Hazardous Waste Landfill Leachate Research Articles

PAHs remediation from hazardous waste landfill leachate using fenton, photo – fenton and electro - fenton oxidation processes – performance evaluation under optimized conditions using RSM and ANN

Polycyclic aromatic hydrocharbons (PAHs) are a class of highly toxic pollutants that are highly detrimental to the ecosystem. Landfill leechate emanated from municipal solid waste are reported to constitute significant PAHs. In the present investigation, three Fenton proceses, namely conventional Fenton, photo-fenton and electro-fenton methods have been employed to treat landfill leehcate for removing PAHs from a waste dumpig yard. Response surface methodology (RSM) and artificial neural network (ANN) methodologies were adopted to optimize and validate the conditions for optimum oxidative removal of COD and PAHs. The statistical analysis results showed that all independent variables chosen in the study are reported to have significant influence of the removal effects with P-values <0.05. Sensitivity analysis by the developed ANN model showed that the pH had the highest significance of 1.89 in PAH removal when compared to the other parameters. However for COD removal, H2O2 had the highest relative importance of 1.15, followed by Fe2+ and pH. Under optimal treatment conditions, the photo-fenton and electro-fenton processes showed better removal of COD and PAH compared to the Fenton process. The photo-fenton and electro-fenton treatment processes removed 85.32% and 74.64% of COD and 93.25% and 81.65% of PAHs, respectively. Also the investigations revelaed the presence of 16 distinct PAH compunds and the removal percentage of each of these PAHs are also reported. The PAH treatment research studies are generally limited to the assay of removal of PAH and COD levels. In the present investigation, in addition to the treatment of landfill leachate, particle size distribution analysis and elemental characterization of the resultant iron sludge by FESEM and EDX are reported. It was revealed that elemental oxygen is present in highest percentage, followed by iron, sulphur, sodium, chlorine, carbon and potassium. However, iron percentage can be reduced by treating the Fenton-treated sample with NaOH.

An approach to quantify the contamination potential of hazardous waste landfill leachate using the leachate pollution index

An approach to quantify the contamination potential of hazardous waste landfill leachate using the leachate pollution index

Using a Mathematical Model with a Calibration Parameter Determination Method for Predicting Concentrations in Hazardous Waste Landfill Leachate, and Verifications by Column Leaching Tests

本研究では廃棄物埋立層からの浸出水濃度を予測するための数理モデル構築とそのモデル検証を行なった。特に予測が難しいと考えられる高濃度の化学物質を含有する特別管理産業廃棄物を対象に検討した。数理モデルは，シリアルバッチ溶出試験の結果を溶出モデルとして加えた移流分散方程式である。本法の課題の一つは，シリアルバッチ溶出試験が液固比 10 での評価であるのに対して，予測対象となる埋立層ではより低い液固比での溶出挙動であり，それをどのように数理モデルに反映させるのかである。本研究では，実用面に優れたモデル構築と高精度化を図るため，液固比を変えたバッチ溶出試験を行い，低液固比での実測値と予測値の差異を調べることで溶出モデルに与える補正係数を導出した。補正係数を用いた数理モデルの有効性を明らかにするためにカラム溶出試験を実施したところ，アルカリ金属とアルカリ土類金属には高精度な予測を与えることがわかった。

Synergistic optimization of electrocoagulation process parameters using response surface methodology for treatment of hazardous waste landfill leachate

