Batch experiments were carried out to investigate the promotive effect of pyridine on indole degradation under denitrifying conditions.The seed sludge was obtained from a local coal-coking wastewater treatment facility and was acclimated in the laboratory.Indole and pyridine were supple-mented to the synthetic wastewater at different ratios.The optimum ratio of chemical oxygen demand(COD)to nitrate(C/N)was 8.4-8.9 for both denitrification and indole and pyridine degradation.At a temperature of 28°C and pH of 7.0-7.5,the nitrate reductase activity(NRA)was in the best state.The addition of pyridine could promote NRA and the degradation of indole.When the initial concentration of indole was 150 mg/L,the concentration ratio of indole to pyridine was in the range of 1-10.Under optimum C/N conditions,the degradation of indole could be described with pseudo-zero-order kinetics.There was no accumulation of nitrite during the reaction.When the concentration ratio of pyridine to indole was less than 0.25 with an increase in the pyridine proportion,there were more significant augment rates for NRA and the degradation of indole than the situation when the concentration ratio was more than 0.25.
Bacterial strain Enterobacter aerogenes TJ-D capable of utilizing 2-methylquinoline as the sole carbon and energy source was isolated from acclimated activated sludge under denitrifying conditions. The ability to degrade 2-methylquinoline by E. aerogenes TJ-D was investigated under denitrifying conditions. Under optimal conditions of temperature （35°C） and initial pH 7, 2-methylquinoline of 100 mg/L was degraded within 176 hr. The degradation of 2-methylquinoline by E. aerogenes TJ-D could be well described by the Haldane model （R 2 〉 0.91）. During the degradation period of 2-methylquinoline （initial concentration 100 mg/L）, nitrate was almost completely consumed （the removal efficiency was 98.5%）, while nitrite remained at low concentration （〈 0.62 mg/L） during the whole denitrification period. 1,2,3,4-Tetrahydro-2-methylquinoline, 4-ethyl-benzenamine, N-butyl-benzenamine, N-ethyl-benzenamine and 2,6-diethyl-benzenamine were metabolites produced during the degradation. The degradation pathway of 2-methylquinoline by E. aerogenes TJ-D was proposed. 2-Methylquinoline is initially hydroxylated at C-4 to form 2-methyl-4-hydroxy-quinoline, and then forms 2-methyl-4-quinolinol as a result of tautomerism. Hydrogenation of the heterocyclic ring at positions 2 and 3 produces 2,3-dihydro-2-methyl-4-quinolinol. The carbon-carbon bond at position 2 and 3 in the heterocyclic ring may cleave and form 2-ethyl-N-ethyl-benzenamine. Tautomerism may result in the formation of 2,6-diethyl-benzenamine and N-butyl-benzenamine. 4- Ethyl-benzenamine and N-ethyl-benzenamine were produced as a result of losing one ethyl group from the above molecules.
