Efficiency And Mechanism In Anaerobic Degradation Of Pentachlorophenol With Intermittent Cosubstrate

PCP (pentachlorophenol, PCP)is a refractory organics which was widely used in industry and agriculture. It is well known for potential toxic, teratogenic, and carcinogenic properties. Many scholars had been conducting studies on PCP because it’s harmful to environment. Cometabolism plays an important role in the anaerobic cometabolic degradation of pentachlorophenol. However, the continuous increase of cosubstrate may lead to metabolic competition between substrates and increasing treatment cost as well. In this paper, the anaerobic degradation efficiency and mechanism of pentachlorophenol were studied through the regulation of metabolic substrates.At first, the efficiency and metabolic properties of the anaerobic degradation of PCP at once feeding mode of sodium acetate was studied. The PCP removal rate of the group with adding sodium acetate was higher than the blank group. The results showed that sodium acetate could promote anaerobic degradation of PCP. When the initial concentration of PCP increased, such promotion behavior was inhibited. The results indicated that the removal rates of PCP were not positively correlated with the doses of NaAc. As a result, it’s important to improve the efficiency of anaerobic degradation of PCP and reduce the cost of the treatment by optimizing dosing method and dosing quantity.Secondly, the process efficiency and anaerobic cometabolic degradation of PCP with the intermittent feeding mode were studied. In this study, the cometabolic degradation of PCP with the intermittent feeding mode, once feeding mode and intermittent gradient feeding mode of sodium acetate were explored. The results indicated that the batch feeding mode could reduce dosages of NaAc. The results also indicated that the removal rates of PCP were not positively correlated with the doses of NaAc at batch feeding mode. Experiments were performed to study the variation of the extracellular and intracellular polysaccharides and Live/Dead cells profiles of sludge. The ratios of extracellular and intracellular polysaccharides content increased from the initial values of 0.401±0.060 to 0.517±0.052 on day 8 at batch addition of 0.2 g NaAc/(L-d). At the same time, the ratios of dead and live cells increased. The results showed the reducing energy of PCP dechlorination did not derive from the acid cleavage and methanogenesis. Compared with the once feeding mode, the batch feeding mode not only saved more than 50% of sodium acetate, but also gained a better performance on PCP removal.Finally, anaerobic metabolic degradation of PCP with the zero-valent iron was researched. The results showed that when both zero-valent iron of 1 g/L and sodium acetate exist, the removal rate of PCP was positively correlated with the dosage of sodium acetate. The strengthen effect of zero-valent iron is not applicable in different mode of cometabolism substrate. According to our work, bacterial diversity and community structure were explored. From the results, the variation of community structure was accompanied by adding zero-valentiron.