Inhibition characteristics of two-phase anaerobic system for real coking wastewater treatment

In this study, real coking wastewater was treated using two-phase up-flow anaerobic sludge bed (UASB) reactors. The results demonstrate that the inhibition of hydrolytic acidification phase may be the key reason for unable to treat high chemical oxygen demand (COD) concentration coking wastewater. With the influent COD concentration of coking wastewater increasing, methane production decreased sharply. And methane production could not be improved by extending the hydraulic retention time (HRT). Analysis of volatile fatty acids (VFAs) showed that VFAs were difficult to accumulate when treating high COD coking wastewater. Further analysis of related enzyme activities, including acid protease, acetate kinase, and coenzyme F420, showed that the ability of microorganisms to produce acid and gas was very low. The archaea which species were relatively simple were dominated by Methanobacterium in hydrolytic acidification phase, and its abundance remained above 92 %. However, the abundance of bacteria at the genus level changed greatly with the change of COD concentration of coking wastewater and HRT of the system. And lots of low taxa appeared to maintain the stability of the system.