Applicability of grid-net detection system for landfill leachate and diesel fuel release in the subsurface

The grid-net system estimating the electrical conductivity changes was evaluated as a potential detection system for the leakage of diesel fuel and landfill leachate. Aspects of electrical conductivity changes were varied upon the type of contaminant. The electrical conductivity in the homogeneous mixtures of soil and landfill leachate linearly increased with the ionic concentration of pore fluid, which became more significant at higher volumetric water contents. However, the electrical conductivity in soil/diesel fuel mixture decreased with diesel fuel content and it was more significant at lower water contents. The electrode spacing should be determined by considering the type of contaminant to enhance the electrode sensitivity especially when two-electrode sensors are to be used. The electrode sensitivity for landfill leachate was constantly maintained regardless of the electrode spacings while that for the diesel fuel significantly increased at smaller electrode spacings. This is possibly due to the fact that the insulating barrier effect of the diesel fuel in non-aqueous phase was less predominant at large electrode spacing because electrical current can form the round-about paths over the volume with relatively small diesel fuel content. The model test results showed that the grid-net detection system can be used to monitor the leakage from waste landfill and underground storage tank sites. However, for a successful application of the detection system in the field, data under various field conditions should be accumulated.     

Solidification/stabilisation of electric arc furnace waste using low grade MgO

This study aims to evaluate the potential of low grade MgO (LGMgO) for the stabilisation/solidification (S/S) of heavy metals in steel electric arc furnace wastes. Relevant characteristics such as setting time, unconfined compressive strength (UCS) and leaching behaviour assessed by acid neutralisation capacity (ANC), monolithic and granular leaching tests were examined in light of the UK landfill Waste Acceptance Criteria (WAC) for disposal. The results demonstrated that all studied mix designs with Portland cement type 1 (CEM1) and LGMgO, CEM1-LGMgO 1:2 and 1:4 at 40% and 70% waste addition met the WAC requirements by means of UCS, initial and final setting times and consistence. Most of the ANC results met the WAC limits where the threshold pH values without acid additions were stable and between 11.9 and 12.2 at 28 d.Granular leaching results indicate fixation of most of the metals at all mix ratios. An optimum ratio was obtained at CEM1-LGMgO 1:4 at 40% waste additions where none of the metals leaching exceeded the WAC limits and hence may be considered for landfill disposal.The monolithic leaching test results showed that LGMgO performed satisfactorily with respect to S/S of Zn, as the metal component present at the highest concentration level in the waste exhibited very little leaching and passed the leaching test requirement at all mix ratios studied. However, its performance with respect to Pb, Cd and Cr was less effective in reducing their leaching suggesting a higher cumulative rate under those leaching regimes.     

Sorption of pentachlorophenol on peat-bentonite mixtures.

Batch kinetic and isotherm studies were carried out to determine the adsorptive characteristics of peat and bentonite mixtures for pentachlorophenol, and to examine the hydraulic conductivity of peat-bentonite mixtures to determine if they are applicable for use as cutoff barriers. Batch kinetic studies showed that over 90% of PCP was removed from water spiked with approximately 1 mg/l of PCP using a peat-bentonite (5%) mixture. The equilibrium time was 8 hours. The optimum pH range for adsorption of PCP by the peat-bentonite mixture was found to be 3-3.5. Batch isotherm studies showed that the adsorption of PCP by the peat-bentonite mixture from aqueous solution was best described by the Freundlich isotherm equation. Batch adsorption studies using various ratios of bentonite in the mixture showed that the adsorption of PCP decreased linearly with increased amount of bentonite in the mixture, indicating that adsorption of PCP by the peat moss portion of the mixture was the dominant process. The inverse of the hydraulic conductivity was found to increase exponentially with an increase in the bentonite content of the mixture over the range studied. The minimum hydraulic conductivity observed was 3.3 x 10(-7) cm/s for a 50% peat-50% bentonite mixture. Peat-bentonite mixtures can be used to successfully remove PCP from aqueous media and can be used effectively as a barrier to attenuate the migration of PCP through soil and groundwater systems.     

Compressibility of municipal solid waste codisposed with fly ash

If a municipal solid waste (MSW) landfill is used as the foundation for a construction site, the change in the loading conditions may cause considerable compression of the landfill. Therefore, reinforcement to compensate for the loose compression nature of a MSW landfill is a very important design factor for geotechnical engineers when considering the end-use of the landfill. In this study, we discuss a possible technique for stabilizing MSW landfills through the codisposal of municipal solid waste and fly ash. To estimate the stabilization based on the compression characteristics of the codisposed landfill, we performed tests using a large compression set and experimental cells. According to the test results, if the proportion of fly ash is increased, initial and long-term compression could be reduced.     

