Potential use of lateritic and marine clay soils as landfill liners to retain heavy metals

The potential of a lateritic soil and a marine clay, typical of those found in hot and humid climatic regions, was assessed for use as a landfill liner material. A series of tests were conducted - physical and chemical, batch adsorption, column, hydraulic conductivity, etc., - to evaluate the heavy metal sorption capacity, chemical compatibility of hydraulic conductivity, and transport parameters of the soils. Experimental results showed that the marine clay had better adsorption capacity than that of the lateritic soil and that its hydraulic conductivity was an order of magnitude lower. In addition, the hydraulic conductivities of both soils when permeated with low concentration heavy metal solutions were below 1x10(-7)cm/s. When permeated with Cr, Pb, Cd, Zn, and Ni solutions, the retardation factors of the lateritic soil and the marine clay ranged from 10 to 98 and 37 to 165, respectively, while the diffusion coefficients ranged from 1.0x10(-5) to 7.5x10(-6) and 3.0 to 9.14x10(-7)cm2/s, respectively. For both soils, Cr and Pb were retained relatively well, while Cd, Zn, and Ni were more mobile. The marine clay had higher retardation factors and lower diffusion coefficients, and its hydraulic conductivity was more compatible with Cr solution, than that of the lateritic soil. In general, the properties of the marine clay indicate that it has significant advantages over the lateritic soil as landfill liner material.     

Salinity, organic content, micronutrients and heavy metals in pig slurries from South-eastern Spain

The increase in commercial pig production is an opportunity to reuse animal manures in arid and semiarid soils as a source of nutrients and organic matter. However, there are components in pig slurry that are potentially dangerous for the environment. In this study, pig slurries of 36 pig farms in South-eastern Spain were evaluated for salt content (electrical conductivity, chloride and sodium), organic load (BOD5 and COD), micronutrients (Fe, Cu, Mn and Zn), and heavy metals (Cd, Co, Cr, Ni and Pb). Except for electrical conductivity, Cu and Zn, components in pig slurries did not vary considerably between animal production stages, indicating similar management of diverse animal types. Assuming an application rate based on the maximum input of nitrogen from animal manure (210 kg total N/ha/yr), the estimates for soil annual load of Cl and Na, 415 kg/ha, could be a significant salinisation risk. Cu and Zn seemed to be the metals that could be accumulated most in soils where application of pig slurries is common (4 and 15 kg/ha/yr, respectively). The estimated heavy metal (Cd, Co, Cr, Ni and Pb) input to soils would be 260 g/ha/yr, with a relative contribution of Cr>Ni>Pb>Co>Cd.     

甲苯在典型土壤中的迁移性能

采用一维土柱装置模拟非水相液体(NAPLs)在我国两种典型土壤(北京潮土与湖南红壤)中的垂向迁移过程,以甲苯为例研究了其在两种土壤中的迁移性能;采用XRD技术测定土壤的矿物组成。实验结果表明,当潮土和红壤孔隙率均为45%时,甲苯在潮土中的迁移速率和最终迁移距离均显著高于在红壤中。甲苯在潮土中的阻滞系数(Rf=18.9)小于在红壤中(Rf=26.5),表明红壤对甲苯的吸附阻滞作用强于潮土。XRD表征结果显示,红壤中粒径小的黏粒含量较高,具有较多的黏土矿物,对甲苯具有更强的吸附阻滞能力,致使甲苯在红壤中垂向迁移速率小,最终迁移距离较短。     

Utilization of sepiolite materials as a bottom liner material in solid waste landfills

