=11111V: :-0F-Ael - i% I20962 November 1999 Guidance Note on 5 Leachate Management for WORKING Ld l 5 td i kk C X X0 11 a n n C55 C 1l C ~~~~P A P E R Municipal Solid Waste Landfil,SRE Lars Mikkel Johannessen LA .J M..,:~~~~~~~~~~~~~~~h The World Bank is committed to knowledge sharing which involves not only the Bank's communities of practice and their partners, but the entire development community. A process of knowledge management is essential to make sense out of and act upon the vast quantities of information available today. Still in the early stages of implementation, knowledge management is expected to change the internal operation of the World Bank and transform the organization's relationships with external clients, partners and stakeholders, becoming a key way of doing business in the 21st Century. 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The Urban and Local Government Working Papers Series is geared to a technical audience and is intended to aid the work and improve the results of both Bank and non-Bank technicians and practitioners working in this field. Angela Griffin Tim Campbell Urban Sector Manager Global Urban Partnership Urban Development Division Transportation, Water and Urban Development Department Finance, Private Sector and Infrastructure Network The World Bank Photo by Lars Mikkel Johannessen GUIDANCE NOTE ON LEACHATE MANAGEMENT FOR MSW LANDFILLS WORKING PAPER SERIES Guidance Note on Leachate Management for Municipal Solid Waste Landfills Lars Mikkel Johannessen Urban Development Division Urban Waste Management Thematic Group GUIDANCE NOTE ON LEACHATE MANAGEMENT FOR MSW LANDFILLS Copyright @D1999 The Inrternational Bank for Reconstruction and Development/THE WORLD BANK 1818 H Street, N.W. Washington, D.C. 20433, U.S.A. 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INTRODUCTION ......................................... 1 1.1 Background . ....................................................... 1 1.2 Objective . ........................................................ 1 1.3 Target groups and limitations of the guidance notes ................ ..... 1..... 1.4 Cross references . . ................................................... 2 2. LEACHATE MANAGEMENT STRATEGY FOR MSW LANDFILLS ... 2 3. REGULATORY AND INSTITUTIONAL ARRANGEMENTS ... ...... 4 3.1 Regulatory requirements .............4.............. .... 4 3.2 Institutional arrangements ............................................ 5 4. LEACHATE GENERATION AND WATER BALANCE .... .......... 5 5. LEACHATE COMPOSITION AND POLLUTION POTENTIAL ...... 7 5.1 Leachate composition ................................................ 8 5.2 Leachate pollution potential ........................................... 9 6. LEACHATE CONTAINMENT AND COLLECTION .. 10 6.1 Leachare containment ....................................... ....... 10 6.2 Leachate collection ...... 11 7. LEACHATE TREATMENT OPTIONS .......................... 12 8. ECONOMIC CONSEQUENCES ............................... 13 8.1 Containment . . .................................................... 13 8.2 Collection systems . . . . 14 8.3 Leachate treatment ..................................1............... 14 8.4 Leachate management costs as part of total landfill costs-comparative examples ... . 1 5 9. CHOICE OF LEACHATE MANAGEMENT SYSTEMS .............. 18 9.1 Strategy .......................................................... 18 9.2 Containment ...................................................... 19 9.3 Collection ................................ ....................... 19 9.4 Treatment ......................................................... 19 9.5 Other leachate management approaches .................................. 20 ANNEXES Annex A: Leachate Composition from German MSW Landfills ....................... 21 Annex B: Leachate Treatment Options .......................................... 22 U GUIDANCE NOTE ON LEACHATE MANAGEMENT FOR MSW LANDFILLS ACKNOWLEDGMENTS The World Bank gratefully acknowledges the financial support of the Danish government agency, DANIDA, in developing this guidance note. Also acknowledged for their patient and valuable comments to draft versions of this guidance note are Carl Bartone and Gabriela Bover, TWU, and Dan Hoornweg, EAS, of the World Bank, and Philip Rushbrook, WHO, Europe. Thanks are also extended to L. Diaz, N. C. Vasuki, and Mike Pugh of the Delaware Solid Waste Authority. Thanks are also extended to Ole Hjelmar of the Water Quality Institute of Denmark for the long discussions on principles of leachate management. In addition, a personal thanks is extended to Tania Hollestelle of TWU for helping prepare the mliall- uscript for this guidance note and Laura DeBrular of TWU for assisting in the final editing. GUIDANCE NOTE ON LEACHATE MANAGEMENT FOR MSW LANDFILLS 1. INTRODUCTION 1.1 Background One of the most important issues related to siting, planning, design, operation, and long-term management of a municipal solid waste (MSW) landfill is the management of leachate. Leachate is the fluid percolating from landfills that is generated from liquids present in the waste and water from outside percolating though the waste. Leachate will be generated wherever water can enter waste in a landfill or dumped. The quantity and strength of the generated leachate depends on several factors, the most important of which are: a) the amount and characteristics of the discharged waste; b) cli- matic conditions; c) cell size and phasing of the disposal area; d) operational techniques applied at the landfill; and e) the final top cover applied. Leachate from MSW landfills contains various contaminants at concentration levels that may have an environmental impact on groundwater and surface water and may therefore be a threat to human health. Leachate may be highly toxic for several decades or even centuries before reaching a level where it is no longer a threat to the environment. "Eternal" leachate collection and treatment at MSW landfills, however, is not a realistic long-term leachate management option because this approach requires external inputs of energy and maintenance. It is therefore necessary to accept that landfills eventually will be left unattended and thus acknowledge the eventual release of some leachate into the environment. Hence, leachate management becomes an important issue in deciding which strategy to apply in any planning process involving closure of dumps and/or siting and development of landfills. The options range from prevention of leachate generation, to sophisticated leachate treat- ment options, to controlled release of leachate into the environment. 1.2 Objective The objective of this technical guidance note is to provide practical guidance for better project prepa- ration involving leachate management for municipal solid waste landfills. 