Internal leachate quality in a municipal solid waste landfill: vertical, horizontal and temporal variation and impacts of leachate recirculation

The aim of this study was to monitor and characterise internal leachate quality at a Finnish municipal solid waste landfill (Lahti, Kujala, in operation for approximately 50 years) to provide information about its horizontal and vertical variation as well as effects of leachate recirculation on leachate quality. The study area (approximately 4 h) of the landfill had 14 monitoring wells for leachate quality monitoring over a 2-year period. The leachate was monitored for COD, BOD, TKN, NH₄–N, Cl, pH and electric conductivity. The results showed high horizontal and vertical variability in leachate quality between monitoring wells, indicating that age and properties of waste, local conditions (e.g., water table) and degradation and dilution processes have a marked effect on local leachate quality. The mean COD values (642–8037 mg/l) and mean BOD/COD ratios (0.08–0.17) from the different monitoring wells were typical of landfills in the methanogenic phase of degradation. The leachate in the monitoring wells was notably more concentrated than the leachate effluent used for leachate recirculation. In the landfill as a whole the effects of the leachate recirculation on leachate quality, although difficult to distinguish from those caused by other factors, appeared to be minor during the study period.     

Influence of temperature on the electrical conductivity of leachate from municipal solid waste

A bioreactor landfill is designed to manage municipal solid waste, through accelerated waste biodegradation, and stabilisation of the process by means of the controlled addition of liquid, i.e. leachate recirculation. The measurement of electrical resistivity by Electrical Resistivity Tomography (ERT) allows to monitor water content present in the bioreactors. Variations in electrical resistivity are linked to variations in moisture content and temperature. In order to overcome this ambiguity, two laboratory experiments were carried out to establish a relationship between temperature and electrical conductivity: the first set of measurements was made for leachate alone, whereas the second set was made with two different granular media saturated with leachate. Both experiments confirm a well known increase in conductivity of about 2% degrees C(-1). However, higher suspended matter concentrations lead to a lower dependence of electrical conductivity on temperature. Furthermore, for various porous media saturated with an identical leachate, the higher the specific surface of the granular matrix, the lower the effective bulk electrical conductivity. These observations show that a correct understanding of the electrical properties of liquids requires the nature and (in particular) the size of the electrical charge carriers to be taken into account.     

Indicating the parameters of the state of degradation of municipal solid waste

This study related to the analysis of the physical (granulometry and composition) and chemical (organic matter, organic carbon and nitrogen contents) characteristics, as well as those relating to release (leaching tests and determining the methanogene potential) of several domestic wastes, with an aim of evaluating stabilization indicators. Values thresholds for a known stabilized waste were thus deduced by correlation (% paper-cardboard = 0-1; % volatile solid (VS) = 18-19; % OC = 5-6; % fines = 44-45; % degraded components = 75-76, COD of leachate = 141-155 mg O2/L; DOC from leachate = 45-49 mg C/L and 0.9-1 m3 CH4/t of dry waste). However, these values thresholds remain specific to the method employed for the analyses. The results obtained represent a considerable advance in the definition of a waste stabilized state and propose the importance of certain parameters, such as the paper-cardboard content and the measurement of leachates by using the SUVA index for determining a stabilization state.     

Influence of leachate recirculation on aerobic and anaerobic decomposition of solid wastes

In this study, the effect of leachate recirculation on aerobic and anaerobic degradation of municipal solid wastes is determined by four laboratory-scale landfill reactors. The options studied and compared with the traditional anaerobic landfill are: leachate recirculation, landfill aeration, and aeration with leachate recirculation. Leachate quality is regularly monitored by the means of pH, alkalinity, total dissolved solids, conductivity, oxidation-reduction potential, chloride, chemical oxygen demand, ammonia, and total Kjeldahl nitrogen, in addition to generated leachate quantity. Aerobic leachate recirculated landfill appears to be the most effective option in the removal of organic matter and ammonia. The main difference between aerobic recirculated and non-recirculated landfill options is determined at leachate quantity. Recirculation is more effective on anaerobic degradation of solid waste than aerobic degradation. Further studies are going on to determine the optimum operational conditions for aeration and leachate recirculation rates, also with the operational costs of aeration and recirculation.     

