| At present, methods for coking wastewater treatment used at home and abroad mainly are biological treatment. And activated sludge process takes a dominant part in the dealing with coking wastewater, it can efficiently remove phenol and cyanide in coking wastewater, but the removal of the refractory organics and NH4+-N is less effective. In order to solve the problem of COD and NH4+-N difficult to treat in the traditional process, scholars optimized and improved coking wastewater treatment process by bioaugmentation.In this research subject, screened advantage denitrifying bacteria by use of adding coking wastewater to the medium, and studied the effect of temperature, pH, C/N ratio, inoculated dose on the nitrogen removal performance of dominant bacteria. To solve industrial application of dominant bacteria, improved and developed the immobilized microbial technology:developed the new immobilized microorganism technology by solid-state fermentation, made rice bran, soybean hulls immobilized products, which can stable and effectively treated coking wastewater, and can fix and save dominant bacteria significantly; improved traditional PVA (polyvinyl alcohol) immobilization method, added mass carriers to improve its mass transfer performance and permeability; used activated carbon fiber felt as the carrier film produced the new immobilized membrane, to search for new biological vector. In the experiment, used the A2/O systems evaluated the effect of dominant bacteria and novel immobilized products on the coking wastewater treatment. The main test process and results were as follow:(1)Eight strains nitrifying bacteria and seven strains denitrifying bacteria were isolated by beef extract peptone medium mixing with the coked waste water (DM100), from Huaibei Coking plant's activated sludge of the A2/O sewage treatment station. And after used gradient increase coking waste water's plate domestication and liquid domestication, five strains advantage nitrifying bacteria(named X0, X1, X2, X6, X7) and four strains advantage denitrifying bacteria(named F4, F8, F9, F10)with high degradability and resistance to coking wastewater were re-isolated.The contrast experiment showed that five mixed nitrifying bacteria(X5Z) and four mixed denitrifying bacteria(F4Z) had higher denitrogenation capacity and grow faster than single strain. In the same conditions, X5Z 48h NH4+-N removal rate can attain 87.59%, and F4Z 48h NO3--N removal rate can attain 98.75%.. Studies had shown that:the most suitable culture conditions of X5Z are:30℃, pH=8.0, inoculate quantity is 20% (bacteria density is 2×107～3×107 per mL). And in that condition, X5Z 24h NH4+-N removal rate is 64.75%. And the most suitable culture conditions of F4Z are:35℃, pH=8.0, C/N=5, inoculate quantity is 25%(bacteria density is 2×107～3×107/mL). After their conditions optimization, the time of F4Z NO3--N removal rate attain 90% reduced form 96h to 18h.(2)The novel immobilized ball intermixed by straw powder, granular active carbon, powdered activated carbon for an improvement on the tradtional PVA immobilization process. Scanning electron microscope (SEM) micro-analysis showed that the PAC make the internal structure of traditional PVA immobilized ball from blocky structure into poriform structure accumulated by small balls, significantly improved its mass transfer performance and permeability. After 24h table culture, the water absorption of the 4%PAC nitrobacteria and denitrifying bacteria immobilized ball increased 45% and 34%, the coefficient of expansion of them increased 79% and 31%, nitrogen and nitrate nitrogen removal rate increased 39.55% and 6.08%. And reused afte they adsorption saturation, 48h nitrogen and 12h nitrate nitrogen removal rate can attain 92.42% and 73.77%. The adsorption of PAC is benefit to fix microorganisms in immobilized ball, and can extend its service life and repeating utilization factor.(3)Used rice bran, soybean hulls as carrier to prepare immobilized products by solid-state fermentation for solve the dominant bacteria engineering applications. Researched save way and retention time of products relationship with their degradation performance. The research indicated that the optimum conditions for solid-state fermentation: nitrifying bacteria temperature is 30℃, denitrifying bacteria is 35℃, pH both are 8.0, moisture content are 0.1g/mL. The best preserved way to the immobilized products depending on their moisture content and loose degree:moisture content of the soybean hulls immobilized product is above 80%, and easily conglomerate, so they need 60℃drying preservation by blast oven. Moisture content of rice bran immobilized product is below 70%, and loose, can preservation at room temperature. After preserved three months, nitrification and denitrification capacity of the rice bran immobilized products are almost unchanged. But degradability of the soybean hulls immobilized product are decreased: NH4+-N removal rate of nitrifying soybean hulls immobilized product descended 11.02%, NO3--N removal rate of denitrifying soybean hulls immobilized product descended 12.52%. SEM Photos microscopic analysis showed that the film structure of soybean hulls can make bacteria evenly immobilized, and maintained their complete morphology. Used solid-state fermentation to immobilized advantage bacteria was simple, immobilized and saved bacteria remarkably, so it can be used as a new way to save bacteria. It will improve shortcomings of traditional save method, which had high requirements to conditions.(4)Three different shape immobilization fillers were prepared using active carbon fibro felt adsorbing bacteria embedded by polyvinyl alcohol and alginate, with elastic plastic filler. Scanning electron microscope (SEM) micro-analysis showed that the pore structure and high adsorption capacity of active carbon fibro felt was beneficial to adsorb and immobilized microorganism, increased its microbial activity. Three-dimensional elastic plastic filler combined with membrane to treat coking wastewater, which can act as a "skeleton" supporting role, to avoid the backlog of membrane, reduced the bulk density of filler, ensured good fluid dynamic characteristics in biochemical reactor.(5) Operated A2/O biofilm systems to treat coking wastewater, dynamic test results showed that:①Put rice bran, soybean hulls immobilized products into lab A2/O craft system to treat coking wastewater, without NO3--N and NO2--N accumulation in anoxic tank and denitrification significant. The NH4+-N degeneration ability of soybean hulls immobilized products can reach 75.46%, was better than rice bran immobilized products (62.55%) and free bacteria (38%). At the same time, rice bran, soybean hulls as natural organic filler was is consumed in the system, can avoid the mud and sludge bulking, save nutrients needed by heterotrophic bacteria. As products can maintain microbial activity after long time stored at room temperature, it can be used for quick-start bio-treatment system and rapid recover microbial activity after system poisoning, provided security for the biological treatment system.②Free bacteria,4% PAC immobilized ball and immobilization fillers were used in experimental A2/O procedure to observe removal efficiency of coking wastewater differently. It is observed that active carbon fiber film immobilization product had a better degradation effect than other products. The concentration of anoxic tank effluent Nitrate-N and Nitrite-N were 1.96 mg/L and 0.49 mg/L respectively, and the COD removal efficiency was 60.92%. The removal efficiency of COD, ammonia in aerobic tank were 78.83%,85.52%.The research indicated that ACF membrane can stable and effective degradation of pollutants in coking wastewater, it can be used as a new immobilization method suitable for process applications.
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