【作者】 明银安；

【导师】 沈蕴芬； 陶涛；

【作者基本信息】 华中科技大学 ， 市政工程， 2009， 博士

【摘要】 随着城市污水处理率的提高，城市污泥的产量也急剧增加。污泥的出路问题在各大城市日益暴露出来，如何安全地处置污水厂产生的大量污泥成为目前最紧迫的任务。土地利用越来越被认为是一种积极、有效、有前途的污泥处置方式。该方法是在避免污泥中有毒有害物质如重金属、有毒有机物等进入食物链危害人类健康的前提条件下，利用污泥中含有的大量营养元素和丰富的有机质改善土壤结构并供给植物养分。该方法既可有效地利用污泥中有用的资源，也可以解决污泥的出路问题。以厦门市为例，对城市污泥用作果树肥料进行研究。厦门市每天产生脱水污泥约260m~3(含水率76％)，污泥主要运至东孚垃圾场进行填埋。因脱水污泥达不到填埋要求，东孚垃圾场开始拒收脱水污泥，因此迫切需求新的污泥出路。本文对厦门市污水处理厂污泥的主要成分进行了检测和分析，并将厦门本岛石渭头污水处理厂污泥经过好氧堆肥后施用于柚子树，重点研究了重金属元素在土壤、树叶及果肉中的迁移特征，为厦门市污泥的土地利用提供理论和技术指导，保证污泥的安全利用。研究内容包括厦门城市污泥重金属含量分析、污泥养分分析及资源化利用评价、石渭头污水处理厂污泥果肥利用试验、污泥施用后土壤环境质量评价、重金属在土壤-作物系统中的迁移特征和迁移模型研究。研究结果表明：厦门本岛城市污泥果肥利用是可行的。厦门本岛城市污泥比岛外城市污泥成分简单，重金属含量较低，TN和TP养分含量高，且TN和TP含量呈上升趋势，有较大的资源化利用前景。石渭头污水处理厂污泥的营养元素含量均略高于农家肥，肥效较好；污泥作为果树肥料施用一年后，能增加柚子树表层土壤TP的肥效，可促进柚子树的生长，柚子果实增大，果期延长；重金属主要在表层土壤(0～15 cm)中迁移和累积，在柚子树叶和果实中也有迁移、累积，但影响不大。柚子树叶对重金属的富集能力强于果肉，树叶中重金属的含量远高于果肉中的含量，其Cr、Cd、Pb、Cu和Ni的含量超出国家食品卫生标准。果肉中重金属的浓度相当低，只有Ni的含量超过食品卫生标准。污泥肥料不可用于根茎、叶类食用植物的施用；污泥使用前需要降低Ni的含量，补充适量的TK营养素。对重金属在土壤-作物系统中的含量及迁移累积特征研究表明，Cd在土壤中的富集能力强，土壤原已受到Cd的污染较重；在土壤中向下迁移能力为：Pb＞Zn＞Hg＞Cr＞As～Cd＞Ni＞Cu，Pb、Zn向下迁移的能力强，而Ni的迁移能力弱，Cu有很强的表聚性，主要停留在O～15cm土层中。重金属从土壤向树叶迁移累积能力比向果肉的大得多，其向树叶的迁移累积能力为：Cr＞Cu＞Ni＞Pb＞Zn＞Cd＞As，Cr向树叶迁移累积能力最强；从土壤向果肉的迁移累积能力为：Ni＞Cu＞Zn＞Cr＞Pb＞As，Ni向果肉迁移累积能力最强。Cd在果肉中未检出，说明Cd基本不向柚子果肉中迁移，土壤中Cd的重度污染对柚子果肉不会造成危害。污泥的果肥利用表明，污泥中含量较高的五种元素中，Zn和Cu是植物生长需要的营养元素，短期内不会造成危害，但长期施用时必须进行监控；泥肥的施用加重了土壤中Cd的污染、提高了Cr向树叶、Ni向果肉的迁移能力，因此污泥土地利用时这三种元素均存在较大的潜在危害，需进行长期跟踪检测。污泥肥料施用后短时间内，重金属主要在表层土壤(0～15 cm)中迁移和累积，除深层土壤(1 5～30 cm)中Cd的含量显著增加，污染加重外，其他重金属含量变化不显著，未对土壤造成污染。本文采用集对分析模型对污泥施用后的土壤进行环境质量评价，结果表明，污泥施用一年后，0-15cm土壤层和15-30cm土壤层均处于尚清洁状态，验证了污泥施用的安全性。以Cd在土壤中的浓度为最大限制因子确定城市污泥土地施用年限，若以最大连续施用量30 t／(hm~2．a)进行施用，最大施用年限为20年。经过对试验数据进行回归统计分析，采用Eviews软件进行模型拟合，建立了柚子树对照样与试验样土壤之间各重金属如As、Hg、Cu、Pb、Cr和Ni等的关系模型、重金属从土壤向树叶和果肉的迁移模型，可以对污泥果肥利用后重金属在土壤-植物中的浓度进行预测。将转移机理与统计学分析相结合，为污泥土地利用提供了一种研究方法，具有实用意义。最后，结合课题研究中的不足及课题的拓展提出了后续研究的建议。更多还原

