Research On The System Of Catalytic Ozonation With Floating Bed And Its Application

Dyeing and printing wastewater is one of the most difficult industrial wastewater because of its high concentration,high salinity,low biodegradability and high chromaticity.With the use of various new dyes and dyeing auxiliaries,the processing of printing and dyeing wastewater is becoming more and more difficult.It is difficult to meet the increasingly stringent national emission standards by using the traditional biochemical methods.Catalytic ozonation through the catalytic decomposition of ozone to produce a large number of strong oxidizing hydroxyl radicals,free radicals in the reaction of rapid decomposition of refractory groups and chromophore groups,making the effluent COD and chroma reduced to reach the national water standards.So,research on the advanced treatment of the printing and dyeing by catalytic ozonation gains important economic and ecological significance.In the course of the study,a catalytic ozonation reactor based on floating bed was designed and assembled to build a treatment system for the advanced treatment of printing and dyeing wastewater.The catalyst inside the reactor was arranged radially from the reactor center to achieve the best dispersion effect and the highest mass transfer effect.The activated carbon felt(ACF)and activated carbon fiber(PANACF)were used as catalyst carriers.manganese-based oxide,magnesium-based oxide and magnesium-manganese bimetallic oxide were loaded on the carriers by solgel method and impregnation method.The results indicated that Mn O2&Mg O/PANACF was the best catalyst by comparing the catalytic effect of each catalyst under uniform treatment conditions.Through the comparison of treatment effects of cationic red X-GRL wastewater and the biochemical secondary effluent of dyeing and printing plant under different operating parameters,the optimal parameters for the two types of wastewater were selected.For the cationic red X-GRL simulated wastewater,when p H value was 8,catalyst usage was 3g/L,mixed gas flow rate was 0.8 L/min,ozone concentration was 35 mg/L,the best treatment effect occurred in the intermittent flow mode;In the continuous flow mode,we gained the best effluent quality when p H value was 8,the catalyst usage was 3 g/L,the ozone concentration was 40 mg/L,the gas flow rate was 0.8 L/min and the hydraulic retention time was 30 min.For the biochemical secondary effluent,when p H value was 8,the catalyst usage was 4 g/L,the gas flow rate was 0.9 L/min,the ozone concentration was 40.6 mg/L and hydraulic retention time was 40 min,the treatment effect achieved the optimal level economically and technically.In the actual performance of the selected catalyst,we researched the catalyst wear rate and catalytic stability.The actual wear rate of the catalyst was about 2% after 15-hour normal operation,the catalytic efficiency decreased by 8% after 25 times normal operations.The wear rate was about 8% after 20-hour high airflow operation,and the catalytic efficiency dropped by about 11%.Under the optimum treatment conditions,the floating bed catalytic ozonation system possessed an efficient and stable treatment effect for the advanced treatment of dyeing and printing wastewater.In the treatment of simulated wastewater,the COD value in the effluent reduced to below 40 mg/L within 30 min by intermittent flow operation,and the chromaticity also reduced to about 20 times at the same time.In the continuous flow state,the COD value dropped to below 40 mg/L and the chroma maintained less than 20 times.In the advanced treatment of the biochemical secondary effluent wastewater,the effluent COD value maintained between 35 mg/L and 50 mg/L,at the same time,the effluent chromaticity maintained about 25 times.According to the "Textile Dyeing and Finishing Industry Water Pollutant Discharge Standard"(GB 4287-2012),Both of the two types of dyeing and printing wastewater can reach the standard after the advanced treatment.