Collaborative Innovation Center for Water Pollution Control and Water Safety in Karst Area, Guilin University of Technology, Guilin, 541004, China.
Environ Sci Pollut Res Int. 2024 Aug;31(38):50733-50745. doi: 10.1007/s11356-024-34597-9. Epub 2024 Aug 5.
In-situ chemical oxidation with persulfate (PS-ISCO) is a preferred approach for the remediation of fuel-contaminated groundwater. Persulfate (PS) can be activated by various methods to produce stronger sulfate radicals for more efficient ISCO. Despite karst aquifers being widespread, there are few reports on PS-ISCO combined with Fe-activated PS. To better understand the effects of Fe-activated PS for the remediation of gasoline-contaminated aquifers in karst areas, a box-column experiment was conducted under flow conditions, using karst groundwater and limestone particles to simulate an aquifer. Gasoline was used as the source of hydrocarbon contaminants. Dissolved oxygen and nitrate were added to enhance bioremediation (EBR) and ferrous sulfate was used to activate PS. The effect of Fe-activated PS combined with biodegradation was compared during the periods of EBR + ISCO and ISCO alone, using the mass flow method for data analysis. The results showed that the initial dissolution of benzene, toluene, and xylene (BTX) from gasoline injection was rapid and variable, with a decaying trend at an average pseudo-first-order degradation rate constant of 0.032 d. Enhanced aerobic biodegradation and denitrification played a significant role in limestone-filled environments, with dissolved oxygen and nitrate utilization ratios of 59 ~ 72% and 12-70%, respectively. The efficiency of EBR + ISCO was the best method for BTX removal, compared with EBR or ISCO alone. The pseudo-first-order degradation rate constants of BTX reached 0.022-0.039, 0.034-0.070, and 0.027-0.036 d, during the periods of EBR alone, EBR + ISCO, and ISCO alone, respectively. The EBR + ISCO had a higher BTX removal ratio range of 71.0 ~ 84.3% than the ISCO alone with 30.1 ~ 45.1%. The presence of Fe-activated PS could increase the degradation rate of BTX with a range of 0.060 ~ 0.070 d, otherwise, with a range of 0.034-0.052 d. However, Fe-activated PS also consumed about 3 times the mass of PS, caused a further decrease in pH with a range of 6.8-7.6, increased 3-4 times the Ca and 1.6-1.8 times the HCO levels, and decreased the BTX removal ratio of ISCO + EBR, compared to the case without Fe activation. In addition, the accumulation of ferric hydroxides within a short distance indicated that the range of PS activated by Fe may be limited. Based on this study, it is suggested that the effect of Fe-activated PS should be evaluated in the remediation of non-carbonate rock aquifers.
原位化学氧化结合过硫酸盐（PS-ISCO）是修复受污染地下水的首选方法。过硫酸盐（PS）可以通过各种方法激活以产生更强的硫酸根自由基，从而实现更有效的 ISCO。尽管岩溶含水层分布广泛，但关于 PS-ISCO 与 Fe 激活过硫酸盐结合的报道很少。为了更好地了解 Fe 激活过硫酸盐对岩溶地区汽油污染含水层修复的影响，进行了一项在流动条件下进行的箱柱实验，使用岩溶地下水和石灰岩颗粒模拟含水层。以汽油为碳氢化合物污染物的来源。添加溶解氧和硝酸盐以增强生物修复（EBR），并使用硫酸亚铁激活过硫酸盐。在 EBR+ISCO 和单独的 ISCO 期间，使用质量流量法进行数据分析，比较了 Fe 激活过硫酸盐与生物降解结合的效果。结果表明，从汽油注入初始时，苯、甲苯和二甲苯（BTX）的快速溶解和变化趋势，平均伪一级降解速率常数为 0.032 d。在充满石灰岩的环境中，好氧生物降解和反硝化作用发挥了重要作用，溶解氧和硝酸盐利用率分别为 5972%和 1270%。与单独的 EBR 或 ISCO 相比，EBR+ISCO 是去除 BTX 的最佳方法。单独的 EBR、EBR+ISCO 和单独的 ISCO 期间，BTX 的伪一级降解速率常数分别达到 0.022-0.039、0.034-0.070 和 0.027-0.036 d。EBR+ISCO 具有比单独的 ISCO 更高的 BTX 去除率范围，为 71.0%84.3%，而单独的 ISCO 为 30.1%45.1%。Fe 激活过硫酸盐的存在可以提高 BTX 的降解速率，范围为 0.060~0.070 d，否则，范围为 0.034-0.052 d。然而，Fe 激活过硫酸盐还消耗了约 3 倍质量的过硫酸盐，导致 pH 值进一步下降，范围为 6.8-7.6，Ca 增加 3-4 倍，HCO 增加 1.6-1.8 倍，降低了 ISCO+EBR 的 BTX 去除率，与不进行 Fe 激活的情况相比。此外，在短距离内积累的三价铁氢氧化物表明，Fe 激活的 PS 范围可能有限。基于这项研究，建议在非碳酸盐岩含水层修复中评估 Fe 激活过硫酸盐的效果。