无机材料对固定化微生物凝胶球性能的影响

为了提高固定化微生物凝胶球的性能,实验研究了在凝胶球中添加无机材料粉末活性炭、SiO2、CaCO3和人造沸石,并从固定化微生物凝胶球的生物活性、机械强度、微观结构和溶出性多方面考核,比较不同无机材料对凝胶球性能的影响。研究结果表明,添加CaCO3能明显提高凝胶球的传质性能,进而提高凝胶球对氨氮的处理效果,添加人造沸石能提高凝胶球的抗拉强度,添加SiO2能提高凝胶球的密度,添加粉末活性炭能提高凝胶球的压缩强度。     

典型危险废物的工程力学特性

掌握填埋废物的工程力学特性是确保危险废物填埋堆体稳定性的重要前提条件,因此,针对6种典型危险废物的工程力学特性开展了调查研究.研究结果表明,污泥类危险废物的含水率和有机质含量远高于非污泥类危险废物,而前者的比重则显著低于后者.污泥类危险废物的渗透系数相对较小,比污染土壤和飞灰炉渣混合物的渗透系数小1个数量级,比滤池填料的渗透系数小2个数量级.不同危险废物的无侧限抗压强度排序为:飞灰炉渣混合物(314.3 kPa)和滤池填料(278.9 kPa)＞污染土壤(124.9 kPa)＞杭州氧气厂污泥(68.6 kPa)、锌铬污泥(71.4 kPa)、油泥(58.4 kPa).不同危险废物的粘聚力排序为:飞灰炉渣混合物(40.8 kPa)、滤池填料(31.1 kPa)＞污染土壤(20.9 kPa)＞杭州氧气厂污泥(1.94kPa)、锌铬污泥(3.10 kPa)、油泥(1.81 kPa).此外,不同危险废物的内摩擦角差异相对较小,其变化范围在18.8°～35.0°之间.综合分析可知,飞灰炉渣混合物和滤池填料的工程力学特性较好,而污泥类危险废物的工程力学特性则较差.     

A comparison between sludge ash and fly ash on the improvement in soft soil

In this study, the strength of soft cohesive subgrade soil was improved by applying sewage sludge ash as a soil stabilizer. Test results obtained were compared with earlier tests conducted on soil samples treated with fly ash. Five different proportions of sludge ash and fly ash were mixed with soft cohesive soil, and tests such as pH value, compaction, California bearing ratio, unconfined compressive strength (UCS), and triaxial compression were performed to understand soil strength improvement because of the addition of both ashes. Results indicate that pH values increase with extending curing age for soil with sludge ash added. The UCS of sludge ash/soil were 1.4-2 times better than untreated soil. However, compressive strength of sludge ash/soil was 20-30 kPa less than fly ash/soil. The bearing capacities for both fly ash/soil and sludge ash/soil were five to six times and four times, respectively, higher than the original capacity. Moreover, the cohesive parameter of shear strength rose with increased amounts of either ash added. Friction angle, however, decreased with increased amounts of either ash. Consequently, results show that sewage sludge ash can potentially replace fly ash in the improvement of the soft cohesive soil.     

Copper and cadmium complexation by high molecular weight materials of dominant microalgae and of water from a eutrophic reservoir

High molecular weight materials (HMWM, >12000-14000 Da) excreted by the two cyanophyte species (Microcystis aeruginosa and Anabaena spiroides) and a diatom (Aulacoseira granulata) which are dominant phytoplankton species in a eutrophic reservoir, Barra Bonita, Brazil were investigated as copper (Cu) and cadmium (Cd) complexation agents and their monosaccharide and elemental analysis of C, H, N and S determined. Also, HMWM obtained from the reservoir water as well as from a mixture of the three algae materials were studied. The HMWM of the cyanophytes and the mixture of the three algae materials complexed Cu and Cd, whereas the HMWM of the diatom and that from the reservoir water complexed only Cu. Two classes of ligands of intermediate to weak binding strength were obtained after Scatchard plot analysis of the titration data. The cyanophytes and the mixture HMWM presented higher conditional stability constants for Cu class-1 ligands (logK1' = 9.2-9.5) than the HMWM derived from the diatom and the reservoir water (logK1' = 8.6-8.8). Higher proportions of acidic monosaccharides corresponded to higher K1' of Cu and Cd complexation, yet no relation was observed among complexation parameters and elemental analysis. This study points out Cu ligands of intermediate to weak binding strength in the excreted HMWM of dominant microalgae and in the HMWM of the reservoir water, while Cd was solely complexed by ligands isolated from the cyanophyte HMWM.     

