Experimental Study On Treatment Of Dividing-quality Coking Wastewater By MAP/Coagulation-fenton Oxidation And SBR

Coking wastewater is an organic industrial wastewater with high concentration,difficult to degrade,so the effluent from treatment process is hard to reach the standard of discharge.It is an important research direction to seek efficient pretreatment methods and improve pretreatment effect for improvement of biodegradability.Exploring new treatment method for coking wastewater is always research emphasis.In order to improve the effect of treatment of coking wastewater,the distillation method is used to separate the ammonia wastewater,the coking wastewater by distillation separation is separated into three components:first component from the intial stagestage of distillation,medium component from the middle stage of distillation and residual liquid left after ammonia distillation.Among them,the volume of first component from the intial stagestage of distillation accounts for 5%of the total volume,the volume is small and the concentration of pollutants is lower;the volume of medium component from the middle stage of distillation accounts for 90%of the total volume,which is the main part of the ammonia distilled wastewater and is the focus of treatment;although the volume of the residual liquid left is small,but the concentration of organic pollutants is very high,which is more than three times higher than that of the raw wastewater.In this study,MAP chemical precipitation is used to treat medium component,and the residual liquid is treated by coagulation,Fenton oxidation and coagulation-Fenton oxidation method.Then the effluent continuously treated by the SBR.The results are as follows:In the test stage of MAP chemical precipitation,the optimum technological conditions determined by single factor test are as follows:the optimal conditions with the initial pH 9.5,the mole ratio of Mg:N 1.3 and the mole ratio of P:N 1.2 are obtained.Under the optimal conditions,the removal rates of ammonia,phosphorus are about 64.58%,83.15%,respectively.MAP precipitation method also has a certain removal effect on COD,than the total removal efficiency is lower than 10%.The results of the orthogonal experiment show that the influencing factors of the precipitation method are pH>Mg:N>P:N,and when the reaction pH is 9.5,the mole ratio of Mg:N and P:N are 1.2,the removal efficiency of ammonia nitrogen is the best.In the test stage of coagulation precipitation method,the results show that the combined use of PAFC and FeCl₃ has a good removal effect on the residual liquid after ammonia distillation of coking wastewater.The optimum operating conditions through single factor optimization test as follows:the dosage of PAFC,Fe Cl₃ and PAM are 2500mg/L,350mg/L,3mg/L,respectively,the pH of the reaction is 9,under the optimum operating conditions,the COD and chroma removal rate of effluent are about 19.51%and 70%respectively.In the test stage of Fenton oxidation,the results show that the optimum reaction conditions are obtained when the dosage of FeSO4·7H₂O and H₂O₂ are 8.75g/L,6ml/L,the reaction time is 2.5h,and the pH is 4.The removal rates of COD,ammonia nitrogen and chroma of residual liquid after ammonia distillation are 37.84%,66.96%and 95%respectively,and the order of the influencing factors is pH>H₂O₂>the reaction time>Fe²⁺.The order of Coagulation-Fenton oxidation and Fenton oxidation-coagulation synergistic treatment have different removal effects on organic matter,but it is not great,the removal rate is 41.38%,46.44%respectively.What's more,the removal efficiency of Fenton oxidation-coagulation is better than coagulation-Fenton oxidation.However,the oxidation effect is not equal to the total removal rate?57.53%?under the optimum conditions of the two tests.The results of SBR test are as follows:the optimal aeration time is 9 h,aeration rate is 0.2 m³/h,and sludge loading under general sludge loading conditions,COD removal rate is best,it is about 90%.The coking wastewater is distilled after what,the removal efficiency is better when the mixing ratio of medium component after ammonia distillation and domestic sewage is 40,however,the removal efficiency of the waste water becomes worse when the mixing ratio is 60.The removal rate of organic pollutants is more than 90%after residual liquid is oxidized by coagulant,Fenton,and SBR biochemical treatment,effluent quality is standard and the process is stable running.The combined process is effective in treating coking wastewater,which shows that this process is feasible.