The Synergetic Reduction And Transformation Of Recalcitrant Contaminants In Reverse Osmosis Concentrates By Humus-reducing Bacteria

As a standard technology of industrial wastewater treatment,reverse osmosis technique has been applied widely due to the stable ability of reverse osmosis membrane to intercept the various inorganic ions,colloidal substances and macromolecule solutes in the water.However,the concentrated water with a high salinity and contains a lot recalcitrant contaminants is produced accordingly in the reverse osmosis process.The main pollutants in reverse osmosis concentrates（ROC）include higher aliphatic hydrocarbon,polyaromatic hydrocarbon and polyhalogenated aromatic compounds,whose molecular structures contain conjugated double bond,benzene ring and other toxic radicals.Those contaminants are hardly removed by general treatment method,and the biodegradability of ROC is restrained owing to their existence.Thus,it is crucial to enhance the biodegradability of ROC and reduce the contents of those recalcitrant contaminants simultaneously.This study combined the advanced oxidation process（AOP）and humus-reducing biological activated carbon system to dispose the ROC wastewater.In this study,the humus-reducing bacteria were isolated and purified firstly,the physiological and biochemical characteristics of humus-reducing bacteria were investigated and the effects of pH values and electron donors on the reduction of humic analog,antraquinone-2,6-disulfonate were explored to optimize the degradation.Then the ROC was pretreated by O₃-assisted UV-Fenton method,the portion of the pollutants was removed by this AOP and the biodegradability of ROC was enhanced accordingly.And then,the AOP treated water was treated by biological activated carbon（BAC）system,in which the humus-reducing bacteria were acclimated to form the bio-membrane.The system was strengthened by the Fe（Ⅲ）reduction characteristic of humus-reducing bacteria,the COD,UV₂₅₄ and other water quality index were tested to explore the mechanism of synergetic reduction and transformation of recalcitrant contaminants in reverse osmosis concentrates by humus-reducing bacteria.The experiment of humus-reducing bacteria isolation and purification indicated that the humus-reducing bacteria were able to reduce the humic analog,antraquinone-2,6-disulfonate（AQDS）by using acetate as electron donor,the optimum conditions for humus-reducing bacteria growth is at 30℃,pH value at neutral and in the darkness.The bacteria showed up strong reduction activity used the glucose and sodium acetate as electron donor.The humus-reducing bacteria were able to adapt the ROC by a long-term accommodation.The single factor experiments of AOP showed that the optimum conditions for O₃-assisted UV-Fenton method were:the pH is at 3.0,the dosage of H₂O₂ is10 mM,the dosage of Fe²⁺is 0.3 g/L,the irradiation time of UV is 60 min,the dosage of O₃ is 15 mg/L.The COD removal rate was arrived at 59.2%in the best conditions by AOP.The biofilm culturing and acclimation experiment of humus-reducing biological activated carbon indicated that the humus-reducing bacteria could accumulate on activated carbon well,and can adapt the ROC water quality by the acclimation process.The combined method with humus-reducing biological activated carbon and O₃-assisted UV-Fenton was showed preferable ability to treat the ROC,the COD and UV₂₅₄54 removal rate arrived at75.9%and 84.5%by the combined treatment with Fe³⁺promoted at the best empty bed contact time（EBCT）of 150 min,meanwhile,the color and the ammonia nitrogen of ROC were also removed at a large extent.