• 关键词：超临界水气化  污泥性质  固相残渣  重金属  生态风险

• 基金项目：江苏省自然科学基金重点专项(No.BK2011025);国家自然科学基金(No.51278165);国家重点基础研究发展计划(973)项目(No.2012CB719804); 江苏省研究生培养创新工程项目(No. KYLX_0506); 中央高校基本科研业务费专项资金资助项目(No.2014B39414)

• 马倩
• 河海大学环境学院, 南京 210098

• 朱伟
• 1. 河海大学环境学院, 南京 210098;2. 水资源高效利用与工程安全国家工程研究中心, 南京 210098

• 龚淼
• 河海大学环境学院, 南京 210098

• 张会文
• 1. 河海大学环境学院, 南京 210098;2. 水资源高效利用与工程安全国家工程研究中心, 南京 210098

• 徐骏
• 河海大学环境学院, 南京 210098

• 摘要：为探究超临界水气化前后脱水污泥中重金属的变化及生态风险,从重金属(Ni、Cu、Zn、Pb、Cr)的含量、化学形态分布及浸出毒性等多方面出发,利用地层累积指数(I_geo)、潜在生态风险指数(RI)和风险评估指数法(RAC)对江苏地区10种不同种脱水污泥超临界水气化前后重金属的环境生态风险进行综合评价.结果表明:不同污水厂脱水污泥经超临界水气化处理后,绝大部分污泥中重金属浸出毒性和生物可利用组分重金属含量明显降低,即处理后重金属的直接环境风险大大降低.不同重金属含量的脱水污泥经超临界水气化处理后,重金属环境污染程度及潜在生态风险程度显著降低,环境风险值被降至相对安全水平,对环境表现出低风险或无风险.pH值在一定程度上影响处理后污泥中重金属的环境风险.超临界处理时,污泥的pH呈现酸性时会引起反应釜腐蚀,从而导致固相残渣中Ni、Cr的生物可利用组分含量增加,当pH呈现碱性时则更利于重金属以稳定形态富集到固相产物中.

• Abstract：In this study, ten different types of dewatered sewage sludge (DSS) were treated in supercritical water (SCW) in a high-pressure autoclave at 400 ℃, 60 min and 23 MPa. The content, chemical speciation and toxicity leaching of heavy metals (HMs, Ni, Cu, Zn, Pb and Cr) were measured. The index of geo-accumulation (I_geo), potential ecological risk (RI) and risk assessment code (RAC) was applied to investigate the changes and ecological risk of HMs during the gasification of DSS in SCW. The results showed that the toxicity leaching and bioavailable fractions of HMs significantly decreased in most cases, which revealed that direct environmental risk of HMs was markedly reduced after the treatment. The potential ecological risk and environmental pollution index of HMs decreased considerably. The environmental risk values of HMs were low enough to be considered at a relatively safe level, indicating that HMs had no or low risk to the environment after treatment. The pH value of DSS also affected the environmental risk of HMs during the supercritical water gasification (SCWG) process. Acidic sludge causes reactor corrosion and contribute to increasing bioavailable fractions of Ni and Cr in solid residues(SR), while alkaline sludge is favorable for the enrichment of HMs in SR.

• Key words：supercritical water gasification  sludge property  solid residues  heavy metals  ecological risk

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