Evaluation of environmental feasibility of steel pipe sheet pile cutoff wall at coastal landfill sites

An evaluation method that can express the local leakage of leachate from joint sections in steel pipe sheet pile (SPSP) cutoff walls is discussed in this study. In particular, the evaluation of environmental feasibility (containment of leachates containing toxic substances) considering a three-dimensional arrangement and hydraulic conductivity distribution of the joint sections in the SPSP cutoff wall is compared with an evaluation that uses the equivalent hydraulic conductivity. This equivalent hydraulic conductivity assumes that the joint section and the steel pipe are integrated; therefore, the hydraulic conductivity is substituted with a uniform permeable layer. However, in an evaluation that employs the equivalent hydraulic conductivity, it is difficult to consider the local leakage of leachate containing toxic substances from the joint sections in the SPSP cutoff wall. It was established that evaluations of the environmental feasibility of SPSP cutoff walls with joint sections must take into account the local leakage of leachates containing toxic substances from the joint sections. Also, it was clarified that technologies that lower the hydraulic conductivities of joint sections in SPSP cutoff walls and also facilitate the use of sparser joint arrangements contribute significantly to increasing the environmental feasibility of SPSP cutoff walls at landfill sites.     

The potential for aeration of MSW landfills to accelerate completion

Landfilling is a popular waste disposal method, but, as it is practised currently, it is fundamentally unsustainable. The low short-term financial costs belie the potential long-term environmental costs, and traditional landfill sites require long-term management in order to mitigate any possible environmental damage. Old landfill sites might require aftercare for decades or even centuries, and in some cases remediation may be necessary. Biological stabilisation of a landfill is the key issue; completion criteria provide a yardstick by which the success of any new technology may be measured. In order for a site to achieve completion it must pose no risk to human health or the environment, meaning that attenuation of any emissions from the site must occur within the local environment without causing harm. Remediation of old landfill sites by aerating the waste has been undertaken in Germany, the United States, Italy and The Netherlands, with considerable success. At a pilot scale, aeration has also been used in newly emplaced waste to accelerate stabilisation. This paper reviews the use of aerobic landfill worldwide, and assesses the ways in which the use of aerobic landfill techniques can decrease the risks associated with current landfill practices, making landfill a more sustainable waste disposal option. It focuses on assessing ways to utilise aeration to enhance stabilisation. The results demonstrated that aeration of old landfill sites may be an efficient and cost-effective method of remediation and allow the date of completion to be brought forward by decades. Similarly, aeration of newly emplaced waste can be effective in enhancing degradation, assisting with completion and reducing environmental risks. However, further research is required to establish what procedure for adding air to a landfill would be most suitable for the UK and to investigate new risks that may arise, such as the possible emission of non-methane organic compounds.     

Environmental diagnosis methodology for municipal waste landfills

A large number of countries are involved in a process of transformation with regard to the management of municipal solid waste. This process is a consequence of environmental requirements that occasionally materialise in legislation, such as the European Council Directive 31/99/EC on waste release in the European Union. In some cases, the remediation of old landfills can be carried out in compliance with environmental requirements; in other cases, it is necessary to proceed with the closure of the landfill and to assimilate it into its own environment. In both cases, it is necessary to undertake a diagnosis and characterisation of the impacted areas in order to develop an adequate action plan. This study presents a new methodology by which environmental diagnosis of landfill sites may be carried out. The methodology involves the formulation of a series of environmental indeces which provide information concerning the potential environmental problems of the landfills and the particular impact on different environmental elements, as well as information related to location, design and operation. On the basis of these results, it would be possible to draw up action plans for the remediation or closure of the landfill site. By applying the methodology to several landfills in a specific area, it would be possible to prioritize the order of actions required.     

利用生活垃圾填埋场上建设飞灰固化物填埋场适宜性探讨

针对利用原有生活垃圾填埋场改扩建飞灰固化物填埋场,从勘查设计和建设角度,通过与常规生活垃圾填埋的安全和环保各相关因素对比,分析扩建前后填埋场稳定性、防渗及导排系统等勘察设计要点,研讨扩建工程新老填埋堆体基础层、防渗及导排系统等安全环保关键技术及扩建的适宜性,为扩建的可行性研究提出较为系统的技术论证思路。     