Landfill bottom liners are generally constructed with natural clay soils due to their high strength and low hydraulic conductivity characteristics. However, in recent years it is increasingly difficult to find locally available clay soils that satisfy the required engineering properties. Fine grained soils such as sepiolite and zeolite may be used as alternative materials in the constructions of landfill bottom liners. A study was conducted to investigate the feasibility of using natural clay rich in kaolinite, sepiolite, zeolite, and their mixtures as a bottom liner material. Unconfined compression tests, swell tests, hydraulic conductivity tests, batch and column adsorption tests were performed on each type of soil and sepiolite–zeolite mixtures. The results of the current study indicate that sepiolite is the dominant material that affects both the geomechanical and geoenvironmental properties of these alternative liners. An increase in sepiolite content in the sepiolite–zeolite mixtures increased the strength, swelling potential and metal adsorption capacities of the soil mixtures. Moreover, hydraulic conductivity of the mixtures decreased significantly with the addition of sepiolite. The utilization of sepiolite–zeolite materials as a bottom liner material allowed for thinner liners with some reduction in construction costs compared to use of a kaolinite-rich clay.     

Pneumatic fracturing to remove VOCS

A new process for enhancing in-situ remediation of low-permeability soil and rock formations is presently under development at the Hazardous Substance Management Research Center (HSMRC). The patented process, known as ?pneumatic fracturing,”? consists of injecting high-pressure air or other gas into contaminated geologic formations at controlled flow rates and pressures. In fine-grained soils such as clay, pneumatic fracturing creates conductive channels in the formation, thereby increasing the permeability and exposed surface area of the contaminated soil. The potential benefits of pneumatic fracturing are significant, since in-situ remedial technologies are essentially limited by the pore gas exchange rate of the soil being treated. This article describes the results of a recent demonstration of pneumatic fracturing at an industrial site to enhance a volatile organic compound (VOC) extraction system. After establishing the baseline removal rate of soil gas effluent from the clay, soil surrounding the extraction system was fractured to enhance VOC with drawal. A substantial improvement in the VOC removal rate was observed, including: (1) flush effluent concentrations that increased up to 200 times; and (2) air flows in the formation that increased up to 1,000 times.     

Simple technologies for on-farm composting of cattle slurry solid fraction

Composting technologies and control systems have reached an advanced stage of development, but these are too complex and expensive for most agricultural practitioners for treating livestock slurries. The development of simple, but robust and cost-effective techniques for composting animal slurries is therefore required to realise the potential benefits of waste sanitation and soil improvement associated with composted livestock manures. Cattle slurry solid fraction (SF) was collected at the rates of 4m(3)h(-1) and 1m(3)h(-1) and composted in tall (1.7 m) and short (1.2m) static piles, to evaluate the physicochemical characteristics and nutrient dynamics of SF during composting without addition of bulking agent materials, and without turning or water addition. Highest maximum temperatures (62-64 °C) were measured in tall piles compared to short piles (52 °C). However, maximum rates of organic matter (OM) destruction were observed at mesophilic temperature ranges in short piles, compared to tall piles, whereas thermophilic temperatures in tall piles maximised sanitation and enhanced moisture reduction. Final OM losses were within the range of 520-660 g kg(-1) dry solids and the net loss of OM significantly (P<0.001) increased nutrient concentrations during the composting period. An advanced degree of stabilization of the SF was indicated by low final pile temperatures and C/N ratio, low concentrations of NH(4)(+) and increased concentrations of NO(3)(-) in SF composts. The results indicated that minimum intervention composting of SF in static piles over 168 days can produce agronomically effective organic soil amendments containing significant amounts of OM (772-856 g kg(-1)) and plant nutrients. The implications of a minimal intervention management approach to composting SF on compost pathogen reduction are discussed and possible measures to improve sanitation are suggested.     

Ammonia volatilization,N2O and CO2 emissions from landfill leachate-irrigated soils

Effects of leachate addition on ammonia volatilization and N₂O and CO₂ emissions from two different soils were investigated using the 10-day laboratory incubation method at two levels of moisture content. Ammonia volatilization was dominated by soil pH and only occurred in alkaline clay soil, where 0.26–0.32% of soil ammonia could be lost. The N₂O emission from the alkaline clay soil was one order of magnitude greater than that from the acidic sandy soil, when either water or leachate was irrigated. Increasing the moisture content from 46% water-filled pore space (WFPS) to 70% WFPS in the alkaline clay soil or the acidic sandy soil by either water or leachate irrigation increased the N₂O emission by over twofold. The CO₂ emission from each soil sample at the two WFPSs was almost the same. The CO₂ emission from the alkaline clay soil with leachate addition was 72% lower than that from the acidic sandy soil with leachate addition, and 6.7 times higher than that from the alkaline clay soil with distilled water addition. Ammonia volatilization and N₂O emission under leachate irrigation could be minimized by avoiding the excessively wet condition and by selecting the acidic sandy soil with low organic carbon and total nitrogen content.     

