Experimental Research And Commissioning On The Microoxygen Environment Moving Bed Biofilm Technology For Coal Chemical Wastewater Treatment

Our country is determined to develop modern coal chemical industry because of the special energy structure,however,modern coal chemical industry is facing problems of high water consumption,high pollution,reverse distribution of coal resources and water resources.Ministry of Environmental Protection(now Ministry of Ecological Environment)had put forward strict requirements for “zero discharge of coal chemical wastewater”.“Zero discharge of coal chemical industry wastewater” is a necessary condition to realize the sustainable development of modern coal chemical industry.The key point and difficulty is biochemical treatment of wastewater containing phenol,which presents disadvantages of low biodegradability,strong biological toxicity and larger number of bubbles.This paper investigated these problems and mainly introduced the research progress of micro-oxygen environment moving bed biofilm technology for coal chemical wastewater treatment.Micro-oxygen moving bed biofilm technology refers to adding suspended filler to the activated sludge system with controlled specific hydraulic conditions.It removes organic pollutants and ammonia nitrogen by simultaneous nitrification and denitrification under the conditions of low dissolved oxygen,high sludge concentration and sludge age.From the perspective of resource utilization of fly ash,the fly ash filler used in micro-oxygen environment moving bed biofilm technology was made from the mix materials such as fly ash and activated carbon powder.The density of fly ash filler is 1.05 g/cm3,and the specific surface area is 89 m2/g.In addition,the surface pores of the filler are developed and rich in functional groups such as hydroxyl group,which shows good adsorption ability.With a p H value of 7,a dosage of 140 g/L and a stirring speed of 100 r/min,COD adsorption and removal rate of fly ash filler was over 70%.Removal efficiencies of COD and total phenol by fresh filler adsorption were 82% and 78% respectively,while after 10 times of filler regeneration by thermal reduction method,the corresponding values were 74% and 70% respectively,both reduced by 8%.The maximum dissolution of Fe,Ca and Al were 0.3 mg/L,0.12 mg/L and 0.19 mg/L respectively,and the dissolution amounts of metal ions were extremely low compared with the addition amounts of fillers.In the experiment,the degradation rates of phenol,p-phenol and m-phenol increased by 28.02%,21.47% and 19.75% respectively after the addition of fly ash filler.The sludge concentration reached 5000 mg/L.Removal efficiency of COD,total phenol,ammonia nitrogen and total nitrogen achieved 80%,79%,60% and 40% respectively.The high sludge concentration contributes to strong organic metabolism and impact resistant ability of moving bed biofilm technology.Meanwhile,the micro-oxygen environment provides a good condition for simultaneous nitrification and denitrification.The testing results of microbial enzyme activity and microbial population structure demonstrated that the activity of activated sludge microorganism was enhanced significantly in the micro-oxygen moving bed biofilm technology.In the pilot test research and commissioning,the removal efficiencies of COD,total phenol,ammonia nitrogen and total nitrogen were stable at 70%,50%,50% and 30% respectively.The sludge concentration was stable at around 5000 mg/L.