城市生活污泥烧结制陶粒的两种工艺比较研究

通过试验比较了"湿法造粒-烧结"和"干化-烧结"2种利用城市生活污泥烧结制陶粒的工艺路线.分析了工艺路线、原料配比和烧结温度对污泥陶粒的产品强度、吸水率和密度等性能指标的影响,同时指出了沸石粉和粘土作为助熔剂的不同作用机理和作用温度.实验结果表明,污泥"干化-烧结"制陶粒更有优势.烧结陶粒不会造成二次污染.综合考虑产品性能与经济性,适宜的物料配比为干污泥50%、粉煤灰30%～40%、粘土10%～20%.     

改性沸石对土壤铅、锌赋存形态的影响简

通过室内土壤培养实验,研究改性沸石对污染土壤中Pb、Zn赋存形态的影响。结果表明,土壤中的Pb主要是以Fe-Mn氧化物结合态存在,土壤Zn主要以残渣态存在。添加天然沸石和改性沸石不同程度地降低土壤酸提取态Pb、Zn的含量,提高土壤残渣态Pb、Zn的含量。与CK处理相比,添加4种沸石导致土壤酸提取态Pb含量降低8.7%~40.3%,土壤酸提取态Zn含量降低10.5%~49.8%（培养1个月）。硝酸钾改性沸石比天然沸石更能显著地降低土壤酸提取态Pb、Zn的含量,而氢氧化钠改性沸石和硝酸钾改性沸石比天然沸石更能显著地降低土壤酸提取态的Zn含量。培养1、2和3月后,不同沸石处理导致土壤残渣态Zn比率分别比CK处理提高14.4%~23.5%、19.6%~23.7%和1.9%~11.1%。研究结果表明,天然沸石经过一定方法改性后,是固定污染土壤Pb、Zn的潜在改良剂。     

Municipal solid waste shear strength parameters defined through laboratorial and in situ tests

This paper presents the parameters of municipal solid waste shear strength determined in the laboratory (triaxial tests) and by in situ tests: standard penetration tests (SPT) and cone penetration tests (CPT). The results analyzed here are part of a study carried out on the Santo Tirso landfill (north of Portugal) between 2001 and 2007. The influence of the strain levels, waste composition, and waste age on the shear strength parameters is presented, as well as an attempt to establish some correlations between the SPT and CPT tests and to estimate municipal solid waste (MSW) friction angles from the SPT tests. The results indicate that the aging of the waste, which is characterized by a decrease in fibrous and organic materials and an increase in inert materials and fine fraction, leads to an increase in frictional resistance and to a decrease in cohesion. The results of the SPT and CPT tests indicate higher penetration resistance in older and deeper waste. Estimating the frictional resistance from the SPT test seems to obey an empirical relationship expressed by a power function, which depends on the strain level.

Implications: Comparison of shear strength parameters of municipal solid waste (MSW) determined through laboratory (triaxial tests) and in situ tests (SPT and CPT) showed that the greater amount of fibrous and granular elements leads to an increase in “cohesion” and in friction angle values, respectively. Waste aging results in an increase in frictional resistance and in a decrease in “cohesive” resistance. This is consistent with the composition changes with aging: increase of the relative quantity of inert materials and fine fraction, and decrease in particle size, in organic matter content, and in fabrics and plastics.     

改性膨润土作为垃圾渗透液防渗层的实验研究

本文以天然钠基膨润土为原料,采用水溶液聚合法,在室温条件下,通过改性聚丙烯酰胺对膨润土进行直接插层改性,制备了一种新型聚丙烯酰胺改性膨润土防渗材料。以此防渗材料作为防渗层,选用沈阳大辛填埋场的垃圾渗透液为处理对象,在动态实验下,就其对实际垃圾渗滤液中主要污染物去除的有效性和控制垃圾渗滤液渗透的可行性进行研究。抗渗性能测试结果表明,改性膨润土防渗性能较好,渗透系数为1．0×10^-7cm/s,达到固体废物填埋场的防渗材料国家标准1．0×10^-7cm／s的使用要求。改性膨润土防渗层对COD、氨氮、重金属离子去除效果较好,吸附作用较强,COD和氨氮最大去除率分别达到81％和91％,TFe、Zn^2＋和TCr的最大去除率分别达到71％、58％和73％。实验结果验证了本研究所制备的改性膨润土防渗材料具有优良的抗渗、截污性能。     

Mitigating environmental impact of waste glass materials: review of the existing reclamation options and future outlook

