Study on deep dewatering and heavy metal stabilization of stocked sludge
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摘要:
堆存污泥具有高含水率和潜在重金属污染特征,对堆存填埋场及周边环境可能产生潜在生态风险。以秸秆(SP)、粉煤灰(FA)、磷石膏(PG)3种固体废物材料搭配2种常用脱水剂氧化钙(CaO)、聚合氯化铝(PAC)组成联合调理剂,对堆存污泥进行脱水以及对其中重金属进行稳定化效果研究,并通过电镜-能谱探究加入调理剂后污泥的微观结构及物质构成。结果表明:添加固体废物材料的联合调理剂对污泥脱水及重金属稳定化效果显著,其中添加PG的组合最优。当CaO、PAC、PG添加量(干基比)分别为20%、25%、23%时,毛细吸水时间为42.1 s,泥饼含水率为49.00%;PG中丰富的孔隙结构及磷酸盐物质对重金属有很好的吸附和沉淀作用;微观结构分析显示,经过调理后CaSO4或Al2(SO4)3构建了污泥的骨架结构。
Abstract:The stocked sludge has the characteristics of high moisture content and potential heavy metal pollution, which may pose potential ecological risks to the landfill site and the surrounding environment. Three solid waste materials, straw powder (SP), fly ash (FA) and phosphogypsum (PG), combined with two common dehydrators, quick lime (CaO) and polyaluminium chloride (PAC), were used to dehydrate the stocked sludge and study the stabilization effect of heavy metals. In addition, the microstructure and composition of the dehydrated sludge cake were studied by SEM-EDS. The results showed that the combined conditioner with solid waste materials had significant effects on sludge dewatering and heavy metal stabilization, and the group with PG was the best. When the addition of CaO, PAC and PG (dry basis ratio) were 20%, 25% and 23% respectively, the capillary water absorption time was 42.1 s and the moisture content of mud cake was 49.00%. The rich pore structure and phosphate impurities in PG had good adsorption and precipitation effects on heavy metals. The microstructure analysis showed that CaSO4 or Al2(SO4)3 formed the skeleton structure of treated sludge.
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Key words:
- stocked sludge /
- solid waste materials /
- deep dewatering /
- heavy metals stabilization /
- microstructure
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表 1 堆存污泥中重金属浓度
Table 1. Heavy metal parameters of stocked sludge
mg/kg As Cd Cr Cu Ni Pb Zn 17.6 1.7 119.8 524.3 78.3 62.1 802.9 表 2 3种脱水泥饼浸出液中的重金属浓度
Table 2. Heavy metal content in three kinds of leaching solution of dehydrated sludge cake
mg/kg 重金属 CaO-PAC-SP CaO-PAC-FA CaO-PAC-PG As 2.4 1.2 0.2 Cd 0.3 0.1 0.3 Cr 6.7 0.8 0.3 Cu 13.5 5.1 4.3 Ni 0.9 0.6 0.1 Pb 3.3 0.3 1.2 Zn 18.1 4.5 3.2 -
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