蚯蚓-稻壳炭联合堆肥对工业污泥中重金属的影响研究

蚯蚓堆肥相关研究多集中在生活污泥方面,对工业污泥的探索较少。该研究以马鞍山某钢铁污水处理站污泥为例,添加不同比例稻壳炭(2%、4%、8%),设置污泥单独堆肥、稻壳炭与污泥堆肥以及蚯蚓-稻壳炭联合污泥堆肥试验,探索蚯蚓与稻壳炭联合堆肥对工业污泥中重金属形态和生物有效性的影响。研究表明,(1)相比污泥单独堆肥,稻壳炭联合污泥堆肥能增加污泥pH、EC、TP和降低TOC、TN,而蚯蚓联合稻壳炭堆肥污泥可增加TN,并进一步增加污泥EC、TP,显著降低污泥的pH、TOC。(2)稻壳炭堆肥中重金属Zn、Cu、Pb、Cd含量因浓缩效应而上升;而蚯蚓联合稻壳炭堆肥,重金属含量显著下降,添加4%稻壳炭时,重金属Zn、Cu、Pb、Cd质量分数达到最小值,分别为856.64、137.10、158.92、15.48mg·kg-1。(3)重金属形态分析表明,随着稻壳炭比例增加,稻壳炭堆肥中重金属Zn、Cu、Pb、Cd的交换态和碳酸盐结合态转化为残渣态及铁锰氧化态的比例增大,添加8%稻壳炭时DTPA提取的有效态重金属质量分数最低,分别为705.72、47.95、50.43、4.47 mg·kg-1;蚯蚓-稻壳炭联合堆肥会使得污泥中重金属交换态、碳酸盐结合态、铁锰结合态和有机结合态均向残渣态转化,添加4%稻壳炭与蚯蚓的协同转化能力最大,Zn、Cu、Pb、Cd有效态重金属质量分数分别为629.84、38.63、36.76、1.63mg·kg-1,说明稻壳炭添加入蚯蚓堆肥可进一步降低工业污泥中重金属有效性,使重金属钝化。本研究可为稻壳炭联合蚯蚓堆肥处理工业污泥提供参考和科学依据。

Effects of Earthworm and Rice Husk Charcoal Composting on Heavy Metals in Industrial Sludge

At present, the study on vermicomposting is mainly from the aspects of domestic sludge, but less from the exploration of industrial sludge. In this study, heavy metals fraction and bioavailability in the industry sludge from Maanshan steel sewage treatment plant was investigated to assess the combination of earthworm and rice husk carbon on the sludge during compost. Different proportions of rice husk charcoal(2%, 4%, 8%) were added in industrial sludge during sludge composting, sludge composting with rice husk charcoal and vermicomposting with rice husk charcoal. Results showed that,(1) Compared with sludge composting, adding rice husk charcoal during sludge composting increased pH value, EC and TP as well as decreased TOC and TN;vermicomposting with rice husk charcoal increased TN, EC and TP but significantly decreased pH value and TOC in the sludge.(2) Sludge composting with rice husk charcoal increased the contents of heavy metals in the sludge due to the concentration effect. However, vermicomposting with rice husk charcoal decreased the contents of heavy metals significantly. At the same time, the minimum heavy metals contents appeared under T5 treatment(addition of 4% rice husk charcoal) with values of 856.64, 137.10, 158.92, 15.48 mg·kg-1 for Zn, Cu, Pb and Cd, respectively. And(3) the analysis of heavy metals forms showed that the sludge composting with rice husk charcoal transformed exchangeable and carbonates fraction into residual fraction and Fe-Mn oxide fraction, meanwhile, added 8% rice husk charcoal, the bioavailable heavy metals extracted by DTPA reached the minimum with the values of 705.72, 47.95, 50.43, 4.47 mg·kg-1 for Zn, Cu, Pb and Cd, respectively;In contrast, sludge vermicomposting with rice husk charcoal transformed exchangeable, carbonates, Fe-Mn oxide fraction and organic fraction of heavy metals in the sludge to the residual fraction, and the ability of transformation and synergy effect were largest under treatment T5(addition of 4% rice husk charcoal), the bioavailable heavy metal extracted by DTPA reached the minimum with the values of 629.84, 38.63, 36.76, 1.63 mg·kg-1 for Zn, Cu, Pb and Cd, respectively. This indicated that sludge vermicomposting combined with rice husk was effectively to deal with industrial sludge and decreased bioavailability of heavy metals and stabilized heavy metals further. This study could provide basic data and scientific basis for vermicomposting the industrial sludge.