Leachate treatment is an essential and integral part of solid waste management system, and its efficient treatment becomes more crucial when the leachate is produced from industrial or hazardous waste landfills (HWLs), as it is multi-fold more toxic than the leachate produced from municipal solid waste landfills (MSWLs). Electrocoagulation has appeared to be a promising technology for treating complex wastewater including MSWL leachate, but specific treatability studies dedicated to HWL leachate are rarely available, and thus pose a demand for fundamental and advance research in this area to bridge the existing gap. The current study delves into systematic design of experiments to check the treatability of HWL leachate through electrocoagulation, considering reduction (maximum) in chemical oxygen demand (COD) as a response variable. Response Surface Methodology (RSM) was used for design of experiments and process optimization and three-dimensional surface response was also created to understand the relationship among process parameters and response variables. After extensive experimental trials and data analysis, it was observed that electrocoagulation can be used as a potential treatment technology for leachate with Galvanized Iron (GI) as preferable electrode material and it resulted up to 90% reduction in COD under optimized condition. Significant reduction in other parameters was also observed with a removal efficiency of 58.1%, 63.6%, 42.4%, 52.5%, 54.7% and 84% for cadmium, zinc, phenolic compounds, lead, TOC, and colour, respectively. The results showed that Electrocoagulation can be used as a replacement of currently practised energy extensive treatment technologies like multiple effect evaporators, which are used by landfill operators for managing their HWL leachate. The methodology and results from this research may be utilized by the researchers and operators of HWL landfills to decide the treatment trail for HWL leachate.

Reduction of chemical oxygen demand through electrocoagulation: an exclusive study for hazardous waste landfill leachate.

Leachate produced from hazardous waste landfills has been observed to exhibit very complex characteristics including the presence of a high amount of refractory organics and toxic elements which make it unfit for conventional treatment. This study is focused on the characterization and treatability of "hazardous waste landfill leachate" through electrocoagulation for the reduction of chemical oxygen demand (COD). Effect of different operating parameters, such as electrode material, interelectrode distance (IED), current density (CD), and electrolysis time (ET), has also been studied. For galvanized iron (GI) electrodes, a significant reduction in phenolic compounds, cadmium, lead, and zinc concentration was observed and more than 80% reduction in COD and color was achieved on a bench-scale reactor for a CD value of 41.64 A/cm2 at IED of 1.5 cm and for ET equating to 240 min. Substantiated by experimental results and statistical analysis like ANOVA and post hoc analysis, it appears that electrocoagulation is a proficient technology for the treatment of hazardous waste landfill leachate which has a huge potential for further research.

Characterisation of Hazardous Waste Landfill Leachate and its Reliance on Landfill Age and Seasonal Variation: A Statistical Approach

Leachate generated due to disposal industrial solid waste into common hazardous waste landfills (HWLs), has high potential to contaminate nearby soil and groundwater and hence its catchment and treatment are crucial for sustainable solid waste management. This research is emphasised on creating an extensive data set generated from analysing three hazardous waste landfills of age 2-year, 11-year and 20-year for a duration of one year to characterise the leachate and to create an in-depth understanding about the effect of landfill age and seasonal variation on leachate characteristics. Results in the form of descriptive statistics showed the simultaneous occurrence of high chemical oxygen demand (COD) (up to 35,000 mg/l) and high concentration of total dissolved solids (TDS) (up to 3,00,000 mg/l), ammoniacal nitrogen (up to 2300 mg/l) and heavy metals. Statistical analysis through ANOVA and Post Hoc analysis indicated that the age of landfill significantly affects the leachate characteristics and for most of the parameters, the concentrations were found to increase till middle age and then subside towards maturity of landfill. In contrast to this, for seasonal variation, less significant influence was observed on the leachate characteristics. Although the concentration of different parameters was found to vary every month, no specific pattern or effect on seasonal variation could be traced from the data.

Photo-Fenton process for removal of polycyclic aromatic hydrocarbons from hazardous waste landfill leachate

