Advanced Treatment Of Biotreated Effluent From Pharmaceutical Industrial Park By Using Catalytic Ozonation Process

Pharmaceutical industrial wastewater contains a large amount of bio-refractory and toxic organic pollutants, which are difficult to be degraded or removed effectively by traditional biochemical treatment process. Some residual pharmaceutical organic matter are toxic, which have serious impact on the stable operation of the biochemical wastewater treatment plant and the aquatic environment. Therefore, the main goal of this research is to study the enhanced treatment process for the bio-treated pharmaceutical industrial wastewater (BPIW).The characterization of BPIW is conducted to find out the main problems in the treatment processes.2,4-Dimethyl phenol (DMP) was chosen as the typical pollutant in BPIW. The physico-chemical treatment separation processes, coagulation-precipitation, adsorption, and the advanced oxidation processes, ozonation and catalytic ozonation, were experimentally studied for the treatment of BPIW and the typical organic pollutant. Catalytic ozonation was chosen due to its economical, available, and efficient characteristics. Further studies were conducted for the treatment of BPIW and the typical pollutant by using catalytic ozonation process.Catalyst is the key factor in the catalytic ozonation process. In this work, different catalysts, including metal (Mn, Ni, Ce, Al, Cu) oxide. MCM-41 and LTA zeolite, activated carbon, manganese sand, natural zeolite, ceramic particles and artificially synthetic Mn/MCM-41 and Ni/AC were compared. The performance of catalyst was evaluated by the mineralization efficiency of BPIW and the removal efficiency of DMP. Among the catalysts. γ-Al2O3 and Mn/MCM-41 showed higher catalytic activity than others. After comprehensive comparisons, γ-Al2O3 was chosen as the most effective catalyst due to its efficiency, economy and convenience for preparation. Therefore, the treatment of BPIW and the typical pollutant by using γ-Al2O3/O3 process was conducted, and the mechanisms were analyzed.Heterogeneous catalytic ozonation of DMP in aqueous solution was carried out in a semi-batch laboratory reactor using γ-Al2O3 as the catalyst. The degradation efficiency was investigated, the degradation intermediates were analyzed, and the degradation mechanisms were studied. The results showed that the presence of γ-Al2O3 significantly improved the mineralization efficiency of DMP and the utilization of ozone, and the reaction followed the first order kinetics. Batch experiments showed that pH was one of the main factors affecting the removal efficiency of the catalytic ozonation process, and the pH presented a positive effect on the mineralization efficiency and the optimum working pH was around 9.0, under which a relatively high removal efficiency could be obtained. The initial concentration of DMP and ozone dosage influenced oxidation degradation efficiency of the pollutant. The normal inorganic ions in water, Cl-, HCO3- showed inhibition to the ozonation oxidation process to some extent; The presence of tert-butanol caused obvious decrease of mineralization efficiency of the γ-Al2O3/O3 process, suggesting that mineralization of DMP followed the mechanism of hydroxyl radical oxidation. DMP was firstly oxidized into its aromatic derivation, esters and low molecular acid, and finally oxidized into CO2 and H2O. The addition of catalyst on the one hand might improve the removal efficiency of DMP by producing extra hydroxyl radical, on the other hand might promote the complete mineralization of the intermediates that were difficult to be degraded.The γ-Al2O3/O3 experiments were conducted, taking the real BPIW as treatment target. The operation conditions were primarily studied by optimizing the ozone dosage, and initial pH of the BPIW. The fluorescence spectrum (EEM), the pollutant components, the variations of toxicity and biodegradability of the BPIW before and after γ-Al2O3/O3 process were analyzed. It showed that, the pollutant removal efficiency was increased with the increase of ozone dosage.15 mg/L DOC removal was achieved by dosing 2.0 g/L ozone, while the removal efficiency could not be obviously improved with further increase of ozone dosage; the mineralization efficiency and the pollutant removal efficiency were relatively high under alkaline conditions, and at the initial pH 12.0,52% DOC was removed after 2.0 h; The EEM analysis showed that both γ-Al2O3/O3 and O3 processes could quickly remove the fluorescent substances in BPIW. O3 process alone achieved more obvious ozonation efficiency, and this showed that ozone reacted with fluorescent substance selectively. While in the γ-Al2O3/O3 process, part of the ozone was degraded and turned into hydroxyl radical which was unselective in oxidation. The analyses of biodegradability, toxicity and components showed that the γ-Al2O3/O3 might improve the biodegradability of the BPIW. and lower the toxicity, thus improving the reduction ability of the pollutants.In conclusion, the toxic and hazardous organic pollutants in BPIW could be largely removed by using γ-Al2O3/O3 treatment process. After the advanced treatment, the toxicity of BPIW could be reduced and the biodegradability be significantly increased. Compared with single ozonation process, γ-AlO3/O3 catalytic process possessed higher ozone utilization efficiency and lowered the operation cost. The research results provided technical supports for the enhanced treatment of BPIW, which has a promising prospect.