Department of Civil and Environmental Engineering, University of Alberta, Edmonton, AB, Canada, T6G 2R3; Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB, Canada, T6G 2R3.
EPCOR Water Services Inc., Edmonton, AB, Canada, T6M 0J2.
Colloids Surf B Biointerfaces. 2019 Sep 1;181:499-505. doi: 10.1016/j.colsurfb.2019.05.065. Epub 2019 May 30.
Pilot-scale direct filtration challenge experiments were conducted to determine the impact of chemical pretreatment and filter design on the removal of Cryptosporidium surrogates dosed into the filter influent water at low temperatures (Average 0.5 °C). Copolymers-modified microspheres were identified as representative Cryptosporidium oocysts surrogates based on our previous findings and were used to evaluate the oocysts filtration removal at this pilot-scale study. The operational parameters examined included coagulant type (aluminum sulfate (alum) versus polyaluminium chloride (PACl)), filter aid polymer type (polyamine Magnafloc LT-7981 versus poly(Dimethyl Diallyl Ammonium Chloride) (polyDADMAC) Magnafloc LT-7995) and dose (0.5 versus 2.0 mg/L), and filter configuration (regular versus deep bed filters). The study found that higher Cryptosporidium surrogate removal was associated with higher polymer dose (2 mg/L) of polyDADMAC polymer and the deep bed filter configuration. The difference in surrogate removal between PACl and alum was no significant at cold temperature conditions tested. The deep bed filters were associated with higher surrogate removal, while exhibiting lower rates of flow reduction and longer filter run time. This work emphasizes the importance of optimizing chemical pretreatment and filter configuration for removing surrogates of Cryptosporidium oocysts in cold-water conditions in granular media water filtration processes. This pilot-scale study also demonstrated the exceed 2.5-log removal of Cryptosporidium surrogates (required from Guideline for Canadian Drinking Water Quality) can be achieved in the direct filtration during Edmonton cold-water condition when the pretreatment processes are optimized using 0.454 mg/L of alum as Al with addition of 0.5 mg/L poly DADMAC.
进行了中试规模的直接过滤挑战实验，以确定化学预处理和过滤设计对低温（平均 0.5°C）下投加到过滤进水的隐孢子虫替代物的去除的影响。共聚体改性微球被确定为代表隐孢子虫卵囊的替代物，基于我们之前的研究结果，用于评估该中试规模研究中的卵囊过滤去除率。研究中考察的操作参数包括混凝剂类型（硫酸铝（明矾）与聚合氯化铝（PACl））、助滤剂聚合物类型（聚胺 Magnafloc LT-7981 与聚（二甲基二烯丙基氯化铵）（polyDADMAC）Magnafloc LT-7995）和剂量（0.5 与 2.0mg/L）以及过滤结构（常规与深床过滤器）。研究发现，较高的隐孢子虫替代物去除率与较高的 polyDADMAC 聚合物剂量（2mg/L）和深床过滤结构有关。在测试的低温条件下，PACl 和明矾之间替代物去除率的差异没有显著性。深床过滤器与较高的替代物去除率相关，同时表现出较低的流速降低率和更长的过滤运行时间。这项工作强调了在颗粒介质水过滤过程中，优化化学预处理和过滤结构对于在冷水条件下去除隐孢子虫卵囊替代物的重要性。这项中试研究还表明，在埃德蒙顿冷水条件下，通过优化预处理工艺，使用 0.454mg/L 的 Al 作为明矾并添加 0.5mg/L 的 polyDADMAC，可以实现超过 2.5 对数的隐孢子虫替代物去除（加拿大饮用水水质指南要求），在直接过滤中可以实现。