Polycyclic aromatic hydrocarbons (PAHs) are the toxic and persistent micro-pollutants recalcitrant to biodegradation. Photo-Fenton process is a commonly adopted advanced oxidation process. Advanced oxidation processes generate highly reactive hydroxyl radicals (OH·) which completely mineralise the organic contaminants. This study aims to find the efficiency of photo-Fenton oxidation process in the removal of PAHs and COD from landfill leachate, and investigate its effect on 16 PAHs according to their number of aromatic rings. Experiments were designed using central composite design, a module of response surface methodology (RSM) in the Design-Expert software. pH, Fe2+ concentration, H2O2 concentration, reaction time and UV intensity were the five experimental variables which were optimised and modeled successfully. The statistical analysis proved that all the variables have significant effect on the model. The value of R2 (0.94) showed a high reliability in the estimation of chemical oxygen demand and polycyclic aromatic hydrocarbons removal efficiency. Optimum experimental conditions of pH 6.5, Fe2+ 1.1 g/L, H2O2 concentration 5.5 g/L, reaction time 40 min and UV intensity 13.5 W resulted in the maximum chemical oxygen demand and polycyclic aromatic hydrocarbons removal efficiency of 84.43% and 92.54%, respectively. Validation was carried out by conducting additional set of experiments, and the small gap between observed and predicted values confirmed that central composite design is the effective tool to optimise the photo-Fenton oxidation process in the degradation of chemical oxygen demand and polycyclic aromatic hydrocarbons.

Characterization of solidification for disposal of hazardous waste landfill leachate.

Hazardous waste landfill leachate (HWLL) with high concentrations of salt and pollutants has created a bottleneck at hazardous waste landfills. This study applied a cement-based curing method to the disposal of HWLL. The highest contaminant fixing rate was achieved by adjusting the composition and proportion of the curing base, the content of additives, and the liquid-solid (L/S) ratio of the leachate to the curing base. The fixing rates for chemical oxygen demand and salt content in HWLL reached the highest values of 95.1% and 86.1%, respectively, when the Portland cement to metakaolin ratio was 3:2; the L/S was 1; and diatomite and activated carbon were added at 0.5% and 0.25%, respectively. The addition of glass fiber to the curing base improved the crack resistance of the solidified product. A simulated landfill experiment further indicated that after 116days of leaching, the leachate effluent pollutant concentrations of the landfill column were lower than the effluent standard. Solidification is a feasible method for HWLL disposal.

Treatment of a pesticide industry wastewater mixture in a moving bed biofilm reactor followed by conventional and membrane processes for water reuse

The treatment of an industrial wastewater (Efmix) composed of sanitary wastewater (91.5%), pretreated wastewater from pesticide production (3.8%) and hazardous waste landfill leachate (4.7%) was investigated in a moving bed biofilm reactor (MBBR) at a hydraulic retention time of 6 h. Treated effluent was then mixed with surface water (EfMBBR + SW) in a 1:9 volumetric ratio and physicochemical processes (coagulation/flocculation, sedimentation, rapid sand filtration and cartridge filter) were applied in lab-scale to reproduce the industrial water treatment plant and verify the efficiency of the combined process for wastewater reclamation. During the 90 days of operation, the moving bed biofilm reactor was efficient and stable regarding the removal of organic matter (64–89% in terms of chemical oxygen demand) and ammonium nitrogen (89–98%). Even with a fluctuating inlet chemical oxygen demand (230–721 mg/L), values below 100 mg/L were always achieved after biological treatment. Ammonium nitrogen (1.3 ± 0.6 mg NH4+-N/L) and nitrate (20 ± 4 mg NO3⁻-N/L) concentrations in treated wastewater showed that nitrification took place without inhibition throughout the bioreactor operation. Advanced treatment results indicated that a microfiltration or ultrafiltration unit must be coupled to the existing conventional reverse osmosis pretreatment in the water treatment plant in order to improve water quality concerning SDI15, turbidity and color, and thus allow for total reclamation of the industrial complex wastewater. An integrated conventional-microfiltration/ultrafiltration system could achieve high turbidity (99.9%) and apparent color (96.7%) removal to produce high quality water for reverse osmosis, minimizing membrane fouling problems and, consequently, the operational costs.

