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Decreasing waste brine volume from anion exchange with nanofiltration: implications for multiple treatment cycles
Environmental Science: Water Research & Technology ( IF 5 ) Pub Date : 2021-3-12 , DOI: 10.1039/d1ew00001b
Julie A. Korak 1 , Leah C. Flint 1, 2 , Miguel Arias-Paić 2
Affiliation  

Ion exchange (IX) is a technology for removing hexavalent chromium from water, but waste brine disposal makes implementation cost prohibitive in many communities. Nanofiltration (NF) can be integrated to decrease the waste brine volume by 70% and reuse the permeate (NF-reuse) as brine in the next IX regeneration. However, the accumulation of impurities and resulting impact on IX regeneration and loading efficiency have not been evaluated through comparative mass balances or post-regeneration batch tests. Combining pilot-scale experiments with response surface modeling, impurities in waste brine are predicted to reach a pseudo steady state over 10 loading–regeneration–NF-reuse cycles, simulating long-term operation at full-scale facilities. Side-by-side regenerations show that NF-reuse brine does not impact the IX regeneration efficiency of chromium, sulfate or inorganic carbon. Regeneration efficiency increases for vanadium and uranium by 30–60% using the NF-reuse brine, which may decrease long-term fouling and reduce the frequency for strong acid regenerations. With NF-reuse, additional nitrate loads onto the IX resin during regeneration, which may impact the timing and magnitude of chromatographic peaking. During loading, arsenic exhibited chromatographic peaking at concentrations 220% higher than the influent concentration, exceeding regulatory thresholds under all regeneration scenarios. Arsenic leakage also occurred during the first 500 bed volumes with NF-reuse. Vanadium and chromium both exhibited faster breakthrough in the second loading cycle, demonstrating the importance of evaluating pilot-scale processes over multiple loading and regeneration cycles. Bench-scale studies need to be guided by full-scale IX operating constraints and evaluate factors beyond the contaminant of concern to fully identify potential impacts of implementing NF brine management. A supplemental spreadsheet is included for utilities to screen NF for system-specific testing.

中文翻译:

通过纳滤进行阴离子交换可减少废盐水的体积:对多个处理周期的影响

离子交换(IX)是一种从水中去除六价铬的技术,但是废盐水的处理使许多社区的实施成本高昂。可以集成纳滤(NF),以将废盐水的体积减少70%,并在下一次IX再生中将渗透物(NF-reuse)用作盐水。但是,尚未通过比较质量平衡或再生后批量测试评估杂质的积累以及对IX再生和负载效率的影响。将中试规模的实验与响应面建模相结合,预计废盐水中的杂质会在10个加载-再生-NF再利用循环中达到伪稳态,从而模拟了大规模设备的长期运行。并排再生显示,NF再利用盐水不会影响铬,硫酸盐或无机碳的IX再生效率。使用NF再利用盐水,钒和铀的再生效率提高30-60%,这可以减少长期结垢并降低强酸再生的频率。随着NF的重复使用,再生过程中额外的硝酸盐会加到IX树脂上,这可能会影响色谱峰化的时间和幅度。在加载过程中,砷的色谱峰浓度比进水浓度高220%,在所有再生情况下均超过监管阈值。重复使用NF的前500个床体积也发生了砷泄漏。钒和铬在第二次加载循环中均表现出更快的突破,证明了评估多个加载和再生周期中的中试规模过程的重要性。基准规模研究需要以完整的IX操作限制为指导,并评估超出所关注污染物的因素,以充分识别实施NF盐水管理的潜在影响。包含一个补充电子表格,用于实用程序筛选NF以进行系统特定的测试。
更新日期:2021-04-20
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