Department of Civil Engineering and Architecture, University of Catania, Viale A. Doria 6, 95125 Catania, Italy; Department of Chemical & Environmental Engineering, University of Arizona, 1133 E. James E. Rogers Way, Tucson, AZ 85721, USA.
United Water, Edward C. Little Water Reclamation Facility, 1935 South Hughes Way, El Segundo, CA 90245, USA.
Water Res. 2015 Mar 1;70:174-83. doi: 10.1016/j.watres.2014.11.051. Epub 2014 Dec 6.
Full-scale experiments to evaluate N-nitrosodimethylamine (NDMA) formation and attenuation were performed within an advanced indirect potable reuse (IPR) treatment system, which includes, sequentially: chloramination for membrane fouling control, microfiltration (MF), reverse osmosis (RO), ultraviolet irradiation with hydrogen peroxide (UV/H₂O₂), final chloramination, and pH stabilization. Results of the study demonstrate that while RO does effectively remove the vast majority of NDMA precursors, RO permeate can still contain significant concentrations of NDMA precursors resulting in additional NDMA formation during chloramination. Thus, it is possible for this advanced treatment system to produce water with NDMA levels higher than regional requirements for potable applications (10 ng/L). The presence of H2O2 during UV oxidation reduced NDMA photolysis efficiency and increased NDMA formation (∼22 ng/L) during the secondary chloramination and lime stabilization. This is likely due to formation of UV/H₂O₂ degradation by-products with higher NDMA formation rate than the parent compounds. However, this effect was diminished with higher UV doses. Bench-scale experiments confirmed an enhanced NDMA formation during chloramination after UV/H2O2 treatment of dimethylformamide, a compound detected in RO permeate and used as model precursor in this study. The effect of pre-ozonation for membrane fouling control on NDMA formation was also evaluated at pilot- (ozone-MF-RO) and bench-scale. Relatively large NDMA formation (117-227 ng/L) occurred through ozone application that was dose dependent, whereas chloramination under typical dosages and contact times of IPR systems resulted in only a relatively small increase of NDMA (∼20 ng/L). Thus, this research shows that NDMA formation within a potable water reuse facility can be challenging and must be carefully evaluated and controlled.
开展了全规模实验，以评估 N-亚硝基二甲胺（NDMA）的形成和衰减，该实验在先进的间接饮用水再利用（IPR）处理系统内进行，该系统依次包括：膜污染控制的氯胺化、微滤（MF）、反渗透（RO）、过氧化氢紫外照射（UV/H₂O₂）、最终氯胺化和 pH 稳定。研究结果表明，虽然 RO 有效地去除了绝大多数 NDMA 前体，但 RO 渗透物仍可能含有大量的 NDMA 前体，从而导致在氯胺化过程中形成额外的 NDMA。因此，这种先进的处理系统有可能产生 NDMA 水平高于饮用水应用区域要求（10ng/L）的水。在 UV 氧化过程中存在 H2O2 会降低 NDMA 光解效率并增加二次氯胺化和石灰稳定过程中的 NDMA 形成（约 22ng/L）。这可能是由于形成了具有比母体化合物更高 NDMA 形成速率的 UV/H₂O₂ 降解副产物。然而，随着 UV 剂量的增加，这种影响会减弱。中试规模实验证实，在 RO 渗透物中检测到的二甲基甲酰胺经 UV/H₂O₂ 处理后，在氯胺化过程中会增强 NDMA 的形成，该化合物在本研究中用作模型前体。还评估了预臭氧化用于膜污染控制对 NDMA 形成的影响，在中试（臭氧-MF-RO）和实验室规模进行了评估。臭氧的应用会导致相对较大的 NDMA 形成（117-227ng/L），这与剂量有关，而在 IPR 系统的典型剂量和接触时间下进行氯胺化只会导致 NDMA 相对较小的增加（约 20ng/L）。因此，这项研究表明，饮用水再利用设施内的 NDMA 形成具有挑战性，必须仔细评估和控制。
