Research On The Combined Catalytic Ozonation-BAF Process For The Advanced Treatment Of The Effluent From The Dyeing Wastewater Biochemical Treatment

Dyeing wastewater is a kind of biorefractory wastewater with complex composition.With the improvement of water environment governance in China,higher requirements have been put forward for the treatment of dyeing wastewater.The combined technology of heterogeneous catalytic ozonation and biological aerated filter(BAF)was studied for the advanced treatment of the effluent of dyeing wastewater biochemical treatment.Based on the selection of ozone catalyst,the controlling parameters of the combiend process were optimized,and the idea of two-stage treatment was proposed which could reduce the operation cost.Through the pilot scale experiment,the long-term stability of the ozone catalyst and the economic characteristics of the combined process were investigated,which provided the partial basic data and theoretical basis for the practical application of this technology.Firstly,the supported catalyst,which is one of the cores of the heterogeneous catalytic ozonationwas studied.Five catalysts were prepared using different transition metal salt solutions and supports.The adsorption and catalytic performance of this five catalysts were compared,and the best catalyst was selected.The catalytic activity and stability of the selected catalyst were investigated by comparing the removal effect of the pollutants by ozonation with or without catalysis.And the performance of the catalyst was characterized by SEM,XPS,BET and other methods.Secondly,taking the effluent of dyeing wastewater biochemical treatment as the object,based on the optimization of pretreatment,the influences of reaction time,catalyst amout,ozone dosing,ozone concentration and other parameters on the removal of pollutants by catalytic ozonation were investigated.The results showed that the optimal values of reaction time,catalyst amout,ozone dosing and ozone concentration were 30-40 min,335g/L,70.65mg/L and 71-90 mg/L,respectively.Thirdly,the advanced treatment effect of the combined process of catalytic ozonation BAF on the biochemical effluent of dyeing wastewater was investigated.The results showed that:catalytic ozonation can effectively improve the biodegradability of the biochemical effluent of dyeing wastewater,and the B/C ratio can be increased by 56.79%on average;the effect of BAF on treating the effluent of catalytic ozonation increased first and then decreased with the change of ozone dosage;the treatment effect of two-stage catalytic ozonation BAF system is better than that of single-stage system,and the optimal ozone dosage ratio of two-stage system is 6:4.Finally,the long-term pilot test was carried out to verify the operation effect of the combined process,and the change of catalyst after long-term use was also investigated.The results showed that the combined process of catalytic ozonation and BAF could withstand the impact load,the average COD value of the system effluent is 36mg/L under the optimal condition.The catalyst remains active after long-term use.The direct operation cost of the combined system was 1.3 yuan/m~3.