Department of Civil and Environmental Engineering, University of Houston, TX 77204-4003, USA.
Water Res. 2012 May 1;46(7):2111-20. doi: 10.1016/j.watres.2012.01.032. Epub 2012 Jan 28.
Results from a laboratory-scale study evaluating virus control by a hybrid iron electrocoagulation - microfiltration process revealed only 1.0-1.5 log MS2 bacteriophage reduction even at relatively high iron dosages (≈ 13 mg/L as Fe) for natural surface water containing moderate natural organic matter (NOM) concentrations (4.5 mg/L dissolved organic carbon, DOC). In contrast, much greater reductions were measured (6.5-log at pH 6.4 and 4-log at pH 7.5) at similar iron dosages for synthetic water that was devoid of NOM. Quantitative agreement with Faraday's law with 2-electron transfer and speciation with phenanthroline demonstrated electrochemical generation of soluble ferrous iron. Near quantitative extraction of viruses by dissolving flocs formed in synthetic water provided direct evidence of their removal by sorption and enmeshment onto iron hydroxide flocs. In contrast, only approximately 1% of the viruses were associated with the flocs formed in natural water consistent with the measured poor removals. 1-2 logs of virus inactivation were also observed in the electrochemical cell for synthetic water (no NOM) but not for surface water (4.5 mg/L DOC). Sweep flocculation was the dominant destabilization mechanism since the ζ potential did not reach zero even when 6-log virus reductions were achieved. Charge neutralization only played a secondary role since ζ potential → 0 with increasing iron electrocoagulant dosage. Importantly, virus removal from synthetic water decreased when Suwanee River Humic Acid was added. Therefore, NOM present in natural waters appears to reduce the effectiveness of iron electrocoagulation pretreatment to microfiltration for virus control by complexing ferrous ions. This inhibits (i) Fe(2+) oxidation, precipitation, and virus destabilization and (ii) virus inactivation through reactive oxygen species intermediates or by direct interactions with Fe(2+) ions.
实验室规模的研究结果表明，即使在含有适量天然有机物 (NOM)（4.5 毫克/升溶解有机碳，DOC）的天然地表水条件下，采用铁电凝聚-微滤联用工艺对病毒进行控制，其效果也仅能达到 1.0-1.5 个对数级的 MS2 噬菌体减少量，而铁的投加量相对较高（约 13 毫克/升作为 Fe）。相比之下，在类似的铁投加量下，对于不含 NOM 的合成水，测量到的减少量要大得多（pH6.4 时为 6.5 个对数级，pH7.5 时为 4 个对数级）。与具有 2 个电子转移的法拉第定律和与邻菲啰啉的形态分析定量一致，证明了电化学生成可溶性二价铁。在合成水中形成的絮体通过溶解而对病毒进行近乎定量的提取，为其通过吸附和网捕到氢氧化铁絮体上而被去除提供了直接证据。相比之下，在天然水中形成的絮体中只有大约 1%的病毒与之相关，这与所测量到的去除效果不佳一致。在用于合成水（不含 NOM）的电化学池中也观察到 1-2 个对数级的病毒灭活，但在地表水（4.5 毫克/升 DOC）中没有观察到。由于 ζ 电位甚至在达到 6 个对数级的病毒减少量时都未达到零，因此扫掠絮凝是主要的失稳机制。由于 ζ 电位随铁电凝聚剂剂量的增加而趋于零，因此电荷中和仅起次要作用。重要的是，当添加苏万尼河腐殖酸时，从合成水中去除病毒的效果降低。因此，天然水中存在的 NOM 似乎通过与二价铁离子络合来降低铁电凝聚预处理对微滤的病毒控制效果。这抑制了 (i) Fe(2+) 的氧化、沉淀和病毒失稳，以及 (ii) 通过活性氧中间体或与 Fe(2+) 离子的直接相互作用进行病毒失活。
