The Study In Shortcut Denitrification With A Mixture Of Phenol And Typical Nitrogenous Heterocyclic Compounds

Nitrogenous heterocyclic compounds(NHCs) mainly come from coking wastewater, dyeing wastewater and pharmacy wastewater, etc. Quinoline, pyridine and indole are typical of this variety with carcinogenicity, abnormality and mutant,which has complex structure and poor biodegradability.Therefore,it is difficult to degrade NHCs completely with conventional biochemical treatment methods. There are many kinds of organic matter in industrial wastewater,for example, phenolic organics accounted for about 60% ~ 90% in coking wastewater. When removed,NHCs would be affected by phenol and other organic matter.Therefore,it is necessary to study the characteristics of a mixture of NHCs and phenol.In this paper,quinoline,pyridine and indole were selected as the typical NHCs to respectively research the degradation characteristics in shortcut denitrification with phenol,and analyze dominant bacterial community of degrading three kinds of substrates.Through long-term continuous test experiment and many batch experiments, the conclusions are drawn as followings:1. The quinoline,pyridine and indole’s degradation rate were determined in different temperature values—20 ℃,25 ℃,30 ℃,35 ℃ and 40 ℃. Experimental results showed that while using a mixture of quinoline and phenol, pyridine and phenol as carbon source, the optimal reaction temperature for shortcut denitrification was 30℃. However, while using a mixture of indole and phenol as carbon source, the optimal reaction temperature for shortcut denitrification was 35℃.2. The quinoline,pyridine and indole’s degradation rate were determined in different p H values—6.0、7.0、7.5、8.0 and 9.0. Experimental results showed that while using a mixture of quinoline and phenol, pyridine and phenol, indole and phenol as carbon source, the optimal reaction p H for shortcut denitrification was 7.5.3.A mixture of phenol and quinoline, phenol and pyridine, phenol and indole as carbon source in the shortcut denitrification system,changing the concentration of NO-2-N, the optimum COD/ NO-2-N were 3.5,7 and 5 respectively.4.Degradation of quinoline can be observed promoted in the presence of phenol and this promotion was more apparent when the concentration of phenol increased. However,the presence of phenol had shown inhibitory effect on pyridine and indole degradation.For pyridine,this inhibition was decreased when the initial phenol concentration increased. For indole, this inhibition was increased when the initial phenol concentration increased.5.Zero-order kinetic model was used to describe the degradation of quinoline, pyridine and indole in the presence of phenol. The predicted and measured values showed a good correlation.The rate constant of quinoline, pyridine and indole’s degradation were 0.0040 h-1,0.0050 h-1,0.0046 h-1 respectively; The rate constant of quinoline, pyridine and indole’s degradation were 0.0045 h-1,0.0039 h-1,0.0039 h-1 while added low concentration of phenol; The rate constant of quinoline, pyridine and indole’s degradation were 0.0048 h-1,0.0041 h-1,0.0030 h-1 while added high concentration of phenol.6.The research had studied the degradation of the electron donors(quinoline and phenol, pyridine and phenol, indole and phenol) and electron acceptor(NO-2-N). The COD and NO-2-N concentrations fitted the double-substrate Monod model.The maximum specific degradation rate was 0.0048h-1,0.0067 h-1,0.0031 h-1, respectively.The half saturation coefficient for nitrite nitrogen were 1.36mg/L,0.66 mg/L,5.29 mg/L, respectively.The half saturation coefficient for organic substance 78.77 mg/L,76.35 mg/L,84.61 mg/L, respectively.The recalcitrant organic matter factor 43.60mg/L, 38.61mg/L,45.95mg/L.7.For the shortcut denitrification system at high COD/ NO-2-N,the research had studied dominant bacterium structure and function,which corresponded to activated sludge acclimated by different carbon sources. The conclusions are as follows: the bacterial diversity was more abundant and the bacterial population was more for quinoline phenol, taking second place for pyridine and phenol,the lowest for indole and phenol. In the presence of phenol, dominant bacterial genera included Longilinea, Belliline, Ignavibacterium, Comamonas, Solitalea, Levilinea and Thauera for the degradation of quinoline, pyridine and indole in the process of anoxic shortcut denitrification.