Chemical Engineering Department, Faculty of Engineering, Universidad de Concepción, P. O Box 160-C, Concepción, Chile.
Chemical Engineering Department, Faculty of Engineering, Universidad de Concepción, P. O Box 160-C, Concepción, Chile..
Sci Total Environ. 2020 Jun 25;723:137809. doi: 10.1016/j.scitotenv.2020.137809. Epub 2020 Mar 9.
Public concern on the groundwater contamination by nitrate has grown significantly in recent years. The objective of this study was to determine the appropriate treatment to reduce the nitrate content in the presence of other ions from groundwater, for which nanofiltration and ion exchange were evaluated. In nanofiltration, the effects of pressure, feed flow, initial composition, and performance were studied, in ion exchange the flow rate, initial composition, and resin regeneration process. Nanofiltration tests were carried out on four different commercial membranes: NF97, NF99, NF99H, and NF90. Among these, all membranes removed chloride but only NF97 and NF90 were able to remove nitrate in compliance with Chilean drinking water standard, showing rejections of 97% and 87%, respectively, in an optimum pressure range of 12-20 bar in which the NF90 produced 3.5 times more permeated water than NF97. For ion exchange tests, Purolite A520E resin was used, which decreased nitrate content to <1 mg/L. Results leading to the optimal flow within the exchange column indicated that residence time must be at least 2.1 min. The higher nitrate concentration in water did not lead to changes in the maximum resin capacity, 47.1 mg NO3/g resin, but it did decrease the resin breakthrough capacity when initial concentration increased. Optimal regeneration was assigned to a 3% w/V NaCl solution and up-flow mode. Due to the ability to remove both nitrate and chloride, and being able to remove iron if necessary, nanofiltration was chosen as the appropriate treatment.
近年来，公众对地下水硝酸盐污染的关注显著增加。本研究旨在确定适当的处理方法，以降低地下水中其他离子存在时的硝酸盐含量，为此评估了纳滤和离子交换。在纳滤中，研究了压力、进料流量、初始组成和性能的影响，在离子交换中，研究了流速、初始组成和树脂再生过程。在四个不同的商业膜上进行了纳滤测试：NF97、NF99、NF99H 和 NF90。在这些膜中，所有膜都去除了氯离子，但只有 NF97 和 NF90 能够去除硝酸盐，符合智利饮用水标准，在 12-20 巴的最佳压力范围内，分别显示出 97%和 87%的排斥率，其中 NF90 的渗透水量是 NF97 的 3.5 倍。对于离子交换测试，使用了 Purolite A520E 树脂，可将硝酸盐含量降低至 <1 mg/L。在交换柱内达到最佳流量的结果表明，停留时间必须至少为 2.1 分钟。水中较高的硝酸盐浓度不会改变最大树脂容量，即 47.1 mg NO3/g 树脂，但会降低初始浓度增加时的树脂穿透容量。最佳再生分配给 3% w/V 的 NaCl 溶液和上流式。由于能够去除硝酸盐和氯离子，如果需要，还能够去除铁，因此选择纳滤作为适当的处理方法。
