污泥干化芦苇床中芦苇内生菌群多样性研究

以污泥干化芦苇床中芦苇内生菌的多样性作为主要研究对象,结合16S rDNA高通量测序技术与PCR-DGGE技术,对污泥干化芦苇床和天然湿地中污泥菌群及芦苇内生菌群多样性进行了比较分析。结果表明,污泥干化芦苇床芦苇内生菌的细菌类群包含了20门、30纲、73目、152科、467属、1 167种细菌。其中变形菌门(65.6%)和拟杆菌门(25.5%)占绝对优势,γ-变形菌纲是丰度最高的纲,占总数的43.4%;排前20位的优势菌种相对百分比之和为46.5%,分属于所对应的18个属、12科、10目、6纲、3门。DGGE分析表明,污泥干化芦苇床中的污泥和芦苇内生菌优势菌群的种类与天然湿地相比差异显著;同时由于污泥的影响,芦苇内生菌群种类也发生了较为明显的变化。     

Experimental investigation of ash deposits on convection heating surfaces of a circulating fluidized bed municipal solid waste incinerator

Incineration of municipal solid waste(MSW) is a waste treatment method which can be sustainable in terms of waste volume reduction, as well as a source of renewable energy.During MSW combustion, increased formation of deposits on convection heating exchanger surfaces can pose severe operational problems, such as fouling, slagging and corrosion.These problems can cause lower heat transfer efficiency from the hot flue gas to the working fluid inside the tubes. A study was performed where experiments were carried out to examine the ash deposition characteristics in a full-scale MSW circulating fluidized bed(CFB) incinerator, using a newly designed deposit probe that was fitted with six thermocouples and four removable half rings. The influence of probe exposure time and probe surface temperature(500, 560, and 700℃) on ash deposit formation rate was investigated. The results indicate that the deposition mass and collection efficiency achieve a minimum at the probe surface temperature of 560℃. Ash particles are deposited on both the windward and leeward sides of the probe by impacting and thermophoretic/condensation behavior. The major inorganic elements present in the ash deposits are Ca,Al and Si. Compared to ash deposits formed on the leeward side of the probe,windward-side ash deposits contain relatively higher Ca and S concentrations, but lower levels of Al and Si. Among all cases at different surface temperatures, the differences in elemental composition of the ash deposits from the leeward side are insignificant.However, as the surface temperature increases, the concentrations of Al, Si, K and Na in the windward-side ash deposits increase, but the Ca concentration is reduced. Finally,governing mechanisms are proposed on the basis of the experimental data, such as deposit morphology, elemental composition and thermodynamic calculations.     

Water softening by induced crystallization in fluidized bed

Fluidized bed and induced crystallization technology were combined to design a new type of induced crystallization fluidized bed reactor. The added particulate matter served as crystal nucleus to induce crystallization so that the insoluble material, which was in a saturated state, could precipitate on its surface. In this study, by filling the fluidized bed with quartz sand and by adjusting water p H, precipitation of calcium carbonate was induced on the surface of quartz sand, and the removal of water hardness was achieved.With a reactor influent flow of 60 L/hr, a fixed-bed height of 0.5 m, pH value of 9.5, quartz sand nuclear diameter of 0.2–0.4 mm, and a reflux ratio of 60%, the effluent concentration of calcium hardness was reduced to 60 mg/L and 86.6% removal efficiency was achieved. The resulting effluent reached the quality standard set for circulating cooling water. Majority of the material on the surface of quartz sand was calculated to be calcium carbonate based on energy spectrum analysis and moisture content was around 15.994%. With the low moisture content, dewatering treatment is no longer required and this results to cost savings on total water treatment process.     

固硫灰固化焦化废水处理外排污泥

采用机械力化学法活化循环流化床燃煤固硫灰,用于固化焦化废水处理外排污泥(CWT污泥)。探讨了固硫灰活化条件,并通过XRD和FTIR分析了固硫灰固化CWT污泥中重金属的机理。实验结果表明:当m(Ca O)∶m(Ca O+固硫灰)为20%、球磨频率为40 Hz、球磨时间为2 h时,养护28 d固硫灰固化体的平均抗压强度达到72.2 MPa;当污泥掺加量为50%(w)时,养护28 d含污泥固化体的抗压强度达到8.5 MPa,固化体浸出液中Pb2+和As5+的质量浓度分别为0.177 mg/L和0.013 mg/L,均远低于GB 5085.3—2007《危险废物鉴别标准浸出毒性鉴别》的规定限值。XRD和FTIR表征结果表明,在固硫灰活化过程中,混合体系水化生成了C—S—H凝胶、斜方钙沸石和钙矾石,可通过物理包裹、吸附及离子交换的形式实现CWT污泥中Pb2+和As5+的固化/稳定化。     

旋转填充床分离沼气中的CO_2

以水为吸收液,采用旋转填充床分离微生物厌氧发酵沼气中的CO_2,考察了工艺条件对CO_2吸收效果的影响。实验结果表明:进液量越大、气液比越小、进口CO_2体积分数越小、操作压力越大、进液温度越低则CO_2的吸收效果越好,而床转速以适中为宜;在进液量60 L/h、气液比3.3、床转速1 000 r/min、进口CO_2体积分数40%、操作压力1.2 MPa、进液温度5℃的条件下,CO_2吸收率为57.4%,提纯后气体的CO_2体积分数为17%。     