Treatment of hazardous waste landfill leachate using Fenton oxidation process

The efficiency of Fenton’s oxidation was assessed in this study for hazardous waste landfill leachate treatment. The two major reagents, which are generally employed in Fenton’s process are H2O2 as oxidizing agent and Fe2+ as catalyst. Batch experiments were conducted to determine the effect of experimental conditions viz., reaction time, molar ratio, and Fenton reagent dosages, which are significant parameters that influence the degradation efficiencies of Fenton process were examined. It was found that under the favorable experimental conditions, maximum COD removal was 56.49%. The optimum experimental conditions were pH=3, H2O2/Fe2+ molar ratio = 3 and reaction time = 150 minutes. The optimal amount of hydrogen peroxide and iron were 0.12 mol/L and 0.04 mol/L respectively. High dosages of H2O2 and iron resulted in scavenging effects on OH• radicals and lowered degradation efficiency of organic compounds in the hazardous waste landfill leachate.

Combination and performance of forward osmosis and membrane distillation (FO-MD) for treatment of high salinity landfill leachate

Abstract Forward osmosis (FO) was combined with membrane distillation (MD) to treat high salinity hazardous waste landfill leachate. Response surface methodology (RSM) was used to optimize the operating conditions of the FO process by maximizing water flux and removal efficiency of pollutants and minimizing the salt reverse flux. Flow rate of FS (feed solution), flow rate of DS (draw solution) and the concentration of DS were selected as independent variables for incorporation in the Box-Behnken design. Results showed that optimal FS flow rate, DS flow rate and DS concentration for FO stage were 0.87 L/min, 0.31 L/min and 4.82 M, respectively. The optimal temperatures of inlet solution in MD stage were 72.5 ± 0.5 °C and 62.5 ± 0.5 °C when salt concentrations in FS were 25,000 mg/L and 60,000 mg/L (calculated as NaCl). Salt rejection rates were higher than 96% while rejection rates of TOC and TN were higher than 98%. NH 4 + -N, Hg, As and Sb were completely removed. The results proved optimized FO-MD combined system was a suitable process to treat high salinity hazardous wastewater.

Utilization of Waste Clay from Boron Production in Bituminous Geosynthetic Barrier (GBR-B) Production as Landfill Liner

Bituminous geomembranes, one type of geosynthetics, include a hot bituminous mixture with mineral filler and reinforcement. In this study, boron production waste clay (CW) was used as filler to produce a geosynthetic barrier with bentonite, waste tire, and bitumen. Bentonite and waste tires were used as auxiliary fillers and bitumen as the binder. CW/bitumen, CW/bentonite/bitumen, and CW/waste tire/bitumen mixtures were prepared by using a laboratory mixer at 100°C. Hot mixtures were extruded into strips by using a lab-scale corotating twin screw extruder (L/D: 40) followed by die casting (2 mm × 100 mm). Glass fleece or nonwoven polyester was used as reinforcement material and while die casting, both sides of the reinforcement materials were covered with bituminous mixture. Thickness, mass per unit area, tensile strength, elongation at yield, and hydraulic conductivity were used to characterize the geomembranes. Among all geomembranes, nonwoven polyester covered with 30% bitumen-70% boron waste clay mixture (PK-BTM30CW70) was found to be the most promising in terms of structure and mechanical behaviour. After that, consequences of its exposure to distilled water (DW), municipal solid waste landfill leachate (L-MSW), and hazardous waste landfill leachate (L-HW) were examined to use for an innovative impermeable liner on solid waste landfills.

Hazardous waste landfill leachate treatment by combined chemical and biological techniques

The efficacies of coagulation, ozonation, Fenton treatment, activated sludge process, Fenton treatment–activated sludge process (CHEM-BIO) and activated sludge process–Fenton treatment (BIO-CHEM) to treat hazardous waste landfill leachate were investigated and compared. The results of the biodegradability test revealed a high content of readily biodegradable organic matter in semicoke landfill leachate, and thus, aerobic biological oxidation was found to be a more reasonable and cost-effective technique for leachate treatment than direct chemical processes (ozonation, Fenton treatment). However, in terms of treatment efficacy, both chemical and biological processes resulted in a high residual organic load, indicating an insufficient leachate quality improvement. The treatment performance of the combined schemes (BIO-CHEM and CHEM-BIO) proved more effective and ensured the removal efficacy percentage met that required by EU legislation as well as the specific target discharge limits of the measured parameters. Accounting for the treatment cost-effectiveness, BIO-CHEM proved to be a more feasible option and could be suggested as the most efficient and practicable technological scheme for hazardous waste landfill leachate treatment.