Phytoremediation of landfill leachate

Leachate emissions from landfill sites are of concern, primarily due to their toxic impact when released unchecked into the environment, and the potential for landfill sites to generate leachate for many hundreds of years following closure. Consequently, economically and environmentally sustainable disposal options are a priority in waste management. One potential option is the use of soil-plant based remediation schemes. In many cases, using either trees (including short rotation coppice) or grassland, phytoremediation of leachate has been successful. However, there are a significant number of examples where phytoremediation has failed. Typically, this failure can be ascribed to excessive leachate application and poor management due to a fundamental lack of understanding of the plant-soil system. On balance, with careful management, phytoremediation can be viewed as a sustainable, cost effective and environmentally sound option which is capable of treating 250m(3)ha(-1)yr(-1). However, these schemes have a requirement for large land areas and must be capable of responding to changes in leachate quality and quantity, problems of scheme establishment and maintenance, continual environmental monitoring and seasonal patterns of plant growth. Although the fundamental underpinning science is well understood, further work is required to create long-term predictive remediation models, full environmental impact assessments, a complete life-cycle analysis and economic analyses for a wide range of landfill scenarios.     

Future landfill emissions and the effect of final cover installation--a case study

Municipal solid waste (MSW) landfills are potential long-term sources of emissions. Hence, they need to be managed after closure until they do not pose a threat to humans or the environment. The case study on the Breitenau MSW landfill was performed to evaluate future emission levels for this site and to illustrate the effect of final cover installation with respect to long-term environmental risks. The methodology was based on a comprehensive assessment of the state of the landfill and included analysis of monitoring data, investigations of landfilled waste, and an evaluation of containment systems. A model to estimate future emission levels was established and site-specific predictions of leachate emissions were presented based on scenario analysis. The results are used to evaluate the future pollution potential of the landfill and to compare different aftercare concepts in view of long-term emissions. As some leachable substances became available for water flow during cover construction due to a change in the water flow pattern of the waste, a substantial increase in leachate concentrations could be observed at the site (e.g. concentrations of chloride increased from 200 to 800 mg/l and of ammonia-nitrogen from 140 to about 500 mg/l). A period of intensive flushing before the final cover installation could have reduced the amount of leachable substances within the landfill body and rapidly decreased the leachate concentrations to 11 mg Cl/l and 79 mg NH₄-N/l within 50 years. Contrarily, the minimization of water infiltration is associated with leachate concentrations in a high range for centuries (above 400 mg Cl/l and 200 mg NH₄-N/l) with low concomitant annual emission loads (below 12 kg/year of Cl or 9 kg/year of NH₄-N, respectively). However, an expected gradual decrease of barrier efficiency over time would be associated with higher emission loads of 50 kg of chloride and 30 kg of ammonia-nitrogen at the maximum, but a faster decrease of leachate concentration levels.     

Assessing the environmental impact of ashes used in a landfill cover construction

Large amounts of construction materials will be needed in Europe in anticipation for capping landfills that will be closed due to the tightening up of landfill legislation. This study was conducted to assess the potential environmental impacts of using refuse derived fuel (RDF) and municipal solid waste incineration (MSWI) ashes as substitutes for natural materials in landfill cover designs. The leaching of substances from a full-scale landfill cover test area built with different fly and bottom ashes was evaluated based on laboratory tests and field monitoring. The water that drained off above the liner (drainage) and the water that percolated through the liner into the landfill (leachate) were contaminated with Cl^?, nitrogen and several trace elements (e.g., As, Cu, Mo, Ni and Se). The drainage from layers containing ash will probably require pre-treatment before discharge. The leachate quality from the ash cover is expected to have a minor influence on overall landfill leachate quality because the amounts generated from the ash covers were low, <3–30 l (m² yr)^?1. Geochemical modelling indicated that precipitation of clay minerals and other secondary compounds in the ash liner was possible within 3 years after construction, which could contribute to the retention of trace elements in the liner in the long term. Hence, from an environmental view point, the placement of ashes in layers above the liner is more critical than within the liner.     

The Bacillus subtilis rec-assay: a powerful tool for the detection of genotoxic substances in the water environment. Prospect for assessing potential impact of pollutants from stabilized wastes

The Bacillus subtilis rec-assay has been specially developed to detect genotoxicity in environmental water samples. The rationale of the B. subtilis rec-assay is based on the relative difference of survival of a DNA repair-recombination proficient strain and its deficient strain, which is interpreted as genotoxicity. This assay method can be very powerful in that it has higher sensitivity for the detection of mutagens in highly polluted waters than other bacterial mutation assays. Hydrophobic fractions from various environmental waters were fractionated by using XAD-2 resins and assayed, targeting the detection of organic genotoxic substances. Genotoxic response was detected in most of them, which revealed that many unknown micropollutants with genotoxicity occur in public water bodies. Positive response was also detected from a treated municipal solid waste (MSW) landfill leachate. Genotoxicity remaining in the treated effluent suggests that genotoxic micropollutants may pass through conventional water treatment processes such as activated sludge treatment process. Without proper control of waste quality and landfill facilities, waste landfill could be a heavy pollution source.     