天然黏土材料附着纳米TiO2对 电解锰渣中锰的吸附固定

采用机械球磨法对膨润土、硅藻土、高岭土3种天然黏土材料进行预处理,通过超声法将纳米TiO_2附着于其上制得复合材料,考察了不同复合材料加入量及养护时间条件下复合材料对电解锰渣中Mn的吸附固定效果。3种天然黏土材料中,硅藻土的平均粒径最小,比表面积和总孔隙度最大,对水中Mn的吸附量也最大。黏土材料附着纳米TiO_2后对电解锰渣中Mn的吸附固定效果较单纯黏土材料有明显改善。在养护时间为12 d、硅藻土附着纳米Ti O_2复合材料加入量为10%(w)的最佳条件下,Mn的TCLP浸出量较原电解锰渣下降了83.04%。     

Utilization of turkey manure as granular activated carbon: physical, chemical and adsorptive properties

The high availability of large quantities of turkey manure generated from turkey production makes it an attractive feedstock for carbon production. Pelletized samples of turkey litter and cake were converted to granular activated carbons (GACs) by steam activation. Water flow rate and activation time were changed to produce a range of activation conditions. The GACs were characterized for select physical (yield, surface area, bulk density, attrition), chemical (pH, surface charge) and adsorptive properties (copper ion uptake). Carbon physical and adsorptive properties were dependent on activation time and quantity of steam used as activant. Yields varied from 23% to 37%, surface area varied from 248 to 472 m(2)/g and copper ion adsorption varied from 0.72 to 1.86 mmol Cu(2+)/g carbon. Copper ion adsorption greatly exceeded the values for two commercial GACs. GACs from turkey litter and cake show considerable potential to remove metal ions from water.     

Modified Fenton's processes for effective in‐situ chemical oxidation—Laboratory and field evaluation

Fenton's reagent in its conventional form, although effective for contaminant treatment, is impractical from an in‐situ field application perspective due to low pH requirements (i.e., pH 3‐4), and limited reagent mobility when introduced into the subsurface. Modified Fenton's processes that use chelated‐iron catalysts and stabilized hydrogen peroxide have been developed with the goal of promoting effective in‐situ field application under native pH conditions (i.e., pH 5‐7), while extending the longevity of hydrogen peroxide. Laboratory experiments conducted in soil columns packed with organic soil to compare modified Fenton's catalysts with conventional catalysts (acidified iron [II]) indicated superior mobility and sorption characteristics for modified Fenton's catalysts. Furthermore, the acidic pH of a conventional catalyst was buffered to the native soil range, leading to increased iron precipitation/adsorption following permeation through the soil column. The chelates present within the modified Fenton's catalyst showed greater affinity toward iron compared with the native soil and, hence, minimized iron loss through adsorption during the permeation process even at pH 5‐7. Field effectiveness of the modified Fenton's process was demonstrated at a former dry‐cleaning facility located in northeast Florida. Preliminary laboratory‐scale experiments were conducted on soil‐slurry and groundwater samples to test the process efficacy for remediation of chlorinated solvents. Based on successful experimental results that indicated a 94 percent (soil slurry) to 99 percent (groundwater) reduction of cis‐1,2‐DCE, PCE, and TCE, a field‐scale treatment program was initiated utilizing a plurality of dual‐zone direct push injection points installed in a grid fashion throughout the site. Results of treatment indicated a 72 percent reduction in total chlorinated contamination detected in the site groundwater following the first injection event; the reduction increased to 90 percent following the second injection event. © 2002 Wiley Periodicals Inc.     

