A comparison of metal attenuation in mine residue and overburden material from an abandoned copper mine

The metal attenuation capacities of secondary acid mine water precipitates is dependent upon such factors as pH, ionic strength, the presence of competing ions, and tailings mineralogy. At the abandoned Spenceville Cu mine in Nevada County, California, approximately 6800 m³ of jarosite overburden and 28,000 m³ of hematite residue are potential sources of heavy metals loading to infiltrating surface waters. A column study was performed to assess the ability of the overburden and the residue to attenuate heavy metals from acidic mine drainage. The study information was needed as part of a remedial design for the abandoned mine, and was designed to simulate a worst-case scenario to examine the plausibility of backfilling a large open pit with the waste materials. Ten pore volumes of acidic mine drainage were allowed to pass through the materials, and the column effluents were analyzed for dissolved Fe, Al, Ca, Mg, Na, K, Mn, Cu, Zn, Pb and Ni using ICP-AES. The oxidation-reduction potential (Eh) was measured with a combination PtAg/AgCl electrode and also calculated from Fe(II) and Fe(III) measurements using the Nernst equation. Ion activities in solution and saturation index (SI) values for various solid phases were calculated using the geochemical speciation model MINTEQA2, and mineralogical compositions of fine (< 2 mm) and coarse ( > 2 mm) fractions were determined by XRD. Geochemical modeling of the column effluent compositions indicate that goethite, jarosite, jurbanite and gypsum are potential solid phases that may control metal solubilities in the column effluents. Excellent agreement was observed between the measured Eh values and those calculated from the activity ratio of Fe²⁺(aq) to Fe³⁺(aq). The large attenuation capacities for Cu and Zn exhibited by the jarosite overburden also suggest that solid solution substitution plays a large role in controlling metal concentrations in the pore waters. Relatively little metal attenuation, however, was provided by the hematite residue.     

Diffusion of municipal waste contaminants in compacted lateritic soil treated with bagasse ash

Compacted clay can minimize infiltration of liquid into waste or control the release of contaminated liquids to the surrounding soils and groundwater. Compacted lateritic soil treated with up to 12 % bagasse ash and municipal solid waste (MSW) leachate sourced from a domestic waste land fill were used in diffusion test studies to access the diffusion characteristics of some inorganic species present in the municipal solid waste leachate. Diffusion set-up were prepared containing 0, 4, 8 and 12 % bagasse ash—soil mixes compacted at 2 % wet of optimum using the modified proctor effort. The set up was saturated with water for 30 days before the introduction of MSW leachate and initiation of diffusion test for another 90 days. After diffusion testing, water content within the soil column showed a decrease with depth. Diffusion test results generally showed that diffusion is an active means of transport of chemical species even at very low flow rates in the compacted soil-bagasse ash mixes, and the effective diffusion coefficient is affected by bagasse ash. The pore fluid concentration profile for the various chemical species tested showed that the compacted soil-bagasse ash mix has the capacity to attenuate Ca²⁺, Pb²⁺ and Cr³⁺ ions.     

Prediction of the long-term performance of abandoned lead zinc mine tailings in a Welsh catchment

In this study we investigated the sulphidic mine tailings from Frongoch and Grogwynion, two abandoned lead zinc mines in mid-Wales, UK. Despite falling within the same ore field the mine waste characterisation has identified differences in the tailings from the two sites. Bulk concentrations range from 10 to 52 g kg^− 1 for Pb, 1.1 to 2.9 g kg^− 1 for Zn in Grogwynion and from 1.0 to 130 g kg^− 1 for Pb, 11 to 110 g kg^− 1 for Zn in Frongoch. An experimental (European standard leaching tests TS 14429 and TS 14405) and geochemical modelling approach was used to study the leaching composition as a function of pH and liquid/solid ratio. There was little correlation between the tailings bulk metal concentrations and the leachate composition, but variations in Pb and Zn concentrations were found to be consistent with control of dissolved Pb and Zn by secondary minerals and the mechanisms of dissolution/precipitation/sorption involving them. Specifically, the Grogwynion mine tailings with near-neutral pH have predominantly lead and zinc carbonates controlling Pb and Zn solubility in the leachates, whereas the Pb and Zn concentrations in Frongoch leachates are best modelled with a surface complexation model for metal sorption to oxyhydroxides. The different speciation results in a greater sensitivity of Grogwynion tailings to acidification with a potential release of Pb in solution up to 10 times higher than in Frongoch, despite similar bulk Pb concentrations. At acid pH, Zn is similarly dissolved to a greater extent in Grogwynion than in Frongoch tailings. There was no evidence of sulphide oxidation during the batch and column leaching tests and the suitability of using these European leaching standards for the characterisation of sulphidic mine waste materials for waste management purposes has been considered.     

