Eawag, Swiss Federal Institute of Aquatic Science and Technology, Überlandstrasse 133, 8600 Dübendorf, Switzerland.
Water Res. 2013 Sep 15;47(14):5381-91. doi: 10.1016/j.watres.2013.06.019. Epub 2013 Jun 20.
Dissolved organic nitrogen (DON) can act as a precursor of nitrogenous disinfection byproducts during oxidative water treatment. Quantification and characterization of DON are still challenging for waters with high concentrations of dissolved inorganic nitrogen (DIN, including ammonia, nitrate and nitrite) relative to total dissolved nitrogen (TDN) due to the cumulative analytical errors of independently measured nitrogen species (i.e., DON = TDN - NO2(-) - NO3(-) - NH4(+)/NH3) and interference of DIN species to TDN quantification. In this study, a novel electrodialysis (ED)-based treatment for selective DIN removal was developed and optimized with respect to type of ion-exchange membrane, sample pH, and ED duration. The optimized ED method was then coupled with size-exclusion chromatography with organic carbon, UV, and nitrogen detection (SEC-OCD-ND) for advanced DON analysis in wastewater effluents. Among the tested ion-exchange membranes, the PC-AR anion- and CMT cation-exchange membranes showed the lowest DOC loss (1-7%) during ED treatment of a wastewater effluent at ambient pH (8.0). A good correlation was found between the decrease of the DIN/TDN ratio and conductivity. Therefore, conductivity has been adopted as a convenient way to determine the optimal duration of the ED treatment. In the pH range of 7.0-8.3, ED treatment of various wastewater effluents with the PC-AR/CMT membranes showed that the relative residual conductivity could be reduced to less than 0.50 (DIN removal >90%; DIN/TDN ratio ≤ 0.60) with lower DOC losses (6%) than the previous dialysis and nanofiltration methods (DOC loss >10%). In addition, the ED method is shorter (0.5 h) than the previous methods (>1-24 h). The relative residual conductivity was further reduced to ≈ 0.20 (DIN removal >95%; DIN/TDN ratio ≤ 0.35) by increasing the ED duration to 0.7 h (DOC loss = 8%) for analysis by SEC-OCD-ND, which provided new information on distribution and ratio of organic carbon and nitrogen in different molecular weight fractions of effluent organic matter.
溶解有机氮 (DON) 在氧化水处理过程中可以作为含氮消毒副产物的前体。由于独立测量的氮物种（即 DON=TDN-NO2(-)-NO3(-)-NH4(+)/NH3）的累积分析误差以及 DIN 物种对 TDN 定量的干扰，对于高浓度溶解无机氮 (DIN，包括氨、硝酸盐和亚硝酸盐）相对于总溶解氮 (TDN) 的水样，DON 的定量和表征仍然具有挑战性。在这项研究中，开发了一种新型电渗析 (ED) 处理方法，用于选择性去除 DIN，并针对离子交换膜的类型、样品 pH 和 ED 持续时间进行了优化。然后，将优化后的 ED 方法与尺寸排阻色谱法与有机碳、紫外线和氮检测 (SEC-OCD-ND) 相结合，用于废水处理厂中高级 DON 分析。在测试的离子交换膜中，在环境 pH（8.0）下，PC-AR 阴离子和 CMT 阳离子交换膜在 ED 处理废水时表现出最低的 DOC 损失（1-7%）。在 DIN/TDN 比值与电导率之间发现了很好的相关性。因此，电导率已被用作确定 ED 处理最佳持续时间的便捷方法。在 pH 值为 7.0-8.3 的范围内，使用 PC-AR/CMT 膜对各种废水处理厂进行 ED 处理表明，相对残留电导率可降低至 0.50 以下（DIN 去除率>90%；DIN/TDN 比值≤0.60），与以前的透析和纳滤方法相比，DOC 损失（6%）较低（DOC 损失>10%）。此外，ED 方法的时间更短（0.5 小时），而以前的方法（>1-24 小时）。通过将 ED 持续时间延长至 0.7 小时（DOC 损失=8%），相对残留电导率进一步降低至≈0.20（DIN 去除率>95%；DIN/TDN 比值≤0.35），用于 SEC-OCD-ND 分析，这为废水中有机碳和氮在不同分子量分数中的分布和比例提供了新的信息。
