Impact of various leachate recirculation regimes on municipal solid waste degradation

Landfilled municipal solid waste can be treated by introducing leachate into the waste matrix. Increasing attention is being given to landfill leachate recirculation as a means for in situ leachate treatment and landfill stabilization. Landfills with leachate recirculation may be operated as municipal solid waste bioreactor treatment system rather than as a conventional waste dumping sites. In order to study the impact of various leachate recirculation regimes on municipal solid waste degradation, two landfill-simulating reactors, one with leachate recycle and one without, were constructed and placed at a constant room temperature (34 degrees C). Both reactors were filled with a municipal solid waste mixture representing the typical solid waste composition determined for the city of Istanbul. For the purpose of this experiment, leachate recirculation volume and frequency were changed periodically. This research showed that increased frequency of leachate recirculation accelerates the stabilization rate of waste matrix. About 2l of recirculated leachate and four times per week recirculation strategy were found to provide the highest degree of waste stabilization. Additionally, this research confirmed that leachate recirculation is a very feasible way for in situ leachate treatment.     

Co-landfilling of pretreated waste: disposal and management strategies at lab-scale

The present paper deals with the possible advantages that can be obtained by co-landfilling of municipal solid waste organic fraction (MSWOF) and bottom ash (BA) from the incineration of municipal solid waste. In particular, the aim of the research hereby presented is to check the effect exerted by different disposal (mixed or layered) and management strategies (anaerobic or semiaerobic conditions) for landfills in which MSWOF and BA are co-disposed. Three lab-scale reactors were set-up: the reactor A with mixed BA and MSWOF in anaerobic conditions, the reactor B with mixed BA and MSWOF in semiaerobic conditions, the reactor C with layered BA and MSWOF in anaerobic conditions. The results obtained showed that the aeration at the beginning of the experimental period for about 60 days led to a more rapid biodegradation of the organic matter and to an improved leachate quality in terms of both organic load and nitrogen content. Also a significant increase in the settling rate was observed at the end of the aeration phase. Therefore, the aerobic management can be advised as the most available strategy providing a more rapid biological and mechanical stabilization of the bulk waste. Otherwise, the disposal strategy did not exert any significant effect on the leachate characteristics; however, the layered configuration may be adopted in order to accelerate the main settlements.     

Hazardous waste generation and management in China: a review

Associated with the rapid economic growth and tremendous industrial prosperity, continues to be the accelerated increase of hazardous waste generation in China. The reported generation of industrial hazardous waste (IHW) was 11.62milliontons in 2005, which accounted for 1.1% of industrial solid waste (ISW) volume. An average of 43.4% of IHW was recycled, 33.0% was stored, 23.0% was securely disposed, and 0.6% was discharged without pollution controlling. By the end of 2004, there were 177 formal treatment and disposal centers for IHW management. The reported quantity of IHW disposed in these centers was only 416,000tons, 65% of which was landfilled, 35% was incinerated. The quantity of waste alkali and acid ranked the first among IHW categories, which accounted for 30.9%. And 39.0% of IHW was generated from the raw chemical materials and chemical products industry sectors. South west China had the maximum generation of IHW, accounted for 40.0%. In addition, it was extrapolated that 740,000tons of medical wastes were generated per year, of which only 10% was soundly managed. The generation of discarded household hazardous waste (HHW) is another important source of hazardous waste. A great proportion of HHW was managed as municipal solid waste (MSW). Hazardous waste pollution controlling has come into being a huge challenge faced to Chinese environmental management.     

Sources, characteristics and treatment and disposal of industrial wastes containing hexachlorobenzene

Hexachlorobenzene (HCB) is a hazardous component of certain industrial wastes. The hazardous characteristics of HCB stem from its toxicity, potential for bioaccumulation and environmental persistence. A study was conducted to identify the sources and characteristics of manufacturing wastes containing hexachlorobenzene and to review and document methods currently used for treatment and disposal of HCB wastes.The chlorinated solvents and pesticide industries were found to account for nearly all HCB wastes produced (4,305 tons per year) by the 14 industries reviewed as sources of HCB wastes.Waste storage methods which are used prior to ultimate disposal include storage of solid waste cubes under plastic cover and use of water-covered lagoons. Methods for transportation of HCB wastes include use of forklift, truck, pipeline, heated tank trucks and rail. Ultimate waste disposal methods include land disposal, incineration (with or without by-product recovery), resource recovery, discharge to municipal sewage treatment plants, and emission to the atmosphere. The majority of the HCB waste handled by the industrial facilities reviewed is currently disposed of in two industrial landfills using a soil cover of 4 to 6 ft. with a polyethylene film placed at approximately the mid-depth of the soil cover. Incineration at a sufficiently elevated temperature can effectively destroy HCB; HCl can be recovered as a by-product.Very limited actual disposal cost data are available on existing facilities handling HCB wastes.     

