Recovery of copper from small grain size fractions of municipal solid waste incineration bottom ash by means of density separation

Small grain size fractions of municipal solid waste incineration (MSWI) bottom ash (BA) contain elemental and chemically bonded metals in appreciable amounts, especially copper. Investigations with a centrifugal concentrator were carried out using samples, which had been treated with different impact devices. Partly the impacts of single devices were visible in outlines, but mostly the surfaces of the metals were still covered with mineral residues. To generate copper rich fractions, parameters of the separation process should ensure mass yields <2%, best between 0.5 and 1%. The density of the concentrates is then generally >3.2 g/cm³. Best results were achieved with material from a special treatment train which is adapted to grain sizes <2 mm. Reliable copper contents between 20 and 40% (single runs >50%) could be realised. However, considering the required mass yields, referred to this subset only 150–170 g copper would be recovered from 1 Mg MSWI BA. Furthermore, this copper is only in parts present in elemental form. A dependable added value of such treatment step seems to be given only, if that enables a recycling of the mineral aggregates (tailings) in parallel to avoid landfill costs.     

Dispersion in Urban Environments; Comparison of Field Measurements with Wind Tunnel Results

A wind tunnel study was performed to determine the dispersion characteristics of vehicle exhaust gases within the urban canopy layer. The results were compared with those from a field monitoring station located in a street canyon with heavy traffic load. The agreement found was fair. In the second part of the paper it is shown how wind tunnel data can be utilized to supplement and thereby enhance the value of field data for model validation purposes. Uncertainty ranges were quantified which are inherent to mean concentration values measured in urban streets.     

A Constant Erosion Rate Model for Fine Sediment in the York River,Virginia

Results of field experiments using the Virginia Institute of Marine Science' Sea Carousel and tripod system reveal a highly dynamic sediment activity at the Clay Bank site in the York River. At the water-sediment interface, the critical bed shear stress for sediment erosion varied between 0.026 Pa and 0.1 Pa. For the well consolidated sediment below the interface, the critical bed shear stress increased significantly, to more than 0.6 Pa. The seasonal variation of erosion rate for the surficial sediment is significant. For the well consolidated sediment below the surficial sediment, however, the seasonal variation diminished and erosion rate approached a constant. Experimental results from the Carousel deployments imply that the erosion process for quasi-steady tidal flows is always near equilibrium. For this reason, a constant rate erosion model is proposed for the time during tidal acceleration phases. For other times, the erosion rate would be zero. The measured suspended sediment concentration at 10 cm above bed from the VIMS tripod system also Supports this model.     

造纸污泥生物干化特性及其影响因素实验研究

采用自主设计的污泥生物干化实验装置,研究了造纸污泥生物干化特性及其影响因素。重点研究了物料配比和评价参数（温度、pH值、含水率、挥发性固体、ATP含量和淀粉分解菌数量等）的变化规律。结果表明：通过正交实验获得生物干化的最优物料配比为：淀粉（25g／500g）、锯末（40g／500g）、接种量（15mL／500g）和磷酸二氢钾（5g／500g）。造纸污泥生物干化过程中,物料温度、pH值、含水率、挥发性固体、ATP含量和淀粉分解菌数量等指标变化规律性强,效果指示性明显,均可作为污泥干化效果的表征参数。在最优工艺条件下,污泥温度达到47．8℃,经过7d生物反应后,含水率降低到50．3％,挥发性固体降低到49．5％,生物干化效果显著。     

正交实验优化超声波预处理污泥的工况研究

在污泥浓度为9 915 mg/L时,选取超声频率、超声声强和超声时间3个因素设计正交实验,以污泥破解度(DDSCOD)、污泥好氧率(SOUR)和脱氢酶(DHA)活性作为指标,对超声波预处理的工况进行了优化。研究结果表明,最佳的超声预处理参数组合为:超声频率28 kHz,声能密度0.15 W/mL,超声时间10 min。此外,研究还发现不同浓度的污泥,对应的最佳超声组合参数也不同。     