Assessment of two thermally treated drill mud wastes for landfill containment applications.

Offshore oil and gas drilling operations generate significant amounts of drill mud waste, some of which is transported onshore for subsequent thermal treatment (i.e. via thermal remediation). This treatment process results in a mineral waste by-product (referred to as thermally treated drill mud waste; TTDMW). Bentonites are originally present in many of the drill mud products and it is hypothesized that TTDMW can be utilized in landfill containment applications (i.e. cover or base liner). The objective of this paper is to examine the feasibility of this application by performing various physical and chemical tests on two TTDMW samples. It is shown that the two TTDMW samples contained relatively small amounts of clay-sized minerals although hydraulic conductivity values are found to be less than 10(-8) m/s. Organic carbon contents of the samples were approximately 2%. Mineralogy characterization of the samples confirmed varying amounts of smectite, however, peak friction angles for a TTDMW sample was greater than 36 degrees. Chemical characterization of the TTDMW samples show potential leaching of barium and small amounts of other heavy metals. Discussion is provided in the paper on suggestions to assist in overcoming regulatory issues associated with utilization of TTDMW in landfill containment applications.     

Sustainable Remediation and Decision Analysis Practices at an Onshore Gas Well Site

Strategies for remediation of drilling mud wastes at a typical deep sour gas well site in the foothills of Alberta were assessed in terms of financial and social costs and benefits, in alignment with established sustainable remediation and decision analysis principles. Managers of contaminated sites containing historical drilling wastes are challenged with managing liability through several regulatory changes over time. Excavation and disposal of the contaminated soil from the site was the only means of securing regulatory release, with the nearest landfill located 150 km away. A perception exists that in many cases excavation and disposal inflicts unnecessary levels of site intrusiveness and public disturbance when other options achieving a similar risk end point may do so for lower social cost. The study tested this hypothesis to ascertain whether the currently accepted solution is the best option when the wider costs and benefits to society and the environment are included. Eight remedial strategies were assessed using cost–benefit analysis, including using environmental economics techniques to quantify social and environmental impacts. The economic model showed that methods such as capping in‐place or engineered encapsulation were superior to full excavation and disposal from financial and sustainability perspectives. Quantified external costs and benefits such as road damage, greenhouse gas emissions, public nuisance and safety, and community amenity value were influential in identifying superior options. It was demonstrated that $0.2 million of societal costs could be avoided by choosing capping over landfill disposal. This represents substantial implications when viewed in the context of this and other operators’ portfolios of hundreds of abandoned wells in the area. ©2016 Wiley Periodicals, Inc.     

Occurrence of phenols in leachates from municipal solid waste landfill sites in Japan

The concentrations of 41 phenols in leachates from 38 municipal solid waste (MSW) landfill sites in Japan were measured. The main phenols detected in leachates were phenol, three cresols, 4-tert-butylphenol, 4-tertoctylphenol, 4-nonylphenol, bisphenol A, and some chlorophenols. The concentration levels of phenols were affected by the pH values of the leachates and the different types of landfill waste. The origins of phenol and p-cresol were considered to be incineration residues, and the major origin of 4-tert-butylphenol, bisphenol A, and 2,4,6-trichlorophenol was considered to be solidified fly ash. In contrast, the major origins of 4-tert-octylphenol and 4-nonylphenol were considered to be incombustibles. The discharge of leachates to the environment around MSW landfill sites without water treatment facilities can cause environmental pollution by phenols. In particular, the disposal of incineration residues including solidified fly ash and the codisposal of solidified fly ash and incombustibles might raise the possibility of environmental pollution. Moreover, the discharge of leachates at pH values of 9.8 or more could pollute the water environment with phenol. However, phenol, 4-nonylphenol, and bisphenol A can be removed to below the con centration levels that impact the environment around landfill sites by a series of conventional water treatment processes.     

