor were Thiobacillus denitrificans (T) andAlviniconcha sp. gill symbiont.Through the research of the concentration of ClO4-and NO3--N at different hightof the reactor, it was convinced that the reactor could simultaneously degrade ClO4-and NO3--N, but degradation rate of NO3--N was obviously higher than ClO4-. It wasconvinced that the time for the reactor to achieve stable operation when anoxiccondition was shorter than in aerobic condition, the shorter time was about2~4d, atsame time the finial concentration of ClO4-in the reactor anoxic condition was lowerthan aerobic condition. When using the same reactor under the same experimentalconditions, concentration of ClO4-and NO3--N at the different hight was varied, theconcentration of the reactor anoxic condition was lower than the reactor aerobiccondition at the same hight.The molar ratio of the reduction of ClO4-and the increment of Cl-was closed to1:1, and there was not the phenomenon of the accumulation of ClO3-and ClO2-. Theeffluent concentration of sulfur section ranged from201.6to240mg/L, differential concentration of hydrogen period and sulfur section was no more than3%. Whenreaching stabilization, pH in the sulfur and hydrogen period ranged from6.95to7.15and7.20to7.40under anoxic condition, ranged from7.30to7.70and7.60to8.10under aerobic condition respectively. ORP in the sulfur and hydrogen period rangedfrom-170to-250mV and-240to-300mV, respectively.