Study On Optimization Of Ozone-activated Carbon Treatment Of Drinking Water

Our study was based on the climate and water conditions of Pearl River downstream. And it was about the optimization of pre-ozonation dosage and the post-ozonation dosage for the Ozone-Biological Activated Carbon(O₃-BAC) system. This paper also analyzed the microbial flora attached on Biological Activated Carbon(BAC) for further understand the effects of the biological activity with addition of ozone. These study were done to provide important theoretical basis for the O₃-BAC effective operation and process parameters and the application in other water plant.Classâ…¡and classâ…¡^â…¢(GB 3838-2002) raw water were selected to carry out the ozone dosage optimization test. Results show that: (1) In the pre-ozonation dosage optimization pilot test of classâ…¡raw water, the coagulation aid effect of pre-ozonation is not obvious. However, in the pre-ozonation dosage optimization pilot test of classâ…¡^â…¢raw water, the coagulation aid effect can be seen and it was regular. The enhance effects of sedimentation and sand filtration is not only the increase of COD_Mn removal, but also affect the running cycle of sand filter and carbon filter and the turbidity of final effluent. (2)Pre-ozonation dosage gradually increased from 0mg/L and to 2.1mg/L, and the pre-ozonation have a certain removal on COD_Mn, UV₂₅₄, NO₂^--N. The pre-ozonation optimization results of classâ…¡^â…¢and classâ…¡raw water are consistent. In addition, pre-ozonation has the function of algae removal, and could be the alternative of pre-chlorination and was effective in reducing by-product of chlorination. (3) The total number of bacteria in the effluent of post-ozonation contact tower and carbon filter is only 1²cfu/ml, no fecal coliform bacteria. the post-ozonation have a certain removal of COD_Mn and UV₂₅₄. The post-ozonation can not only improve the biodegradability of organic compounds, but also increase the removal of precursors of disinfection by-product, thereby reducing the disinfection by-products. For O₃-BAC process, the removal of COD_Mn, UV₂₅₄, NO₂^--N were not the main task during pre-ozonation stage, the follow-up process of main O₃ and carbon filters can remove these substances more effectively. Generally speaking, when the post-ozonation dosage is 2.0mg/L, the NO₂^--N removal rate is nearly 100% after post-ozonation contact treatment.To understand the effects of the biological activity with addition of ozone and the biological safety of O₃-BAC system, Scanning Electron Microscopy(SEM), ATP bioluminescence, 16srDNA molecular techniques and classical methods of microbial isolation were adopted in this paper and these methods were used for: the rapid assessment of microorganisms attached on the carbon and its biomass and microorganisms in water. The study on the enrichment conditions of pathogenic bacteria on BAC.Through comparison and analysis, and refer to the domestic and international experience, and leave space for the changes in water quality, the optimized ozone dosage was recommended as follows: the pre-ozonation dosage is 0.5¹.5mg/L in a certain water plant in Guangdong, usually dosing 0.8¹.2mg/L; the post-ozonation maximum dosage of 2.5mg/L, usually dosing 1.0².0mg/L. At the same time, research shows that: this certain water plant in Guangdong whose pre-ozonation dosage of 0.5¹.5mg/L, the post-ozonation dosage of 1.0².5mg/L, the contact time of water and carbon layer of 12.6min, it has good pathogens removal effect, and it doesn't have significant effect on microbial activity.