Experimental Study Of Oil Hydrocarbons In Coal Chemical Wastewater By Hydrolytic Acidification+AO Process

China’s energy structure is “rich coal, poor oil, less gas”, oil and gas is scarced andwe depend a lot on importation, which has become one of the important factorsrestricting China’s rapid economic development. Coal chemical products are cheaperand more environmentally friendly compared to traditional petrochemicals, therefore,the development of coal chemical industry to make coal as the substitute for oil is oneof the main ways to solve our energy problems.Oil hydrocarbons, as a kind of toxic and non-degradation matter, is one of themajor pollutants in coal chemical industrial wastewater, and the concent of oilhydrocaibons constitute a huge amount of the effluent COD. When discharged intowater and soil, oil hydrocarbons contaminant was highly possible to cause seriousenvironmental pollution and cause harm to humans, animals and plants. Therefore, it isof great importance to study how to improve the removal efficiency of oil hydrocarbonsin the coal chemical industry wastewater.The sequencing batch reactor（SBR）was firstly used for coal chemical wastewatertreatment. By analyzing the relationship between different cecle, pH, dissolvedoxygen(DO), temperature and performance, the optimal operation parameters of SBR totreat coal chemical wastewater were determined. The experiment results showed: underthe condition of24h SBR treatment cycle, pH6.8to7.1, DO3.5mg/L, and temperature25℃, this process had the best removal effect on COD and oil hydrocarbons with theremoval rates of85%and71%respectively, and the effluent COD was198.32mg/L, oilhydrocarbons14.90mg/L, however, which failed to attain a class standard of nationalwaste synthetical discharge. In addition, SBR process had a limited ability to removaloil hydrocarbons, its removal rates had a sharp fall when the influent concentration ofoil hydrocarbons exceeded50mg/L～60mg/L.Secondly, hydrolytic acidification+AO process was used to deal with the coalchemical industry wastewater, and the effect was good. By analyzing and studying theoptimal operation parameters of hrdrolytic and AO process, the results expressed: underthe condition of hydrolytic acidification HRT10h, DO0.3mg/L, temperature about30℃, the AO process HRT16h, R175%, r=70%, DO(O pool)3.0mg/L, this process had the best removal effect on COD and oil hydrocarbons with the removal rates ofabout95%and86%respectively, and the effluent COD was less than100mg/L, oilhydrocarbons less than10mg/L, which was consistent with a class standard of nationalwaste synthetical discharge. Meanwhile, this combined process had excellent ability toresist impact load and still had a good, stable removal results when he influentconcentration of oil hydrocarbons increased to70mg/L～80mg/L.The article studied how the common pollutants（phenols, sulfide, cyanide）in coalchemical industry wastewater affect the removal efficiency of oil hydrocarbons byhydrolytic acidification+AO process. The experiment results showed: the combinedprocess’s degradation ability was largely affectd when the effluent phenols concentincreased by more than200mg/L; there was, to some extent, a linear relationshipbetween the decline of COD and oil hydrocarbons removal capacity and the enfluentsulfide content; the effluent cyanide content had a large influence on the degradationability of the system, the removal rates of COD and oil hydrocarbons redyced to about32%and18%respectively when the effluent CN-increased by100mg/L.Sludge bulking and foam are usual problems in the operation of hydrolyticacidification+AO process, the reasons of sludge bulking and foam occurring in thecombined process when dealing with oil hydrocarbons in the coal chemical industrywastewater were studied and analyzed, and the corresponding solutions were proposedcombined with the actual case.