Evides Water Company, P.O. Box 4472, 3006 AL, Rotterdam, the Netherlands; Department of Environmental Technology, Wageningen University, Bornse Weilanden 9, 6708 WG, Wageningen, the Netherlands; IHE Delft Institute for Water Education, Environmental Engineering and Water Technology Department, Westvest 7, 2611 AX, Delft, the Netherlands.
IHE Delft Institute for Water Education, Environmental Engineering and Water Technology Department, Westvest 7, 2611 AX, Delft, the Netherlands.
Water Res. 2019 Nov 1;164:114927. doi: 10.1016/j.watres.2019.114927. Epub 2019 Jul 29.
The production of biologically stable drinking water is challenging in conventional surface water treatment plants. However, attainment of biological stability is essential to avoid regrowth in disinfectant-free distribution systems. A novel application of ultrafiltration as a posttreatment step to enhance biological stability of drinking water produced in an existing conventional surface water treatment plant was investigated. The conventional full-scale plant comprised coagulation/sedimentation/filtration, UV-disinfection, biological activated carbon filtration and chlorine dioxide post-disinfection. The produced water exhibited substantial regrowth of Aeromonads, invertebrates and colony counts in the distribution network. Recent literature attributes this phenomenon to the specific presence of slowly biodegradable, high molecular weight (MW) biopolymeric organic compounds. Hence, the aim of this study is to enhance the biological stability of conventionally treated surface water by reducing the concentration of high-MW organic compounds. For this purpose, biological active carbon filtrate was subjected to ultrafiltration with membrane pore sizes of 10 kDa, 150 kDa and 0.12 μm respectively, operating in parallel. The UF performance was evaluated in terms of the achieved reduction in particulate and high-MW organic carbon (PHMOC); the biopolymer fraction in Liquid Chromatography-Organic Carbon Detection; biomass (cells, ATP); Assimilable Organic Carbon (AOC) by the AOC-P17/NOX method for easily biodegradable, low-MW compounds and by the AOC-A3 method for slowly biodegradable, high-MW compounds; and overall microbial growth potential (MGP) as assessed by Biomass Production Potential (BPP) and Bacterial Growth Potential (BGP) bio-assays. Results showed increasing removal of high-MW organic carbon with decreasing UF pore size, i.e., 30%, 60% and 70% removal was observed for the 0.12 μm, 150 kDa and 10 kDa membranes, respectively. Biomass and particulates retention was more than 95% for all UF membranes. AOC-A3, BPP and BGP were substantially reduced by 90%, 70% and 50%, respectively. These respective reductions were similar for all three UF membranes despite their difference in pore size. Easily biodegradable organic compounds (as AOC-P17/NOX) were not reduced by any of the membranes, which was in accordance with expectations considering the low MW of the compounds involved. Based on the obtained results, growth potential appears to be largely attributable to high-MW organic compounds which are retained by a 0.12 μm UF membrane. Furthermore, the quality of all three UF permeates was equal to or better than in reference cases (literature data) which exhibit little regrowth in their disinfectant-free distribution networks. The results demonstrate that ultrafiltration posttreatment in conventional surface water treatment plants is a potentially promising approach to enhance the biological stability of drinking water.
生产具有生物稳定性的饮用水在常规地表水水厂具有挑战性。然而，实现生物稳定性对于避免在无消毒剂的分配系统中再生长是至关重要的。超滤作为一种后处理步骤，用于增强现有常规地表水水厂生产的饮用水的生物稳定性，这是一种新的应用。该常规全规模水厂包括混凝/沉淀/过滤、紫外线消毒、生物活性炭过滤和二氧化氯后消毒。生产的水中在配水网络中表现出气单胞菌、无脊椎动物和菌落计数的大量再生长。最近的文献将这种现象归因于特定的缓慢生物降解、高分子量（MW）生物聚合物有机化合物的存在。因此，本研究的目的是通过降低高分子量有机化合物的浓度来提高常规处理地表水的生物稳定性。为此，生物活性炭滤出物分别用膜孔径为 10 kDa、150 kDa 和 0.12 µm 的超滤进行处理，分别以并联方式操作。超滤性能根据颗粒和高分子量有机碳（PHMOC）的去除率、液相色谱-有机碳检测中的生物聚合物分数、生物量（细胞、ATP）、通过 AOC-P17/NOX 方法测定的可同化有机碳（AOC），用于易生物降解的低分子量化合物，以及通过 AOC-A3 方法测定的用于缓慢生物降解的高分子量化合物；以及通过生物量生产潜力（BPP）和细菌生长潜力（BGP）生物测定评估的总微生物生长潜力（MGP）。结果表明，随着 UF 孔径的减小，高分子量有机碳的去除率增加，即 0.12 µm、150 kDa 和 10 kDa 膜的去除率分别为 30%、60%和 70%。所有 UF 膜对生物量和颗粒物的截留率均大于 95%。AOC-A3、BPP 和 BGP 分别减少了 90%、70%和 50%。尽管三种 UF 膜的孔径不同，但这些各自的减少率相似。所有三种 UF 膜都没有减少易生物降解的有机化合物（如 AOC-P17/NOX），这与所涉及化合物的低分子量相符。根据获得的结果，生长潜力似乎主要归因于高分子量有机化合物，而这些有机化合物被 0.12 µm UF 膜截留。此外，所有三种 UF 渗透物的质量均等于或优于参考情况（文献数据），这些参考情况在其无消毒剂的分配网络中几乎没有再生长。结果表明，超滤后处理在常规地表水厂是一种提高饮用水生物稳定性的潜在有前景的方法。
