Determination of Polycyclic Aromatic Compounds in Asphalt and in Corresponding Leachate Water

The environmental impact of polycyclic aromatic compounds (PACs) in asphalt (bitumen) materials is related to their availability for environmental transport and biouptake, rather than their total concentrations. This study examines six Strategic Highway Research Program (SHRP) paving asphalts and four commercial roofing asphalts. Three cleanup procedures for the neat asphalt samples are evaluated. This study reports on analyses for 29 PACs, including the EPA 16 priority pollutant PAHs and additional Persistent Bioaccumulative Toxins. These require reporting by the U.S. EPA under the Emergency Planning and Community Right-to-Know Act (EPCRA) section 313. The analytical protocol for analysis of the higher molecular weight PACs by GC/MS is reported, with inclusion of GC/MS/MS verification of some of the detectable compounds. Additionally, each asphalt was taken through a toxicity characteristic leaching procedure following U.S. EPA method SW846-1311. Results of the paving and roofing asphalts and their corresponding leachate waters are presented in this study.     

Municipal Landfill Leachate Treatment Using the Combined Action of Activated Carbon and Ozone

A municipal landfill leachate was treated only with ozone, only with activated carbon and by a combined action of activated carbon and ozone. It is shown that the best results in terms of COD (Chemical Oxygen demand) reduction, color improvement, removal of the transition metals and final sterilization of the treated water derived from the leachate can be achieved by combining the activated carbon treatment with the ozonolysis, reserving the latter as the final step of the treatment so that the water from leachate is produced completely sterilized. The COD can be brought down to less than 10% of the starting value found in the pristine leachate together with a complete removal of the transition metals and the best possible color improvement from the original brown and turbid of the pristine leachate to the water-white color of the resulting purified water.     

Equilibrium and intra-particle diffusion of stabilized landfill leachate onto micro- and meso-porous activated carbon

Stabilized landfill leachate has previously been treated with activated carbon (AC); however, information on the selectivity of AC depending upon the pore size is minimal. Isotherm and kinetic experiments were conducted using three commercially available AC products, one micro-porous and two meso-porous. Equilibrium adsorption and intra-particle diffusion of organic matter from stabilized leachate was studied. Isotherm experimental data were fitted to Langmuir, Freundlich, and Redlich-Peterson isotherm models in non-linear forms. Of the three isotherm models, the Redlich-Peterson model provided the best fit to the experimental data and showed a similar organic matter adsorption capacity (approximately 0.2 g total organic carbon (TOC) g⁻¹ AC) for both micro-porous and meso-porous AC. The organic matter effective intra-particle diffusion coefficients (D_e) in both AC types were on the order of 10⁻¹⁰ m² s⁻¹ for AC particle sizes greater than 0.5 mm. Meso-porous ACs showed slightly higher D_e compared to micro-porous AC. Rapid small-scale tests showed a maximum of 80% TOC removal from leachate by each AC investigated. Fluorescence spectroscopy showed a preferential adsorption of fulvic-type organic matter with an increase in empty bed contact time by each AC.     

Treatment of Landfill Leachates: Lapeyrouse and Satrod Case Studies

Two case studies of domestic landfill leachates are reported in order to prove the suitability of treatment lines based on biological and physicochemical processes with the aim to connect their relative effectiveness to the raw leachate composition.     

垃圾渗滤液中好氧反硝化生物脱氮的最佳条件

对垃圾渗滤液间歇曝气(曝气时DO为5.5～7 mg/L;停止时DO为1.1～5.5 mg/L),在仅有有机碳、无机氮的条件下进行好氧反硝化作用.通过正交试验确定了好氧反硝化的最佳条件为水力停留时间168 h,DO为5.5～7 mg/L,有机碳源为乙醇,当有机碳源为乙醇时C/N为10.并得出影响好氧反硝化作用因素的重要性排序依次为C/N＞水力停留时间＞有机碳源＞DO.C/N是影响好氧反硝化的主要因素,对TN去除率有高度显著的影响;水力停留时间对TN去除率有显著影响;有机碳源对TN去除率有一定影响;DO对TN去除率没有显著影响.     