The environmental impact of waste glass (WG) is one of the major challenges crippling sustainable waste management and mitigation. Reclamation of recycled materials from waste glass remains a tedious task amidst complex technological approaches. The challenge as seen in the global containment measures increase the proportion of waste glass and minimize the existing capacity of landfill space. In many works, findings have shown how best to minimize the impact of waste glass as evidenced in their inclusion as building materials such as cement, mortars, concretes and blocks. The concept of this paper is to appraise previous studies carried out on the use of waste glass as key contributing factor in structural building. The scope of this paper will be broaden to include various successes recorded in the evolution of concrete mixtures containing different proportion of recycle glass. Part of the setbacks noted in the inclusion of these recycled materials as matrix, filler or fibre are also reported in this paper. Also discussed is the durability of glass materials in varying conglomerate involving cement in reinforcement of building and structures. Thermal insulating properties of recycled glass are also considered in this work where considerable energy is saved due to their low thermal conductivity. Based on the analysis of various studies and other factors considered in this paper, it is established that recycled glass materials can be accommodated in structural buildings, while continuous research is necessary to adapt waste glass to high pH value of Portland cement.

     

Adsorption properties of kaolinite-based nanocomposites for Fe and Mn pollutants from aqueous solutions and raw ground water: kinetics and equilibrium studies

Raw kaolinite was used in the synthesis of metakaolinite/carbon nanotubes (K/CNTs) and kaolinite/starch (K/starch) nanocomposites. Raw kaolinite and the synthetic composites were characterized using XRD, SEM, and TEM techniques. The synthetic composites were used as adsorbents for Fe and Mn ions from aqueous solutions and natural underground water. The adsorption by the both composites is highly pH dependent and achieves high efficiency within the neutral pH range. The experimental adsorption data for the uptake of Fe and Mn ions by K/CNTs were found to be well represented by the pseudo-second-order kinetic model rather than the intra-particle diffusion model or Elovich model. For the adsorption using K/starch, the uptake results of Fe ions was well fitted by the second-order model, whereas the uptake of Mn ions fitted well to the Elovich model rather than pseudo-second-order and intra-particle diffusion models The equilibrium studies revealed the excellent fitting of the removal of Fe and Mn ions by K/CNTs and Fe using K/starch with the Langmuir isotherm model rather than with Freundlich and Temkin models. But the adsorption of Mn ions by K/starch is well fitted with Freundlich rather than Temkin and Langmuir isotherm models. The thermodynamic studies reflected the endothermic nature and the exothermic nature for the adsorption by K/CNTs and K/starch nanocomposites, respectively. Natural ground water contaminated by 0.4 mg/L Fe and 0.5 mg/L Mn was treated at the optimum conditions of pH 6 and 120 min contact time. Under these conditions, 92.5 and 72.5% Fe removal efficiencies were achieved using 20 mg of K/CNTs and K/starch nanocomposites, respectively. Also, K/CNTs nanocomposite shows higher efficiency in the removal of Mn ions as compared to K/starch nanocomposite.     

Leaching characteristics of polybrominated diphenyl ethers (PBDEs) from flame-retardant plastics

To investigate the effect of leachant on the leachability of polybrominated diphenyl ethers (PBDEs), we determined the leaching concentrations of PBDEs from flame-retardant plastic samples (TV housings and raw materials before molding processing) that are regarded as a source of PBDEs in landfill sites. The leachants used were distilled water, 20% methanol solution, and dissolved humic solution (DHS) of 1000 mg/l based on organic carbon. The leaching test conditions were a liquid-to-solid ratio of 100:1, and a contact period of five days, with twice-daily agitation in a temperature-controlled room of 30 degrees C without pH or ionic strength control. The leaching concentrations of PBDEs increased with increased content, and were found to be remarkably enhanced when methanol and DHS were used instead of distilled water. The enhancement of leachability in the presence of the latter was attributed to the cosolvency effect, and complex formations between the PBDEs and dissolved humic matter (DHM). PBDE concentrations in the leachate obtained from the leaching test and an actual landfill site revealed a significant presence of congeners below heptabromodiphenyl ethers (H7BDEs), detected in the leachate of the actual landfill, while significant amounts of nonabromodiphenyl ethers (N9BDEs) and decabromodiphenyl ether (D10BDE) were detected in the leachate of the leaching test.     

