【作者】 黄明；

【导师】 何强；

【作者基本信息】 重庆大学 ， 市政工程， 2009， 博士

【摘要】 随着我国城市化进程的加快,各城市(城镇)污水处理厂相继建成,大大减轻了城市生活污水和工业废水对水环境的污染。但是,城市污水处理率的提高也带来了新的问题,即城市污水污泥如何安全处理和处置。一方面,城市污泥中含有丰富的氮、磷、钾和有机质等植物性营养元素,是很好的肥源和良好的土壤改良剂,具有广阔的资源化农用前景。而另一方面,城市污泥中存在的高浓度有毒有害重金属元素,则严重制约了城市污泥资源化农用。在我国由于城市污水处理工艺、城市污水性质和城市经济类型的差异,使得我国多数城市污水厂的剩余污泥中的Cu、Zn等重金属元素普遍超过《农用污泥污染物控制标准》GB 4248-84的相关标准,因此,采取有效的措施对城市污泥中高浓度重金属的生物毒性和含量加以控制显得十分迫切和必要。针对这一课题,不少学者提出一些新颖的城市污泥中重金剔除技术和方法,其中生物沥滤技术被众多学者誉为城市污泥的绿色洁净化技术,其处理成本较低、处理效果好、易于大规模推广等特点,成为当前污泥(沉积物)中重金属污染治理的热点。目前,对于生物沥滤法去除污泥中重金属的研究仍以纯菌种的玻皿实验为主,而对该技术的工程应用时的实际情况缺乏系统研究。因此,从生物沥滤的工程应用角度出发,按工程化运行特点对这一技术进行全面研究显得十分重要。本文以桂林城市污水处理厂的剩余污泥为研究对象,以有效去除和降低城市污泥中高浓度重金属含量和生物毒性为目标,在研究氧化亚铁硫杆菌(Acidithiobacillus ferrooxidans)和氧化硫硫杆菌(Acidithiobacillus thiooxidans)两类沥滤微生物的生长特征基础上,从生物沥滤装置的选择、工艺流程的设计、沥滤运行参数优选、沥后污泥潜在生物毒性评价等几个方面对工程中应用生物沥滤技术这一课题进行了系统地研究。本文对桂林城市污水污泥成分进行详细分析,得出桂林城市污泥有机质和总养分分别为426g/kg和99.1g/kg,具有较高的农用价值。污泥中Cu、Zn、Cd含量超过我国污泥农用的相关标准,是研究生物沥滤去除的主要对象。采用Tessier连续提取法对污泥中重金属化学形态进行了分析,污泥中Cu、Pb、Ni、Cr主要以稳定性较好的硫化物及有机结合态(Organ)和残渣态(Resd)形式存在,Zn和Cd以不稳定态形式存在为主,污泥中各重金属的潜在生物有效性强弱为:Cd>Zn>Ni>Pb>Cu>Cr。为提高生物沥滤技术去除城市污泥重金属的工程应用价值,本研究在分析我国中小城镇污水处理厂现有污水污泥处理设施完善程度的基础上首次提出了采用序批式生物反应器为沥滤主体构筑物的生物沥滤除污泥重金属工艺。文中对分别采用氧化亚铁硫杆菌和氧化硫硫杆菌进行生物沥滤的各主要影响因素进行了研究,确定了以二沉池出泥(剩余污泥)为沥滤对象时的生物沥滤各运行参数。其中氧化亚铁硫杆菌沥滤体系的最佳运行条件为:底物投加量10g/L、温度25℃、曝气强度0.4L/(min·L)、接种量为30%。氧化硫硫杆菌沥滤体系的最佳运行条件为:底物投加量3g/L、硫颗粒平均粒径165um、温度20~30℃、曝气强度1.0 L/(min·L)、接种量10%。并对两嗜酸菌沥滤在最佳运行条件下的工程运行周期进行了分析,确定氧化亚铁硫杆菌和氧化硫硫杆菌沥滤体系的适宜运行周期和多批次运行的稳定性进行了分析,表明此两沥滤体系的最佳运行周期为2天和3天,经多批次运行时污泥的酸化和重金属去除效果较好且运行稳定。为了解嗜酸微生物的微观生长特征,研究以桂林城市污泥为培养介质,经多次富集纯化得到污泥土著氧化硫硫杆菌和氧化亚铁硫杆菌,并根据嗜酸菌生长及代谢底物特点,引入Michaelis-Menten方程,推导出嗜酸菌的生长动力学方程。得到氧化亚铁硫杆菌生长动力学参数Ks=13.763g/L,μm=0.169 h-1;氧化硫硫杆菌的生长动力学参数Ks=1.836 g/L,μm=0.075 h-1。为研究沥滤过程中污泥中重金属迁移及各化学形态释放特征,对沥滤过程中污泥中重金属的含量和化学形态进行了分析,结果表明经过生物沥滤处理后,污泥中主要高浓度重金属Cu、Zn和Cd的残余浓度均符合《农用污泥污染物控制标准》GB 4248-84的相关标准,沥滤后污泥中Cu, Zn和Cd均能以化学性质较稳定的硫化物及有机物结合态(Organ态)和残渣态(Resd态)形式存在,并对Cu、Zn、Cd的各化学形态在沥滤体系中的释放能力进行分析研究。采用了当前较为先进的沉积物质量基准法(SQGs)和Hakanson指数法对沥滤前后污泥中重金属的潜在生物毒性进行了定性和定量的评价,结果表明A.ferrooxidans菌对Cu、Cd的脱毒作用强于A.thiooxidans菌;沥滤前、后污泥中Cu、Zn、Cd、Pb、Cr、Ni的潜在生态危害性强弱表现为:Cd>Cu>Zn>Ni>Pb>Cr和Cd>Cu>Zn>Pb>Ni>Cr。沥滤后污泥的综合潜在生态危害指数下降91.0%以上,且A.ferrooxidans菌沥后污泥的潜在生物毒性最弱,其综合潜在生态危害指数为84.75,是生物沥滤去除城市污泥重金属工程应用的适合菌种。更多还原

