Influence of fertilizer and sewage sludge compost on yield and heavy metal accumulation by lettuce grown in urban soils

Previous research has demonstrated that many urban soils are enriched in Pb, Cd and Zn. Culture of vegetable crops in these soils could allow transfer of potentially toxic metals to foods. Tanya lettuce (Lactuca sativa L.) was grown in pots of five urban garden soils and one control agricultural soil to assess the effect of urban-soil metal enrichment, and the effect of soil amendments, on heavy metal uptake by garden vegetables. The amendments included NPK fertilizer, limestone, Ca(H₂PO₄)₂, and two rates of limed sewage sludge compost. Soil Cd ranged from 0.08 to 9.6 mg kg^–1; soil Zn from 38 to 3490 mg kg^–1; and soil Pb from 12 to 5210 mg kg^–1. Lettuce yield on the urban garden soils was as great as or greater than that on the control soil. Lettuce Cd, Zn and Pb concentrations increased from 0.65, 23, and 2.2 mg kg^–1 dry matter in the control soil to as high as 3.53, 422 and 37.0 mg kg^–1 on the metal-rich urban garden soils. Adding limestone or limed sewage sludge compost raised soil pH and significantly reduced lettuce Cd and Zn, while phosphate fertilizer lowered soil pH and had little effect on Zn but increased Cd concentration in lettuce. Urban garden soils caused a significant increase in lettuce leaf Pb concentration, especially on the highest Pb soil. Adding NPK fertilizer, phosphate, or sludge compost to two high Pb soils lowered lettuce Pb concentration, but adding limestone generally did not. On normally fertilized soils, Pb uptake by lettuce was not exceptionally high until soil Pb substantially exceeded 500 mg kg^–1. Comparing garden vegetables and soil as potential sources of Pb risk to children, it is clear that the risk is greater through ingestion of soil or dust than through ingestion of garden vegetables grown on the soil. Urban dwellers should obtain soil metal analyses before selecting garden locations to reduce Pb risk to their children.     

城市污水污泥对环境的污染及其防治

本文论述了城市污水污泥对水源和土壤的污染,并对其污泥特性作了分析,指出在我国的现有条件下污泥的处置主要为农业上的利用.     

SBR法在小区生活污水处理上的应用

SBR法工艺流程简单、造价低，主体设备只有一个序批式间歇反应器，无二沉池、污泥回流系统，初沉池也可省略，布置紧凑、占地面积省，可根据水质、水量情况灵活运行，具有良好的脱氮除磷效果。而生活小区土地面积有限，景观要求高。通过采用SBR法处理小区生活污水，处理效果好，COD、BOD、SS、TNP和NH3-N去除率分别达到88．75％、87．50％、86．10％、84．50％和51．70％，且都达到GB8978—1996中一级排放标准。     

低耗高效城镇污水处理研发新进展——以厌氧生物处理为核心技术的城镇污水处理成套工艺中试研究

介绍以厌氧生物为核心技术的城镇污水处理成套工艺中试研究。HABR处理城镇污水 ,容积负荷控制在1～ 2kg m3·d,CODCr去除率可达 70 %～ 80 % ,出水CODCr和SS的浓度可达到污水综合排放标准的二级标准 ,经后续好氧处理后 ,出水CODCr和SS的浓度可达一级排放标准。试验结果表明 ,以厌氧生物为核心技术、好氧生物为后续处理的成套工艺 ,具有低耗高效、管理简便的特点 ,适合于我国城镇污水处理。试验获取的技术参数可作为工程设计的依据。     

北方地区市政污水氨氮强化处理技术研究

污水中氨氮的处理较为困难,在寒冷地区冬季生物脱氮效果几乎为零.本文从反应机理和影响因素研究入手,探讨低温季节强化处理措施、生物脱氮运行参数,最后确定了处理工艺流程,及其经济分析结果.     

集散控制系统在广州港西基污水厂处理工艺中的应用方案研究

分析了广州港西基污水处理厂的污水处理系统的结构和存在的问题，提出了基于集散控制系统的解决方案。     

生物脱氮处理城市污水初探

本文介绍了城市污水生物脱氮的基本原理，研究现状和进展。     

浅析公路附属设施污水处理的主要问题及对策

根据现场调查及有关资料，分析了目前我国一些地区公路附属设施污水处理的现状和特点，针对调查中发现的问题，提出了对策：应尽快出台相关标准，使产品市场规范化，保证设备质量；从实际情况与未来发展两方面考虑工艺和设计；提高人员专业素质，加强设备运行的管理和维护。在此基础上，对公路附属设施污水处理装置的设计提出了建议。     

改性污泥灰去除废水中Cu~(2+)试验研究

测试了污泥灰的化学成分并对其进行酸化改性,考察了振荡时间、溶液pH值和反应温度对改性污泥灰去除废水中Cu2+的影响;改性污泥灰对Cu2+的吸附符合Langmuir和Freundlich吸附等温模型,其对Cu2+的最大吸附容量可达7.78mg/g。     

城市污水厂污泥低温热解动力学模型研究

依据对城市污水厂污泥低温热化学转化（热解）反应机理研究的结果，提出污泥热解反应的二级串联竞争反应模型。由非等温（恒速升温）和拟等温污泥T GA实验数据支持，对反应模式导出的动力学模型进行了参数估值。模型可对相关反应器的发展提供支持。