The influences on leachate from landfill of incineration residuals by acid precipitation

Incineration of municipal solid wastes (MSW) is the main method of waste management in Taiwan. Although the incineration of MSW processes the solid wastes at 850-950 degrees C and destroys most of the organics, the content of incineration ashes is still a problem for landfill. Moreover, acid precipitation is much worse than before in Taiwan, especially in the northern areas. For instance, the occurrence probabilities of acid precipitation measured from 1991 to 1998 in Taipei increase from 73% to 85%. Therefore, it is more important to get a series of data that will help explore the influence of acid precipitation during disposal on characterization of pollutants than to analyze the ash properties after the incinerators have been constructed and regularly used. In this investigation, the disposal site of incineration ashes is simulated in laboratory by test columns. An irrigation experiment is taken to simulate the acid precipitation at room temperature. In order to explore the exact influence on leachate quality of the main chemical composition of acid precipitation, columns are migrated with different concentrations of sulfate in acid precipitation. This investigation showed that the sulfate concentration of acid precipitation has an increasing effect on the accumulative release of heavy metals, such as Zn, Pb and Cu, from leachate. The sulfate concentration of acid precipitation, however, will not influence the trend of chemical oxygen demand (COD), biochemical oxygen demand (BOD(5)) and total organic carbon (TOC) in the leachate release.     

Quantitative geochemical modelling using leaching tests: application for coal ashes produced by two South African thermal processes

The present work focuses on the reactivity of coal fly ash in aqueous solutions studied through geochemical modelling. The studied coal fly ashes originate from South African industrial sites. The adopted methodology is based on mineralogical analysis, laboratory leaching tests and geochemical modelling. A quantitative modelling approach is developed here in order to determine the quantities of different solid phases composing the coal fly ash. It employs a geochemical code (PHREEQC) and a numerical optimisation tool developed under MATLAB, by the intermediate of a coupling program. The experimental conditions are those of the laboratory leaching test, i.e. liquid/solid ratio of 10 L/kg and 48 h contact time. The simulation results compared with the experimental data demonstrate the feasibility of such approach, which is the scope of the present work. The perspective of the quantitative geochemical modelling is the waste reactivity prediction in different leaching conditions and time frames. This work is part of a largest research project initiated by Sasol and Eskom companies, the largest South African coal consumers, aiming to address the issue of waste management of coal combustion residues and the environmental impact assessment of coal ash disposal on land.     

Treatment and disposal of hazardous wastes in Western Europe

In western Europe, as in other industrialised areas, there has been growing concern about the disposal of wastes of a hazardous or toxic nature. The increasing quantities and complexities of wastes from industrial processes, and the greater awareness of potential risks to health of present and future generations arising from indiscriminate or inadequate methods of disposal, are causing governments to undertake an intensive examination of the whole field of waste management.Reliable data on the types and quantities of hazardous wastes are very difficult to acquire and information available is generally based on estimates.Legislative and administrative measures are being proposed and developed, which will provide a framework for better control and improved standards for the handling, treatment and disposal of toxic and other hazardous wastes.In planning disposal systems, more attention will be given to methods of recovering and recycling materials which are becoming scarce or expensive. As stricter environmental controls raise disposal costs, there will be more incentive on industry to recycle wastes, where practicable.     

