Environmental footprint analysis of remediation of contaminated soil based on chemical oxidation and ex-situ thermal pile desorption technology
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摘要:
在“双碳”背景下,我国土壤修复工程使用技术类型不断向低碳、低能耗和绿色可持续修复技术转变,修复活动本身所产生的环境足迹受到了广泛关注和重视。采用环境足迹评估工具SiteWiseTM对重庆市某钢铁厂汞和多环芳烃污染场地化学氧化和堆式热脱附修复全过程的环境足迹进行了定量评价。结果表明:修复3 483 m3污染土壤,共排放温室气体(GHG)990.52 t,消耗能源1.57×107 MJ,排放空气污染物4.94×103 kg;GHG排放量、能源消耗量、空气污染物排放量占整个工程的比例在施工准备阶段为6.0%~9.1%,化学氧化阶段为43.6%~48.1%,化学氧化+堆式热脱附阶段为45.9%~47.5%;化学氧化+堆式热脱附技术相比化学氧化技术的环境影响更大,修复单方量污染土壤的GHG排放量、能源消耗量、空气污染物排放量为化学氧化技术的5.28~5.97倍。案例研究结果显示,材料消耗是对环境足迹贡献度最高的环节,其次为设备使用、运输、废物处理。
Abstract:Under the background of "Peak Carbon Dioxide Emissions" and "Carbon Neutrality", the technology type of China's soil remediation projects is continuously shifting towards low-carbon, low-energy, green and sustainable remediation technologies. The environmental footprint of remediation activities has been widely noticed and evaluated. SiteWiseTM, an environmental footprint assessment tool, was used to quantitatively assess the environmental footprint of the whole remediation process of a mercury and PAHs contaminated site in a steel plant in Chongqing. The results showed that the remediation of
3483 m3 of contaminated soil emitted a total of 990.52 t of greenhouse gases (GHGs), consumed 1.57×107 MJ of energy and emitted 4.94×103 kg of air pollutants. GHG emissions, energy consumption and air pollutant emissions at the construction preparation stage accounted for 6.0%-9.1% of the project, while those at the chemical oxidation stage accounted for 43.6%-48.1%. The GHG emissions, energy consumption and air pollutant emissions at the chemical oxidation + ex-situ thermal pile desorption stage accounted for 45.9%-47.5%. The chemical oxidation + ex-situ thermal pile desorption technology had a greater environmental impact compared to the chemical oxidation technology, and the environmental footprint for remediation of a single cubic volume of contaminated soil was about 5.28-5.97 times that of the chemical oxidation technology. The case study results showed that material consumption was the largest contributor to the environmental footprint, followed by equipment use, transport and residual handling. -
表 1 目标污染物浓度及修复目标值
Table 1. Concentrations of target pollutants and remediation target values
mg/kg 污染物类别 污染物浓度 场地修复目标值 汞 ND~8.74 8 萘 ND~237 25 苯并[a]蒽 ND~93.7 5.5 苯并[b]荧蒽 ND~88.2 5.5 苯并[a]芘 0.57~72.7 0.55 茚并[1,2,3-c,d]芘 ND~45.5 5.5 二苯并[a,h]蒽 ND~0.91 0.55 注:ND表示未检出。 表 2 案例钢铁厂修复工程数据清单
Table 2. Data list of the case steel plant remediation project
类别 Stage Ⅰ Stage Ⅱ Stage Ⅲ 化学氧化+堆式热脱附 废水废气处理 材料消耗 钢铁/kg 1 600 0 14 062 0 PVC/kg 840 0 0 0 HDPE/kg 3 780 0 801 71 混凝土/t 160 0 400 60 药剂使用 过硫酸钠/t 0 104.5 15 0 氢氧化钠/t 0 209 29 0 氧化钙/t 0 51.5 9.5 0 活性炭/kg 0 0 0 1 000 能源消耗 天然气/kg 0 0 15 042 0 电/(kW·h) 0 0 149 760 193 440 柴油/L 24 000 4 230 846 0 运输 人员运输/(人/km) 10/300 0 0 0 货物运输/(t·km) 132 000 1 239 130.4 195 人员工作时间/h 施工人员 240 0 30 25 工程师 0 250 180 50 检测人员 0 8 5 5 表 3 案例工程修复后目标污染物浓度
Table 3. Concentrations of target pollutants after the case project remediation
mg/kg 污染物类别 修复后污染物浓度 修复后二次影响区污染物浓度 汞 0.043~0.05 0.003~0.091 萘 ND ND 苯并[a]蒽 ND 0.1~0.7 苯并[b]荧蒽 ND 0.4~0.8 苯并[a]芘 ND 0.1~0.5 茚并[1,2,3-c,d]芘 ND 0.3~0.5 二苯并[a,h]蒽 ND ND 注:ND表示未检出。 -
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