卫生填埋场垃圾渗滤液的处理技术

卫生填埋是国内外广泛采用的城市生活垃圾处置方法 ,而渗滤液的处理则是其最大难点。本文总结了当前各种渗滤液处理技术的使用条件及其优缺点 ,并提出了渗滤液处理的改进措施及建议     

Pharmaceutical compound content of municipal solid waste

The occurrence and fate of pharmaceuticals in landfills has been largely neglected. Once discarded in municipal solid waste (MSW), pharmaceuticals within a landfill may undergo degradation, adsorption, or enter the leachate and eventually exit the landfill. The active pharmaceutical ingredient (API) concentration of MSW was predicted using available statistics on medication usage and directly measured by a MSW composition study. Estimation calculations resulted in a potential concentration of APIs from 7.4 to 45 mg/kg of MSW, varying with the percentage of dispensed medications assumed to become unused. Direct measurement resulted in the collection of 22 APIs comprising a total of 22,910 mg. This resulted in a final concentration of 8.1 mg/kg within MSW. Additionally, 45 empty medication containers were collected which potentially contained 33 differing APIs upon disposal.     

Characterization of dissolved organic matter in leachate discharged from final disposal sites which contained municipal solid waste incineration residues

The properties of dissolved organic matter (DOM) in the leachates discharged from lysimeters and landfill sites containing municipal solid waste incineration residues (MSWIRs) were studied. DOM samples were divided into hydrophobic acid, base, neutral (Hpo-A, Hpo-B, Hpo-N) and hydrophilic (Hpi) fractions using the fractionation method employing DAX-8 resin. Hpi was the smallest fraction of all the raw leachate samples. The proportion of Hpo-N increased with increasing operating time. Landfill sites containing abundant non-combustible wastes showed a higher proportion of Hpo-B than Hpo-A. The molecular weights and functional groups of the DOM fractions were studied by using gel permeation chromatography and FTIR, respectively. In addition, the fluorescent properties and binding sites of the DOM fractions were investigated using fluorescence analysis. In the synchronous scan spectra of each DOM fraction, most of DOM fractions showed an emission peak for the main fluorophores at around 300 nm or 350 nm, which are regarded as aromatic amino acid-like fluorophores. The interaction between the DOM fraction and the pollutants (Cu(2+), pyrene and phenanthrene) was investigated using the fluorescence quenching method. It was observed that the aromatic amino acid-like fluorophores in the DOM fractions could be an important factor affecting complexation with the pollutants.     

Possible applications for municipal solid waste fly ash

The present study focuses on existing practices related to the reuse of Municipal Solid Waste (MSW) fly ash and identifies new potential uses. Nine possible applications were identified and grouped into four main categories: construction materials (cement, concrete, ceramics, glass and glass-ceramics); geotechnical applications (road pavement, embankments); "agriculture" (soil amendment); and, miscellaneous (sorbent, sludge conditioning). Each application is analysed in detail, including final-product technical characteristics, with a special emphasis on environmental impacts. A comparative analysis of the different options is performed, stressing the advantages but also the weaknesses of each option. This information is systemized in order to provide a framework for the selection of best technology and final products. The results presented here show new possibilities for this waste reuse in a short-term, in a wide range of fields, resulting in great advantages in waste minimization as well as resources conservation.     

Electrolytic recovery of lead in used lime leachate from municipal waste incinerator

The purification of municipal incinerator gases generates huge quantities of both fly ashes and used lime, containing high amount of heavy metals (Pb, Cd, Zn and Hg). The used lime is mainly contaminated by Pb and often considered as hazardous waste. This paper is related to a laboratory study on the performance of electrochemical techniques used to recover Pb from leachate produced during used lime decontamination. Two types of electrolytic units (monopolar and bipolar electrode cells) using different electrode materials were studied. Effectiveness was measured in terms of energy consumed, weight of residue sludge produced and reduction in Pb concentration. Results showed that the best performances for Pb removal (in terms of effectiveness and cost) were obtained by initially adjusting the pH of UL leachate to pH 7.5–8.5 with sulphuric acid followed by electrochemical treatment using bipolar electrode (mild steel) system operated at current intensity of 1.5 A through only 5 min. The yield of Pb removal was 98.8 ± 1.3% and an amount of 4.9 ± 1.3 kg trt⁻¹ of metallic sludge was produced. The optimal conditions determined for Pb recovery involved a total cost of CAN$ 1.66 t⁻¹ of dry residue treated, including acid consumption, energy consumption and metallic sludge disposal.     