城市生活垃圾的工程特性及填埋场的岩土工程问题

填埋法是目前处理城市固体废弃物(MSW)的主要方法。从沉降、稳定、渗透、扩散四个方面分析了在城市固体废弃物填埋场中存在的问题。总结了国内外城市固体废弃物的工程特性,并给出了浙江大学岩土工程研究所对杭州市某填埋场的固体废弃物试样进行室内和现场试验的结果。填埋体的工程性质与其组成成分、填埋方式、环境条件有关、并随不同地点及时间有关。由于MSW工程性质的复杂性,这里所给出的各个工程指标仅供参考使用,对于在正式进行填埋场设计时,还需根据当地固体废弃物进行专门试验。     

Effect of landfill leachate on cell cycle, micronucleus, and sister chromatid exchange in Triticum aestivum

With increasing use of municipal solid waste landfills for waste disposal, the leachate generated has become a serious environmental concern. Therefore, it is important to set up simple and accurate methods for monitoring leachate toxicity. In the present study, the physiological and genetic toxicity of the leachate, generated from Xingou Municipal Landfill in China, were investigated with Triticum aestivum (wheat) bioassay. The results indicate that the lower leachate concentrations stimulated the germination, growth and cell division, and did not induce obvious increase in micronucleus (MN) frequency in root tips; while the higher concentrations inhibited the processes, and significantly augmented the MN frequency in a concentration- and time-dependent manner. In addition, pycnotic cells (PNC) and sister chromatid exchange (SCE) occurred in root tips at all leachate concentrations tested, and the frequencies had positive relation with the treatment concentration and time. The results imply that components of leachate from the landfill may be genotoxic in plant cells, and exposure to leachate in the aquatic environment may pose a potential genotoxic risk to organisms. The results also suggest that the wheat bioassay is efficient, simple and reproducible in monitoring genotoxicity of the leachate.     

Hazardous waste management and weight-based indicators--the case of Haifa Metropolis

The quantity control of hazardous waste in Israel relies primarily on the Environmental Services Company (ESC) reports. With limited management tools, the Ministry of Environmental Protection (MoEP) has no applicable methodology to confirm or monitor the actual amounts of hazardous waste produced by various industrial sectors. The main goal of this research was to develop a method for estimating the amounts of hazardous waste produced by various sectors. In order to achieve this goal, sector-specific indicators were tested on three hazardous waste producing sectors in the Haifa Metropolis: petroleum refineries, dry cleaners, and public hospitals. The findings reveal poor practice of hazardous waste management in the dry cleaning sector and in the public hospitals sector. Large discrepancies were found in the dry cleaning sector, between the quantities of hazardous waste reported and the corresponding indicator estimates. Furthermore, a lack of documentation on hospitals' pharmaceutical and chemical waste production volume was observed. Only in the case of petroleum refineries, the reported amount was consistent with the estimate.     

Long-term reactive transport modelling of stabilized/solidified waste: from dynamic leaching tests to disposal scenarios

Environmental impact assessment of hazardous waste disposal relies, among others, on standardized leaching tests characterized by a strong coupling between diffusion and chemical processes. In that respect, this study shows that reactive transport modelling is a useful tool to extrapolate laboratory results to site conditions characterized by lower solution/solid (L/S) ratios, site specific geometry, infiltration, etc. A cement solidified/stabilized (S/S) waste containing lead is investigated as a typical example. The reactive transport model developed in a previous study to simulate the initial state of the waste as well as laboratory batch and dynamic tests is first summarized. Using the same numerical code (HYTEC), this model is then integrated to a simplified waste disposal scenario assuming a defective cover and rain water infiltration. The coupled evolution of the S/S waste chemistry and the pollutant plume migration are modelled assessing the importance of the cracking state of the monolithic waste. The studied configurations correspond to an undamaged and fully sealed system, a few main fractures between undamaged monoliths and, finally, a dense crack-network in the monoliths. The model considers the potential effects of cracking, first the increase of rain water and carbon dioxide infiltration and, secondly, the increase of L/S ratio and reactive surfaces, using either explicit fracture representation or dual porosity approaches.     

Treatment of MSW landfill leachate by a thin gap annular UV/H2O2 photoreactor with multi-UV lamps

The treatment of leachate from landfills is a major disposal problem for municipal solid waste. The leachate is generally recalcitrant to be treated according to complicated characteristics and high color intensity resulting further threat for environment and human health. In this work, the designed thin gap annular photoreactor with 4-UV lamps in UV/H2O2 process was proposed to decolor and remove chemical oxygen demand (COD) from the landfill leachate for solving this environmental problem. Meanwhile, the operating parameters such as UV dosage, hydrogen peroxide concentration and leachate strength were evaluated. The landfill leachate treated with the maximum dosage of 4-UV lamps and 232.7 mM of hydrogen peroxide concentration achieved 72 and 65% of color and COD removal efficiencies in 300 min. As for less concentrated leachate of 20% strength, 91% of color and 87% of COD were removed within only 120 min. From the experimental results, the UV/H2O2 process in this work was an effective pre-treatment or treatment technology for landfill leachate.     

