A Study On O₃-BAC Combined Process Treating Organic Matters Contained In Micropolluted Source Water

In this study, O3 and GAC processes in pilot-scale were selected to treat the typical micropollutant, 2,4-dichlorophenol (2,4-DCP), and the parameters influencing their performance were investigated. Afterwards, a 2m3/h O3-BAC process was established in the Water Plant of Yangtze Petrochemical Corp. Ltd. to treat the raw water from the Yangtze River and the artificial raw water. The ozone and the BAC filter characteristics of the process, and the comparison with other processes were investigated.When ozone was applied at the rate of 0~10mg/L, relative to lower dosage and longer contacting time, higher dosage of ozone and shorter contracting time more benefited their impact on the 2,4-DCP. The conditions for 2,4-DCP degradation were optimal at the dosage of 10mg/L and contact time of 15 min. The removal of 2,4-DCP increased with the increase of pH value. GAC was used as absorbent of 2,4-DCP in micropolluted water sources and the effect of absorbent time, pH, the temperature and the concentration of humic acids on the adsorption efficiency was studied. And the results could be described by Langmuir, Freundlich and BET models. The results showed that the adsorptive efficiency of 2,4-DCP on GAC (PJ-20) was a little better than on GAC (ZJ-15). The higher temperature was of great benefit to the adsorption and the adsorptive capacity was high in the lower pH. Humic acids quantity had certain influence on the 2,4-DCP removal efficiency.In the process of 2m /h scale, ozone couldn't result in a substantial removal of organic substances. But organic matters with larger molecules were broken into smaller ones, which improved the biodegradability of organic substances in the water; ozone combined with BAC filer could even achieve the removal of 95.8% for UV254. The dissolved oxygen in the effluent of BAC with pre-ozone was 2.5mg/L higher than that without pre-ozone. The ozone dosage of 2.0 mg/L was suitable for the process consideringboth the removal efficiency and the running cost. The removals of NH/-N, CODMn and UV254 in the BAC filer mostly occurred at the upper part of the filer, which showed the same trend of the biomass and the DO consumption distribution. The optimal EBCT was about 14.5min.The combined process of conventional one and the biofiltration was selected to compare with the combined one with O3-BAC as the core technique. The result showed the former performed not so well as the later except in the removal of turbidity. The later, i.e. O3-BAC-GAC-NF (nanofiltration), even could degrade organic matter expressed by UV254 under the detectable limit. For the seriously polluted water source, if fund permits, GAC and NF advanced treatment following the conventional one is helpful to enhance the quality and safety of water supply.