4种重金属离子对间接火焰原子吸收光谱法测定铝的干扰

空气-乙炔间接火焰原子吸收法是我国目前运用较多且易于推广的铝检测方法,研究了Mg2+、Ca2+、Zn2+和Ni2+4种离子对此法测定0.40 mg/L Al3+的干扰情况。得出如下结论:(1)在±5%误差范围内,15.10 mg/L Mg2+、105.00mg/L Ca2+、0.23 mg/L Zn2+、0.88 mg/L Ni2+对0.40 mg/L Al3+无干扰。(2)本方法虽然操作复杂,但成本较低、灵敏度高,检测的浓度范围宽、稳定性好,加标回收率为96%~99%,检出限为0.04 mg/L,适宜测定范围为0.05~100.00 mg/L,适用于饮用水、河水及地下水中Al3+的测定。     

Using discrete choice experiments to value preferences for air quality improvement: the case of curbing haze in urban China

China's top legislature amended a law that “sets environmental protection as the country's basic policy”, which planned to force regulators to make improvements in air quality. Limited studies have attempted to estimate separate values for attributes of air quality improvements from the perspective of how residents value the reduction of haze and health benefits. We apply a discrete choice experiment to estimate the economic benefits involved in these changes. The analysis demonstrates that residents from urban areas are positively willing to pay for air quality improvement. We further employ a mixed logit model and a latent class model to investigate potential heterogeneity in preferences. The preference heterogeneity is significantly related to individuals' exposure to health risks relating to air quality, which is represented by whether the residence location of the respondent is covered by haze/smog on the interview day.     

The significance of heterogeneity on mass flux from DNAPL source zones: an experimental investigation

Understanding the process of mass transfer from source zones of aquifers contaminated with organic chemicals in the form of dense non-aqueous phase liquids (DNAPL) is of importance in site management and remediation. A series of intermediate-scale tank experiments was conducted to examine the influence of aquifer heterogeneity on DNAPL mass transfer contributing to dissolved mass emission from source zone into groundwater under natural flow before and after remediation. A Tetrachloroethylene (PCE) spill was performed into six source zone models of increasing heterogeneity, and both the spatial distribution of the dissolution behavior and the net effluent mass flux were examined. Experimentally created initial PCE entrapment architecture resulting from the PCE migration was largely influenced by the coarser sand lenses and the PCE occupied between 30 and 60% of the model aquifer depth. The presence of DNAPL had no apparent effect on the bulk hydraulic conductivity of the porous media. Up to 71% of PCE mass in each of the tested source zone was removed during a series of surfactant flushes, with associated induced PCE mobilization responsible for increasing vertical DNAPL distributions. Effluent mass flux due to water dissolution was also found to increase progressively due to the increase in NAPL-water contact area even though the PCE mass was reduced. Doubling of local groundwater flow velocities showed negligible rate-limited effects at the scale of these experiments. Thus, mass transfer behavior was directly controlled by the morphology of DNAPL within each source zone. Effluent mass flux values were normalized by the up-gradient DNAPL distributions. For the suite of aquifer heterogeneities and all remedial stages, normalized flux values fell within a narrow band with mean of 0.39 and showed insensitivity to average source zone saturations.     

Experimental research on recolonisation with <Emphasis Type="Italic">Anemone nemorosa</Emphasis> of the beech forests of the Ruhr district (Germany) floristically impoverished by air pollution