Evaluation of engineering properties for the use of leached brown coal ash in soil covers

The need to engineer cover systems for the successful rehabilitation or remediation of a wide variety of solid wastes is increasing. Some common applications include landfills, hazardous waste repositories, or mine tailings dams and waste rock/overburden dumps. The brown coal industry of the Latrobe Valley region of Victoria, Australia, produces significant quantities of coal ash and overburden annually. There are some site-specific acid mine drainage (AMD) issues associated with overburden material. This needs to be addressed both during the operational phase of a project and during rehabilitation. An innovative approach was taken to investigate the potential to use leached brown coal ash in engineered soil covers on this overburden dump. The basis for this is two-fold: first, the ash has favourable physical characteristics for use in cover systems (such as high storage capacity/porosity, moderately low permeability, and an ability to act as a capillary break layer generating minimal leachate or seepage); and second, the leachate from the ash is mildly alkaline (which can help to mitigate and reduce the risk of AMD). This paper will review the engineering issues involved in using leached brown coal ash in designing soil covers for potentially acid-forming overburden dumps. It presents the results of laboratory work investigating the technical feasibility of using leached brown coal ash in engineered solid waste cover systems.     

Co-digestion of mixed industrial sludge with municipal solid wastes in anaerobic simulated landfilling bioreactors

In this study, the feasibility of the anaerobic co-digestion of a mixed industrial sludge with municipal solid wastes (MSW) was investigated in three simulated anaerobic landfilling bioreactors during a 150-day period. All of the reactors were operated with leachate recirculation. One of them was loaded only with MSW (control reactor); the second reactor was loaded with mixed industrial sludge and MSW, the weight ratio of the MSW to mixed industrial sludge was 1:1 (based on dry solid) (Run 1); the third reactor was loaded with mixed industrial sludge and MSW, the weight ratio of the MSW to mixed industrial sludge was 1:2 (based on dry solid) (Run 2). The VFA concentrations decreased significantly in Run 1 and Run 2 reactors at the end of 150 days. The pH values were higher in Run 1 and Run 2 reactors compared to control reactor. The differences between leachate characteristics, the biodegradation and the bioefficiency of the reactors were compared. The NH(4)-N concentrations released to leachate from mixed sludge in Run 1 and Run 2 reactors were lower than that of control reactor. The BOD(5)/COD ratios in Run 1 and Run 2 reactors were lower than that of control reactor at the end of 150 days. Cumulative methane gas productions and methane percentages were higher in Run 1 and Run 2 reactors. Reductions in waste quantity, carbon percentage and settlement of the waste were better in Run 1 and Run 2 reactors compared to control reactor at the end of 150 days. Furthermore, TN and TP removals in waste were higher in reactors containing industrial sludge compared to control. The toxicity test results showed that toxicity was observed in reactors containing industrial mixed sludge.     

Current municipal solid waste management in the cities of Astana and Almaty of Kazakhstan and evaluation of alternative management scenarios

Clean Technologies and Environmental Policy - The present paper provides a detailed analysis of the current situation on municipal solid waste (MSW) management in Kazakhstan with focus on the two...     

Use of fly ash,phosphogypsum and red mud as a liner material for the disposal of hazardous zinc leach residue waste

Increasing amounts of residues and waste materials coming from industrial activities in different processes have become an increasingly urgent problem for the future. The release of large quantities of heavy metals into the environment has resulted in a number of environmental problems. The present study investigated the safe disposal of the zinc leach residue waste using industrial residues such as fly ash, phosphogypsum and red mud. In the study, leachability of heavy metals from the zinc leach residue has been evaluated by mine water leaching procedure (MWLP) and toxicity characteristic leaching procedure (TCLP). Zinc removal from leachate was studied using fly ash, phosphogypsum and red mud. The adsorption capacities and adsorption efficiencies were determined. The adsorption rate data was analyzed according to the pseudo-second-order kinetic, Elovich kinetic and intra-particle diffusion kinetic models. The pseudo-second-order kinetic was the best fit kinetic model for the experimental data. The results show that addition of fly ash, phosphogypsum and red mud to the zinc leach residue drastically reduces the heavy metal content in the leachate and could be used as liner materials.     

