Corona Environmental Consulting, Newark, CA, USA.
Corona Environmental Consulting, Louisville, CO, USA.
Water Res. 2018 Aug 1;139:420-433. doi: 10.1016/j.watres.2018.04.011. Epub 2018 Apr 10.
Hexavalent chromium [Cr(VI)] in drinking water is pending regulation in California and is being considered for regulation in other locations. While strong-base anion exchange (SBA-IX) can efficiently remove Cr(VI) to low-levels that may be required to comply with future MCLs, operational and maintenance (O&M) costs can be considerable if the spent brine is disposed of as hazardous waste. Through bench- and pilot-scale experiments and full-scale demonstrations, this study examined the ability of emerging and established brine treatment and reuse techniques as well as recently developed resins to decrease O&M costs. When profiling anion elution during regeneration with nanofiltration treated and untreated spent brine, it appeared that at least 1 and 3 reuse cycles were feasible, respectively. Stannous- and ferrous-based reductants were more efficient than sulfur-based reductants when treating spent brine. Bed volumes to 8 μg/L chromium breakthrough with 7 resins varied by as much as a factor of 2 and correlated (R = 0.84) with resin total exchange capacities. Spent brine reuse, segmented regeneration (an optimized brine reuse method), ferrous reduction, and nanofiltration of spent brine were estimated to decrease O&M costs by 30, 70, 63, and 61%, respectively. Selection of high performing resins was the most simple way to decrease O&M costs (up to 70% savings). The sum of nitrate and sulfate raw water equivalent concentrations was found to be the principal water quality parameter that influenced the performance of 4 resins in 7 different groundwaters because nitrate and sulfate concentrations were orders of magnitude greater than chromium concentrations. Resins with higher chromium capacities eluted more co-contaminants including arsenic, selenium, uranium, and vanadium because they likely had higher co-contaminant capacities. Co-contaminant elution was found to be complex because associations can form between regenerant and co-eluting anions. Sodium chloride was the most efficient regenerant, though other regenerants provided benefits such as enhanced uranium elution most likely by complexing with uranium to inhibit its precipitation. Nitrate peaking was found to be limited even when reusing untreated and nanofiltration treated spent brine.
饮用水中的六价铬[Cr(VI)]在加利福尼亚州仍在等待监管，并正在考虑在其他地方进行监管。虽然强碱阴离子交换（SBA-IX）可以有效地将 Cr(VI)去除到可能需要遵守未来 MCL 的低水平，但如果用过的盐水被作为危险废物处置，则运营和维护（O&M）成本可能相当高。通过中试和示范试验以及全规模示范，本研究考察了新兴和成熟的盐水处理和再利用技术以及最近开发的树脂降低 O&M 成本的能力。在对纳滤处理和未处理的用过的盐水进行再生时分析阴离子洗脱情况时，似乎分别可以进行至少 1 和 3 次再利用循环。与基于硫的还原剂相比，基于亚锡和亚铁的还原剂在处理用过的盐水时更有效。在 7 种树脂中，床体积达到 8μg/L 铬穿透时，差异高达 2 倍，并且与树脂总交换容量相关（R=0.84）。用过的盐水再利用、分段再生（一种优化的盐水再利用方法）、亚铁还原和用过的盐水纳滤估计可分别降低 O&M 成本 30%、70%、63%和 61%。选择高性能树脂是降低 O&M 成本的最简单方法（最多可节省 70%）。发现硝酸盐和硫酸盐的原水当量浓度之和是影响 4 种树脂在 7 种不同地下水中性能的主要水质参数，因为硝酸盐和硫酸盐浓度比铬浓度大几个数量级。具有较高铬容量的树脂洗脱了更多的共污染物，包括砷、硒、铀和钒，因为它们可能具有更高的共污染物容量。共污染物洗脱很复杂，因为再生剂和共洗脱阴离子之间可能形成缔合。氯化钠是最有效的再生剂，尽管其他再生剂也提供了一些好处，例如增强铀的洗脱，这很可能是通过与铀络合来抑制其沉淀。即使在再利用未处理和纳滤处理过的盐水时，硝酸盐峰值也受到限制。
