Study On Degradation Of Substituted Chlorophenol By Domesticated Complex Bacteria

Dominant mixed bacteria which were able to utilize chlorophenol as sole carbon source and energy source were isolated, incubated and domesticated from the activated sludge collected from the returned sludge well hole in the Nanjing chemical Company's industrial wastewater treatment plant. By identification, dominant mixed bacteria included four kinds of bacteria, i.e. Pseudomonas,Alcaligenes,Mycopiana,Flavobacterium. By bacteria growth-inhibition test, the isolated mixed bacteria were found to be more tolerant to chlorophenols than the bacteria from natural waters (Qinghuai River). In addition, the toleration of dominant mixed bacteria by domesticated with 4-chlorophenol selective medium was improved significently, and the toxicty of compounds studied on bacteria was affected by the substituent'kinds, quantity and position.Using domesticated complex bacteria as an inoculum, the biodegradability of 2-chlorophenol ,3-chlorophenol,4-chlorophenol,2, 4-dichlorophenol,m-dihydroxybenzene,p-dihydroxybenzene,m-nitrophenol and p-nitrophenol was determined by shaking-flask test: under different water environment. The metabolismic relationships of the dominant mixed bacteria and river bacteria were studied.It was proved that mixed bacteria domesticated by 4-chlorophenol could grow and metabolize taking chlorophenols studied as sole carbon source and energy source. However, 4-chlorophenol was most ready biodegradable, and the order of the final removal rate was: 4-chlorophenol(93%)>2-chlorophenol(87%)>3-chlorophenol(80%) >2,4-chlorophenol(69%); m-dihydroxybenzene (93%) > p-dihydroxybenzene (81%); and m-Nitrophenol (94%) > p-Nitrophenol (88%). The degradation rate of aborigine microbe in water to all target compounds was unsatisfied, but the degradation rates of compounds were greatly improved when adding the domesticated mixed bacteria in water. There were co-metabolism effects between aborigine microbe and mixed bacteria to different target compounds, and the suspend substances and organic substances could also affect the mixed bacterial growth, propagation and metabolism. The biodegradability of two coexistent substituted phenols, such as 2-chlorophenol and 3-chlorophenol, 2-chlorophenol and 4-chlorophenol, 2-chlorophenol and 2,4-chlorophenol, 3-chlorophenol and 2,4-chlorophenol, and 4-chlorophenol and 2,4-chlorophenol were studied.By comparing the degradation curve of coexistent compounds with that of the single ones, we could find that the presence of 2,4-chlorophenol inhibited the degradation rate of 4-chlorophenol in the initial stages due to the increased total toxicant concentration, howerer didn't influence obviously its final removal rate. The metabolic efficiency of 2,4-chlorophenol was improved when more readily degradable 4-chlorophenol coexisted, and the removal rate of 2,4-chlorophenol was 100%, and the degradation rate constant was increased by more than 20%.In summery, the lag phase and the time to reach degradation balance appeared longer compared with only one situation. Tne coexisted chlorophenols inhibited mixed bacterial metabolismic activity. There were competition effect for co-existant compounds at the beginning, but an additive effect or antagonism was found when taking final removal rate as test endpoint.