Study On Mechanism And Scaling Of Electricity Assisted Biologic Treatment System For Fluorinated Nitrobenzene Treatment

Fluoro-nitrobenzene derivatives,as a kind of typical biorefractory fluorine-containing pollutant,have characteristics of three-consistency and fat-soluble.Compared to the equivalent structure of chloro-nitrobenzene derivatives,fluoro-nitrobenzene derivatives have higher chemical stability and biological toxicity.The fluorine-containing wastewater was discharged into the river,which will cause the serious harm to the human and environment.Therefore,it was extremely urgent to develop an environmentally friendly,efficient and economical technology for the treatment of organic fluorine wastewater.In this study,electricity assisted biologic treatment(EA/BT)was constructed for enhancing fluoro-nitrobenzene-containing wastewater treatment.The contribution and mechanism of electrode biofilm(EB)and suspended sludge(SS)in the p-FNB degradation were discussed.Meanwhile,the effect of fluorine-substituent on o-fluoronitrobenzene(o-FNB),m-fluoronitrobenzene(o-FNB)and p-fluoronitrobenzene(p-FNB)degradation in EABT with different electrodes were investigated.From the perspective of engineering application,the technological potential of scaling up on the p-FNB degradation in EABT was discussed.The main conclusions are as follows:1.EABT was constructed to achieve highly efficient p-FNB degradation and defluorination.SS and EB were proved that have similar contributions to p-FNB degradation in EABT.Specifically,p-FNB was completely removed in 25 h by SS and BE.The defluorination efficiencies of 53.1%and 54.7%were achieved in both systems.Obvious shift of potential and significant current intensity variation were not observed in SS,BE and ECS.At the same time,the p-FA removal and defluorination performance of EB and SS were similar under open and closed circuits.These results showed that p-FNB degradation process in EB and SS were a synergistic metabolic mechanism of electrochemical reduction and non-electroactive microbial oxidation.The dominant bacteria and community were highly similar in EB and SS,which indicated that they have a similar biological metabolic mechanism.2.o-FNB,m-FNB and p-FNB removal and defluorination performance in EABT were discussed.The result showed that o-FNB and m-FNB are more difficult to be degraded than p-FNB.In addition,o-FNB,m-FNB and p-FNB defluorination performance in EABT with different electrodes(titanium,stainless steel and graphite plate)as cathodes were investigated.The defluorination efficiency in EABT with graphite plate(66.9%,70.9%and 86.9%)and stainless steel(66.9%,70.9%and 86.9%)were significantly higher than that of titanium(11.0%,15.0%and 36.0%).Moreover,LSV and open circuit experiments indicated that the advantage of EABT with stainless steel and graphite plate were due to the p-FNB reduction.Meanwhile,the same functional microorganisms Pseudomonas and Klebsiel.l were enriched in stainless steel and graphite electrodes.3.EABT which combined electrolysis and aeration was constructed and operated in the sequencing batch mode to study its application potential in the expansion.The effects of different initial concentrations,CON ratio and applied voltage in EABT were investigated.The highest defluorination rate was found to be 63.5 mol m-3 d-1 at an initial concentration of 0.8 mmol L-1,in whcih the microbial activity was not significantly inhibited.The highest p-FNB removal and defluorination efficiency were 98.9%and 71.4%at C/N ratio 8.6.The lowest energy consumption in EABT was 0.13 kWh kg-p-FNB-1 at 1.8V.Therefore,the optimum process parameters of scaling up on the p-FNB degradation in EABT were 1.8V voltage,0.8 mmol L-1 p-FNB concentration and C/N ratio 8.6.The pitting corrosion potential shows that the system has good electrochemical stability.Besides,the same functional microorganisms Fltavobacteriia and Gammaproteobacteria were enriched in EABT based on 1.5V,1.8V and 2.1V.Moreover,EABT showed exhibited impact resistance when initial concentration was four times the original.CV curve and pitting corrosion potential were almost unchanged during operation,which confirmed that the system had good electrochemical stability.