1.3. Target groups and limitations of the guidance notes The document is aimed at local and donor agency task team leaders and their task teams for urban, envi- ronmental, and solid waste projects. The guidance note also provides essential information for solid waste and environment decision makers and professionals involved in project preparation in client countries. The guidance note may not apply to arid climates, as the assumption is that disposal of waste in arid climates rarely generates excess leachate that can affect the environment. However, monitoring may still be essential in arid areas. The guidance note does not provide detailed technical advice on specific leachate containment (i.e., lining and drainage) or treatment, nor does it set specific discharge standards. I, GUIDANCE NOTE ON LEACHATE MANAGEMENT FOR MSW LANDFILLS 1.4. Cross references Technical guidelines for designing and construction MSW landfills are provided in the newly devel- oped "Solid Waste Landfills in Middle- and Lower-Income Countries: A Technical Guide to Planning, Design, and Operation," by P. E. Rushbrook and M. P. Pugh. (Published by the World Bank, World Hcalth Organization (WHO), the Swiss Agency for Development and Cooperation (SDC), and the Swiss Center for Development Cooperation in Technology and Management (SKAT), 1998.) Other World Bank technical guidance notes in this series include: * Haukohl, J., Marxen, U., and Rand, T., "Decisionmakers' Guide to Municipal Solid Waste Incineration," The World Bank, (under preparation, expecred 1999). * Haukohl, J., Marxen, U., and Rand, T., "Municipal Solid Waste Incineration," The World Bank. (under preparation, expected 1999). d Johannessen, L. M., Dijkman, M. "Health Care Waste Management," (under preparation, expected 1999). * Johannessen, L. M., "Guidance Note on Recuperation of Landfill Gas from Municipal Solid Waste Landfills," The World Bank, Urban and Local Government Working Paper Series, September 1999). * Johannessen, L.M., Bartone, C., "Guidance Note on Approach to Siting of New Landfills," (under preparation, expected early 2000). In addition, further details on leachate management may be found in: * Christensen, T.H., Cossu, R., Stegmann, R. (ed.), "Landfilling of Waste: Leachate." Elsevier Applied Science, Elsevier Science Publisher, England, 1992. 2. LEACHATE MANAGEMENT STRATEGIES FOR MSW LANDFILLS The main objective of leachate management is to ensure that landfilled waste does not impose any unacceptable short- or long-term risks to the environment or to public health. Throughout the world, one of four distinct leachate management philosophies is applied to a lesser or greater extent to meet this objective, either as part of the regulatory framework or as a general practice. The four philoso- phies and their consequences are as follows: * Encapsulation and total containment, also known as the "dry tomb" concept, is meant to prevent leachate generation by halting the percolation of water through the waste, apart from what may be generated from the moisture content in the waste at the time of disposal, and any moisture generated during the period before final capping. This philosophy makes sense only in wet climates. U _ _ _ __ _ _ _ _ GUIDANCE NOTE ON LEACHATE MANAGEMENT FOR MSW_LANDFILLS The result of this strategy is that the waste is virtually preserved and therefore the environmental risk from the waste may remain virtually unchanged for a very long time. As the encapsulation eventually will fail (due to settling and unforeseen events or activities), perhaps centuries after installation, uncontrolled release of leachate may occur. This strategy therefore passes on the responsibility for leachate management of today's waste to future generations. Hence, this approach should be seen as a preliminary storage strategy and not as a long-term sustainable leachate management option for MSW landfills. * Containment, collection, and disposal of leachate, in principle also known as a "sanitary" landfill, is a strategy in which generated leachate is collected from a liner system of low impermeability, sent through a drainage system, and normally led or pumped for treatment before final discharge to a surface water body. The rate of leachate formation depends on climatic conditions and, after final infilling, is also controlled by the top cover. This strategy enhances stabilization and mineralization of the disposed waste (e.g., through an enhanced bioreactor landfill with options for recirculation of leachate and/or enhanced infiltration of water). The containment, collection, and disposal of leachate strategy is often built on the "eternal" system philosophy. This type of leachate treatment system often requires inputs of energy and may therefore have an active lifetime of 30-50 years after closure, after which it eventually fails (through lack of maintenance, cessation of power, etc.). Consequently, uncontrolled release of leachate may eventually occur and therefore impose unexpected environmental effects from today's waste onto future generations. In combination with other leachate management measures, however, this leachate management strategy can be a first step toward acceptable leachate release. - Controlled contaminant release is a strategy in which the release of the quality and/or quantity of leachate is maintained at all times at an environmentally acceptable level without inputs of energy or other required maintenance. Prior to any release of leachate, the environmental impacts must be assessed and the acceptable level of leachate release determined. MSW leachate may, in the short term (i.e., < 30-50 years), exceed requirements for controlled release. For most MSW landfills under wet climatic conditions, the containment, collection, and disposal strategy may be required as the initial leachate management step. During this time settling will occur and landfill gas will be generated. Consequently, stable sloped top covers, surface drainage systems, and vegetation may require significant maintenance. Hence, the long-term strategy of controlled contaminant release from a MSW landfill may apply only when the waste is stabilized and limited settling will occur. A long-term control measure may be the installation of geologically stable and sloped top covers with a surface drainage system and surface vegetation with high potential evaportranspiration. * Unrestricted contaminant release occurs where no precautions are taken to prevent or reduce the release of leachate. As a strategy, this may be applied to inert waste landfills (i.e., for construction waste or soil) and to MSW landfills in arid climates. However, dumps for MSW apply this leachate management method in wet climates as a lack of strategy. Consequently, the uncontrolled release of leachate will eventually occur and have unpredicted (and often . t~~~~ GUIDANCE NOTE ON LEACHATE MANAGEMENT FOR MSW LANDFILLS unacceptable) environmental effects on groundwater and/or surface water. This approach is therefore not a valid leachate management strategy for MSW landfills. 