Study On Degradation Of Chloroanilines By Dominant Mixed Bacteria

Chlorinated aromatic hydrocarbons and their derivative are chemical materials, intermediate products of organic compounds and organic solvents which are widely applied in industry, such as chemical, medicine, curry, electron and so on. Most of them are persistent in the environment. They are toxic to aquatic organisms, and non-ready to be biodegraded by the microorganisms in nature water. At present, many researches have been done about the biodegradation of chlorinated aromatic hydrocarbons. However, there are few reports about the biodegradability of chloroanilines. It is very important to protect water resources to study the biodegradation characteristic of chloroanilines.Dominant mixed bacteria, which was able to utilize chloroanilines as sole carbon source, was isolated, incubated and domesticated from the activated sludge collected from the returned sludge well hole in the industrial wastewater treatment plant of Yangtse Petrochemical Company. By identification, the dominant mixed bacteria included four kinds of bacteria, which were Xanthomonas, Alcaligenes, Pseudomonas and Actinomycetaceae nocardia. By bacteria growth-inhibition experiment, it has been shown that the isolated mixed bacteria were more tolerant to chloroanilines than the bacteria from nature water (Yangtze River), and after the domestication with aniline and 2-chloroaniline selective medium, the toleration of dominant mixed bacteria was improved evidently.The biodegradability to the chloroanilines used the dominant mixed bacteria as degradation microorganism by laboratory simulation method. The result showed that dominant mixed bacteria domesticated with aniline and 2-chloroaniline was able to utilize 3- chloroaniline, 4- chloroaniline and 2,4- dichloroaniline as sole carbon source and energy source. However, 2-chloroaniline, which was used to domesticate the dominant mixed bacteria, was the most easily to be biodegraded, while 4-chloroaniline was the most difficultly to be biodegraded. The biodegradation rate of 2,4- dichloroaniline is higher than 3- chloroaniline and 4- chloroaniline.Compared with existence lonely, when 2-chloroaniline and 2,4-dichloroaniline co-existing, 2,4-dichloroaniline would inhibit the biodegradation of 2-chloroaniline in the initial stage. But it would not have a notable effect on the final biodegradation rate of 2-chloroaniline. However, the biodegradation rate of 2,4-dichloroaniline was improved obviously because of the existence of 2-chloroaniline which was moreeasily degraded. The biodegradation rate of 2,4-dichloroaniline was improved 22%, and its biodegradation rate constant was improved more than 50%.Using 2-chloroaniline as object pollutant, we researched the effects of condition factors to object compound's biodegradation rate and ultimate degreased rate, such as the exposure concentration of compound, the mixed bacteria's inoculum size, the water's pH value and appending growth matrix. The experimental results showed that the dominant mixed bacteria could adapt the extensive pH value. However, the biodegradation would be obviously restrained when pH value was below 2.5. Besides, decreasing initial concentration, increasing bacterial concentration and appending growth matrix could improve the biodegradation rate.