张家口市某机械厂原址电镀污染场地土壤修复工程实践

机械厂电镀加工过程中产生的电镀废水,会造成土壤六价铬和氰化物污染。以长期利用电镀工艺的污染场地修复项目为依托,通过前期场地环境调查和风险评估结果,分析场地土壤污染程度和污染范围,确定修复目标和工程量;综合场地特性和污染特征,进行修复技术筛选,确定以"化学氧化+化学还原-固化/稳定化"为核心的污染土壤修复技术工艺;通过小试和中试,获得最佳修复药剂组成和添加比例,并进行工程实施。结果表明:Cr(Ⅵ)和氰化物复合污染土壤经化学氧化+化学还原-固化/稳定化工艺处理后,最大超标浓度由原来的37.3,186.0 mg/kg,分别降低至对应的标准限值3.0,22 mg/kg以下,Cr(Ⅵ)浸出浓度<0.5 mg/L,满足修复要求。该修复工程的成功实践,可以为其他复合污染场地修复工程的设计与实施提供参考。

REMEDIATION PRACTICE OF HEXAVALENT CHROMIUM AND CYANIDE CONTAMINATED SOIL AT THE ORIGINAL SITE OF A MACHINERY PLANT IN ZHANGJIAKOU,CHINA

The electroplating wastewater generated during the electroplating process of the machinery factory will cause soil hexavalent chromium and cyanide pollution. Relying on the long-term use of the electroplating process of contaminated site remediation projects, the remediation target and the amount of work were determined through the preliminary site environmental investigation and risk assessment results, and the site soil pollution degree and pollution scope analysis; synthesis of site features and pollution characteristics, conduction of remediation technology screening determined that chemical oxidation, chemical reduction and solidification or stabilization was the core remediation technology for the project. The optimal composition and appending proportion of repairing agents were obtained by conducting small-scale and pilot-scale experiments, and used to implement the project. The results showed that after the chemical oxidation, chemical reduction and solidification or stabilization processing procedure of the hexavalent chromium and cyanide compound contaminated soil, the maximum exceeded concentration was reduced from the original 37.3, 186.0 mg/kg to below the corresponding standard limits of 3.0, 22 mg/kg, respectively; the leaching concentration of hexavalent chromium was lower than 0.5 mg/L, meeting the remediation requirements. The successful practice of the remediation project could provide reference for the design and implementation of remediation projects of other compound contaminated sites.