3. REGULATORY AND INSTITUTIONAL ARRANGEMENTS 3.1 Regulatory requirements Leachate management should be seen as an integral part of landfill siting, planning, design, construc- tion, operation, and maintenance. Leachate management should therefore be integrated into the reg- ulatory framework for landfills. Where legislation on landfills exists, short-term impacts are often covered. Long-term impacts from leachate, however, should also be reflected in regulations concerned with the landfilling of waste. Leachate management regulations should consider the following factors: * Siting is often controlled by several factors. Leachate management strategy and siting should be an iterative process, in which the optimal site for a landfill also provides environmentally acceptable properties for long-term leachate management. Knowledge of hydrogeology and hydrological connection to surface waters becomes important in long-term leachate management strategies, as leachate eventually will be released to groundwater. Groundwater downstream from a landfill may therefore have to be written off and alternative water supplies may be necessary. * Design/construction requirements for leachate management should be flexible and based on functional demanids rather than specific criteria, as no two landfill sites are identical. * Discharge standards for leachate treatment plants under normal conditions may be set as standards for industrial sewage treatment or for municipal sewage treatment plants. For a discussion of direct release, see below. * Monitoring requirements should be the single most important regulatory factor in leachate management. From a regulatory point of view, monitoring should: a) track the development and fate of leachate composition; b) either detect if any leachate has leaked to groundwater, or follow development of the intentionally released leachate; c) include indicators for leachate treatment effluent; and d) determine the effects on the receiving surface water. Bio-monitoring of the cumulative effects on the surface water may be required because traditional monitoring of chemical parameters is often inefficient due to dilution and masking effects blur from other sources. * Release of leachate to groundwater should only be permitted based on predetermined requirements. These could include a requirement that leachate composition must constantly remain below set site-specific standards (based on dispersion and dilution potential in GUIDANCE NOTE ON LEACHATE MANAGEMENT_FOR MSW LANDFILLS groundwater and the vulnerability of surface water) for a period of at least two years. These standards may be based on criteria dictating that: a) the dilution potential in the groundwater be sufficient to ensure that the leachate plume entering the receiving surface water does not exceed discharge standards set for the treatment plant otherwise treating the leachate and discharging to the same receiving water; and b) ensuring that the total flux of contaminants out of the landfill is environmentally acceptable to the receiving surface water. Other requiirements might include assumptions for groundwater and surface water that should be fulfilled at least five years prior to release of the leachate, and that monitoring of groundwater should be carried out for five years after the onset of leachate rclease from the landfill. After that point, monitoring should no longer be necessary, as any leachate that is released is unlikely to pose any environmental risk. 3.2. Institutional arrangements In addition to including the relevant authority on landfilling of waste, institutional arrangements should involve competent authorities on discharge standards for treatment plants and on the protec- tion of groundwater and surface water. Leachate will pose an environmental risk longer than any other potential environmental hazards from a landfill. If the decision is made for eventual release of leachate from the landfill, the capacity to do so at a competent authority level is essential. For many countries, this capacity may (and should) exist only at the national level. To ensure a basis for decisionmaking, a mechanism to store and convey leachate monitoring data to the competent authority at the national level should be established. 4. LEACHATE GENERATION AND WATER BALANCE Leachate is generated primarily from precipitation and thus is principally influenced by climatic con- ditions such as rainfall and evaporation. In arid climates, virtually no excess leachate occurs; in semi-arid areas, leachate may be generated irregularly or only at certain times of the year. In wet climates, landfills may produce significant quantities of leachate year-round. It is thus essential to predict the quantity of leachate that will be generated at the location selected for a landfill, in order to accomplish the following steps: a) Decide which leachate management strategy to employ. For arid and semi-arid areas, the quantity of leachate generated may be insignificant and may have no unacceptable impact on the environment; therefore, leachate management may be limited. For wet areas, where significant quantities of leachate may be generated, containment and leachate treatment may be required as a short-term leachate management strategy [see d) below]. U GUIDANCE NOTE ON LEACHATE MANAGEMENT FOR MSW LANDFILLS b) Enable properly designed leachate treatmentfacilities. The quantity of leachate is often one of the essential design criteria for leachate collection systems and treatment facilities plant. Where a significant quantity of leachate will be generated, the design should aim to handle large quantity fluctuations (wet/dry season fluctuations) and still meet effluent standards. An alternative is providing for adequate storage of leachate. This may also add flexibility into the design of a leachate treatment facility. c) Enable proper design of disposal areas and leachate collection system. Where significant quantities of leachate are generated, it may be necessary to reduce the areas exposed to direct precipitation, as these areas may produce large fluctuations in leachate generation. Construction of small cells to reduce leachate generation should be considered. The leachate collection system should be designed to accommodate average peak leachate quantities. d) Assess the potentialfor recirculation of leachate. In some climatic zones with heavy precipitation during the wet season, recirculation of leachate may be restricted to reduce the risk of landfill slides and "spilling over" of leachate to the surrounding environment. e) Estimate the hydraulic pressure on the designed liner system to estimate the magnitude of leachate released to the environment. f) Assess the pollution potential as a function of flux (i.e., leachate quality times leachate quantity per frequency). Calculating leachate generation can be done through water balance models. Several models exist, from the very advanced and sophisticated, like the U.S. Environmental Protection Agency's (EPA) HELP model (version 3.07) with high demands for data input, to the simplest version: L = R - E Where: L represents the leachate volume R represents the volume of precipitation E, represents the volume of actual evaportranspiration (or simpler evaporation from the ground surface) Both rainfall and evaporation data are collected routinely by meteorological stations and are usually available. Any model used to estimate leachate quantity should consider calculations of maximum daily quanti- ty, average quantity for each month of the year, and average annual quantity. As the quantity of gen- erated leachate varies significantly from open cells to closed cells, the evolution in leachate quantity throughout the lifetime (i.e., from the first cell to final cover of the entire disposal area) of the landfill Prepared by Paul Schroeder for the U.S. EIPA, this model can be downloaded from the Internet at the following address: http://vww.wes.army.mil/el/elmodels/helpinfo.html. GUIDANCE NOTE ON LEACHATE MANAGEMENT FOR MSW LANDFILLS should be reflected in leachate quantity estimates. Water balance models are often subject to consid- erable uncertainties, given the need to predict or estimate some of the pararneters in the equation. Any water balance model should only be used to indicate the magnitude of leachate generation. Thus, for this purpose, a relatively simple model may prove just as useful as the more sophisticated models. 