The effect of humic acids on the reverse osmosis treatment of hazardous landfill leachate

This study deals with the treatment of hazardous waste landfill leachate with the help of reverse osmosis. The landfill is located in an abandoned brown coal pit in northern Bohemia. The leachate contained 7.2g/L of dissolved inorganic salts. Among other contaminants were heavy metals, arsenic, ammonia nitrogen and associated organic pollutants, especially chlorinated compounds. A mobile membrane unit (LAB M30) equipped with a spiral wound element (FILMTEC SW30-4040), with a membrane area equaling 7.4m2 was used for the pilot plant experiments. All experiments were carried out in batch mode. 94% conversion of the input stream into the permeate was achieved by use of a two-stage arrangement. Removal efficiencies of the monitored contaminants in the feed ranged from 94% for ammonia nitrogen to 99% for the two-valent ions. Removal efficiency for total dissolved solids was 99.3% on average.Due to varying levels of humic acids in the leachate throughout the year, fouling experiments were performed to investigate the separation process under different conditions than those used in the pilot plant. Leachates containing different concentrations of added humic acids were separated using a thin film composite on a propylene membrane. The added humic acids were obtained from samples of contaminated oxihumolite.

Bisphenol A removal by the Dracaena plant and the role of plant-associating bacteria

Dracaena sanderiana and Dracaena fragrans plants, as representatives of native, tropical, evergreen plants with fibrous root systems, were evaluated for bisphenol A (BPA) tolerance and uptake capability. D. sanderiana demonstrated significantly higher BPA removal capability than D. fragrans. Therefore, it was chosen for further study. D. sanderiana tolerated BPA toxicity levels up to 80 microM, while higher BPA concentrations damaged the plant. In the sterile hydroponic system with an initial BPA concentration of 20 microM, the plant could uptake approximately 50% of the BPA. The plant's ability to translocate BPA was confirmed by the detection of BPA that accumulated at the roots and stems, but not at the leaves of the plant. Upon BPA exposure, the D. sanderiana secreted extracellular plant mucilage as a protective barrier to the toxic compound. In the non-sterile treatment, the BPA dissipation was contributed not only by the D. sanderiana plant, but also by the co-existing microbes. The BPA reached 85% of the initial concentration at 20 microM. Among the six plant-associating bacterial isolates, Bacillus cereus strain BPW4 and Enterobacter sp. strain BPW5 colonized the D. sanderiana root surface and facilitated BPA dissipation in the hydroponic treatment system. In addition, the success of the BPA treatment in the hazardous waste landfill leachate demonstrated the potential application of D. sanderiana plant in the phytoremediation of BPA contaminated wastewater or industrial leachate.

Hazardous waste landfill leachate treatment using an activated sludge-membrane system

This research was aimed to investigate the capability of a combined system of activated sludge and microfiltration processes with backflushing technique to reduce organic carbon and nitrogen compounds in hazardous landfill leachates. The experiments included acclimation, batch and continuous processes. The continuous process was conducted with a 24 hour HRT (Hydraulic Retention Time), and the SRT (Solid Retention Time) ranged from 16 to 36 days. The aeration basin volume was 5 L and the membrane filter used was a hollow fiber module made from polypropylene with pore size of 0.2 microm. The batch process (without membrane separation) achieved its steady state condition over a period of 33 days. The removal of COD, BOD5 and ammonia-N were 52.5%, 94.3% and 75.5%, respectively. The kinetic parameters obtained are as followed: the maximum specific growth rate constant (microm): 0.96/day and the saturation substrate constant (Ks): 16,445.32 mg/L. The high value of Ks indicated that the leachate was not easily biodegraded. The continuous process revealed that the system with SRT of 32 days was more stable than that of 16 and 24 days. The reduction of COD, BOD5 and ammonia-N were 31.3%; 66% and 98%, respectively. The stable flux was achieved around 5 L/m2 x hour.