Oxidation of Aged Raw Landfill Leachate with O3 Only and O3/H2O2: Treatment Efficiency and Molecular Size Distribution Analysis

An aged raw landfill leachate was taken from the equalization storage tank at Clover Bar Landfill Leachate Treatment Plant, Edmonton, Alberta, Canada. The average quality parameters of this leachate were: COD=1,090mg/L, BOD₅=39mg/L, color=1,130 TCU, NH₃-N=455mgN/L, alkalinity=4,030mg/L as CaCO₃and pH=8.30. The major fraction of this leachate was large refractory organic compounds. Ozone (O₃) only and O₃ combined with hydrogen peroxide (O₃/H₂O₂) were applied to treat this leachate, aiming at enhancing COD and color reduction and increasing its biodegradability (i.e., the ratio of BOD₅/COD). All of the O₃ only and O₃/H₂O₂ oxidation experiments were performed in a gas washing bottle equipped with a fine bubble diffuser. The used ozone dose ranged from 1.2 to 12.5g O₃/L leachate for O₃ only treatment, and 1.8 to 13.8g O₃/L leachate for O₃/H₂O₂ treatment. H₂O₂ dose for O₃/H₂O₂ treatment was 0.63g H₂O₂/L leachate. COD, BOD₅, color, NH₃-N, nitrite+nitrate, and alkalinity were measured before and after treatment. Meanwhile the molecular size distribution of the leachate, before and after treatment, was analyzed by using a high-performance liquid chromatograph (HPLC) with gel filtration column and UV detector at 254nm. The addition of H₂O₂ had an insignificant effect (at 5% significance level) on enhancing COD and color reduction. After oxidation, the maximum BOD₅ increase was about 110% for O₃/H₂O₂ treatment and about 141% for O₃ only treatment at a used ozone dose of 3.6g O₃/L leachate and 2.6g O₃/L leachate for O₃/H₂O₂ and O₃ only, respectively. As the used ozone dose increased, NH₃-N and alkalinity decreased considerably, and nitrite+nitrate increased accordingly. Treatment efficiency models, which describe the changes in COD, BOD₅/COD, NH₃-N, nitrite+nitrate, and alkalinity as functions of the used ozone dose, were developed. Statistically (at 5% significance level), the treatment efficiency models for both treatments are not different. According to the results of molecular size distribution analysis, no correlation was observed between the BOD₅ increase and oxidation by-products’ formation.     

Treatment of a sanitary landfill leachate using combined solar photo-Fenton and biological immobilized biomass reactor at a pilot scale

A solar photo-Fenton process combined with a biological nitrification and denitrification system is proposed for the decontamination of a landfill leachate in a pilot plant using photocatalytic (4.16 m² of Compound Parabolic Collectors - CPCs) and biological systems (immobilized biomass reactor). The optimum iron concentration for the photo-Fenton reaction of the leachate is 60 mg Fe²⁺ L⁻¹. The organic carbon degradation follows a first-order reaction kinetics (k = 0.020 L kJ_UV⁻¹, r₀ = 12.5 mg kJ_UV⁻¹) with a H₂O₂ consumption rate of 3.0 mmol H₂O₂ kJ_UV⁻¹. Complete removal of ammonium, nitrates and nitrites of the photo-pre-treated leachate was achieved by biological denitrification and nitrification, after previous neutralization/sedimentation of iron sludge (40 mL of iron sludge per liter of photo-treated leachate after 3 h of sedimentation). The optimum C/N ratio obtained for the denitrification reaction was 2.8 mg CH₃OH per mg N-NO₃⁻, consuming 7.9 g/8.2 mL of commercial methanol per liter of leachate. The maximum nitrification rate obtained was 68 mg N-NH₄⁺ per day, consuming 33 mmol (1.3 g) of NaOH per liter during nitrification and 27.5 mmol of H₂SO₄ per liter during denitrification. The optimal phototreatment energy estimated to reach a biodegradable effluent, considering Zahn-Wellens, respirometry and biological oxidation tests, at pilot plant scale, is 29.2 kJ_UV L⁻¹ (3.3 h of photo-Fenton at a constant solar UV power of 30 W m⁻²), consuming 90 mM of H₂O₂ when used in excess, which means almost 57% mineralization of the leachate, 57% reduction of polyphenols concentration and 86% reduction of aromatic content.     

