Study On Advanced Treatment Of Pharmaceutical Wastewater By Heterogeneous Ozone

Pharmaceutical wastewater becomes one of the high concentration organic wastewater which is difficult to be degraded because of its complex composition,many kinds of organic species,high concentration,high COD and BOD5,high concentration of NH3-N and SS.At present,physicochemical pretreatment and secondary biochemical treatment are generally used in domestic and foreign pharmaceutical enterprises to treat wastewater.However,the wastewater after secondary biochemical treatment still contains more organic substances which are difficult to be degraded,and it is difficult to meet the new standards for the discharge of pollutants from pharmaceutical enterprises in China?GB21903-2008?.Therefore,it's necessary to carry out the advanced treatment of the pharmaceutical wastewater.In this paper,high efficient catalysts were prepared by impregnation method.The study was carried out that selection of catalyst carrier,activation mode,active components and preparation conditions.The catalysts prepared under the optimal conditions were subjected to the continuous small-scale experiments of ozone catalytic oxidation in the laboratory.The continuous experimental conditions were studied including catalyst dosage,ozone dosage,residence time,gas-liquid contact mode,ozone utilization rate.According to the optimal treatment conditions obtained by continuous small-scale experiments,the scale-up experiments and coupled biochemical experiments were carried out in the sewage treatment plant.The ozone-coupled activated sludge process and the ozone-coupled MBR process were compared with the direct activated sludge process and the direct MBR process respectively for the treatment of secondary biochemical effluent in the plant.The catalysts were prepared by impregnation method.The results showed that the NiO-Fe2O3/ceramsite catalysts had high activity which prepared under the conditions of impregnation solution concentration of 1 mol/L?in terms of metal ion content?,C(Fe³⁺):C(Ni²⁺)=1:1,the calcination temperature of 600?and the calcination time of 5h.The NiO-Fe2O3/ceramsite catalyst was prepared under the optimum conditions and characterized by SEM,XRD and XRF detection.The results showed that the active components of the catalyst were NiO and Fe2O3,and that the NiO content was 5.549%,the Fe3O4 content was 4.748%.In the continuous small test in the laboratory,the optimal continuous running conditions were obtained as follows:the dosage of the catalyst was 100g/L,the residence time was 90min,the concentration of ozone was 96.61mg/L,and the ozone utilization rate was 92.8%.The COD removal rate was still stable above 58%after continuous operation for 96 hours.In the ozone catalytic oxidation scale-up experiments in the plant,the COD removal rate of pharmaceutical wastewater can be maintained at about 50%under the conditions of that the residence time is 90 minutes and the continuous operation time is 21 days.The experiment of ozone catalytic oxidation combined with biochemical treatment included two steps:ozone catalytic oxidation treatment and then biochemical treatment.In the second step,the removal rates of COD and NH3-N were 44.24%and 41.77%respectively in activated sludge treatment and 56.2%and 57.17%respectively in MBR treatment.In the experiment of direct biological treatment of the secondary effluent,the removal rates of COD and NH3-N were only 11.21%and 17.03%respectively in activated sludge treatment and 37.84%and 44.58%respectively in MBR treatment.It was showed that the ozone catalytic oxidation coupled MBR process is an effective advanced treatment process for pharmaceutical wastewater.