生物质材料预处理餐饮废水

采用4种廉价的生物质材料（水葫芦、柚子皮、木屑、核桃壳）用于餐饮废水的预处理。通过静态烧杯实验,研究了各生物质材料预处理废水的效果及最佳处理条件。结果表明,生物质材料对废水中COD的去除率均在45％以上,油脂吸附量为4～16mg／g,最优吸附材料为水葫芦,COD去除率达65％,油脂吸附量为16mg／g;水葫芦和柚子皮的最佳处理条件为：粒径〈0．2mm,投加量为20g／L,废水pH为4,处理时间为2h,温度为20℃;木屑和核桃壳的最佳实验条件为：粒径〈0．2mm,投加量为28g／L,pH为2,处理时间为2．5h,温度为20℃。生物质对餐饮废水的预处理,为废水中大量有机物和废弃油脂的去除提供了新思路和途径。     

Are individual NOEC levels safe for mixtures? A study on mixture toxicity of brominated flame-retardants in the copepod Nitocra spinipes

In aquatic ecosystems organisms are exposed to mixtures of pollutants. Still, risk assessment focuses almost exclusively on effect characterization of individual substances. The main objective of the current study was therefore to study mixture toxicity of a common group of industrial substances, i.e., brominated flame-retardants (BFRs), in the harpacticoid copepod Nitocra spinipes. Initially, 10 BFRs with high hydrophobicity but otherwise varying chemical characteristics were selected based on multivariate chemical characterization and tested individually for effects on mortality and development using a partial life cycle test (six days) where silica gel is used as a carrier of the hydrophobic substances. Based on these findings, six of the 10 BFRs were mixed in a series of NOEC proportions (which were set to 0.008, 0.04, 0.2, 1, and five times the NOEC concentrations for each individual BFR), loaded on silica gel and tested in a full life cycle test (26 days). Significantly increased mortality was observed in N. spinipes after six and 26 days exposure at a NOEC proportion that equals the NOEC LDR value (x1) for each BFR in the mixture (p=0.0015 and p=0.0105, respectively). At the NOECx5 proportion all animals were dead. None of the other NOEC proportions caused significant negative responses related to development and reproduction. This shows that low concentrations of individual substances can cause toxicity if exposed in mixtures, which highlights the need to consider mixture toxicity to a greater extent in regulatory work.     

NORMACAT project: normalized closed chamber tests for evaluation of photocatalytic VOC treatment in indoor air and formaldehyde determination

Background, aim

The aims of the NORMACAT project are: to develop tools and unbiased standardized methods to measure the performance and to validate the safety of new materials and systems integrating photocatalysis, to develop new photocatalytic media with higher efficiency and to give recommendations aimed at improving the tested materials and systems.

Method

To achieve this objective, it was necessary to design standardized test benches and protocols to assess photocatalytic efficiency of materials or systems used in the treatment of volatile organic compounds (VOCs) and odour under conditions close to applications. The tests are based on the validation of robust analytical methods at the parts per billion by volume level that not only follow the disappearance of the initial VOCs but also identify the secondary species and calculate the mineralization rates.

Results

The first results of inter-laboratory closed chamber tests, according to XP B44-013 AFNOR standard, are described. The photocatalytic degradation of mixtures of several defined pollutants under controlled conditions (temperature, relative humidity, initial concentration) was carried out in two independent laboratories with the same photocatalytic device and with various analytical procedures. Comparison of the degradation rate and of the mineralization efficiency allowed the determination of the clean air delivery rate in both cases. Formaldehyde was the only by-product detected during photocatalytic test under standardized experimental conditions. The concentration of transient formaldehyde varied according to the initial VOC concentration. Moreover the photocatalytic reaction rate of formaldehyde in mixture with other pollutants was analysed. It was concluded that formaldehyde concentration did not increase with time.

Conclusion??perspective

This type of experiment should allow the comparison of the performances of different photoreactors and of photocatalytic media under controlled and reproducible conditions against mixtures of pollutants including formaldehyde.     

Investigation of solution chemistry effects on sorption behavior of Cu(II) on ZSM-5 zeolite

The sorption of Cu(II) from an aqueous solution using ZSM-5 zeolite was investigated by batch technique under ambient conditions. Sorption was investigated as a function of pH, ionic strength, foreign ions, humic substances, and temperature. The results indicate that the sorption of Cu(II) on ZSM-5 zeolite is strongly dependent on pH. Sorption is dependent on ionic strength at low pH, but independent of ionic strength at high pH values. The presence of humic/fluvic acid (HA/FA) enhances the sorption of Cu(II) on ZSM-5 zeolite at low pH values, and reduces Cu(II) sorption at high pH values. Sorption isotherms were well simulated by the Langmuir model. Thermodynamic parameters (i.e., deltaH0, deltaS0 and deltaG0) for the sorption of Cu(II) were determined from temperature-dependent sorption isotherms at 293.15, 313.15, and 333.15 K, respectively. Results indicate that the sorption process of Cu(II) on ZSM-5 zeolite is spontaneous and endothermic.