Assessment and analysis of industrial liquid waste and sludge disposal at unlined landfill sites in arid climate

Municipal solid waste disposal sites in arid countries such as Kuwait receive various types of waste materials like sewage sludge, chemical waste and other debris. Large amounts of leachate are expected to be generated due to the improper disposal of industrial wastewater, sewage sludge and chemical wastes with municipal solid waste at landfill sites even though the rainwater is scarce. Almost 95% of all solid waste generated in Kuwait during the last 10 years was dumped in five unlined landfills. The sites accepting liquid waste consist of old sand quarries that do not follow any specific engineering guidelines. With the current practice, contamination of the ground water table is possible due to the close location of the water table beneath the bottom of the waste disposal sites. This study determined the percentage of industrial liquid waste and sludge of the total waste dumped at the landfill sites, analyzed the chemical characteristics of liquid waste stream and contaminated water at disposal sites, and finally evaluated the possible risk posed by the continuous dumping of such wastes at the unlined landfills. Statistical analysis has been performed on the disposal and characterization of industrial wastewater and sludge at five active landfill sites. The chemical analysis shows that all the industrial wastes and sludge have high concentrations of COD, suspended solids, and heavy metals. Results show that from 1993 to 2000, 5.14+/-1.13 million t of total wastes were disposed per year in all active landfill sites in Kuwait. The share of industrial liquid and sludge waste was 1.85+/-0.19 million t representing 37.22+/-6.85% of total waste disposed in all landfill sites. Such wastes contribute to landfill leachate which pollutes groundwater and may enter the food chain causing adverse health effects. Lined evaporation ponds are suggested as an economical and safe solution for industrial wastewater and sludge disposal in the arid climate of Kuwait.     

Expect the best but plan for the worst: Negotiating contracts for remediation services

The risks associated with environmental remediation projects are of concern to engineers, consultants, contractors, owners, and the public. The cost, scheduling, and other uncertainties inherent in performance of construction at sites contaminated by hazardous substances dictate caution with respect to contract terms. Further, the possibility that conditions will be exacerbated by the work, or the public or workers exposed to on-site substances, makes remediation projects of particular concern to those who will be held accountable for the effects and impacts of such substances. This article discusses particularly important contractual issues and suggests approaches for liability allocation and incentives. Practical, effective, realistic approaches to management of environmental remediation are presented, including the form of contract utilized, negotiated terms, attention to contractor selection and management, and the parties' relative economic strength.     

A RE-EVALUATION OF OBJECTIONS TO TREE PLANTING ON CONTAINMENT LANDFILLS

Legislation from developed countries indicates that planting trees on containment landfills is generally forbidden. Concerns centre on the supposition that tree roots can penetrate into and through capping materials, and will thus compromise control of water ingress into waste, and allow the escape of landfill gas. An associated anxiety is that if roots penetrate a clay cap they could cause desiccation and cracking of the clay through excessive moisture abstraction. It is also considered that trees growing on the relatively shallow soil above a landfill cap could be especially prone to uprooting. However, a review of the world literature indicates that maximum depths achieved by tree roots are usually between 1–2 m. Almost 90% of a tree's roots may be found in the upper 0.6 m of soil. Tree roots are highly sensitive to environmental conditions and their downward penetration can be restricted by a number of soil factors including compaction, poor aeration and infertility. A detailed study of these factors indicates that the materials used for capping landfill sites, such as HDPE (high density polyethylene) and compacted clays, can provide an effective barrier to downward root growth. The available information also suggests that tree roots are extremely unlikely to be a primary cause of desiccation cracking in a clay cap owing to their inability to extract more than about one-quarter of the total moisture held in a clay of the density required to ensure a permeability of 1×10⁻⁹m s⁻¹. Trees growing on landfill sites with a rootable soil depth of at least 1.5 m should be at no greater risk of windthrow than most forest trees on undisturbed sites. Methods are available to assess the likelihood of windthrow. In any event, windthrow should not cause disruption of a cap, due to the inability of tree roots to penetrate HDPE, or mineral materials compacted to a bulk density of 1.8 g cm⁻³.     

Modelling of environmental impacts of solid waste landfilling within the life-cycle analysis program EASEWASTE

A new computer-based life-cycle assessment model (EASEWASTE) has been developed to evaluate resource and environmental consequences of solid waste management systems. This paper describes the landfilling sub-model used in the life-cycle assessment program EASEWASTE, and examines some of the implications of this sub-model. All quantities and concentrations of leachate and landfill gas can be modified by the user in order to bring them in agreement with the actual landfill that is assessed by the model. All emissions, except the generation of landfill gas, are process specific. The landfill gas generation is calculated on the basis of organic matter in the landfilled waste. A landfill assessment example is provided. For this example, the normalised environmental effects of landfill gas on global warming and photochemical smog are much greater than the environmental effects for landfill leachate or for landfill construction. A sensitivity analysis for this example indicates that the overall environmental impact is sensitive to the gas collection efficiency and the use of the gas, but not to the amount of leachate generated, or the amount of soil or liner material used in construction. The landfill model can be used for evaluating different technologies with different liners, gas and leachate collection efficiencies, and to compare the environmental consequences of landfilling with alternative waste treatment options such as incineration or anaerobic digestion.     