垃圾填埋场反渗透浓缩液回喷至附近垃圾焚烧厂焚烧研究

为解决垃圾渗滤液经两级碟管式反渗透装置(DTRO)的处理后形成的高浓度浓缩液难以处理的问题,实现垃圾渗滤液反渗透浓缩液的高效无害化处理,以山东省某垃圾填埋场经两级碟管式反渗透装置(DTRO)分离形成的浓缩液为例,拟将其回喷至隔路建设的垃圾焚烧厂焚烧炉中,结合已有的垃圾填埋场浓缩液的COD浓度以及附近垃圾焚烧厂中焚烧炉的性能参数,研究了浓缩液的最大回喷比,以及回喷燃烧废气对大气环境的影响。结果表明:将回喷比控制在3.96%以内,采用该工艺既不会影响垃圾焚烧工况,又能实现对垃圾浓缩液的高效处理;该工艺产生的烟气焚烧污染物均满足该行业的污染物排放标准。     

焚烧厂周边居民重金属污染物多途径暴露的健康风险

焚烧厂排放的重金属污染物会通过不同途径富集于周围环境介质中,如土壤、地表水、地下水、大气、蔬菜和家禽等.焚烧厂周边人群通过上述各种环境介质暴露于重金属,并产生累计的健康危害.然而目前研究很少关注人群通过多途径暴露的累计健康风险.本研究调查了一座典型医疗废物焚烧厂周边不同环境介质中的重金属含量,分析其与人体暴露关系,并计算了其不同途径暴露的健康风险及累计风险.结果表明重金属产生的非致癌风险大小As(298.1)Cr(35.4)Mn(14.0)Pb(7.0)Cu(2.3)Hg(1.9)Zn(1),致癌风险大小依次为As(1.32×10-2)Cr(1.31×10-2)10-5,均超过风险可接受水平;食用自产蔬菜是主要的暴露途径(贡献率为68%~92%)其次为自养家禽贡献率为10%左右.这说明区别于通常关注的通过土壤、水体、空气等介质暴露的风险相比,食用研究区周边的动植物产品导致的风险更大,需要引起重点关注;不确定分析结果表明考虑污染物浓度不确定条件下,场地健康风险大约有0.54~2.28倍的增加;风险管理研究表明通过截断食用本地蔬菜和家禽,除Cr的致癌风险外,其他重金属对厂区居民的健康风险水平会迅速降低至可接受水平.     

Modes of governing Canadian waste management: a case study of Metro Vancouver’s energy-from-waste controversy

Managing municipal solid waste is a pressing environmental and political concern for Canadian municipalities who bear the primary responsibility for waste management (WM). In 2015, Metro Vancouver’s (MV’s) plans to expand their capacity to expand their WM capacity with energy-from-waste technology was abandoned, despite shrinking landfill space and persistent public opposition to new landfills. Using Bulkeley et al.’s [(2005). Governing municipal waste: towards a new analytical framework. Journal of Environmental Policy and Planning, 7(1), 1–23. doi:10.1080/15239080500251700] ‘modes of governing framework’, we analyse MV’s failed attempt to expand their energy-from-waste capacity to better understand the challenges associated with governing WM in Canada. We argue that a history of downloading responsibility for WM to municipalities, regional districts, and industry has fragmented WM governance, posing a challenge for developing new waste infrastructure. We find that this localization of responsibility is incompatible with contemporary WM challenges. The scalar mismatch between waste’s material impacts and the scale at which waste is managed has resulted in co-dependence and conflict between putatively independent municipalities, regional districts, and private companies. This inhibits higher-level WM coordination while the autonomy of individual municipalities is simultaneously undermined.     

Evaluating the Applicability of a Two‐dimensional Flow Model of a Highly Heterogeneous Domain to Flow and Environmental Management

Two‐dimensional simulation of highly heterogeneous domains, especially those with disparate length scales, roughness conditions, and geometries, often leads to challenges such as long computation times and numerical instability. Simulation of challenging domains is often needed to guide flood management and environmental regulation agencies in operation and potential domain modifications. This work evaluates the ability of a two‐dimensional unsteady hydrodynamic model to represent long‐duration transient flows over a domain with highly heterogeneous roughness, geometric characteristics, and length scales through bed roughness representation. The domain includes 13 km of Cache Creek and the 14.5 km² Cache Creek Settling Basin, which traps both sediment and mercury. Calibration under different bed roughness methods, validation, and modeling results of bathymetric modification scenarios are presented. The modeling approach's performance supports its application as a tool for management of similar domains, such as settling basins, leveed floodplains, and reservoirs. Accurate representation of flow dynamics can also inform environmental management that involves transport of sediments, nutrients, and heavy metals. This study found that a two‐dimensional unsteady flow model can accurately represent long‐duration transient flow in a large settling basin with highly heterogeneous characteristics without parsing of the domain or flow events simulated.     

北京市生活垃圾焚烧飞灰安全处置技术路线分析

调研了北京市生活垃圾焚烧处理及飞灰产生现状、污染特性以及处置方式,剖析了现行飞灰环境管理的技术政策标准法规,对比分析北京市目前处置生活垃圾焚烧飞灰采用的固化/稳定化—填埋和水泥窑协同处理两种技术路线,结合北京市水泥窑协同处置生活垃圾焚烧飞灰实例,深入分析了水泥窑协同处置生活垃圾焚烧飞灰技术路线及存在问题,分析了改进后的水泥窑协同处置方式的技术特点。文章最后提出北京市生活垃圾焚烧飞灰处置应选择适宜的技术路线、加强相关技术规范和标准制定和完善与推广安全可行的飞灰资源化处置技术等对策建议。