Templeton Michael R, Andrews Robert C, Hofmann Ron
Department of Civil Engineering, University of Toronto, 35 St. George Street, Toronto, Ont., Canada M5S 1A4.
Water Res. 2007 Jun;41(11):2393-406. doi: 10.1016/j.watres.2007.02.047. Epub 2007 Apr 12.
This bench-scale study investigated the passage of particle-associated bacteriophage through a dual-media (anthracite-sand) filter over a complete filter cycle and the effect on subsequent ultraviolet (UV) disinfection. Two model viruses, bacteriophages MS2 and T4, were considered. The water matrix was de-chlorinated tap water with either kaolin or Aldrich humic acid (AHA) added and coagulated with alum to form floc before filtration. The turbidity of the influent flocculated water was 6.4+/-1.5 NTU. Influent and filter effluent turbidity and particle counts were measured as well as headloss across the filter media. Filter effluent samples were collected for phage enumeration during three filter cycle stages: (i) filter ripening; (ii) stable operation; and (iii) end of filter cycle. Stable filter operation was defined according to a filter effluent turbidity goal of <0.3 NTU. Influent and filter effluent samples were subsequently exposed to UV light (254 nm) at 40 mJ/cm(2) using a low pressure UV collimated beam. The study found statistically significant differences (alpha=0.05) in the quantity of particle-associated phage present in the filter effluent during the three stages of filtration. There was reduced UV disinfection efficiency due to the presence of particle-associated phage in the filter effluent in trials with bacteriophage MS2 and humic acid floc. Unfiltered influent water samples also resulted in reduced UV inactivation of phage relative to particle-free control conditions for both phages. Trends in filter effluent turbidity corresponded with breakthrough of particle-associated phage in the filter effluent. The results therefore suggest that maintenance of optimum filtration conditions upstream of UV disinfection is a critical barrier to particle-associated viruses.
这项实验室规模的研究调查了颗粒结合噬菌体在完整过滤周期内通过双介质（无烟煤 - 砂）过滤器的情况以及对后续紫外线（UV）消毒的影响。研究考虑了两种模型病毒，即噬菌体MS2和T4。水基质为去氯自来水，添加高岭土或奥尔德里奇腐殖酸（AHA），并用明矾混凝形成絮体后进行过滤。进水絮凝水的浊度为6.4±1.5 NTU。测量了进水和过滤后出水的浊度、颗粒计数以及过滤介质上的水头损失。在过滤周期的三个阶段收集过滤后出水样本进行噬菌体计数：（i）过滤器成熟阶段；（ii）稳定运行阶段；（iii）过滤周期结束阶段。稳定的过滤运行根据过滤后出水浊度目标<0.3 NTU来定义。随后，进水和过滤后出水样本使用低压紫外线准直光束在40 mJ/cm²的剂量下暴露于紫外线（254 nm）。研究发现，在过滤的三个阶段中，过滤后出水中颗粒结合噬菌体的数量存在统计学上的显著差异（α = 0.05）。在含有噬菌体MS2和腐殖酸絮体的试验中，由于过滤后出水中存在颗粒结合噬菌体，紫外线消毒效率降低。对于两种噬菌体，未过滤的进水样本相对于无颗粒对照条件也导致噬菌体的紫外线灭活率降低。过滤后出水浊度的趋势与过滤后出水中颗粒结合噬菌体的穿透情况相对应。因此，结果表明在紫外线消毒上游维持最佳过滤条件是防止颗粒结合病毒的关键屏障。