5. LEACHATE COMPOSITION AND POLLUTION POTENTLkL The chemical composition of leachate is affccted by several factors, such as the characteristics of the disposed waste, its moisture content, depth of the disposed waste, the availability of oxygen (redox potential), the temperature and micro flora, compaction rate, and the dissolving of organic and in- organic components in the waste. The biodegradation of organic waste follows a pattern of five phases. These five phases are fundamen- tal and affect both leacliate collmposition and landfill gas generation anid composition. The five phases are illustrated in Figure 1. Figure 1: Optimal Development of Leachate Composition within a Landfill Cell' 80 N. C N1 so ~~~~ ~~CH4 N 40- 20 - :, i4 0 I COD~~~~~~~~~~~~~~~~O Z.; F, Ph, I [ III IV, V Amended from Christensen, T.H., Kjeldsen, P., "Basic Biochemical Processes in Landfills." Christensen, Cossu, Stegmann (ed.), "Sanitary Landfilling: Process, Technology and Environmental Impact." London, Academic Press, 1989. GUIDANCE NOTE ON LEACHATE MANAGEMENT FOR MSW LANDFILLS Each layer of disposed waste in a landfill will undergo the biodegradation phases illustrated in Figure 1. The overall factors intluencing the tinse that elapses for each phase art climatic conditionis and operational factors- Phases I and Il last from some weeks to two years (and sometimes longer). A higher ambient air tem- perature will enhance the biodegradation processes, as will high compaction rates, placing waste in thin layers, and the use of small landfill cells. Phases III and IV may last at high peak for some 15 years and fade thereafter, depending on the oper- ation of the landfill and, in particular, on the moisture content of the waste. As high moisture con- tent is essential to stimulate bioreactions, high precipitation will reduce the times for Phases III and IV and thus reduce the organic load in the leachate. Operational measures to enhance the biodegra- dation includes recirculation of leachate and extraction of generated landfill gas. Phase V of the landfill lifecycle is very dependent on the operational steps taken earlier in the landfill's life. Howcver, it may take several decades before the disposcd waste is finally stabilized and no longer constitutes a pollution potential. Ammonia is the limiting factor and will constitute poten- tial pollution for 100 years or longer. 5.1. Leachate composition The typical composition of leachate from a MSW landfill is given in Table 1. For simplicity, the composition is displayed for the so-called "acidic phase" (Phases I and II of Annex A) and the methanogenic phase (Phases IIT and IV of Annex A). As for the landfill gas, there are wide variations influenced by climatic and operational factors. For a detailed description of leachate composition, please refer to Annex A. Parameter Unit Acidic Phase Methanogenic Phase (6 months - 2 years) (2- 100+ years) pH 5-6.5 7.5-9 COD" n mg/l 20,000-30,000 1,500-2,000 BODs" mg/l 10,000-25,000 500-1,000 Iron mg/I 5-20 < 5 Zinc mg/l 1-5 0.03-1 Cadmium ,ug/l < 30 6 Ammonia mg/l 900-1,500 900-1,500 Chloride mg/l 1,200-3,000 1,000-3,000 Ch-mi-al Oxygen Demaind Biological Oxygen Demand Table 1: Typical Leachate Composition from Landfill with MSW 3Please note that leachate composition is based on data from wet climate conditions in the Northern Hemisphere. Adequate data are not available from developing countries. GUIDANCE NOTE ON LEACHATE MANAGEMENT FOR MSW LANDFILLS 5.2. Leachate pollution potential Leachate from MSW landfills frequently exceeds standards for drinking water and surface water, often for several decades. The leachate therefore often has the frequently significant potential to pollute groundwater and surface water. The most common pathway for leachate to the environment is from the bottom of the landfill through the unsaturated soil layers to the groundwater. then by groundwater through hydraulic con- nections to surface water. However, pollution may also result from the discharge of leachate through trcatment plants or by direct discharge of untreated leachate. The main factors influcncing the pollu- tion potential from leachate are: * the concentration and flux of the leachate; * the landfill siting, i.e., the hydrogeological setting and the degree of protection provided; and * the basic quality, volume, and sensitivity of the receiving groundwater and surface water. The primary components in leachate from MSW landfills that constitute a significant pollution potential are dissolved organic matter and inorganic salts. Trace elements in leachate are limited and generally do not constitute a groundwater pollution problem due to strong attenuation. Where groundwater is used (as drinking water or for irrigation) downstream from the landfill, leachate has great potential to pollute. Where groundwater is not used or is not usable downstream, the leachate's pollution potential (if not diluted to ambient concentrations) is transferred to where the groundwater is hydraulically connected to the receiving surface water. The dilution of leachate is faster in surface water than in groundwater. but the contaminants may also spread over larger areas much faster. As well as becoming diluted, biodegradable matter in surface water decomposes, leading to oxygen depletion. Some organic substances in leachate may be toxic to aquatic organisms. The major concern about organic matter from leachate in surface water may therefore be the ecotoxicolog- ical effects. Some components (inorganic trace elements) may also have cumulative effects on aquatic organisms. The inorganic component of concern in leachate is ammonia. Ammonia is toxic to fish and other aquatic organisms and may generate eutrofication.' During nitrification of ammonia in surface water, oxygen depletion will occur and may affect the aquatic ecosystem. For freshwater courses, discharge of leachate with high salt concentrations may alter the salinity and thereby affect the aquatic ecosys- tem. If a body of surface water (e.g., brackish waters) is not sensitivc to these cffects, however, the byproducts of leachate discharge may not have any adverse environmental impact. Significant growth of algae in water where nutrients are in surplus, resulting in a lack of oxygen in the water. GUIDANCE NOTE ON LEACHATE MANAGEMENT FOR MSW LANDFILLS 6. LEACHATE CONTAINMENT AND COLLECTION To prevent leachate from emanating in an uncontrolled manner into the surrounding environment, the leachate in a landfill must be contained and collected. 