Process kinetics of inoculation composting of municipal solid waste

A method was used to improve the composting efficiency by seeding with Inoculum A (a blend of Bacillus azotofixams, Bacillus megaterium and Bacillus mucilaginosus), Inoculum B (a blend of effective cellulolytic strains, i.e. Trichoderma koningii, Streptomyces cellulosae, and White-rot fungi), and Inoculum C (a mixture of Inoculum A and Inoculum B). There were four runs: the control run (not inoculated), Run A, Run B and Run C. During the runs, parameters such as temperature, O2, CO2 and H2S emissions, and microbial concentration were investigated to study the efficiencies of inoculation composting. The maximum oxygen uptake rates in the control run, Run A, Run B and Run C were calculated as 0.22, 0.32; 0.28 and 0.34 mol/hkg while the corresponding total O2 quantities accumulated were 511.18, 684.57, 659.74 and 778.47 g/hkg, respectively. In addition, odorous gases were highly reduced by inoculation. In order to understand the mechanisms of inoculation composting process, two stages kinetics equations were developed from the viewpoint of microbial kinetics. These equations showed that, in the first stage, microbial concentration was the main limiting factor of the degradation rate. The degradation rates in control, Run A, Run B and Run C were 10.5, 13.61, 13.08, and 15.671 g/kgh, respectively. In the second stage, the degradation rate was mainly affected by substrate concentration. Although the degradation rates were at almost the same level for both with and without inoculation, inoculation could reduce the half velocity coefficient K(m) and in turn stabilize the composting products efficiently. Therefore, inoculation could improve the efficiency of the composting process.     

Mapping incinerability of municipal solid waste in Indian sub-continent

Clean Technologies and Environmental Policy - Effective municipal solid waste (MSW) management is essential for sustainable development of a region. Waste management strategies are, consequently,...     

Vitrification of fly ash from municipal solid waste incinerator

Fly ash from municipal solid wastes (MSW) incinerators in Korea contains a large amount of toxic materials and requires pertinent treatments. However, since fly ash in Korea has a high chlorine concentration, it is difficult to apply cementation and chemical treatment techniques. In this study, we report the vitrification of fly ash along with the properties of the glasses and leaching characteristics of heavy metal ions.Fly ash can be vitrified by melting at 1500 degrees C for 30 min with the addition of >5 wt.% of SiO2. Glasses showed Vickers hardness of 4000-5000 MPa, bending strength of 60-90 MPa and indentation fracture toughness of approximately 0.9 MPa m(1/2). Glasses also showed the excellent resistance against leaching of heavy metal ions with Cd2+ <0.04 ppm, Cr3+ <0.02 ppm, Cu2+ <0.04 ppm and Pb2+ <0.2 ppm. These results indicate that the vitrification technique is effective for the stabilization and recycling of toxic incinerator fly ash.     

Dose-mortality assessment on municipal solid waste incinerator (MSWI) ash

This study provides a novel attempt to put forward, in general toxicological terms, quantitative series of toxicity of various ashes of municipal solid waste incinerator (MSWI) for reusability in various applications. Previous study disclosed that growth inhibition of Escherichia coli DH5alpha occurred at concentrations above 0.156, 0.625 and 0.0195 gL(-1) for bottom ash (BA), cyclone ash (CA), scrubber ash (SA), respectively, suggesting the toxicity series of SA>BA>CA. However, the severity of such a toxicity series was not clearly revealed, thus whether ashes were still feasible for reuse in further applications was still remained uncertain. Compared to NaNO3, CrCl2 and CdCl2, the existing toxicities of ashes were apparently significant even these ashes were all satisfied by the TCLP guidelines for EPA regulations. Dose-response analysis based upon loss of cell viability (e.g., EC50) stated a toxicity series of SA>CrCl2>BA>CdCl2>CA>NaNO3. The ranking of Hill slope B in BA>SA>CA>NaNO3>CrCl2>CdCl2 clearly suggested the smallest tolerance (e.g., ranges from EC20 to EC50) for ashes very likely due to synergistic toxicity of multiple species present in ashes. The findings showed that toxicity attenuation of ashes should be the first-ranking task prior to practical reuse and recycle in applications.     

垃圾填埋场的地震响应特性分析

采用二维等效线性有限元程序对典型山谷型填埋场进行非线性动力分析。综合考虑了地基刚度、动荷周期、幅值及填埋体的刚度对填埋场顶部加速度响应特性的影响,从地基基本周期 、地震卓越周期 和填埋场的基本周期 三者相互关系的角度得出了填埋场地震响应的普适性规律：各种影响因素都是通过改变这三个周期的相对大小关系来改变填埋场的响应情况。当 ＝ ＝ 时,填埋场顶部的响应达到最大;如果 ＝ 或者 ＝ ,则填埋场的动力响应值中等;三个周期相差甚远时,填埋场的响应值最小。通常情况下 较大, 较小,对于压得很密实或者填埋时间长久的填埋场,剪切波速增加使 减小;地震幅值的增加,由于材料的非线性使得 和 增加,从而容易使周期接近,而激发较大响应。该结果对填埋场抗震设计有指导意义。     