Temperature and pH Dependence of Some Metals Leaching from Fly Ash of Municipal Solid Waste

Abstract. Municipal solid waste combustion leads to concentration of various metals in the solid residue (fly ash) remaining after combustion. These metals pose serious environmental hazard and require proper handling and monitoring in order to control their harmful effects. Leachability of some metals from fly ash was examined in fly ash and Milli-Q water mixture (liquid-to-solid ratio, 100) under various temperature and pH conditions in the laboratory. The leaching experiments conducted for 24 hours showed that pH was generally more important than temperature in controlling the amount of metals leached out of the fly ash. However, at a given pH, rise in temperature led to different degree of (usually one to two fold) enhanced or reduced leaching of metals. Owing to amphoteric nature of oxides of Al, Cr, Pb and Zn, these metals often yielded typical pattern of increase and decrease in their concentrations with change in pH. The extent of leaching of Cr and Pb in our experiments suggests that decrease of pH to acidic range in the case of Pb and to neutral to acidic range for Cr over a long period of storage of fly ash at solid waste dumping site may facilitate leaching of these metals from fly ash, leading to contamination of groundwater to the level that exceeds beyond the level permitted by the environmental laws.     

泥水盾构隧道废弃泥浆改性固化及强度特性试验

泥水盾构隧道施工产生大量的废弃泥浆,可能带来环境污染、侵占土地等问题,影响城市的正常运转。本文以厦门市某隧道施工现场产生的废弃泥浆为研究对象,采用化学固化技术处置泥浆,测试不同影响因素（固化剂种类、固化剂掺入比、泥浆初始含水率）对改性固化后泥浆抗压强度、pH值、含水率等特性的影响,分析固化机理并解释相关现象,获取最优固化剂种类、掺入比、泥浆初始含水率。对比试验结果表明最优固化剂种类为CERSM泥浆固化剂Ⅱ,掺入比为10%,泥浆初始含水率为100%。在此基础上,本文进一步探讨改性固化后泥浆的强度特性,28 d后固化泥浆抗压强度可达1.5 MPa,是普通水泥固化泥浆强度的4倍,可用做建筑填料,解决环境污染问题,并实现废弃泥浆的资源化利用。     

Biosorption an innovative tool for bioremediation of metal-contaminated municipal solid waste leachate: optimization and mechanisms exploration

Municipal solid waste poses a risk on surrounding environment and public health, mainly because of unscientific disposal and shortage of facilities for proper handling and recycling of leachate. This research article objective is to pinpoint the indigenous fungal isolates of waste leachate samples. Therefore, we carried out biosorption of Cd²⁺ tested the applicability by applying indigenous fungal isolates. The limited number of fungal isolates was found based on their ability for biosorption of Cd²⁺ metal. The fungal strains Trichoderma sp., Aspergillus niger and Aspergillus flavus were reported as potential strains for metal exclusion ability from the leachate. Among them, the Trichoderma sp. was found as excellent fungal agent for Cd²⁺ absorption. The optimum pH was 5.5 ± 1, temperature 45 °C, and spore concentration 10^?5 to achieve the maximum biosorption, and 35 days of incubation period were required by three strains. The maximum metal biosorption achieved was comparable for the three isolates: 56.34% by Trichoderma sp., 44.74 and 42.04% by A. niger and A. flavus, respectively. Concluding, the further intending application to identified potentially fungal isolates is able to improve the efficiency of metal biosorption. These strains are recommended for development of consortia could become a best technique for MSW leachate treatment if its reliability and applicability should be verified prior to technology acceptance.     

A study of factors affecting on the zeta potential of kaolinite and quartz powder

The purpose of this study was to determine the effects of pH, ion type (salt and metal cations), ionic strength, cation valence, hydrated ionic radius, and solid concentration on the zeta potential of kaolinite and quartz powder in the presence of NaCl, KCl, CaCl₂, CuCl₂, BaCl₂, and AlCl₃ solutions. The kaolinite and quartz powder have no isoelectric point (iep) within the entire pH range (3 < pH < 11). In the presence of hydrolysable metal ions, kaolinite and quartz powder have two ieps. As the cationic valence increases, the zeta potential of kaolinite and quartz powder becomes less negative. Monovalent cation, K⁺, yields more negative zeta potential values than the divalent cation Ba²⁺. As concentration of solid increases, the zeta potential of the minerals becomes more positive under acidic conditions; however, under alkaline conditions as solid concentration increases the zeta potential becomes more negative. Hydrated ionic radius also affects the zeta potential; the larger the ion, the thicker the layer and the more negative zeta potential for both kaolinite and quartz powder.     