【Abstract】 The water environment pollution caused by the discharge of industrial wastewater and urban wastewater in china has been controlled effectively with sewage treatment plants’building and operation in many cities of china. But another problem was arised with the increase of urban sewage treatment rate,that is how to treat sewage sludge safely.As we know, sewage sludge is the potential fertilizer source and soil amendment for agricultural production, because of the abundant Nitrogen, Phosphorus, Kalium and organic matters. At the same time, the exist of high content heavy metals in sewage sludge had severely restricted the popularization and application of the technology of municipal sludge agricultural resources use. Actually, the contents of Cu , Zn , Cd of sewage sludge were exceed the relevant limits of the control standards for pollutants in sludges from agricultural use(GB4248-84) in most cities of china .So it was an important and urgent mission for us to take effective measures to control the concentration and biotoxicity of the high content heavy metals. Most researches have been carried out for the problem, and many new technologies on removing heavy metals from municipal sludge were exploited. Among which the bioleaching was praised as a green sludge cleaning technology and become the research focus on heavy metal pollution control. Presently, bioleaching as a new technology on removing heavy metals from sludge was systematic studied rarely. Most researches on bioleaching were operated in glassware with pure strain, however, the systematic research based on the engineering application of bioleaching was in scarce. Therefore, to promote the application value of bioleaching, it is very important to implement research from the viewpoint of engineering application.The sewage sludge from Guilin sewage treatment plant was taken and studied. The research aims are to effectively remove the poisonous heavy metals and reduce the biological toxicity. Based on the studies of the growth characters of Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxians, one systematic research about the engineering applying was conducted from the four aspects: the selection of bioleaching reactor, the design of bioleaching process, the optimization of bioleaching parameters and the potential toxicity assessment of treated sludge.The analysis of sludge components showed higher agricultural value for Guilin sewage sludge , and the contents of organic matter and total nutrition were 426g/kg and 99.1g/kg.respectively.Cu, Zn, Cd existed in Guilin sewage sludge were selected as the main removal objects in this study due to the contents of those elements exceeding the agricultural standard. The Tessier method was adopted to continually extract various chemical speciations of sludge heavy metals. The results showed that most Cu, Pb, Ni, Cr in sludge existed in their forms of sulfide, organic combination and residual, and the majority of Zn, Cd were bound to the unstable forms, as exchangeable, carbonates and Fe-Mn oxides. The heavy metal stability was decided as Cd>Zn>Ni>Pb>Cu>Cr.Through the status analysis of sewage sludge treatment facilities, the Sequence Batch Reactor(SBR) was adopted as the main reactor for bioleaching heavy metals from sewage sludge. The surplus sludge was the treatment object in this study. The major effect factors of Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans were researched signally. The bioleaching optimum operation parameters for Acidithiobacillus ferrooxidans are as follows: substrate dosage,10g/L;temperature,25℃; aeration rate, 0.4L/(min·L); inoculation volume, 30%. The bioleaching optimum condition for Acidithiobacillus thiooxidans is that: substrate dosage was 3g/L, average particle size of elemental sulfur was 165um, temperature was 20~30℃,aeration rate was 1.0 L/(min·L),inoculation volume was 10% the further study on optimum operation period and stability of bioleaching under the optimum treatment condition indicated that the proper operation periods were 2 days for Acidithiobacillus ferrooxidans and 3days for Acidithiobacillus thiooxidans.In this experiment, the indigenous Acidithiobacillus ferrooxidans and indigenous Acidithiobacillus thiooxidans were attained from Guilin sewage sludge by enrichment and purification. The Michaelis-Menten Modle was introduced into derive the equations of bioleaching Acidophile, the kinetic constants of saturation constant (Ks) and specific growth rate(μm) for Acidithiobacillus ferrooxidans were 13.763 g/L and 0.169 h-1, that for Acidithiobacillus thiooxidans were 1.836 g/Land 0.075h-1.The characteristics of transfer and release of different speciations were discussed by the analysis of the content of Cu, Zn, Cd in fresh sewage sludge and treated sludge. The result showed that the residual contents of Cu, Zn, Cd all are accord with control standard for pollutants in sludges from agricultural use (GB4248-84). The organic combination and residual were the major speciations of Cu, Zn and Cd in bioleached sludge. The Sediment Quality Guidelines (SQGs) and Hakanson index method were used to assess the potential biological toxicity of fresh sludge and bioleached sludge. The assessment results showed that the detoxication efficiency of Acidithiobacillus ferrooxidans was better than that of Acidithiobacillus thiooxidans. The potential biological toxicities of main heavy metals were in the following order: Cd>Cu>Zn>Ni>Pb>Cr(fresh sludge)and Cd>Cu>Zn>Pb>Ni>Cr(bioleached sludge). The synthetic potential biological risk indexes of sludge were decreased by more than 90% through the bioleaching process. The sludge bioleached by Acidithiobacillus ferrooxidans was at the low potential biological toxicity, the synthetic potential biological risk index was 84.75. So the Acidithiobacillus ferrooxidans was considered as the proper bioleaching bacteria for removing heavy metals from sewage sludge.更多还原