生活垃圾腐殖土物化性质及资源化利用途径——以浙江省某高龄期填埋场为例

以填埋龄期23~37a、粒径<15mm腐殖土为对象,测试分析了其物质组成、理化性质和浸出液性质.测试与分析结果表明:腐殖土中粒径范围2~15mm、0.075~2mm和<0.075mm的组分分别占比42.9%~53.9%、40.9%~44.1%和5.1%~13.0%,属于细粒砂土;随着填埋龄期增加,腐殖土特征粒径d₅₀和d₁₀呈现减小趋势,比重明显增大,并在30a后趋于稳定.腐殖土中有机质含量(18.1%~19.1%,)、氮磷钾含量、浸出液pH值(7.26~8.30)及电导率(1.08~2.51mS/cm)等指标均满足国家现行《绿化用有机基质》要求.腐殖土中重金属Cu、Zn、Cd、Cr含量均超出国家现行《土壤环境质量农用地土壤污染风险管控标准(试行)》、《绿化种植土壤》和《绿化用有机基质》的标准要求,内梅罗综合污染指数高达15.48~17.95,属于重度污染类型,且重金属主要富集在粒径<2mm的细颗粒.建议将腐殖土进一步精细化筛分为粒径2~15mm与粒径<2mm两部分,针对粒径<2mm部分采用微生物诱导碳酸盐沉淀等技术,降低重金属浸出浓度.处理后的腐殖土可作为园林绿化、填埋场覆盖以及废弃矿山修复的绿化土层.

Physicochemical properties and reuse of municipal solid waste fine fraction: Case of an aged landfill site in Zhejiang Province

This study is to investigate the physicochemical properties for the fine fraction (particle size <15mm) of the excavated municipal solid wastes (MSWs) with fill ages ranging from 23 to 37a. The composition, physicochemical properties and leaching solution properties of the materials were measured and analyzed. The experimental results showed that the particle size ranges (2~15mm, 0.075~2mm and <0.075mm) for the materials account for 42.9%~53.9%, 40.9%~44.1% and 5.1%~13.0%, respectively. The materials can be classified as a fine-grained sand. With a increase of fill age, the characteristic particle size d₅₀ and d₁₀ decreased, the specific gravity increased greatly, and tended to be stable after 30 years. The organic matter content (18.1%~19.1%), the content of nitrogen, phosphorus and potassium, the pH of the leaching solution (7.26~8.30), and the electrical conductivity (1.08~2.51mS/cm) all met the standard of Organic media for greening. The contents of Cu, Zn, Cd, Cr and Ni in the materials exceeded the standards of Soil environmental quality Risk control standard for soil contamination of agricultural land, Planting soil for greening and Organic media for greening. The calculated value of Nemerow comprehensive pollution index was as high as 15.48~17.95, indicating the materials were heavily contaminated. It was found that the heavy metals concentrated in the fine-grained fraction with particle sizes less than 2mm. It was suggested that the fine fraction should be further screened into two parts with a particle size of 2~15mm and less than 2mm. For the part with particle size less than 2mm, the technology of microbial induced carbonate precipitation could be used to stabilize the contained heavy metals. The treated materials can be reused as a planting soil layer for landscaping, landfill closure and abandoned mine site reclamation.