Estimation of nutrient values of pig slurries in Southeast Spain using easily determined properties

The contents of available nutrients in pig slurries are not easy to quantify in situ without laboratory facilities, but chemical analyses using standard laboratory methods also take time and are costly and not practical for most farms. Thus, when animal slurries are applied to land, their fertiliser potential is often unknown. In addition, in the last years, the changes in the management of industrial piggeries has changed the nature of the pig slurries vg. decrease of the dry matter content, and consequently the methods and equations used for estimating the nutrient contents in these residues must be checked. In our study, slurry samples were collected from the storage tanks of 36 commercial farms in Southeast Spain. Samples were analysed for pH, electrical conductivity (EC), redox potential (RP), specific density (D), total solids (TS), sedimentable solids (SS), biological oxygen demand (BOD(5)), chemical oxygen demand (COD), total nitrogen (TKN), ammonium nitrogen (AN), organic nitrogen (ON), and total contents of phosphorus, potassium, calcium and magnesium. Relationships between major nutrient levels of pig slurries and a range of physical and chemical properties were investigated. We also analysed the variability of pig slurries according to the production stage. TKN, AN and K were closely related to EC. The P content in slurries was related more closely to solids-derived parameters such as D. The use of multiple properties to estimate nutrient contents in pig slurries, especially for AN and K, seemed unnecessary due to the limited improvement achieved with an additional property. Therefore, electrical conductivity seemed to be the most appropriate single, easily determined parameter for estimation of total and ammonium nitrogen and potassium in pig slurries, with more than 83% of the variance explained. P seemed to be the worst key nutrient for estimation using any easily determined parameter.     

Adsorption/Desorption of Polyvinyl Alcohol on Solid Substrates and Relevant Biodegradation

The rates and extents of absorption and desorption of polyvinyl alcohol (PVA) samples on different solid substrates comprising montmorillonite, quartz sand, and farm soil, as well as humic acid mixture are reported. The uptake of PVA by the substrates was analyzed as a function of PVA hydrolysis (72–98%), molecular weight, and molecular weight distribution. Higher adsorption was detected on montmorillonite followed by farm soil, whereas the quartz sand did not display any specific adsorption affinity for the PVA. An increase in the hydrolysis degree of PVA increased the adsorption rate and extent whereas this feature was reversed by an increase in PVA molecular weight. The desorption of PVA samples from the different substrates was performed both under various pH conditions and in the presence of concentrated HF that was used to dissolve the silicon derivatives present in the substrates. Biodegradation experiments carried out in liquid cultures of PVA adsorbed on montmorillonite showed that the mineralization of the adsorbed PVA was much lower than that detected for the nonadsorbed PVA. This investigation suggests that irreversible adsorption of PVA on the clay component occurs in soil, thus substantially inhibiting PVA biodegradation.     

Recycling and recovery routes for incinerated sewage sludge ash (ISSA): A review

The drivers for increasing incineration of sewage sludge and the characteristics of the resulting incinerated sewage sludge ash (ISSA) are reviewed. It is estimated that approximately 1.7 million tonnes of ISSA are produced annually world-wide and is likely to increase in the future. Although most ISSA is currently landfilled, various options have been investigated that allow recycling and beneficial resource recovery. These include the use of ISSA as a substitute for clay in sintered bricks, tiles and pavers, and as a raw material for the manufacture of lightweight aggregate. ISSA has also been used to form high density glass–ceramics. Significant research has investigated the potential use of ISSA in blended cements for use in mortars and concrete, and as a raw material for the production of Portland cement. However, all these applications represent a loss of the valuable phosphate content in ISSA, which is typically comparable to that of a low grade phosphate ore. ISSA has significant potential to be used as a secondary source of phosphate for the production of fertilisers and phosphoric acid. Resource efficient approaches to recycling will increasingly require phosphate recovery from ISSA, with the remaining residual fraction also considered a useful material, and therefore further research is required in this area.     