电感耦合等离子体串联质谱法测定电解二氧化锰废渣浸出液中的重金属元素

电解二氧化锰废渣中的重金属元素在雨水淋滤下,通过地表径流对下游水生态系统及农业生态系统造成不同程度的环境污染和安全隐患,因此,准确测定电解二氧化锰废渣浸出液中的重金属元素含量具有重要的现实意义。电解二氧化锰废渣浸出液中的重金属元素含量通常很低,采用原子吸收光谱法、电感耦合等离子体发射光谱法测定,检出限通常难以满足测定要求。采用电感耦合等离子体质谱法(ICP-MS)测定,消除复杂质谱干扰面临挑战。本文采用电感耦合等离子体串联质谱(ICP-MS/MS)测定电解二氧化锰废渣浸出液中的重金属元素含量。电解二氧化锰废渣中6种重金属元素Cr、Ni、As、Cd、Hg、Pb经硫酸和硝酸混合酸浸出后直接采用ICP-MS/MS进行测定,利用串联质谱的O_2反应模式消除分析过程中Cr、Ni、As、Cd受到的质谱干扰,通过考察不同分析模式下~(52)Cr、~(60)Ni、~(75)As、~(111)Cd的背景等效浓度(BEC),评价质谱干扰对分析结果的影响。结果表明:在MS/MS模式下选择O_2为反应气,采用质量转移法和原位质量法可以消除~(52)Cr、~(60)Ni、~(75)As、~(111)Cd的所有质谱干扰。Cr、Ni、As、Cd、Hg、Pb检出限分别为3.06、9.31、3.50、2.72、2.03、1.89ng/L,加标回收率在95.6%～106.2%之间,相对标准偏差(RSD)≤3.9%。所建立的方法已应用于电解二氧化锰废渣浸出液中重金属元素的测定。     

Effect of multifactors interaction on competitive adsorption of Zn<Superscript>2+</Superscript> and Cd<Superscript>2+</Superscript> by response surface methodology

The problem associated with multi-metals contaminated soils has generated increasingly more attention. Thus, it is necessary within the field to study the mutual influence of environmental factors on competitive adsorption. The majority of studies carried out to date have concentrated on the variation of adsorption capacity or the removal efficiency, with only a single factor changed (including pH, ionic strength, and metal concentration). However, the interaction effect among various environmental factors was ignored in these studies. The purpose of this study was mainly aimed toward the investigation of the interaction of two influential factors, as well as the influential degree of each factor (such as the initial pH, ionic strength, initial metal concentration, and the competitive metal concentration) on competitive adsorption using the response surface method. These results demonstrated that the influential degree of each factor studied on the competitive adsorption of Zn²⁺ and Cd²⁺ followed the trend of having the initial concentration of the target metal?>?initial pH?>?concentration of competitive metal?>?ionic strength. When the metal concentration was held constant, we found that the competitive adsorption of Zn²⁺ initially increased, followed by a decrease with increasing initial pH. However, this was found to change minimally with increasing ionic strength. When the initial pH or ionic strength was held constant, the competitive ability was observed to increase with increasing Zn²⁺ concentration. However, with increasing Zn²⁺ or Cd²⁺ concentrations, the variation degree of the competitive adsorption was found to become smaller. These results provide novel information toward a better understanding of the effect of multifactors on the competitive adsorption of Zn²⁺ and Cd²⁺.     