BACKGROUND, AIM, AND SCOPE: High SO(2) concentrations as have been observed over decades in the Ruhr district lead to a remarkable reduction of leaf area in the majority of the characteristic broad-leafed herbs of the Central European beech forests even after only a few months of experimental fumigation. Thus, it is no wonder in the time of high SO(2) pollution, e.g., in the town of Herne (centre of the Ruhr district), that there was not a single beech forest hosting, for instance, Viola reichenbachiana or Anemone nemorosa. As air quality has improved very much over some decades in the Ruhr district, one can expect a recolonisation of the beech forests by the species of former time characteristic for the herb layer. However, one has to consider that only the air pollution was reduced, while soil acidification and contamination with heavy metals and PAH are, on the short run, irreversible. That is why experiments were carried out, considering the question as to whether recolonisation of the forests of the Ruhr district by the aforementioned species is possible and why such a recolonisation up to now has not occurred. MATERIALS AND METHODS: The experiments were carried out in a beech forest situated in the centre of the Ruhr district in the City of Herne. The wood anemone (A. nemorosa) was chosen as test plant because of its high frequency in beech forests on loess soils outside the Ruhr district, and its absence in beech forests in the Ruhr district. The experiments with A. nemorosa were carried out in three variants with different soils: (a): soil of the local forests (R); (b): soil of the local forests whose soot layer was removed (r); (c): imported soil from a clean air region far away from the Ruhr district (Odenwald). RESULTS: Survival of rhizomes of A. nemorosa is possible for some years in the soils of the Ruhr district; however, the establishment of a population could not be achieved. The results obtained by the imported soil show that it is no longer air pollution, but the soil which prevents the establishment of a population. Sexual reproduction is rather impossible because of the thick litter layer with which all of the Ruhr district's beech forests are covered. DISCUSSION: With respect to the unfavourable chemistry of the soil of the Ruhr district and in consideration of the unfavourable attributes of the soot layer, the author expected the following order of the development of shoot numbers: O > r > R. However, the result is: O > R > r. In contrast to the expected result, the soot layer has no negative but slightly positive effects on the implanted rhizomes. A possible explanation is that the soot layer, which is situated immediately below the top soil, prevents the top soil from drying up and thus even protects the rhizomes from desiccation. Also, the possibility has to be considered that the soot layer functions as a nutrient storage area. CONCLUSIONS: At present, a survival of the rhizomes of A. nemorosa in the soils of the Ruhr district is temporarily possible but does not lead to the establishment of a permanent population. This only can be achieved by additional sexual reproduction. However, the thick litter layer present in all beech forests of the Ruhr district prevents the establishment of seedlings, i.e., it does not allow sexual reproduction to contribute to the population. The soot layer situated below the litter layer represents a second hindrance for germination. Other than seedlings, rhizomes are not negatively affected by the soot layer but even a slight stabilisation has to be stated. As a reason for this slightly positive effect, a protection of the upper mineral soil from desiccation by the hydrophob soot layer has to be considered. Secondly, the soot layer may serve as a nutrient storage which is of particular importance in acid soils, because acidification generally leads to a leeching of nutrients. To answer these questions, detailed further research is necessary. RECOMMENDATIONS AND PERSPECTIVES: In order to restore the formerly rich herbaceous layer of the forests of the Ruhr district, experiments (removal of the litter layer; liming; ploughing) should be carried out at broad-scale to solve the question of how the strong negative effects of the established thick raw humus layer can be reduced or even be avoided. When the problem of the humus layer is solved, the beech forests of the Ruhr district today highly impoverished in species will become a vivid ecosystem, rich in flowering herbaceous species and thus much more attractive for the people of the Ruhr district than at present.     

The use of clays to sequestrate organic pollutants. Leaching experiments

Leaching experiments are performed from clay-pollutant systems in order to evaluate the capability of clays to sequestrate organic pollutants from wastewaters. Reference kaolinite KGa-1b, montmorrillonite SWy-2 and reference soil BCR^®-700 are the sorbent materials. 2,4,6-trichloroaniline (2,4,6-TCA) and 4-chlorophenol (4-CP) are the typical pollutants, sorbed at amounts of 10.0 mg g⁻¹ and 5.8 mg g⁻¹ on SWy-2 and 7.3 mg g⁻¹ and 2.2 mg g⁻¹ on KGa-1b, respectively.The leaching agents are ultrapure water and model solutions of acid rain and surface waters that simulate meteoric leaching. 1.0 mM HNO₃, 1.0 mM H₂SO₄ solutions and a methanol/water 50/50 (v/v) mixture simulate leaching agents of industrial source.The results are compared and the preferential capability of the clays to sequestrate the more lipophilic 2,4,6-TCA is evidenced.The bond interactions are discussed and explained through preferential adsorption reactions. For montmorrillonite also a simultaneous intercalation in the phyllosilicate interlayer is proposed.