Effects of fly ash addition on physical properties of porous clay-fly ash composites via polymeric replica technique

The porous composites of clay and fly ash have the potential to be used in many fields, such as catalyst support and gas adsorbents. In this study, various ratios of fly ash (1–2) with different percentage of suspension (50–70 wt%) were applied to produce porous clay-fly ash composites via polymeric replica technique. Fabrication process starts by mixing clay and fly ash in distilled water to form slurry. The process is followed by fully immersing polymer sponge in slurry. The excess slurry is then removed through squeezing. Finally, the sponge coated with slurry is sintered at 500 and 1250 °C for 1 h. It is found that the compressive strength of porous composites improves significantly (0.178–1.28 MPa) when the amount of clay-fly ash suspension mixture (50–70 wt%) increases. The compressive strength of porous composites is mainly attributed to the mullite, quartz and amorphous phase formations. These results are supported by X-ray diffraction analysis. On the other hand, increase in the amount of suspension reduces the apparent density (from 2.44 to 2.32 g/cm³) and porosity (from 97 to 85 %). The reduction in apparent density is believed to be caused by the presence of high fly ash content in porous composites. The melted fly ash cenospheres have closed the internal pores and increased density of samples. Higher suspension level not only reduces porosity, but also increases close pores of the porous composites. The results are justified through the observation from the structures of porous clay-fly ash composites.     

Bioremediation of Dinitrotoluene in Aged Clay and Sandy Soils Using Pseudomonas Organisms,Spizizen Nutrient Medium and Prairie Silt Loam

This article describes the utility of Spizizen medium in effecting the release of 2,4 dinitrotoluene (DNT) from plasticized propellant in aged clay soil and of added Pseudomonas organisms in enhancing the rate of degradation of DNT in clay and sandy soils. DNT is an environmental problem because of its toxicity to mammals. It is proposed that the citrate in Spizizen medium chelates metals that form the aggregates of humin in aged clay soils, thereby releasing propellant components. Lack of awareness of DNT mobilization by citrate or other polyanions may lead to a potential underestimation of the 2,4 DNT present in aged contaminated soil and a potential increased release of DNT following exposure to solvents containing citrate or other polyanions. DNT in contaminated sandy soils was rapidly degraded when Pseudomonas and Spizizen medium were added (85% degraded in 20 days). Pseudomonas isolated/Torn soils at the Badger Plant have particular utility for the in situ degradation of 2,4 DNT in clay and sandy soils because they metabolize Spizizen medium, thrive in diverse climates, and have been selected for their ability to grow in soils contaminated with DNT. Mixture of either the contaminated clay soil or the contaminated sandy soil with uncontaminated prairie silt loam (20:80 ratio) facilitated management of the treatment process. This observation is important because of the widespread distribution, and hence low cost, of this soil type in the central United States.     

The use of volcanic soil as mineral landfill liner--I. Physicochemical characterization and comparison with zeolites.

The main physicochemical characteristics of the volcanic soil of Southern Chile, with allophane as the main pedogenic mineral phase were analysed and compared with common zeolites (clinoptilolite) of the European market. The ultimate goal of this study was to test volcanic soil for the use as mineral landfill liner. The main results indicated that the clay and silt fractions together of the volcanic soil were between 38 and 54%. The buffering capacity of the volcanic soil was higher compared with the studied zeolites, whereas the cationic exchange capacity of the volcanic soil (between 5.2 and 6.5 cmol + kg(-1)) is of the same order of magnitude of the studied zeolites (between 9.7 and 11.4 cmol + kg(-1)). Moreover, the anionic exchange capacity of the volcanic soil was higher compared to the zeolites analysed. The hydraulic conductivity of the volcanic soil, measured in the laboratory at maximum proctor density, ranges between 5.16 x 10(-9) and 6.48 x 10(-9) m s(-1), a range that is comparable to the value of 4.51 x 10(-9) m s(-1) of the studied zeolite. The Proctor densities of the volcanic soil are in a lower range (between 1.11 and 1.15 g ml(-1)) compared with zeolites (between 1.19 and 1.34 g ml(-1)). The volcanic soil physicochemical characteristics are comparable to all the requirements established in the Austrian landfill directive (DVO, 2000). Therefore, the use as mineral landfill basal sealing of the analysed volcanic soil appears reasonable, having a pollutant adsorption capacity comparable to zeolites. It is of special interest for Southern Chile, because there are no alternative mineral raw materials for basal liners of landfills.     