Thermal behaviour of ESP ash from municipal solid waste incinerators

Stricter environmental regulations demand safer treatment and disposal of incinerator fly ashes. So far no sound technology or a process is available for a sustainable and ecological treatment of the waste incineration ashes, and only partial treatment is practised for temporary and short-term solutions. New processes and technology need to be developed for comprehensive utilization and detoxification of the municipal solid waste (MSW) incinerator residues. To explore the efficiency of thermal stabilisation and controlled vitrification, the thermal behaviour of electrostatic precipitator (ESP) ash was investigated under controlled conditions. The reaction stages are identified with the initial moisture removal, volatilisation, melting and slag formation. At the temperature higher than 1100 °C, the ESP ashes have a quicker weight loss, and the total weight loss reaches up to 52%, higher than the boiler ash. At 1400 °C a salt layer and a homogeneous glassy slag were formed. The effect of thermal treatment on the leaching characteristics of various elements in the ESP ash was evaluated with the availability-leaching test. The leaching values of the vitrified slag are significantly lowered than that of the original ash.     

Production of biogas from municipal solid waste with domestic sewage

In this study, experiments were conducted to investigate the production of biogas from municipal solid waste (MSW) and domestic sewage by using anaerobic digestion process. The batch type of reactor was operated at room temperature varying from 26 to 36 degrees C with a fixed hydraulic retention time (HRT) of 25 days. The digester was operated at different organic feeding rates of 0.5, 1.0, 2.3, 2.9, 3.5 and 4.3kg of volatile solids (VS)/m(3) of digester slurry per day. Biogas generation was enhanced by the addition of domestic sewage to MSW. The maximum biogas production of 0.36m(3)/kg of VS added per day occurred at the optimum organic feeding rate of 2.9kg of VS/m(3)/day. The maximum reduction of total solids (TS) (87.6%), VS (88.1%) and chemical oxygen demand (COD) (89.3%) occurred at the optimum organic loading rate of 2.9kg of VS/m(3)/day. The quality of biogas produced during anaerobic digestion process was 68-72%.     

Characterization and sustainable management strategies of municipal solid waste in Egypt

Clean Technologies and Environmental Policy - The aim of the present study was to establish a national database of waste characteristics for Egypt to support the assessment of various waste...     

Utilization of municipal solid waste incineration ash in Portland cement clinker

Municipal solid waste incineration (MSWI) ash is used in part as raw materials for cement clinker production by taking advantage of the high contents of SiO₂, Al₂O₃, and CaO. It is necessary for environmental reasons to establish a material utilization system for the incineration waste ash residue instead of disposing these ashes into landfill. The aim of this paper is to study the feasibility of replacing clinker raw materials by waste ash residue for cement clinker production. MSWI bottom ash and MSWI fly ash are the main types of ashes being evaluated. The ashes were mixed into raw mixture with different portions of ash residue to produce cement clinker in a laboratory furnace at approximately 1400°C. X-ray diffraction and X-ray florescence techniques were used to analyze the phase chemistry and chemical composition of clinkers in order to compare these ash-based clinkers with commercial Portland cement clinker.     

Biotoxicity assessment on reusability of municipal solid waste incinerator (MSWI) ash

This study provides a first attempt of dose-response analysis and margin of safety using Escherichia coli DH5alpha, Bacillus subtilis as indicator microorganisms to put forward, in general terms and explanations, the toxicity rankings of various ashes of municipal solid waste incinerator (MSWI) for feasibility in further applications. Since the MSWI ash often contains cations of Si, Ca, Al and Fe, it is frequently considered to be recycled for construction building-materials. Growth inhibition of E. coli DH5alpha occurred at concentrations over 0.156, 0.625 and 0.0195 g/L for bottom ash (BA), cyclone ash (CA), scrubber ash (SA), respectively, suggesting the toxicity ranking of SA>BA>CA. In contrast, except for SA (ca. 0.313 g/L), almost same inhibitory levels of ashes to cell growth were also observed in Bacillus subtilis. Evidently, biotoxicity responses were strongly dependent upon the characteristics of indicator microorganism. Based on DH5alpha, the margins of safety (MOS) were thus 0.195, 1.56 and 6.25 mg/L for SA, BA and CA, respectively. Nearly identical levels of MOS were also suggested by B. subtilis, except for SA (3.13 mg/L). Although MSWI residual ashes qualified EPA's standard test of Toxicity Characteristic Leaching Procedure (TCLP), they might still contain other toxic residues (e.g., chloride ions and/or anions) to cause existing toxicity as indicated in this toxicity study.