【Abstract】 With the improve of municipal sewage treatment rate, the output of sewage sludge increased rapidly. The outlet of sewage sludge faces a severe problem in big cities increasingly. How to dispose so many biosolids safely is the special pressing task currently. Land utilization is increasingly considered as a positive and effective method for sludge disposal. This method take use of a large number of rich nutrients and organic matter from sewage sludge to improve soil structure and supply crop nutrient, which can not only take the appropriate use of the sludge resources and solve the problem of sludge, but also will not endanger human’s health because toxic and harmful substances such as heavy metals and organic pollutants can not enter the food chain.As an example for Xiamen City, study has been done on municipal sewage sludge as fertilizer for fruit trees. In Xiamen City approximately 260m~3 dewatered sewage sludge (Contained 76 percent of water) was produced evry day, which was transported to refuse dump of Dongfu for landfill. But it was rejected by refuse dump now because it couldn’t reach the demand for landfill. New outlet for municipal sewage sludge must be cried for. In this paper, lots of experiments were carried out on the main constituent of sludge from municipal sewage treatment plant of Xiamen City. To offer guidance of theory and technology for land utilization and insure the safe reuse of sludge, experiment was done on grapefruit trees fertilized by arerobic compost of sludge from Shiweitou wastewater treatment plant in Xiamen Island. The study focused on the impact of heavy metals transfer from soil to grapefruit leaves and pulp. The paper includes analysis on the content of heavy metals in sludge of municipal sewage treatment plants in Xiamen City, analysis on nutriments and value on recycling of sludg, experiment on grapefruit trees fertilized by compost of sludge from Shiweitou wastewater treatment plant, safety evaluation of soil on heavy metals after sludge application, and study on transfer characteristic and model of heavy metals from soil to plant system.Results showed that it was feasible for municipal sewage sludge from Xiamen City as fertilizer for fruit trees. Sludge composition of Shiweitou wastewater treatment plant was simpler than that of the outside of the Island. Content of heavy metals was low and nutrient of TN and TP was high in sludge of Xiamen Island. Further more there was an increase of TN and TP. The foreground of land application of sludge of Xiamen Island was very considerable. The nutrient content in sludge of Shiweitou treatment plant were slightly higher than the nutrient content of farmyard manure, fertilizer efficiency of which was better. After the grapefruit trees were fertilized sludge compost for a year, the efficiency of TP was increaced in surface soil. Sludge application could promote the growth of grapefruit tree. The dimension of fruits increased and the period of fruits prolonged. Heavy metals mainly transfered and concentrated in surface soil (0～15 cm), also in leaves and fruits but with little affect. Leaves of grapefruit trees could concentrate more heavy metals than pulp, and therefore leaves contained much more heavy metals than pulp, with the content of Cr, Cd, Pb, Cu, and Ni beyond National Food Sanitation Standard. The concentration of heavy metals in pulp is quite low, with only the content of Ni beyond National Food Sanitation Standard. Sludge compost couldn’t be used for rootstalk and leave edible plants. The content of Ni must be reduced and the nutriment of TK must be supplemented before land utilization for sludge.The study of content and transfer characteristic of heavy metals in soil-plant system showed that Cd had high enrichment in soil; the downward transfer ability in soil was Pb>Zn>Hg>Cr>As~Cd>Ni; Pb and Zn had greater ability and Ni relatively weak; Cu largely concentrateds in the surface soil layer of 0～15 cm. Heavy metals tended to transfer and concentrate much more to leaves than to pulp. Their transfer and concentration ability from soil to pulp is Ni>Cu>Zn>Cr>Pb>As. Cd was not teste in pulp which indicated that basically Cd didn’t transfer to pulp and the heavy pollution of Cd in soil would not harm the pulp. The utilization of sewage sludge to fruit trees showed that among the five elements that were mostly highly contained in sludge, Zn and Cu were the required nutriments for plants growth and would exert no harm in short period, but monitor was a must if they would be used for long term. Sludge fertilization increased the pollution of Cd in the soil, and the transfer ability of Cr from soil to leaves, and Ni to pulp. The three elements all had large potential harm in sludge utilization in soil and therefore long term tests should be followed.In short period that sludge was fertilized to grapefruit trees, heavy metals mainly transfered and concentrated in the surface soil (0～15 cm). The content of heavy metals didn’t show significant changes and had no pollution to soil except that the content of Cd in depth was significantly increased and burden the pollution. By adopting set pair analysis model, this paper evaluated the quality of soil environment after sludge application and the results showed that after one year of sludge application, 0～15cm layer of soil and 15～30cm layer of soil were both relatively clean and thus it proved the safety of sludge application. Cd in the soil was considered as the limiting factor whose largest concentration decided the age of urban sludge land application, if the largest continuous application was 30 t / (hm~2.a) to the farmland, the largest application period would be 20 years.By adopting regressive analysis and the software of Eview 5.1 for Windows, the paper further established the correlation model of heavy metals like As, Hg, Cu, Pb, Cr and Ni between grapefruit trees comparable soil sample and experimental soil, as well as the transfering model of heavy metals from soil to leaves and pulp. It also predicted the concentration of heavy metals in soil-plants system after sludge application. This paper combined the analysis of transfer mechanism and statistics and provided a very practical research method for sludge utilization in soil.Finally, some suggestions about the shortages of the research and its possible expansion were proposed for future study.更多还原