重金属作用下改性水泥系隔离墙化学相容性研究

水泥系隔离墙被广泛应用于工业污染场地修复工程,但其防渗性能有待改善,且在高浓度、毒理性重金属污染作用下的化学相容性有待研究。通过室内试验研究了不同粒化高炉矿渣（GGBS）掺量、膨润土掺量和固化剂总掺量对水泥系隔离墙的强度和渗透特性的影响;综合考虑成墙效果和成本,选出固化剂掺量为20%（水泥、粒化高炉矿渣和膨润土掺量分别为8%、8%和4%）作为改性水泥系竖向隔离墙的最优配比。通过柔性壁渗透试验研究了重金属锌、铅污染作用下改性水泥系隔离墙试样的化学相容性。结果表明,重金属溶液作用下试样防渗性能的下降由重金属种类、重金属浓度以及试样孔隙液pH值三者共同决定。重金属种类对防渗性能的不利影响为：硝酸锌-硝酸铅>硝酸锌>硝酸铅。锌、铅溶液作用下试样的渗透系数为自来水作用下渗透系数的1.49～10.10倍,且重金属溶液的浓度越高渗透系数越大。在满足防渗要求前提下,该配比墙体材料能阻挡50 mmol/L的硝酸锌污染液、100 mmol/L的硝酸铅污染液和10 mmol/L硝酸锌-硝酸铅污染液。     

Response surface methodology for lead biosorption on Aspergillus terreus

A central composite face-centered design was used to study and to optimize lead biosorption from aqueous solution on Aspergillus terreus biomass. Four factors such as stirring speed, temperature, solution pH and biomass dose at different levels were studied.The hierarchical quadratic model were established by adding replicates at the central point and axial points to the initial full factorial design (2⁴). The percentage removal of lead was affected by biomass dose, pH, and interactions between pH and biomass dose, pH and stirring speed, pH and temperature. The hierarchical quadratic model described adequately the response surface based on the adjusted determination coefficient (R² _Adj= 0.97) and the adequate precision ratio (42.21). According to this model, the optimal conditions to remove lead completely from aqueous solutions (at initial lead concentration of 50 mg/L and solutions of 100 mL) with Aspergillus terreus were at pH 5.2, 50 °C, stirring speed of 102/min and a biomass dose of 139 mg.The response surface methodology can be used to determine the optimal conditions for metal adsorption on several adsorbents. In addition, results reported in this research demonstrated the feasibility of employing A. terreus as biosorbent for lead removal.     

The Diavik Waste Rock Project: Geochemical and microbiological characterization of low sulfide content large-scale waste rock test piles

Two experimental waste-rock piles (test piles), each 15 m in height × 60 m × 50 m, were constructed at the Diavik diamond mine in Northern Canada to study the behavior of low-sulfide content waste rock, with a similarly low acid-neutralization potential, in a continuous permafrost region. One test pile with an average of 0.035 wt.% S (<50 mm fraction; referred to as Type I) and a second test pile with an average of 0.053 wt.% S (<50 mm fraction; referred to as Type III) were constructed in 2006. The average carbon content in the <50 mm fraction of waste rock in the Type I test pile was 0.031 wt.% as C and in the Type III test pile was 0.030 wt.% as C. The NP:AP ratio, based on the arithmetic mean of particle-size weighted NP and AP values, for the Type I test pile was 12.2, suggesting this test pile was non-acid generating and for the Type III test pile was 2.2, suggesting an uncertain acid-generating potential. The Type I test pile maintained near-neutral pH for the 4-year duration of the study. Sulfate and dissolved metal concentrations were low, with the exception of Ni, Zn, Cd, and Co in the fourth year following construction. The pore water in the Type III test pile contained higher concentrations of SO₄²⁻ and dissolved metals, with a decrease in pH to <4.7 and an annual depletion of alkalinity. Maximum concentrations of dissolved metals (20 mg L⁻¹ Ni, 2.3 mg L⁻¹ Cu, 3.7 mg L⁻¹ Zn, 35 μg L⁻¹ Cd, and 3.8 mg L⁻¹ Co) corresponded to decreases in flow rate, which were observed at the end of each field season when the contribution of the total outflow from the central portion of the test pile was greatest. Bacteria were present each year in spite of annual freeze/thaw cycles. The microbial community within the Type I test pile included a population of neutrophilic S-oxidizing bacteria. Each year, changes in the water quality of the Type III test-pile effluent were accompanied by changes in the microbial populations. Populations of acidophilic S-oxidizing bacteria and Fe-oxidizing bacteria became more abundant as the pH decreased and internal test pile temperatures increased. Irrespective of the cold-climate conditions and low S content of the waste rock, the geochemical and microbiological results of this study are consistent with other acid mine drainage studies; indicating that a series of mineral dissolution–precipitation reactions controls pH and metal mobility, and transport is controlled by matrix-dominated flow and internal temperatures.     