6.1. Leachate containment A seal/liner system is used to contain leachate. Prices for the different liner types are given in Chapter 8. There are a number of containment option with different installation requirements and varying degrees of leakage (see Table 2): * Natural liners of either in-situ clay or clay brought to the site offer a low permeability. The requirements for the thickness of the clay layer and permeability are often set in national regulations and may vary from 0.5 meter-2 meters, with a theoretical permeability of less than 10 -10 ' meters per second (m/sec). The theoretical leakage from this type of liner may be some 5-50 mm of leachate per year. Artificial mineral liners such as benronite-enhanced sand spread in thin layers or geosynthetic clay liners (a sandwich with bentonite between two geotextiles or glued to a geomembrane) may achieve theoretical (saturated) permeability of less than 10" m/sec. The unsaturated permeability may be as high as 108 m/sec. The theoretical (saturated) leakage may be in the range of 6-10 mm per year. Sodium bentonite is the predominant type of bentonite used as it can withstand chemically aggressive coniponenits in Icachate better than calcium bentonite. * Synthetic liners of various materials are used, most commonly HDPE, LDPE6, and latex. The thickness of the liners varies from 0.5 mm-2.5 mm. The thickness may be less important for performance than the material's physical, chemical, and biological resistance. The theoretical leak- age of leachate through a synthetic liner may be as much as 40 mm per year. * Liner combinations comes in many versions. Double liner systems with a leak-detection system may only indicate when leachate leaks through the primary liner. It is now widely accepted that a leak-detection layer between two independent liners simply results in an increased need for leakage control, withIout increasing the level of security. In contrast, composite liners, where two linlers of different materials (e.g., a natural clay liner and a synthetic liner) are in direct internal contact, may achieve a significant increase in security. The theoretical leak through a composite liner may be less than 0.2 mm per year. High Density Polyethylene 6Low Density Polyethylene GUIDANCE NOTE ON LEACHATE MANAGEMENT FOR MSW LANDFILLS Liner Type Theoretical Leakage Sophistication of Installation in mmnyear Natural clay/ 5 - 50 High demand for local (e.g., road) in-situ clay contractor in-situ clay to install the liner. Price greatly dependent on local availability of clay. Bentonite mats 6- 10 Shipment often required; installation may be carried out by local contractor with local labor. Synthetic liner - 40 Shipment often required and highly specialized welding labor and equipment required. Composite liner < 0.2 Shipment often required and highly (e.g., synthetic/ specialized welding labor and equipment bentonite matemats) required for the synthetic liner-local labor may install bentonite mats. Table 2: Overview of Different Liner Types and Their Theoretical Annual Leakage 6.2. Leachate collection If a landfill is equipped with a containment system. the hydraulic head of leachate on the liner must be controlled by a leachate collection system at the base of the disposal area. A leachate collection sys- teri genlerally consists of the following: * Drainage blanket, consisting of inert (non-calcareous) coarse gravel, typically designed to keep the hydraulic head over the liner below 0.3 meters. With a sufficient thickness (> 0.3 meters), the drainage blanket also serves as a protection layer for the liner system. Artificial drainage grids have been introduced, but have not yet proven adequate, as they are prone to rapid clogging. * Drainage elements (i.e., a means of transporting leachate to the leachate collection point) range from the use of coarse gravel alone to the installation of 300 mm HDPE drainage pipes. Drainage elements surrounded by geotextiles to prevent fine materials from entering the drainage element can develop biological growths and a build-up of chemical precipitates, leading to a reduction in permeability. For this reason, geotextiles should not be used around drains. Leachate collection point, the lowest point of each cell at the base of the disposal area to which leachate is led by gravity through the drainage system. The collection point may be a shaft m GUIDANCE NOTE ON LEACHATE MANAGEMENT FOR MSW LANDFILLS constructed of coated concrete or an artificial material such as fiberglass or HDPE. The collection point is the focus for monitoring leachate and removing leachate from the disposal area for treatment and/or discharge. Removal should be by gravity wherever possible. However, if it is not possible and pumping is required, the pumps must be suitable for pumping agressive liquid. These pumps must be changed at least every five years, and possibly more often. 7. LEACHATE TREATMENT OPTIONS Wherever leachate is collected, a discharge option must be provided. Most often, leachate requires treatment before final discharge to the environment. Where a municipal sewage treatment plant exists, the preferred discharge of leachate may occur there, providing the plant has the capacity to receive the leachate (i.e., it can meet effluent standards after receiving the leachate). With the expect- ed composition of leachate (see Table 1 andaAnnexA), many municipal sewage treatment plants in developing countries may not be suited to receive the leachate, in particular due to high loading rates of ammonia and chloride and, to a certain extent, organic matter. Large fluctuations in the quantity of leachate may also render certain plants unable to meet basic standards. Where leachate is dis- charged to a mechanical sewage treatment plant, the treatment will have virtually no effect other than dilution. In many developing countries, therefore, on-site leachate treatment may be necessary. The main com- ponents to be treated in MSW leachate are organic matter, ammonia, and (where the leachate will be discharged to fresh water) chlorides. The degree and type of treatment varies greatly, depending on standards for discharge or, where such standards do not exist, the vulnerability of the receiving water, climatic conditions, and the quality and quantity of leachate generated. A combination of different treatment methods may therefore be required. The three most common treatment methods are: e Physical/chemical treatment, which primarily includes the addition of simple chemicals followed by mixing, flocculation, coagulation, and settlement before or after other treatment. The physical/chemical treatment primarily reduces suspended solids; precipitates iron, manganese, calcium carbonate, and heavy metals; removes turbidity and color; and removes some of the organic matter. Air stripping can be used to remove ammonia by increasing the alkalinity (pH > 10) and aerating the leachate. * Biological treatment, which is often the most important and most commonly used method to treat leachate