Effects To Toxicity Of Anaerobic Granular Sludge By2,4,6-trichlorophenol And Its Reductive Dechlorination Mechanism

Pulp and paper industry bleaching wastewater often contains lots of chlorophenols hard-degradation organic matters, most of this kind of compound has the carcinogenicity, teratogenicity, and the mutability, so it was significant to research on the degradation of chlorophenol.The existing physical and chemical method was difficult to realize in engineering application because of its high processing cost. However, the biological treatment technology was more economical and easy to manage. Under anaerobic conditions, chlorophenols served as electron acceptors of reductive dechlorination, but chlorophenol has strong toxicity and resistance to degradation due to its aromatic structure and chloro atom. Therefore, the higher content2,4,6-TCP in papermaking wastewater was treated as the target pollutants, toxicity effects of2,4,6-TCP to anaerobic granular sludge, influence of physiological and biochemical characteristics of anaerobic granular sludge were researched. Also, the degradation mechanism of2,4,6-TCP under different electron donors was studied to realize the relationship between the microbial mechanism and the electron donors. Then, highly efficient degradation of cholrophenols was realize in the papermaking plant. It was found that:2,4,6-TCP was a type of fungicides, it has an inhibitory effect on methanogenic activity. It indicated that the inhibition of methanogens was positively correlated with the concentration of2,4,6-TCP, and the recovery of methanogenic activity was negative.The anaerobic granular sludge retrieved from the papermaking plant has the potential on the degradation of2,4,6-TCP. After domestication, the potential could be induced. In addition, a variety of substrates acclimation is more conductive to induce the2,4,6-TCP degrading enzyme.It proved the formation of large particles and the activity of granular sludge were promoted when the concentrations of2,4,6-TCP was high, while a cavity was formed. The main metabolic pathway was metabolic reductive dechlorination, so the amount of biomass increased. Furthermore, sufficient nutrients were offered by high concentration2,4,6-TCP for reductive dechlorination and anaerobic microorganisms to increase the biological activity, and the concentration of coenzyme also increased. In the situations of high concentration of2,4,6-TCP, bacteria were decomposed and permeated to the extracellular, thus the total content of extracellular polymeric substance was risen, which lead to the smooth and fewer pore surface of the thallus. When the concentration of2,4,6-TCP was less than l0mg/L, the degradation of2,4,6-TCP was effected by adsorption, and effected by biodegradation when the concentration of2,4,6-TCP was high. The higher the concentration of2,4,6-TCP was, the faster the degradation rate was.Compared with the effect of glucose, sodium lactate, sodium pyruvate and sodium acetate enhanced the dechlorination of2,4,6-TCP effectively, in which sodium lactate could serve as a kind of hydrogen release compounds continued to supply electrons that reductive dechlorination of2,4,6-TCP required. Substrate metabolism dehydrogenase activity was improved by the external electron donor, after reaction for240h, dehydrogenase activity growth in the four electron donor system, followed by21.49%,25.78%,136.85%and139.3%.The main reductive dechlorination products of2,4,6-TCP included2,4-dichlorophenol (2,4-DCP),4-chlorophenol (4-CP) and phenol, when sodium acetate as electron donor,4-CP was its main degradation products, and conversion rate from2,4,6-TCP to4-CP was more than22%.