Bench scale percolation tests on radioactive Cs-contaminated soil in Fukushima and soil modified with water-absorbing polymer agent

The reuse of removed soil generated from decontamination projects in Fukushima as a recycled material for the construction of embankments has been under consideration for the sake of reducing the volume of this soil for its final disposal. Agents containing water-absorbing polymers are used in Fukushima to modify the removed soil in order to increase the separation efficiency of foreign materials and to improve the easiness of handling. As the reuse of modified soil containing organic water-absorbing materials, such as a superabsorbent polymer, is rather rare in the geotechnical field, it necessitates an investigation into the impact of the modifying agent on the leachate quality to ensure the environmental safety of the recycling project. In this study, therefore, bench scale percolation tests were conducted to examine the changes in the leachate quality of the removed soil with and without modification by an agent containing a superabsorbent polymer. The tests lasted for more than 950 days (liquid/solid ratio of over 10). The peak ¹³⁷Cs concentration in the leachate from the removed soil was 8.6 Bq/L and the accumulated leaching ratio was 0.243 %. The leaching of ¹³⁷Cs from the modified soil decreased by 60 % after mixing the removed soil with a 3 % water-absorbing polymer agent. The leaching of K⁺ and ammonia nitrogen (NH₄⁺-N) was 40 % and 60 % lower, respectively, after the soil modification, while the accumulated amount of leaching of the dissolved organic carbon in the initial stage was 60 % higher. The total leachate amount collected from the modified soil was 4 % lower than that collected from the removed soil.     

Ammonia removal from leachate solution using natural Chinese clinoptilolite

This paper assesses the potential of natural Chinese clinoptilolite for ammonia removal from the leachate solution of sewage sludge. In batch study the effects of relevant parameters, such as contact time, initial ammonia concentration and particle size of clinoptilolite, were examined respectively. The results show that the data obtained from batch studies were fit to Langmuir and Freundlich isotherms and the Langmuir isotherms reflect more reasonable for ammonium ion uptake onto clinoptilolite; the clinoptilolite adsorption process has been proved effective, at laboratory scale, the maximum adsorption capacity of the clinoptilolite, for ammonium concentration ranging from 11.12 to 115.16 mg NH(4)-N L(-1) in leachate solution, was about 1.74 mg NH(4)-Ng(-1); the time to adsorption equilibrium was 2.5 h in leachate solution and 1.5 h more than for in NH(4)Cl synthetic solution; ammonium adsorption increased with decreasing clinoptilolite particle size; the ammonia removal capacity of clinoptilolite increased with increasing initial ammonia concentration. It is believed that as adsorption agent for NH(4)-N removal from sludge leachate, natural Chinese clinoptilolite can be feasible.     

Bearing ratio and leachate analysis of pond ash stabilized with lime and lime sludge

Recycling of industrial waste is one of the effective ways to overcome their disposal problem. Ash produced by thermal power plants and lime sludge produced by paper mills require huge disposal land and may create environmental problems such as dusting and leaching of harmful heavy metals. Stabilization of the ash can improve its engineering properties and address the environmental problems. This paper reports the laboratory test results of a Class F pond ash stabilized with lime (2%, 4%, 6% and 8% by weight) alone and in combination with lime sludge (5%, 10% and 15% by weight). The X-ray diffraction (XRD) and scanning electron micrograph (SEM) tests were also performed to identify the possible formation of crystalline phases after stabilization. The effects of lime sludge on the unsoaked and soaked bearing ratios of pond ash with different lime contents, after 7 d, 28 d and 45 d of curing, were observed. Test results indicated that the bearing ratio increased considerably up to a 4% lime content which can be taken as the optimum lime content. Further increase in lime content increased bearing ratio gradually but at a slower rate. The effect of lime sludge was more pronounced at the optimum lime content, particularly at a low curing period. Lime sludge improved the bearing ratio in soaked condition significantly. Leachate analysis of stabilized ash was performed using toxicity characteristic leaching procedure (TCLP-1311) method. The concentrations of toxic elements Zn, Cu, Cd, Ni and Cr in the stabilized mixes were lower than those in the unstabilized waste. The results indicated that the pond ash-lime-lime sludge mixes have potential application as road subbase material.