for ammonia and organic matter. However, it is not effective in removing inorganic salts. The treatment is predominantly performed by aerobic bacterial degradation of organic matter and nitrification of ammonical nitrogen to nitrite and nitrate. The cheapest and most robust biological process is aeration in lagoons, although lagoons often demand large areas. Activated sludge and rotating biological contractors may also be applied, although these are more sophisticated and entail much higher costs. U ~~~~~~~~~~~~~~~~~~ GUIDANCE NOTE ON LEACHATE MANAGEMENT FOR MSW LANDFILLS Tertiary treatment, which is often accomplished by highly sophisticated and expensive measures such as reverse osmosis and activated carbon adsorption. These methods are usually not appropriate in low-income countries. However, less sophisticated methods for the final stages may be achieved by creating artificial wetlands (which can also be used for pre-treatment) for nitrification and removal of residual organic matter; or land treatment by spraying leachate across sloped grasslands or woods to achieve evaporation, precipitation, oxidation, nitrification, and plant uptake. Fast-growing plants such as bamboo, poplar, or other non-sensitive plants may be used to boost evaporation and removal of nutrients. One disadvantage of the latter two treatment methods is the risk of damaging soil and vegetation, and the possibility of leakage to groundwater. In semi-arid areas and in wet areas with a long dry season, simple evaporation schemes may be used to eliminate leachate discharge. However, if there is no pre-treatment, the final residue after evaporation will contain extremely high concentrations of dry organic rmatter and salts, which may be considered hazardous and therefore difficult and/or expensive to dispose of. An overview of different treatment options for various components in leachate is given in Annex B. 8. ECONOMIC CONSEQUENCES The costs of leachate management can be divided among the areas of: a) containment; b) collection; c) treatment; and d) final top cover. All of these depend on several factors, the most important of which are: * the annual precipitation in the area where the landfill is situated; * the strategy chosen for leachate management; * the level of environmental protection (liner system applied and level of leachate treatment); and * the size of the landfill. Mbst landfills are constructed to expand continuously, with expected investments in leachate manage- ment systems (primarily liners) for most years during operation. As investment schemes depend heavily on these four factors, the following section provides only unit costs and price ranges. 8.1. Containment Liner systems for containment are described in Section 6. The minimum size landfill cell feasible to line will be some 2.5-5 ha. The factors influencing the price for liners include: a) shipping distance; b) size of the job; c) market demand in the region; and d) time of year when the liner is to be installed. The price ranges for the various liner types are given in Table 3. * 13~~~ GUIDANCE NOTE ON LEACHATE MANAGEMENT FOR MSW LANDFILLS Liner Type Theoretical Price RanFe for Liner Leakage Installed in US$/m2 in mm/year Natural clay/ 5 - 50 3 - 6 in-situ clay Bentonite mats 6- 10 4 - 10 Synthetic liner - 40 5 - 8 b) Composite liner < 0.2 9- 18 (e.g., synthetic/ bentonite matemats) The price is based on a minimum area of 2.5 ha liner installed. b For certain parts of the world, this price may be significantly higher due to shipping and/or labor costs. Table 3: Theoretical Leakage and Aproximate Price Range for Installed Liniers (1996 price levels) 8.2. Collection systems Most leachate collection systems can be made from local materials and can be installed by local con- tractors. The price for leachate collection systems may also depend on the sophistication of the system and specific needs, ranging from less than US$1/m2 to more than US$4/mi. 8.3. Leachate treatment Data available on leachate treatment costs are very scarce. No cost data have been available from developing countries, partly because leachate treatment plants rarely exist and partly because there is little incentive for landfill operators to reveal their leachate treatment costs. The following costs range widely and can therefore only be indicative, reflecting the fact that the available data are very site-spe- cific. Factors likely to affect leachate treatment costs include: a) treatment capacity volume (size of landfill and precipitation in area); b) loading rates of leachate (stage of decomposition of the waste); and c) required effluent standards for the final receiving water body. The initial investment in a plant that treats 100 mr/day of leachate (equivalent to 400 mm/year at a 10 ha disposal area) may range from less than US$1.8 million to more than US$5.4 million, depend- ing on the level of sophistication of the plant. GUIDANCE NOTE ON LEACHATE MANAGEMENT FOR MSW LANDFILLS Leachate treatment has relatively high operation and maintenance costs, which constitute 40-60% of the total investment, operation, and maintenance costs per cubic meter. The cost of biological treat- ment with air stripping, meeting standards for discharge to a robust receiving water, falls in the range of US$6-US$20/my. 8.4. Leachate management costs as part of total landfill costs-comparative examples The magnitude of leachate management investment and operational costs, as compared with all other landfill investment and operational costs, are illustrated with the following examples. The examples assume a 10 ha landfill, which receives 300-350 tonnes per day over a 10-year period. The total capacity of the landfill is 1 million tonnes. Investment and recurrent costs for construction and oper- ation of the landfill are based on 1996 prices from the Philippines. The liner is assumed installed as natural clay. Leachate treatment is assumed as aerobic biological treatment with ammonia stripping. It is assumed that the initial treatment costs (amortized investments and recurrent costs) are US$10/m3 (100% of costs) reduced linearly to zero following the end of aftercarc. The normal aftercare, monitoring, and liability period for a landfill is 30 years. If it is assumed that the landfill can be left unattended 30 years after closure, the total landfill costs will, as indicated in Table 4, range from US$10-US$15/tonne of waste disposed. Leachate treatment costs (investment and operational) constitute 50-67% of the total landfilling costs, as indicated in Figures 2 and 3. GUIDANCE NOTE ON LEACHATE MANAGEMENT FOR MSW LANDFILLS Annual Leachate Treatment Costs Liner/Leachate All Other Landfill Operation and Total Landfill Generation (investment and Collection Investments Maintenance Costs operational costs) (except leachate trcatuient) 200 mm/year 5.1 1.2 2.4 1.4 10.1 400 mm/year 9.9 1.2 2.4 1.4 14.9 Table 4: Leachate Treatment Costs Compared with Total Investment and Operation Costs with a 30-year Aftercare Period (US$/tonne)-An Example Figure 2 Landfill costs with 30 year aftercare (US/tonne; % of total) 200 mm leachate generated per year O&M Treatment costs Other LF costs __50% 24% Liner/leachate