| Coking industry brought a considerable boost to the industrial development of China and it raised environmental issues at the same time. Coking sewage contains diversified poisonous and harmful organics and a certain amount of ammonia nitrogen, which make it a kind of refractory wastewater. At present, the most widely used methods are biochemical process in the treatment system of coking wastewater. Biological denitrification is seen as the most appropriate technology for removing nitrogen from the wastewater due to its unique advantages including low-cost, strong maneuverability, free secondary pollution and so on. In recent years, people are more and more interested in the applications of nitrogen removal by heterotrophic nitrification-aerobic denitrification bacteria. Heterotrophic nitrifier convert NH4+-N to NO, N2 O and N2 under aerobic condition. Its nitrogen removal efficiency was superior to the conventional ways. Furthermore, heterotrophic nitrification microorganisms widely exist in the natural environment, which benefits its application in actual wastewater treatment.On account of the complexity of structure and the diversity of species of the pollutants, various microorganisms were combined to form a efficient system, which make each strain reach its optimal efficacy. In order to degrade organics and the ammonia simultaneously, Pseudomonas sp. Z1 was combined with heterotrophic nitrifier Acinetobacter sp. Y1 to build FB2 and Pseudomonas sp. Z1 was combined with heterotrophic nitrifier Acinetobacter sp.Y1 and Alcaligenes sp. C16, C17 to build FB4. The degradation effects of mixed bacteria were measured and the degradation conditions were optimized. The main results were shown as follows:(1) The inoculation time and the combination proportions of Z1 and Y1 were studied. On the premise of Z1 and Y1 inoculated at the same time, the combination ratios of Z1 and Y1 were 1:3, 1:1, and 3:1(v/v), respectively. When the combination ratio of Z1 and Y1 was 1:1, inoculating Y1 after culturing Z1 0 h, 12 h and 24 h were studied respectively. The results were shown that the efficiency of compound bacteria degrading aniline and ammonia-nitrogen was the best when Z1 and Y1 were inoculated into the culture simultaneously and the combination ratio was 1:1. Degradation efficiencies of aniline, TN, and COD were 99.9%, 86.6%, and 84.9% and the accumulation of ammonia nitrogen was always below 6 mg/L.(2) The influence factors of compound bacteria FB2 were studied, including additional carbon source type, C/N(mol), aniline concentrations, and additional(NH4)2SO4. Results showed that the optimal additional carbon source of compound bacteria FB2 was sodium citrate and the most appropriate C/N was 16. Compound bacteria FB2 could efficiently degrade aniline and ammonia-nitrogen simultaneously in the aniline concentrations of 400-800 mg/L. Additional(NH4)2SO4 did not restrain the performance of compound bacteria FB2 and it could remove the two kinds of nitrogen source.(3) Compound bacteria FB2 was domesticated in actual coking wastewater and the treatment effects of actual coking wastewater by domesticated FB2 were compared with undomesticated FB2. The domesticated FB2 could degrade the harmful contaminant in coke wastewater. The degradation rate of phenol and aniline were 96.3% and 91.6% respectively. Compared with unacclimated FB2, degradation efficiencies of NH4+-N, TN, and COD increased by 52.2%, 22.8% and 41.2%, respectively.(4) The combination proportions of Z1, Y1, C16 and C17 were studied. Its optimum combination ratio was 3:1:1:1. Additional refractory organics, 200 mg/L benzene, 200 mg/L phenol, 100 mg/L nitrobenzene or 100 mg/L quinoline were added to the primary medium to study their inhibiting effect on compound bacteria FB4, respectively. The results indicated that these organics in studied concentration did not restrain the removal of aniline and ammonia-nitrogen by compound bacteria FB4 by and large. |
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