Research On The System Of Heterogeneous Catalytic Ozonation And Its’ Advanced Treatment Of Dyeding Wastewater

Dyeing wastewater is a kind of high concentration of refractory organic wastewater, as the invention of new dyes, and the improving of textile dyeing industry wastewater discharge standards, nowadays the dyeing wastewater’s COD, B/C value and chromaticity are difficult to degrade,in the discharge of wastewater still contains many nonbiodegradable organic molecules. As an important technology of AOPs, heterogeneous catalytic ozonation process can quickly break the dye molecules’ color group in the reaction, and can quickly reach a stable state emission standard in a short time, so as to achieve the discharge standard; therefore this study has great economic and ecological significance.In this research, we build a lab-scale and a pilot-scale treatment process of heterogeneous catalytic ozonation, which are based on the three-phase inner circulating fluidized bed reactor. By comparing three kinds carriers’（ACF, PAN-ACF, GAC） and different metal load types’（separate load, composite load） physical and catalytic properties of these new types of catalysts before and after loading, we found MnO₂&MgO/GAC has the best effect of loading MnO₂&MgO, it has superior catalytic performance, the time of reaching to stability state of treatment is short, it also has a high degree of degradation, so we choose MnO₂&MgO/GAC as the optimal catalyst in this study.Then we explore two parameters of experimental device（gas flow rate, ozone concentration） and other four process parameters（the dosage of catalyst, initial p H, initial concentration of wastewater, temperature）. Through a series of preliminary and orthogonal experiment, we choose gas flow rate 0.8/min, ozone concentration 30 mg/L, dosage of catalyst 2 g/L, initial p H 8, initial concentration of wastewater 0.9, temperature 20 or 25℃ as the best process parameters, at this condition the whole system is at the intersection of treatment efficiency and reasonable cost. Through the operation of the pilot-scale system, we found there has small difference of lab-scale system, so it is suitable for the application of the actual processing.Through the study of this system’s practicability and its’ mechanism, we found the optimal catalyst’s wear rate is below 5% after running 30 h, and the relative reduction in the degradation efficiency is only 6% after nine times, so MnO₂&MgO /GAC has a good stability and durability. We also found the free radical reations in this system accounted for 71% of total oxidation reaction. It proved MnO₂&MgO/GAC with O3 can generate large number of free radicals in the system, which can greatly improve the speed and depth of degradation.Under the optimum process parameters, we found that the heterogeneous catalytic ozonation system for dyeing wastewater can reach high removal efficiency, the removal of COD and chrominance is fast and stable, COD can reach to 50 mg/L after 20 mines, chrominance down to 30 unit or less at about 10 to 15 minutes, and the B/C can rise to 0.39 from 0.04 in 20 mins. The effluent can reach the prescribed discharge standards of The dyeing Industrial Water Pollutant Discharge Standard（GB 4287-2012）.