填埋污泥固化改性作回填土工程特性与环境风险

王磊，谭学军，郑晓光

摘要:

上海某城镇污水处理厂自2004年开始填埋脱水污泥,2010年填埋场封场,近期拟征用填埋场土地,需将污泥挖出进行二次处理。本文针对填埋污泥开展固化改性研究,分析改性产物用作回填土的技术可行性和环境风险,得到以下主要结论：填埋污泥7 d无侧限抗压强度仅为0.1 MPa,不满足机械作业要求,且无法压实。掺加5 %固化剂后,污泥强度提高至0.9 MPa,可满足机械作业以及各种不同等级道路路基要求,碾压后较为平整密实。进一步提高固化剂比例至7.5%,强度提高至1.9MPa,碾压后平整度更好。污泥中重金属含量均低于建设用地筛选值以及园林绿化用泥质标准限值,硫酸根离子、碳酸氢根离子、氯离子、镁离子的腐蚀等级均为微,用作回填土的环境风险较小。污泥填埋过程中经过10余年降解,有机物含量从50%~55%降低至32.90%,仍然高于建筑地基垫层材料对有机质的要求,不宜直接用于有压实要求的回填区域。

Abstract:

An urban sewage treatment plant in Shanghai began to bury dehydrated sludge since 2004, and the landfill was covered with film in 2010. In order to expropriate the landfill land, the sludge needs to be dug out and treated again. The study on solidification and modification of sludge from a landfill was carried out, and the technical feasibility and environmental risks of using the modified product as backfill soil were analyzed, and the following conclusions were drawn: The 7 days unconfined compressive strength of landfill sludge is only 0.1MPa, which doesn’t meet the requirements of mechanical operation and can not be compacted. After adding 5% curing agent, the strength of sludge is increased to 0.9 MPa, which can meet the requirements of mechanical operation and roadbed of different grades, and is more smooth and compact after rolling. While the proportion of curing agent is further increased to 7.5%, the strength is increased to 1.9 MPa, and the flatness is better after rolling. The heavy metal content in the sludge is lower than the limit value of construction land and landscaping. The corrosion grade of sulfate ion, bicarbon ion, chloride ion and magnesium ion is small, and the environmental risk of backfill is small. After more than 10 years of degradation in the process of sludge landfill, the content of organic matter decreases from 50%~55% to 32.90%, which is still higher than the requirements of building foundation cushion material for organic matter, so it is not suitable to be directly used in the backfill area with compaction requirements..