Hazardous waste remedial action — Picillo Farm,Coventry, Rhode Island; an overview

Following the discovery of buried chemical wastes which caused a fire and explosion at the Picillo Farm in Coventry, Rhode Island, the State of Rhode IA hydrogeological site investigation was conducted which included ground and surface water monitoring, seismic studies and ground penetrating radar. FoCleanup of the first trench began in summer 1980 and concluded that fall, with 2300 barrels being removed. Planning for the second trench excavation anIn November 1980, invitation to bid on the excavation and disposal of barrels from the so called northwest trench was requested. When the U.S. EPA offeSubsequently, Rhode Island decided to assume the excavation portion of the project and dispose of the wastes as far as funding would allow. MobilizatioIn the excavation phase of the work effort, a total of 4400 barrels of hazardous wastes were removed: 40% contained liquid hazardous waste, 40% solid hSite preparation, placement of work areas, excavation and waste transfer techniques, air quality monitoring and operational problem areas are among topThis paper addresses the chronology of events which took place during the 1981 cleanup efforts, comments upon the variety of problems encountered and dThe cleanup of unauthorized hazardous waste sites presents varied operational and environmental problems. This paper attempts to provide insight into tField and off-site disposal analyses proved to be a problem in terms of turnaround time and procedural techniques. Particular attention must be paid toOne of the primary operational constraints involves reducing the risk of injury and adverse health effects to personnel working on site and the surrounFunding of a project of this scope must account for the significant unknown factors associated with hazardous wast cleanup, i.e., What is the amount anEvery attempt must be made closely monitor contractual obligations. Thorough negotiations and understanding prior to commencement of a project will redNo hazardous waste disposal activity can be risk free. Therefore, safety precautions are paramount. Yet budget limitations are real and require consideThe generation of contaminated soil poses a significant disposal problem. Successful efforts were made to limit this problem in Phase II in terms of thFinally, and most importantly, all activities should be closely coordinated with any citizens organization or affected group that deals with the issues     

Leather waste--potential threat to human health, and a new technology of its treatment

In this paper, the authors deal with the problem of processing various types of waste generated by leather industry, with special emphasis to chrome-tanned waste. The agent that makes this waste potentially hazardous is hexavalent chromium. Its compounds can have negative effects on human health and some CrVI salts are considered carcinogens. The authors present the risks of spontaneous oxidization of CrIII to CrVI in the open-air dumps as well as the possible risks of wearing bad quality shoes, in which the chromium content is not controlled. There are several ways of handling primary leather waste, but no satisfactory technology has been developed for the secondary waste (manipulation waste, e.g. leather scraps and used leather products). In this contribution, a new three-step hybrid technology of processing manipulation waste is presented and tested under laboratory, pilot-scale and industrial conditions. The filtrate can be used as a good quality NPK fertilizer. The solid product, titanium–chromium sludge, can serve as an inorganic pigment in glass and ceramic industry. Further, the authors propose selective collection of used leather products (e.g. old shoes), the hydrolysable parts of which can be also processed by the new hybrid technology.     

Mass-balance estimation of heavy metals and selected anions at a landfill receiving MSWI bottom ash and mixed construction wastes

An estimation of the heavy metal and anion mass-balance was made for municipal solid waste incinerator bottom ash deposited at a construction and industrial waste landfill. The mass-balance was found by comparing the content of metals and anions in the landfill leachate to the metal and anion content in the deposited bottom ash. The discharge of heavy metals ranged from 0.001% for Pb to 0.55% for Cr, which is approximately at the same level as in regular municipal solid waste (MSW) landfills. Landfilled organic material and silicates from construction waste might have contributed to the retention of metals. Chloride, and to a lesser extent sulphate, appeared to be readily released from the landfill. It was estimated that a mass corresponding to 80% of the Cl- and 18% of the SO(4)2- in the bottom ash was discharged annually. Low retention, especially of chloride, may lead to a rapid decline in the discharge of this ion in the future when the landfilling of bottom ash is discontinued.     

垃圾土的强度与变形特性

简要回顾了环境岩土工程的发展历史,论述了垃圾土的分类和特性,从岩土力学的角度对有关垃圾土力学性质的研究现状进行了综述,其中重点讨论了垃圾土的强度和压缩变形特性,并对岩土工程师比较感兴趣的垃圾有机成分降解规律进行了介绍。还介绍了清华大学岩土工程研究所在相关方面所取得的研究成果。