废泥浆固液分离的正交试验研究

运用正交设计原理,通过具有代表性的试验,研究分析了各因素对泥浆固发离效果的影响,结果表明,影响混凝析主次因素为：混凝剂浓度、加量、搅拌时间。并指出混凝剂选择的方法和应注意的问题,以供工程参考。     

Growth and Cu accumulation by plants grown on Cu containing mine tailings in Cyprus

The Skouriotissa Cu mine in the northern part of Cyprus has produced large amounts of mine waste. Phytoremediation could stabilise the erosion or extract the metals of this waste. The aim of this study was to find out if Pistacia terebinthus, Cistus creticus, Pinus brutia and/or Bosea cypria could grow and tolerate or maybe accumulate Cu from the mine waste containing up to 787 mg Cu (kg DW)⁻¹. Another aim was to see if the liquid wine waste product Vinassa, containing organic acids and having a low pH, or chicken fertilizer could improve plant growth and/or Cu accumulation. The four species were planted at the mine waste site untreated or with the addition of Vinassa or chicken fertilizer as mine waste modifiers. After 3 months, shoot length growth was measured and the plants were analysed for Cu concentration. The pH and Cu concentration of the mine waste mixture in the different treatments was also measured. To find out if plants accumulated Cu to the highest extent in roots or shoot, a greenhouse study was undertaken where the plant species were cultivated for 3 weeks in Cu spiked soil. The results showed that all of the tested species survived and grew on the mine waste site, which indicates that they tolerate the high level of Cu at the mine waste site. The leaves of C. creticus had the highest Cu accumulation of all tested species. Copper accumulation varied with plant species. They seemed to have different distribution strategies for Cu: in Pistacia terebinthus and C. creticus most of the Cu was found in the roots, while B. cypria accumulated most of the Cu in the leaves. Addition of Vinassa and chicken fertilizer did not increase plant growth or Cu accumulation, but did affect the Cu distribution in B. cypria.     

Application of a novel definitive screening design to decolorization of an azo dye on boron-doped diamond electrodes

The electrochemical decolorization of the Reactive Violet 5 azo dye on a boron-doped diamond anode was used as a model process to test a novel definitive screening design (DSD). This method allows a dramatic reduction in the number of experiments needed to investigate those systems characterized by a large number of variables. In this study, the effect of nine quantitative parameters was investigated: initial dye concentration (60–120 mg L^?1), current density (100–500 A m^?2), NaCl concentration (5–20 mM), Na₂SO₄ concentration (35–65 mM), pH (3–11), temperature (20–45 °C), inter-electrode distance (0.5–3.5 cm), stirring rate (250–750 rpm) and electrolysis time (2–8 min). Analysis of DSD data showed that four out of the nine factors (initial dye concentration, current density, pH and electrolysis time) were statistically significant. These factors were retained for process characterization using a subsequent central composite design. Overall, the number of experiments was reduced from over 500 to only 41, thus confirming the validity of the proposed approach as a time-saving and efficient method.     

Adsorption of copper and cobalt from fresh and marine systems

The adsorption of copper and cobalt from aqueous solution on to illite and other substrates has been studied as a function of pH, solution composition and solid phase concentration. The results are interpreted in terms of a model whereby the trace metals are adsorbed in exchange for surface bound H⁺ ions. Adsorption varies with solution ionic strength and the concentrations of complex forming ligands; both of these parameters tend to reduce the trace metal adsorption. The Cu²⁺ is two orders of magnitude more reactive toward solid surfaces than Co²⁺ , which is consistent with the general reactivities of these two metal ions. It is also found that Mg₂₊ interferes with adsorption, presumably by competing with the trace metals for the surface sites. A quantitative model was developed which describes adsorption of these metals from natural waters ranging from river water to sea water as a function of pH, complexing ligands and magnesium activity.     

Solubility relationships of aluminum and iron minerals associated with acid mine drainage