Risk assessment of landfill disposal sites--State of the art

A risk assessment process can assist in drawing a cost-effective compromise between economic and environmental costs, thereby assuring that the philosophy of 'sustainable development' is adhered to. Nowadays risk analysis is in wide use to effectively manage environmental issues. Risk assessment is also applied to other subjects including health and safety, food, finance, ecology and epidemiology. The literature review of environmental risk assessments in general and risk assessment approaches particularly regarding landfill disposal sites undertaken by the authors, reveals that an integrated risk assessment methodology for landfill gas, leachate or degraded waste does not exist. A range of knowledge gaps is discovered in the literature reviewed to date. From the perspective of landfill leachate, this paper identifies the extent to which various risk analysis aspects are absent in the existing approaches.     

Passive drainage and biofiltration of landfill gas: Australian field trial

In Australia a significant number of landfill waste disposal sites do not incorporate measures for the collection and treatment of landfill gas. This includes many old/former landfill sites, rural landfill sites, non-putrescible solid waste and inert waste landfill sites, where landfill gas generation is low and it is not commercially viable to extract and beneficially utilize the landfill gas. Previous research has demonstrated that biofiltration has the potential to degrade methane in landfill gas, however, the microbial processes can be affected by many local conditions and factors including moisture content, temperature, nutrient supply, including the availability of oxygen and methane, and the movement of gas (oxygen and methane) to/from the micro-organisms. A field scale trial is being undertaken at a landfill site in Sydney, Australia, to investigate passive drainage and biofiltration of landfill gas as a means of managing landfill gas emissions at low to moderate gas generation landfill sites. The design and construction of the trial is described and the experimental results will provide in-depth knowledge on the application of passive gas drainage and landfill gas biofiltration under Sydney (Australian) conditions, including the performance of recycled materials for the management of landfill gas emissions.     

Changes in carbon and nitrogen pool during in-situ aeration of old landfills under varying conditions

Emissions from old landfills via leachate and the gas phase are influenced by state and stability of the organic matter in the solid waste and by environmental conditions within the landfill. Remediation of landfills by means of in-situ aeration is one possibility to reduce these emissions. By establishing aerobic conditions, biological processes in the landfill are accelerated. To investigate the effects of this remediation technology, lab-scale experiments with column tests have been carried out. The main goal of the present work is to characterize the changes of the carbon and nitrogen compounds in the aerated solid waste, the leachate and the gas phase under varying conditions. The results demonstrate a clear reduction of emissions and a stabilization of the organic matter. Furthermore, it is shown that both the intensity of aeration and the amount of water affect biological processes to a certain extent. Even when columns were operated under anaerobic conditions after a long running period of aeration, the emissions remained low.     

Superfund site remediation by landfilling—overview of landfill design,operation, closure,and postclosure issues

This article discusses the appropriateness of using landfills as part of remediating hazardous chemical and Superfund sites, with particular emphasis on providing for true long‐term public health and environmental protection from the wastes and contaminated soils that are placed in the landfills. On‐site landfilling or capping of existing wastes is typically the least expensive approach for gaining some remediation of existing hazardous chemical/Superfund sites. The issues of the deficiencies in US EPA and state landfilling approaches discussed herein are also applicable to the landfilling of municipal and industrial solid “nonhazardous” wastes. These deficiencies were presented in part as “Problems with Landfills for Superfund Site Remediation” at the US EPA National Superfund Technical Assistance Grant Workshop held in Albuquerque, New Mexico, in February 2003. They are based on the author's experience in investigating the properties of landfill liners and the characteristics of today's landfills, relative to their ability to prevent groundwater pollution and to cause other environmental impacts. Discussed are issues related to both solid and hazardous waste landfills and approaches for improving the ability of landfills to contain wastes and monitor for leachate escape from the landfill for as long as the wastes in the landfill will be a threat. © 2004 Wiley Periodicals, Inc.     

Case study: An innovative approach to chemical landfill remediation

This article presents a case history of hazardous waste landfill remediation activities at General Electric's Silicone's (GES's) manufacturing facility in Waterford, New York. The approach presented describes the development of the remedial program and its subsequent modification in achieving regulatory compliance goals, providing environmental benefit, and satisfying business considerations and budgetary constraints.