Evaluation of in situ application of sodium persulfate sustained release rod for treating trichloroethylene contamination

• Main Authors: Su-Lian Jiang, 江素蓮
• Other Authors: 梁振儒
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/cgi-bin/gs32/gsweb.cgi/login?o=dnclcdr&s=id=%22107NCHU5087026%22.&searchmode=basic

碩士 === 國立中興大學 === 環境工程學系所 === 107 === Sodium persulfate sustained release rod (SPS SR-rod), which was prepared by a mixture of wax and SPS, can be adopted as a semi-passive groundwater remediation material for supplying SPS oxidant. In this study, the application of SPS SR-rod was evaluated in one-dimensional column (silica sand and sandy soil) for determining SPS release rate (rSPS) and feasibility of oxidizing trichloroethylene (TCE) dense non-aqueous phases liquid (DNAPL) and residual phase at different water flushing velocities. Additionally, a field pilot test was conducted to investigate the applicability of SPS SR-rod at a TCE contaminated site. The water parameters monitored included pH, ORP, concentrations of TCE, SPS, sulfate and chloride. In TCE DNAPL flushing (10 mL TCE, ~14.6 g TCE), it was seen that SPS SR-rod could maintain a stable SPS concentration effluent (rSPS = 0.021~0.016 g/h) and chloride liberation upon mineralized TCE was observed at a water flushing velocity of 0.016 cm/min. In treating TCE residual phase (TCE contaminated tablet, containing ~2 g TCE) and water flushing at a velocity of 0.016 cm/min in silica sand and soil porous media, the rSPS was 0.127~172 g/h. Additionally, because of the adsorption and the reaction competition between TCE and natural organic matter (NOM) in soil, lower TCE concentrations released and mineralized from the TCE contaminated tablet test in soil porous media was observed, comparted to those in silica sands (i.e., 92% and 61% TCE released with 82% and 20% TCE mineralized in silica sand and soil media, respectively). In the field pilot test, possibly due to the soil oxidant demand (SOD) depletion, SPS released by SPS SR-rod could not be detected at 1 m away from a SPS SR-rod placed well in the 1st phase test. However, the ORP was observed to rise, showing an oxidative oxidizing condition. The concentration of SPS in the rod placed well was more evenly distributed by enhancing air sparging efficiency using an air diffuser in the 2nd phase test ([SPS] = 0.6~2 mM). Additionally, there were residual SPS concentrations detected (0.01~0.09 mM) at monitor well 1 m away the rod placed well in the 2nd phase test, possibly because the SOD was depleted in the 1st phase test and thereby allowing further SPS distribution. The results of this study showed that SPS SR-rod revealed the ability to oxidize TCE and intercept the transportation of TCE plume.