Research On Hydrolysis Acidification-UASB Process Treating Coal Gasification Wastewater

As a typical high-concentration refractory industrial wastewater,coal gasification wastewater contains many toxic and harmful pollutants such as phenols,polycyclic aromatic hydrocarbons,nitrogen-containing heterocycles and etc.Traditional anaerobic biological treatment of coal gasification wastewater has the problems of bad treatment performance and poor anti-shock load performance.In order to further improve the performance of anaerobic treatment,this paper adopts the hydrolysis acidification-UASB process to treat coal gasification wastewater,which fully removes and transforms refractory organics,improves biodegradability,and reduces toxicity.In this paper,the effectiveness of the hybrid hydrolysis acidification tank with dosing fillers and the upflow hydrolysis acidification tank without dosing fillers combined with UASB for the treatment of coal gasification wastewater was investigated.The morphology of active sludge in two reaction prcesses,which respectively called H-UASB?hybrid hydrolysis acidification-UASB?and U-UASB?Upflow hydrolysis acidification-UASB?,was observed and summarized.During stable operation,the U-UASB process had a higher removal rate of COD and total phenols for coal gasification wastewater treatment,which was about 37% and 36%,respectively,while the COD and total phenols removal rate in H-UASB was only about 25% and 23%.By scanning electron microscopy,it was found that the hydrolysis acidification reactor of U-UASB promoted the adsorption of inorganic metal ions by the sludge,which benefited the formation of sludge particles.At the same time,the sludge in the back UASB reactor was relatively rich in microbial species,and had a distinct characteristic of the clusters of dominant bacteria.The microbial species and quantity in H-UASB sludge were greatly reduced,and it had the characteristics of “hiding” under EPS.In the experiments,the change of dissolved organic matters and the change of biodegradability and toxicity in the influent and effluent of the reactor were measured.It was found that the upflow hydrolysis acidification was superior to the hybrid hydrolysis acidification in the removal of aromatic compounds,the removal of macromolecule organics,and the conversion of small-molecule organics,thereby greatly improving the overall processing efficiency.At the same time,U-UASB reactor greatly improved the biodegradability,and reduced the toxicity of the influent,which was more conducive to subsequent biological treatment.In order to further improve the treatment efficiency of the hydrolysis acidification reactor,the influence of temperature and the type and dosage of trivalent iron compounds on the efficiency of hydrolysis acidification was investigated.The results showed that the optimum reaction temperature of the hydrolysis acidification reactor was 30°C,and the microorganism was active.The 96 h removal rates of COD and total phenols were 14% and 12.63%,respectively in 30°C.The addition of Fe₂O₄ helped to enhance the dissimilatory iron reduction in the reaction system and enhanced the removal of aromatic compounds such as phenols,but it was vulnerable to be inhibited by intermediate metabolites under conditions of low Fe2+ concentration.The addition of Fe₃O₄ can sustainably release Fe2+,which helped to improve the overall treatment efficiency of the reactor.However,due to the relative lack of Fe3+,the effect of dissimilatory iron reduction was not obvious,and the removal of aromatic compounds such as phenols was not significantly enhanced.Under the conditions of dosage of 10 g/L,the effect of Fe₂O₄ on the enhancement of hydrolysis and acidification was more significant.