Impact of MSW landfill on the environmental contamination of phthalate esters

This study aims to investigate the impact of MSW landfill on the contamination of phthalate esters (PAEs) in nearby environment. Landfill leachate, surface water, groundwater and soil profile samples were collected from a MSW landfill area in Wuhan, China. Contents of 16 PAEs were detected for each sample using gas chromatography method. Results showed that landfill had an obvious effect on the contamination of PAEs in groundwater, whereas showed no tremendous effect on the PAEs contamination in surface water and topsoil. Seven possible transportation processes of PAEs in landfill area were put forward. However, the especially important processes are the invasion of PAEs into aquifer through weathered crevice, horizontal transportation in aquifer and upward infiltration with groundwater. It is suggested that the whole landfill area should be engineered with seepage-proof membrane and clay so as to prevent landfill leachate from flowing out of the filling area. On the other hand, no weathering crevice is permitted in the landfill area as it will affect groundwater seriously.     

Chemistry,Mineralogy and Morphology of Spodosols at Two Swedish Sites Used to Assess Methods of Counteracting Acidification

The chemistry, mineralogy and morphology of two soil profiles developed on till material of granitic and gneissic composition in south-western Sweden were studied in relation to podzolization processes. These soils were used for treatments with lime and wood ash. The profiles do not show characteristic Podzol morphology but qualify as Spodosols under Soil Taxonomy criteria and are probably typical for the coniferous forest soils of south-western Sweden. Podzolization features are clear but less well expressed than in classic Podzols. The distribution of major elements shows podzolization features with accumulation of sesquioxides in the B horizons and depletion in the eluvial horizons. Quartz and feldspars dominate the bulk soils reflecting the clear relationship between the composition of the soil and the underlying bedrock. Low amounts of clay contain an interlayered vermiculitic phase as the main phyllosilicate in which the degree of interlayering, known to be pH dependent, varies with depth and is at a maximum in the Bhs horizon. In the B horizons there are small but significant amounts of imogolite-type material which affect the adsorption of sulphate.     

湿法脱硫多因素引起的浆液恶化原因分析及处理措施

在石灰石—石膏湿法脱硫系统中,吸收塔浆液恶化是系统运行经常出现的问题,浆液恶化不仅易影响浆液pH值,降低系统的脱硫效率,还会造成脱硫副产物石膏脱水困难。为此,结合2×600 MW机组湿法脱硫系统浆液恶化问题,通过检测与分析探讨了引起浆液品质变差的原因,并提出了解决措施。     

Alternative method of groundwater sparging for petroleum hydrocarbon remediation

An alternative method of in-situ groundwater sparging, termed density-driven convection (patent pending), is presented. This method has been successfully used to remediate eight underground storage tank releases involving a wide distillation range of petroleum hydrocarbons (gasoline to waste oil) and in a variety of site soils (clay to sandy gravel). Application of the density-driven convection method is detailed in a case study. The system, installed to remediate a gasoline and diesel release from an underground storage tank, was operated and monitored for a period of one year. Monitoring data indicate reductions in total petroleum hydrocarbon concentrations in groundwater and in soil. Concentrations of aromatic hydrocarbons (benzene, toluene, ethylbenzene, xylenes, and naphthalene) also decreased in both media. Stimulation of natural biodegradation, the primary mechanism of removal, occurred rapidly. Natural biological activity gradually declined over the subsequent 150 days. After one year of operation, the sparging system has achieved or is rapidly approaching the regulatory cleanup goals for both soil and groundwater, including reduction of dissolved concentrations below maximum contaminant levels established under the Safe Drinking Water Act.