Submerged Filter Biotreatment of Hazardous Leachate in Aerobic, Anaerobic, and Anaerobic/Aerobic Systems

ABSTRACT Aerobic, anaerobic, and anaerobic/aerobic biotreatment of an industrial hazardous waste landfill leachate was evaluated in bench scale biofilm reactor systems operated under steady- and non-steady-state conditions. The leachate contained volatile and semi-volatile organics that exceeded the best-demonstrated-available-technology (BDAT) standards established for multi-source leachate wastewater under the Resources Conservation and Recovery Act (RCRA). The influent leachate stream was continuously applied to three parallel systems: 1) an upflow anaerobic filter followed by a submerged aerobic filter, both with plastic packing, 2) an anaerobic granular activated carbon column, and 3) an upflow, plastic packed aerobic filter. All systems achieved steady-state COD removals of 66-82 percent. The sequential anaerobic/aerobic filter system was most resistant to hydraulic and organic shock loading, whereas the aerobic filter performance deteriorated significantly. Though transformations of specific chemic...

Matrix effects of leachates in the determination of volatile priority pollutants by headspace analysis

In order to investigate the matrix effects of a hazardous waste landfill leachate in the analysis of priority pollutants by headspace gas chromatography, spiking experiments were performed (a) with the untreated leachate, (b) with the leachate after separation of oil and (c) with blanc water samples as a reference. A standard mixture containing volatile chlorinated hydrocarbons, benzene and alkylated benzenes (100–200 μg) were spiked into 50 ml-samples of (a)–(c). The samples were thermostated at 40°C for 20 min and analyzed by headspace GC. Serious matrix effects were observed for all reference compounds, resulting in significant enhancement or depression of the corresponding peak areas compared with the spiked water control samples. The data sets are discussed with respect to the contents of leachate oil and chloride. From the findings of this study, recommendations for the application of headspace analysis to leachates are given.

Stabilization of hazardous waste landfill leachate treatment residue

Hazardous organic wastes lend themselves primarily to destructive treatment by processes such as incineration, biodegradation, chemical oxidation, and dechlorination. When these methods are feasible, all the problems associated with long-term effects are eliminated; thus, they are high on everyone's list of preferred treatment methods. However, many industrial wastes and contaminated materials contain small amounts of toxic organics at levels which make organic destruction processes not only very expensive, but sometimes ineffective. It seems likely now that the EPA intends to establish organic levels at which stabilization can be used in soil remediation and, perhaps at RCRA central treatment, storage, and disposal facilities (TSDFs). Also, in the case of “characteristic” wastes, the Toxicity Characteristic Leaching Procedure (TCLP) test when fully in force, will make it possible to remove wastes from the RCRA hazardous waste system if they meet both inorganic and organic leaching limits. While a number of vendors of stabilization services are offering organic “stabilization,” very little data has been forthcoming at least publicly. The present paper focusses on dilute aqueous hazardous waste streams treatment.

Characteristics of leachates from hazardous waste landfills

Abstract A hazardous waste landfill leachate data base covering some thirty leachates from eleven disposal sites has been developed. The sites cover a range of sizes, liner designs, waste types and leachate collection systems and the leachate data cover a range of organic and inorganic constituents. For the cases included, the inorganic constituents appearing in highest concentrations in the leachate are iron, calcium, magnesium, cadmium, and arsenic, and the organic constituents appearing in highest concentrations are acetic acid, methylene chloride, butyric acid, 1,1‐dichloroethane, and trichlorofluoromethane. The constituent concentrations in the leachate from hazardous waste landfills fall within the reported ranges for municipal landfill leachate. Based on preliminary data, only gross correlations could be made between leachate quality and waste input.