collection 12% Figure 3 Landfill costs with 30 year aftercare (US/tonne; % of total costs) 400 mm leachate generated per year O&M Other LF costs 9% Liner/leachate Treatment costs collection 67% 8% It is asstumed that leachate will be treated until the polhltion potential is at a level where the leachate can be released into the environment with no adverse impacts; under such a scenario, treatment may be required for 150 years or more. Table 5 indicates that the total landfilling costs should then range from USS21 - US$37 per tonne of svaste. Leachate treatment may then constitute some 77-87% of the total landfill costs, as illustrated in Figures 4 and 5. U GUIDANCE NOTE ON LEACHATE MANAGEMENT FOR MSW LANDFILLS Annual Leachate Treatment Costs Liner/Leachate All Other Landfill Operation and Total landfill Generation (investment and Collection Investments Maintenance Costs operational costs) (except leachate - -~~~~~~~~~~~~~~~~~~treatment) 200 mm/year 16.6 1.2 2.4 1.4 21.6 400 mm/year 32.4 1.2 2.4 1.4 37.4 Table 5: Leachate Treatment Costs Compared with Total Investment and Operation Costs, Assuming a 150-year Aftercare Period (US$/tonne)-An Example Figure 4 Landfill costs with 150 year aftercare (US/tonne; % of total costs) 200 mm leachate generated per year Other LF costs O&M 110/ 60/ Liner/leachate collection _______ 6% Treatment costs 77% Figure 5 Landfill costs with 150 year aftercare (US/tonne; % of total costs) 400 mm leachate generated per year Other LF costs Liner/leachate 6% 0O&M collection 4% Treatment costs 87% It should be emphasized that local conditions will create many uncertainties and variations for these estimates of leachate management costs. It is, however, clear that leachate management constitutes by far the largest investment and operational costs for a landfill and therefore should have a significant influence on the actual tipping fees to be charged for disposal of each tonne of waste. This is true whether the leachate is managed for 30 years or until the leachate reaches direct discharge standards. The choice of leachate management system therefore becomes extremely important during the initial stages of landfill planning and development. GUIDANCE NOTE ON LEACHATE MANAGEMENT FOR MSW LANDFILLS 9. CHOICE OF LEACHATE MANAGEMENT SYSTEMS The choice of leachate management system may be tied to regulations at the national or regional level. In some countries, regulations may allow flexibility as long as the final choice is justified with an in-depth environmental assessment, including serious evaluation of alternatives. Other countries have very specific standards, leaving little flexibility in the choice of which leacliate naisagemneuit sys- tem to apply. 9.1. Strategy Leachate management is usually not an issue for landfills in arid climates where no excess leachate is generated. For landfills in semi-arid climates, where excess leachate is generated occasionally, there may be a need for leachate containment, collection, and treatment/handling. Leachate treatment/han- dling may simply include storage and evaporation, or the adoption of a more sophisticated approach with recirculation of leachate into already disposed waste, with the intention of stabilizing the waste and evaporating excess leachate during recirculation. However, under some semi-arid climatic condi- tions, the leachate levels may be low enough to allow for controlled releases into the environment. The assessment in this circumstance should be based on the same considerations as those for long- term leachate management in wet climatic conditions, as outlined below. AMl landfills subjected to wet climatic conditions, where excess leachate is generated, will have an impact on groundwater and/or surface water. These landfills will require some type of leachate con- tainment. If containment is applied, it is imperative that leachate collection and treatment also be part of the short-term leachate management strategy. Long-term leachare management is necessary when the landfill has reached stable conditions and there is no longer a potential for unacceptable environmental impacts from release of leachate into the environment. The release of leachate into the environment requires that the following conditions be met: * There is no potable use of groundwater that can be adversely affected downstream from the land fill; * The dilution potential in the grounidwatcr is sufficient Lo cnsure that the leachate plumlle clntering the receiving surface water does not exceed discharge standards set for the treatment plant that would otherwise treat the leachate and discharge to the same receiving surface water; and * The total flux of contaminants out of the landfill is environmentally acceptable to the receiving surface water. Long-term leachate management thus requires extensive knowledge of a) the quantity and quality of leachate generated; b) development and composition of the potential contaminants in the leachate; c) the quality and flow of groundwater downstream from the landfill; d) the potential for dilution and dispersion in the groundwater; and e) the vulnerability of the receiving surface water body. U GUIDANCE_NOTE ON LEACHATE MANAGEMENT FOR MSW LANDFILLS 9.2. Containment Containment for leachate should always be based on site-specific conditions, primarily the vulnerabil- ity of groundwater and, eventually, the receiving surface water body. In comparison with a single liner (natural or synthetic), a composite liner (two liners internally in direct contact) may reduce the leakage of leachate to groundwater by a factor of 25-50. However, the increased security may double the cost for the liner system. There is often less reason to justify the additional cost if long-term leachate management is taken into consideration during siting of MSW landfills. For most developing countries, a liner of natural clay (including geo-synthetic clay liners) may be preferable because the installation and construction of these liners often can be provided by local con- tractors. Synthetic liners, if correctly installed, may provide the same level of security as clay liners. However, installation requires highly specialized equipment and often requires international contrac- tors to carry out the installation. Phased installation, which is required for each cell expansion, may therefore become difficult and more expensive. 9.3. Collection Where containment of leachate is part of the leachate management system, leachate collection should be provided. To the extent possible, natural materials such as coarse gravel should be used for the drainage blanket and drainage elements of disposal areas. Natural flow (by gravity) of leachate will add to the long-term sustainability of leachate management. Siting of landfills may help to provide natural flow of leachate and should be preferable to pumping. 