Study The Mechanism And Dynamics Of Nitrite Denitrifying Regulated By Redox Mediators

Facing the increasing nitrogen pollution,biological denitrification technology has been concerned.And how to improve the denitrification efficiency becomes a hot topic.Recentlyt,more and more reports show that redox mediators can accelerate degradation of pollutants in anaerobic conditions.But there is no literautre about the accelerating nitrite denitrification by redox mediators.Therefore,the regulating nitrite denitrification characteristics,mechanism and dynamics of redox mediators are carried out in detail.Firstly,the nitrite denitrifying sludge was acclimated,and the accelerating effect of five similar structure redox mediators was compared,in which AQS was selected best redox mediator.The results suggested that the optimal condition of nitrite denitrification was 35?,pH=8.0,the C/N rate of 4,and 0.16mmol/L of AQS.The ORP value was lower 100mV and the pH also changed faster than the controls during the denitrification process.The accelerating effect of redox mediator was found a linear correlation between the denitrification rate(Y)and the redox concentration(C).When the tendency of,the relationship between the LnC and denitrification rate were Y = LnCAQS 0.5069 + 0.5069(R2 = 0.9958)and Y = LnCAQDS 1.1879 + 1.1879(R2 = 0.9794)for 0-0.32 mmol/L anthraquinone-2-sulfonate(AQS)and anthraquinone-2,6-disulfonate(AQDS),respectively;The linear equation was Y = 19.179 C1,5-AQDS+11.72(R2 = 0.9860)for 0-0.16mmol/L anthraquinone-1,5-disulfonate(1,5-AQDS);The linear equation was Y =11.035 C2,7-AQDS + 10.768(R2 = 0.9825)for 0.008?0.16 mmol/L anthraquinone-2,7-disulfonate(2,7-AQDS);The linear equation was Y = 2.0462 Ca-AQS +12.286(R2 = 0.9697)for 0.008-0.32mmol/L anthraquinone-1-sulfonate(a-AQS).Secondly,the catalyzing effect of functional electropolymerization biocarrier m odified by AQS(ACF/PPy/AQS)on nitrite denitrification was investigated.The res ults showed that the optimal AQS concentration was 0.22mmol/L.With AQS,the pH changed fast and the ORP first stabilized with higher about 55mV than the co ntrols during the denitrification process;the acceleration effect of the five similar s tructure redox mediator was compared and ACF/PPy/AQS was the best.In four re peated-batch operations indicated that the denitrification rate of ACF/PPy/AQS main tained over 80%.For AQS and 2,7-AQDS,their accelerating denitrification capaciti es during the nitrite denitrification process were elucidated by their characteristics o f cyclic.voltammograms(CVs).At the same time,the optimal denitrification conditions with cellulose acetate embedding 1,4,5,8-tetrachloroanthraquinone was 35?,pH=9.0,the C/N rate of 8,t he optimal 1,4,5,8-tetrachloroanthraquinone concentration was 0.016mol/L.The pH c hanged with nitrite removal fast and the ORP was first stability,which was lowere r about 75mV than the controls during the denitrification process.The acceleration effects of five similar structure redox mediator were compared and 1,4,5,8-tetrachlo roanthraquinone was the best one.Compared to their characteristics of cyclic volta mmograms,the oxidation reduction potential of 1,4,5,8-tetrachloroanthraquinone was minimum and closed to the nitrite denitrification oxidation reduction potential,so it presented obvious acceleration during the nitrite denitrification process.At last,by investigating the effect of cellulose acetate embedding non-dissolve mediators during the denitrification process,the results showed that denitrification rate was highest with initial nitrite concentration of 2000 mg/L.Nitrite denitrification rates in phosphoric acid buffer(pH 7.2)system and unbuffered system were similar,and the pH change in the buffer system was obviously slower than that of the unbuffered system.Under the same condition of inlet concentration and hydraulic retention time,the effluent nitrite concentration in the reactor with redox mediators was significantly lower than blank control,and nitrite removal rate increased by 10%.In a word,different redox mediators all accelerated nitrite denitrification,whic h expanded the effective biological denitrification process and enriched the applicati on of accelerating pollutants degradation by redox mediators.And it also provided the optimal parameters for practical application of redox mediator by the experimen tal study on reactor.