Endogenous Electron Donor Accelerates Quinoline Biodegradation And Mineralization

Quinoline is a kind of typical nitrogen heterocyclic compound, its molecular structure is made up of a benzene ring and a pyridine ring coupling, which is a kind of aromatic compounds. Quinoline have biological toxicity, it is poisonous to plants and animals in different levels. It can lead to teratogenic, carcinogenic and mutagenic effects if it enters into humans body. And with the wide use of this kind of chemical raw materials----quinoline, many parts of the soil, surface water and groundwater were detected the presence of quinoline.Therefore, the study about the treatment of wastewater containing quinoline is becoming more and more valued. At present, the treatment technology of wastewater containing quinoline mainly including: physical method, chemical method and biological method.Alone with the biological degradation of quinoline, microbial growth would be suppressed, which will affect the biodegradation efficiency. And the energy consumption of separate method using uv light is large, the degradation rate is also slow.This study will use the method of coupling UV irradiation with biodegradation, make sure quinoline that is harder to biodegradation and have microbial toxicity can get transformation and degradation fully, thus to improve the processing efficiency. At the same time, quinoline UV photolysis intermediates were analyzed to explore the mechanism how intermediates accelerate quinoline biodegradation. Based on the research, an internal circulation baffled biofilm reactor was developed and used for the biodegradation of quinoline. The experimental results are as follows:(1) Many intermediates will be created during the process of biodegradation and ultraviolet solution.In this study 2 – hydroxyquinoline and oxalic acid will be created in the process of quinoline biodegradation, and oxalic acid can also be produced in the process of ultraviolet light solution.(2) Quinoline transformation is limiting step of quinoline mineralization.When quinoline transformed into 2- hydroxyquinoline fully, COD removal rate increased together with 2- hydroxyquinoline decreased quickly.(3) Quinoline removal rate was faster after UV photolysis compared with original quinoline without photolysis. The acceleration is due to oxalic acid, accelerated quinoline biodegradation by producing intracellular electron carrier(H) to drive initial mono-oxygenation reactions,which is the step of quinoline transforned into 2-hydroquinoline.(4) Many kinds of carboxylic acids will created duirng UV photolysis, oxalic acid is the one being detected. Therefore, the degradation rate of biodegradation after UV photolysis directly was faster than added a certain amount of oxalic acid in the experimental process. Because of carboxylic acids created by UV photolysis can provide more electron carrier than add oxalic acid directly.(5) Different UV photolysis time will have different effects to biodegradation. The concentration of carboxylic acid will increase if extension of UV photolysis time,so as to accelerate the quinoline biodegradation. But economic efficiency must be considered in actual applications.(6) New domesticated ctivated sludge can degradate quinoline quickly and quinoline transformed into 2- hydroxyquinoline in great quantities, but the speed of degradate 2- hydroxyquinoline mud degradation is slow, so there will be a large number of 2- hydroxyquinoline accumulation, the detected concentration of the reaction of 2- hydroxyquinoline is high. On the other hand, the speed of degradation of quinoline is slow used the activated sludge domesticated for a period of time, and the same the speed of quinoline transformed into 2- hydroxyquinoline is very slow, but the speed of degradate 2- hydroxyquinoline mud degradation is fast, so the less 2-hydroxyquinoline is accumulated in the solution, the lower concentration is measured.