The combination of low-dose ozone with ultraviolet (UV) irradiation should be an option to give benefit to disinfection and reduce drawbacks of UV and ozone disinfection. However, less is known about the disinfection performance of UV and ozone (UV/ozone) coexposure and sequential UV-followed-by-ozone (UV- ozone) and ozone-followed-by-UV (ozone-UV) expo- sures. In this study, inactivation of E. coli and bacterioph- age MS2 by UV, ozone, UV/ozone coexposure, and sequential UV-ozone and ozone-UV exposures was investigated and compared. Synergistic effects of 0.5-0.9 log kill on E. coli inactivation, including increases in the rate and efficiency, were observed after the UV/ozone coexposure at ozone concentrations as low as 0.05 mg-L-1 in ultrapure water. The coexposure with 0.02-mg.L-1 ozone did not enhance the inactivation but repressed E. coli photoreactivation. Little enhancement on E. coli inactivation was found after the sequential UV-ozone or ozone-UV exposures. The synergistic effect on MS2 inactivation was less significant after the UV/ozone coexposure, and more significant after the sequential ozone-UV and UV-ozone exposures, which was 0.2 log kill for the former and 0.8 log kill for the latter two processes, at ozone dose of 0.1 mg. t-1 and UV dose of 8.55 mJ. cm 2 in ultrapure water. The synergistic effects on disinfection were also observed in tap water. These results show that the combination of UV and low-dose ozone is a promising technology for securing microbiological quality of water. 相似文献
A new 210Pb-dated record of Hg accumulation derived from a sediment core from a Hg-enriched area in Huguangyan Lake (HGY) in South China is presented. Based on synthetic analyses of multi-proxy records including chemical composition, total organic matter, and grain-size distribution in surface sediments and nearby soil samples, it is inferred that the influx of Hg into the lake is mainly a result of atmospheric deposition, with no or minor hydroclimate-induced lithogenic input from the catchment and limited adsorption effects of organic matter and clay. Significantly enhanced anthropogenic input of Hg started in the early 1900s. Since then, several anomalies of Hg accumulation have been the results of wars or intensified economic activities in China. HGY sediments provide a rare and reliable natural archive for detecting atmospheric Hg deposition, which is closely related to anthropogenic activities.