Effects Of CODO₃^--N And Salinity On Denitrification Properties For Typical Nitrogen Heterocyclic Compounds

Nitrogen-containing heterocyclic compound, as a kind of refractory organics, is widely spread in wastewater of the coking, pharmaceutical, printing, dyeing and chemical industry. It has the characteristics of wide range of pollution, difficult bio-degradation and three-induced effect, thus there is a serious threat to the water environment and human health. Numerous studies have found that compared with the process of aerobic and anaerobic degradation, nitrogen-containing heterocyclic compound has a better removal effect in anoxic denitrification process. Meanwhile, with high salinity, industrial wastewater has an effect on membrane osmotic pressure and enzyme activity of functional microbes. However, most current studies have paid attention to the potential impacts of factors such as temperature, pH, ORP in the process of anaerobic degradation on typical nitrogen-containing heterocyclic compound. Few studies take the effect of salinity into consideration. Therefore, taken three kinds of typical nitrogen-containing heterocyclic compounds（i.e. pyridine, indole and quinoline） as the research objects, this study will primarily investigate the effect of COD/NO₃^--N ratio and salinity on denitrification degradation performance of the three organics under the hypoxia condition. Besides, denitrification dynamics in the presence of salinity will be studied in order to provide guidance for bio-degradation of nitrogen-containing heterocyclic compound in industrial wastewater with high salinity.The temperature was 30℃ and the reaction was conducted in batch device. Under the condition of different C/N ratio（4,8,10,12） and salinity（0g/L²0g/L） and based on the research and analysis of degradation characteristics of three typical nitrogen-containing heterocyclic compounds（such as pyridine, indole and quinoline） and nitrate nitrogen, accumulation characteristics of nitrite nitrogen and denitrification dynamics characteristic in the denitrification process, the following conclusions have been made in this paper.To begin with, nitrite nitrogen will accumulate when these three kinds of nitrogen-containing heterocyclic compounds are taken as carbon source. The accumulation quantity and rate of nitrite nitrogen are on the decline with the increase of COD/NO₃^--N, and the best COD/NO₃^--N of pyridine, indole and quinoline is 8, 10 and10 respectively. The results show that the best COD/NO₃^--N is affected by carbon source and activated sludge species. After denitrification begins, the density of carbon source and nitric nitrogen decrease rapidly because of the interaction between adsorption of activated sludge and denitrification of microorganism. Hereafter, the density of nitric nitrogen goes down slowly, and even denitrification ends. At the same time, denitrification is a complex process, in which multiple reductase should be required to participate. Based on the powerful competitiveness of nitrate reductase on electronic matrix, nitrite reductase gains electrons slowly when electronic matrix is comparatively inadequate, resulting in the accumulation of nitrite nitrogen.Secondly, under the best COD/NO₃^--N ratio, with the increase of salinity, the accumulation of nitrite nitrogen will be increased accordingly. When taken pyridine as carbon source,the max concentration of NO2--N is 13.42mg/L. When taken indole as carbon source, the max concentration of NO2--N is 10.30mg/L. When taken quinoline as carbon source, the max concentration of NO2--N is 7.90mg/L. In addition, the density of ammonia will rise in a period of time. This illustrate that ammonia in each carbon source link will transform ammonia and nitrogen in the process of denitrification taken pyridine, indole and quinoline as carbon resource.Lastly, this thesis also makes an inference on the denitrification dynamics parameters of three kinds of nitrogen-containing heterocyclic compounds under the condition of optimal salinity.When taken pyridine as carbon source, the value of μ_max, K_s and K_i is 1.86, 4.88 mg/L and 1177.4 mg/L respectively; when taken indole as carbon source, these three values are 2.06, 10.21 mg/L and 563.7 mg/L; when taken quinoline as carbon source, the values are 2.21, 8.99mg/L and 602.2mg/L.