The ability to properly manage the oxidation of pyritic minerals and associated acid mine drainage is dependent upon understanding the chemistry of the disposal environment. One accepted disposal method is placing pyritic-containing materials in the groundwater environment. The objective of this study was to examine solubility relationships of Al and Fe minerals associated with pyritic waste disposed in a low leaching aerobic saturated environment. Two eastern oil shales were used in this oxidizing equilibration study, a New Albany Shale (unweathered, 4.6 percent pyrite), and a Chattanooga Shale (weathered, 1.5 percent pyrite). Oil shale samples were equilibrated with distilled-deionized water from 1 to 180 d with a 1∶1 solid-to-solution ratio. The suspensions were filtered and the clear filtrates were analyzed for total cations and anions. Ion activities were calculated from total concentrations. Below pH 6.0, depending upon SO ₄ ²⁻ activity, Al³⁺ solubility was controlled by AlOHSO₄ (solid phase) for both shales. Initially, Al³⁺ solubility for the New Albany Shale showed equilibrium with amorphous Al(OH)₃. The pH decreased with time, and Al³⁺ solubility approached equilibrium with AlOHSO_4(s). Below pH 6.0, Fe³⁺ solubility appeared to be regulated by a basic iron sulfate solid phase with the stoichiometric composition of FeOHSO_4(s). The results of this study indicate that below pH 6.0, Al³⁺ solubilities, are limited by basic Al and Fe sulfate solid phases (AlOHSO_4(s) and FeHSO_4(s)). The results from this study further indicate that the acidity in oil shale waters is produced from the hydrolysis of Al³⁺ and Fe³⁺ activities in solution. These results indicate a fundamental change in the stoichiometric equations used to predict acidity from iron sulfide oxidation. The results of this study also indicate that water quality predictions associated with acid mine drainage can be based on fundamental thermodynamic relationships. As a result, waste management decisions can be based on waste-specific/site-specific test methods.     

Applications on agricultural and forest waste adsorbents for the removal of lead (II) from contaminated waters

At present, there is growing interest in using low cost, commercially available materials for the adsorption of heavy metals. The major advantages of adsorption technologies are its effectiveness in reducing the concentration of heavy metal ions to very low levels and the use of inexpensive adsorbent materials. In this review, agricultural and forest waste adsorbents were used to remove Pb²⁺ ions in wastewater treatment, and their technical feasibilities were reviewed in studies mainly from 2000 to 2010. They all were compared with each other by metal binding capacities, metal removal performances, sorbent dose, optimum pH, temperature, initial concentration and contact time. Although commercial activated carbon is widely used in wastewater treatment applications, it has high costs. The use of agricultural by-products as adsorbent material to purify heavy metal contaminated water has become increasingly popular through the past decade because they are less expensive, biodegradable, abundant and efficient. Instead of activated carbon, this study was focused on the inexpensive materials such as agricultural and forest waste. It was shown that these alternative adsorbents had sufficient binding capacity to remove Pb²⁺ ions from wastewater.     

Removal of hazardous hexavalent chromium from aqueous solution using divinylbenzene copolymer resin

This paper presents the removal of hazardous hexavalent chromium from liquid waste streams using divinylbenzene copolymer resin Amberlite IRA 96. Important sorption parameters such as contact time, pH, resin dosage and initial metal concentration were studied at 30?°C. The kinetic study was conducted using pseudo-first and pseudo-second-order kinetics at 30?°C. The sorption process was found to be pH dependent. Maximum removal was obtained at pH 2 under optimized conditions. The sorption process was rapid and 99?% of the removal was achieved in first 30?min. The equilibrium data were fitted to both Langmuir and Freundlich models. The better regression coefficient (R ²) in Freundlich model suggests the multilayer sorption process. The value of Gibbs free energy for sorption process was found to be ?12.394?kJmol^?1. The negative value indicated the spontaneity of the sorption process. Scanning electron microscope and energy dispersive X-ray spectroscopy studies were conducted to find the role of surface morphology during sorption process. The Fourier transform infrared study was conducted to identify the functional groups responsible for interaction between the resin and chromium. Desorption and regeneration studies were also carried out.     

Application of the Haug model for process design of petroleum hydrocarbon-contaminated soil bioremediation by composting process

The main scope of this work is applying an aerobic composting model for remediation of petroleum hydrocarbon-contaminated soil. For this purpose, the reaction kinetics was integrated with the mass and energy balances over the composting system. Literature pilot scale data for bioremediation of diesel oil-contaminated soil was used for model validation. Comparisons of simulation results with experimental data for diesel concentration and oxygen concentration showed good agreement during the remediation process. With validated model for bioremediation of diesel oil-contaminated soil, the influence of amendment type, bulking agent, amendment/soil ratio, bulking agent/soil ratio, moisture content and airflow rate were investigated on diesel biodegradation. The simulation results showed that maximum degradation of diesel occurred in the presence of yard waste as amendment. Furthermore, addition of bulking agent (wood chips) increased the diesel degradation about 6 %. In presence of yard waste as amendment and wood chips as bulking agent, the optimal values for maximum remediation were amendment/soil ratio (2.5 kg kg^?1), bulking agent/soil ratio (2.25 kg kg^?1), initial moisture content (62.5 %) and airflow (0.520 m³ day^?1 kgBVS^?1).