| Coal chemical wastewater has a large amount of water,complex water quality and high processing difficulty,which has always been a difficult problem in wastewater treatment of the domestic and foregin coal chemical industry.With the shortage of water resources and the increasing environmental protection,the effective treatment of coal chemical wastewater has become one of the bottlenecks of the rapid development of the industry.Exploring efficient and economical wastewater treatment processes is of great significance to the development of coal chemical industry and ecological environment protection.This paper taked coal chemical wastewater as the research object,adopted magnetic coagulation technology to treat coal chemical gasification wastewater and comprehensive wastewater?mixed wastewater of biochemical effluent,circulating wastewater and desalinated wastewater?,and adopted activated carbon catalytic ozone oxidation technology to treat coal chemical reclaimed water.The main factors affecting the treatment effect were investigated.The processing efficiency and cost were comprehensively analyzed,and the best processing conditions were obtained,which provided technical support for the wastewater treatment of coal chemical enterprises.The main findings are as follows:?1?The optimal treatment conditions for conventional coagulation of gasification wastewater:the dosage of coagulant PAC was 150mg/L,and the dosage of flocculant PAM was 2.0mg/L.The best treatment conditions for magnetic coagulation of gasification wastewater:the dosage of coagulant PAC was 120mg/L,the dosage of flocculant PAM was 1.5mg/L,initial pH was 7.0,the optimal particle size of magnetic powder was 200 mesh,the dosage of magnetic powder was 200mg/L,in addition to the dosage of silicon agent?MgCl2?was 200mg/L.The main order of the main factors affecting the removal of pollutants by orthogonal test was:initial pH value>PAC dosage>MgCl2 dosage>magnetic powder dosage.?2?When the dosage of gasification wastewater was at the same level?PAC:120mg/L,PAM:1.0mg/L,MgCl2:200mg/L?,the COD removal rate was increased by5.1%compared with the conventional coagulation,the turbidity removal rate was 6.2%,and the dissolved SiO2 removal rate was increased by 4.8%.The traditional coagulation settlement reached stability after 30 min,and the magnetic coagulation could be stabilized after 2 min,and the average sedimentation speed was 16 times faster than the conventional coagulation.The magnetic powder had a high recovery rate,and the average recovery rate was 97.38%.After repeated use of the recovered magnetic powder,the properties were still stable.Except for slight fluctuations in COD,turbidity and dissolved SiO2 removal rate,the pollutant removal efficiency was not significantly affected.?3?The optimal treatment conditions for traditional coagulation of integrated wastewater:the dosage of coagulant PAC was 50mg/L,and the dosage of flocculant PAM was 1.5mg/L.The optimal treatment conditions for comprehensive wastewater magnetic coagulation:the dosage of coagulant PAC was 40mg/L,the dosage of flocculant PAM was 1.0mg/L,initial pH was 7.0,the dosage magnetic powder was80mg/L.The main order of the main factors affecting the removal of pollutants by orthogonal test was:PAC dosage>initial pH value>PAM dosage>magnetic powder dosage.?4?When the dosage of the integrated wastewater was at the same level?PAC:40mg/L,PAM:1.0 mg/L?,the COD removal rate was increased by 2.8%compared with the conventional coagulation,and the turbidity removal rate was increased by 2.6%,the removal rate of dissolved SiO2 increased by 2.3%,the traditional coagulation sedimentation reached stability after 30 min,the magnetic coagulation could reach stability after 2min,and the average sedimentation speed was 14 times faster than the traditional coagulation.The average recovery rate of magnetic powder was 96.99%.After repeated use of the recovered magnetic powder,the properties were still stable.The removal rate of COD,turbidity and dissolved SiO2 had no significant effect on the removal efficiency of pollutants except slight fluctuation.?5?The best conditions for activated carbon catalytic ozone treatment of coal chemical reclaimed water:the dosage of ozone was 20mg/min,the initial pH of wastewater was 8.5,and the hydraulic retention time was 0.5h.Under the optimal treatment conditions,the COD removal rate of wastewater was 48.2%,and the UV254removal rate was 61.2%.?6?The continuous flow test of ozone oxidation showed that the double reactor had better treatment effect than the single reactor,and the pollutants were further degraded.The average COD of the single reactor effluent was 43.5mg/L,the average removal rate was 47.5%,the effluent UV254 averaged 0.320,and the removal rate reached 62.2%.The COD of the double reactor effluent was more stable,and the effluent COD averaged 36.3mg/L.Up to 55.3%,compared to a single reactor increased by 7.8%,the effluent UV254 averaged 0.230,the removal rate reached 72.4%,compared to a single reactor increased by 10.2%.?7?The operation effect of continuous flow single reactor showed that after the system was stable,the ozone concentration in the effluent was about 0.2mg/L,the ozone concentration in the exhaust gas was about 9.5mg/L,the ozone utilization rate was52.3%,and the pollutant removal effect reaches 0.61 mgCOD/mgO3.Compared with the single reactor,the ozone utilization rate of the double reactor was obviously improved.After the system was stable,the effluent ozone concentration was about 0.4mg/L,the tail gas ozone concentration was about 6.7 mg/L,and the ozone utilization rate was 66.2%,which was higher than that of the single reactor.With 13.9%,the COD removal effect reached 0.56 mg COD/mgO3.?8?Feasibility analysis of magnetic coagulation and activated carbon catalytic ozone technology for treating coal chemical wastewater.Under the premise of ensuring treatment efficiency,magnetic coagulation and activated carbon catalytic ozone technology have lower cost and obvious economic advantages. |
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