9.4. Treatment Treatment of leachate to almost any desired discharge statidard is possible. The dischargc standards are often receiving water-specific; the volume of leachate varies and the composition of leachate may vary. The required extent of leachate treatment therefore varies. The choice of leachate treatment may be made based on the following key issues: * The availability of appropriate capacity at the local sewage treatment plant; * local discharge standards and the vulnerability of the receiving water body; * the operational capacity for on-site treatment; * provisions for recirculation, through appropriate operational procedures; e.g., limited if any daily soil cover and avoiding the use of soil with clay content; * power prices/affordability/willingness to pay for treatment; and * the area available for construction of an on-site treatment facility. In general, highly sophisticated treatment methods should not be applied on-site. Regardless of the level of sophistication, leachate treatment is the costliest item in a landfill's budget, even if leachate is U GUIDANCE NOTE ON LEACHATE MANAGEMENT FOR MSW LANDFILLS only treated for a 30-year period. As "eternal" leachate treatment is both unrealistic and prohibitively expensive, landfill planners must accept that leachate will eventually be released into the environ- ment. It is therefore advisable to use a treatment system that is simple to operate and that provides some level of treatment even if it fails. In warmer climates, this may be achieved through aerobic bio- logical treatment (e.g., aerated lagoons) followed by finishing and post-treatment in a natural or arti- ficial wetland system before final discharge to the receiving water or groundwater. 9.5. Other leachate management approaches Other options for leachate management to be considered include: * Afinal top cover may be used to control the volume of leachate generated. A simple top cover with vegetation will reduce infiltration through evaporation. More significant reductions in infiltration may be achieved by applying a low-permeable top cover, such as clay. Reduced infiltration will lessen the annual release of contaminants from the landfill, while at the same time extending the time during which leachate management is required. * Recirculation of leachate may have multiple purposes: a) treatment, by reducing the load of organic matter in the leachate' with virtually no other leachate components affected; and b) leachate storage, by building up leachate inside the landfill until treatment capacity is available. In a worst-case scenario, this can lead to disastrous landfill slides. A further goal may be c) leachate reduction, by sprinkling and consequent evaporation, wlhich, over longer time periods, may lead to increased concentration and precipitation of salts and may introduce occupational health hazards. * "Flushing" by water is one method to increase infiltration and thus boost leachate generation for a period. Flushing washes out salts in the disposed waste, allowing it to more rapidly reach a level where leachate can be released into the environment. This method has not yet been widely applied. Please refer also to Johannessen, L. M., Bartone, C., "Guidance Note on Approach to Siting of New Landfills," (under preparation, expected early 2000). See also Johannessen, L. M., "Guidance Note on Recuperation of Landfill Gas for Municipal Solid Waste Landfills," World Bank, Washington, DC, September 1999. GUIDANCE NOTE ON LEACHATE MANAGEMENT FOR MSW LANDFILLS ANNEX A: LEACHATE COMPOSITION FROM GERMAN MSW LANDFILLS Average Range Acidic phase pH 6.1 4.5 - 7.5 BOD5 (mg/i) 13,000 4,000 -40,000 COD (mg/i) 22,000 6,000 - 60,000 BODJCOD 0.58 SO, (mg/i) 500 70 - 1,750 Ca (mg/i) 1,200 10- 2,500 Mg (mg/i) 470 50- 1,150 Fe (mg/i) 780 20 - 2,100 Mn (mg/I) 25 0.3 - 65 Zn (mg/I) 5 0.1 - 120 Methanogenic phase pH 8 7.5-9 BOD5 (mg/l) 180 20 550 COD (mg/i) 3,000 500 - 4,500 BOD4/COD 0.06 SO (mg/i) 80 10- 420 Ca (mg/1) 60 20 - 600 Mg (mg/i) 180 40 - 350 Fe (mg/1) 15 3-280 Mn (mg/i) 0.7 0.03 - 45 Zn (mg/I) 0.6 0.03 - 4 No differences Average Range between phases Cl (mg/i) 2,100 100 - 5,000 Na (mg/i) 1,350 50 -4,000 K (mg/1) 1,100 10 - 2,500 Alkalinity (mg CaCO3/1) 6,700 300 - 11,500 NH, (mg N/i) 750 30 - 3,000 orgN (mg N/I) 600 10 - 4,250 total N (mg N/1) 1,250 50 - 5,000 NO, (mg N/i) 3 0.1- 50 NO, (mg N/I) 0.5 0 - 25 total P (mg P/I) 6 0.1 - 30 AOX (pg Cl/1)' 2,000 320 - 3,500 As (pg/i) 160 5- 1,600 Cd (pg/i) 6 0.5 - 140 Co (pg/i) 55 4 - 950 Ni (pg/i) 200 20 - 2,050 Pb (pg/I) 90 8 - 1,020 Cr (pg/I) 300 30 - 1,600 Cu (pg/i) 80 4 - 1,400 Hg (pg/i) 10 0.2 - 50 *absorbable organic halogen Source: Ehrig, H-J., "Quantity and Quality of MSW Landfill Leachate" Sardinia, Second International Landfill Symposium, 1989. GUIDANCE NOTE ON LEACHATE MANAGEMENT FOR MSW LANDFILLS ANNEX B: LEACHATE TREATMENT OPTIONS Treatment Objectives Main Treatment Options Removal of degradable organic (BOD) Aerobic biological: Aerated lagoon/extended aeration Activated sludge Sequencing batch reactor (SBR) Anaerobic biological: Upflow sludge blanket Removal of ammonia Aerobic nitrification: Activated sludge Aerated lagoon/extended aeration Rotating biological concractor Sequencing batch reactor Vegetated ditch (Artificial wetlands) Air stripping Denitrification Anoxic biological Sequencing batch reactor Vegetated ditch Removal of non-degradable organic and color Lime/coagulant addition Activated carbon Reverse osmosis Chemical oxidation Removal of hazardous trace organic Activated carbon Reverse osmosis Chemical oxidation Odor removal Hydrogen peroxide Removal of dissolved iron and heavy metals and Lime/coagulant addition, aeration suspended solids and setting Final polishing Artificial wetlands (e.g., reed beds, ponds) Disinfection Hypochlorire Volume reducrion/pre-concentration Reverse osmosis Evaporation Main treatment options in bold may be preferable in many low-income countries. Source: Adapted from Hjelmar, O., Johannessen, L. M., Knox, K., Ehrig, H.-J., Flyvbjerg, J., Whinter, P., Christensen, T.H., " Management and Composition of Leachate from Landfills" Final report prepared for DGXI, A.4. Waste 92 Contract no.: B4-3040/013665/92. Denmark, 1994. URBAN AND LOCAL GOVERNMENT WORKING PAPER SERIES Current Publications UWP 1 What a Waste: Solid Waste Management in Asia. Daniel Hoornweg with Laura Thomas UWP 2 Learnino from the World Bank's Experience of Natural Disaster Related Assistance. Roy Gilbert and Alcira Kreimer UWP 3 Observations of Solid Waste Landfills in Developing Countries: Africa, Asia, and Latin America. Lars Mikkel Johannessen with Gabriela Boyer UWP 4 Guidance Note on Recuperation of Landfill Gas from Municipal Solid Waste Landfills. Lars Mikkel Johannessen UWP 5 Guidance Note on Leachate Management for Municipal Solid Waste Landfills. Lars Mikkel Johannessen INFORMATION For more information about the Urban and Local Govemment Working Paper Series, contact: Urban Publications Coordinator Urban Development Division Transportation, Water & Urban Development Department The World Bank 1818 H Street, NW Washington, D.C. 20433 U.S.A. Facsimile: (202) 522-3232 Email: urbanhelp@worldbank.org Internet: www.worldbank.org/urban ' Recycled Paper I EE *_ NjifjAi,i,,>S,ii.iij,,fi.,j},R W w '\ S k rsii , :iq i $$' 'tt "' ''"' (0jj, g ; j-^ ti , ; ;0 j .!it$;tijjj,.X i, Z 42j , j jiqiiii:i;cj;j;j4ii4 4jj ij: 0 fi5:|ir;ittjitn, 2 S S i jjifi2 wg:0 S 2- S< ; -00- tige jj:44^ M;Cf: -., '' fffbtfif K'S K;; t0f 0