By: Jorge Jaramillo
Adapted and edited by: Francisco Zepeda
Washington, D.C. 1993
In Latin America and the Caribbean, demographic growth, industrial development, urbanization, and other processes and consequences of economic development are producing a significant increase in the quantity and variety of solid waste that is being generated by the population of this Region.
Poor management of wastes is affecting both large cities and its marginal areas, and small rural populations. In many municipalities, the empirical management of urban cleaning services without technical, economic, and social standards leads to poor service planning and organization. As a consequence, public cleaning entails high operating costs that municipalities are forced to subsidize, allocating a substantial part of their budgets to this purpose.
The result is that most cleaning services are in permanent economic shortfall. Besides, due either to lack of resources, interest or technical knowledge, refuse is inappropriately disposed of inside or outside urban areas, creating scattered open dumps that constitute, inter alia, a social problem and a threat to public health.
Scavengers who sort and sell wastes from open dumps are a social problem since they work under precarious and risky conditions. These open dumps are a threat to public health because in addition to bad odors and aesthetic problem, are a breeding site for flies, rats, and other disease vectors, as well as a source of air pollution and contamination of surface and ground waters.
These problems could be controlled if final disposal could be carried out in a properly run landfill, which would also help to prevent pollution.
Urban cleaning service consists basically of sweeping, storage, collection, transportation, and final sanitary disposal of solid waste. Since disposal is the last step and economic resources are scarce, final disposal is the critical point in urban cleaning services in the Region.
The Pan American Health Organization, considering that manual sanitary landfills are available to municipalities since they do not require much technical or financial resources for their operation, has been promoting them as a final disposal practice in the countries.
To continue the effort and taking into account the need of numerous small cities and rural towns in the Region, the Environmental and Health Division, HEP/PAHO/WHO, through CEPIS, considered the preparation of this manual, which is particularly aimed at towns with less than 40.000 population.
The methodology presented in these guidelines was used successfully during the first phase of the urban cleaning program for municipalities of the Government of Antioquia, Colombia. We acknowledge the collaboration of the Planning Administrative Department of the Government of Antioquia for their collaboration, and for giving us permission to use the document they produced as the basis for these guidelines.
Through the dissemination of this document we want to contribute to improve the operation of cleaning services and, as a result, to enhance the environmental conditions and health of the population of the countries of Latin America and the Caribbean.
This guide contains the basic principles for a manual sanitary landfill and is largely based on field experience from the first phase of the urban cleaning program for municipalities conducted by the Government of Antioquia, Medellín, Colombia. As well, it is based on the experiences I shared with technicians from different countries during visits to sanitary landfills in 1989, when I participated in the program for resident professionals of the Pan American Center for Sanitary Engineering and Environmental Sciences (CEPIS).
The main audience of this guide are local administrators and sanitation technicians. It is based on "Relleno Sanitario Manual", published by the Government of Antioquia, Planning Administrative Department, Medellín, the unit I work for and which authorized the use of this document. I would like to thank them for their collaboration.
I am also grateful to Mr. Francisco Zepeda Porras, Regional Advisor in Solid Waste of the Environmental Health Program (HPE), for his valuable orientation and to Mr. Alberto Flórez Muñoz, CEPIS Director, for the encouragement and support I received during my residence at that Center.
Finally, I would like to express that the purpose of preparing this guide was to facilitate the decision-making process to build manual sanitary landfills. Although these basic sanitation facilities are small in scale, they play an important role in improving community quality of life, preserving the environment and protecting natural resources.
1.1 The importance of the solid waste problem
In most countries, especially in certain regions, the problem of solid wastes is worsening due to rapid population growth, industrial development, changes in consumer patterns, higher life standards, and other factors that lead to environmental contamination and deterioration of natural resources.
Economic development is generally accompanied by increased generation of solid wastes, which plays an important role among the various factors that affect the health of the community. This reason triggers the search of solutions to the problem of waste management and final disposal.
1.2 Solid waste effects on human health
The importance of solid wastes as a direct cause of diseases has not been established yet. Nevertheless, concomitant with other factors, they are blamed for the transmission of certain diseases through indirect routes.
To better understand the effects of solid wastes on human health, it is necessary to distinguish between direct and indirect risks.
1.2.1 Direct risks to health
Direct risks are posed by contact with refuse containing human and animal excreta and hazardous materials. Those most at risk are garbage collectors that handle containers unsuitable for refuse storage, use inappropriate equipment, or do not wear clean clothes and protective gloves and shoes. People who make the sorting and separation of wastes are also under risk since their working conditions are the worst. The incidence of intestinal parasites is higher in both collectors and separators than among the general population. Besides, the rate of injuries in hands, feet and back, as well of hernias, wounds, respiratory diseases, and skin problems is higher than in industrial workers.
1.2.2 Indirect risks to health
1.3 Solid waste effects on the environment
The most obvious environmental effect of inadequate refuse management is the aesthetic deterioration of cities and natural landscapes. This increasing problem is destroying the beauty of our few parks, beaches and landscapes. Figure 1.2.
1.3.1 Water pollution
The most serious but least recognized environmental effect of solid wastes is water pollution caused by dumping refuse into rivers and streams, and leachate from open dumps.
The dumping of refuse into streams produce organic load and depletes dissolved oxygen. It increases nutrients and algae causing eutrophication; kills fish; and generates unpleasant odors and color. As a result, this resource which is so important to water supply and recreation is being destroyed.
Refuse dumping into watercourses or along the streets obstructs gutters, and reduce the flow of channels. In the rainy season this can cause floods that may result in loss of crops, material goods, and even human lives.
1.3.2 Soil contamination
The accumulation of solid wastes in open dumps contaminates the soil, creates a public nuisance and reduces the value of the surrounding land. Uncontrolled disposal of hazardous wastes also pollutes the soil.
1.3.3 Air pollution
Smoke from frequent fires in open dumps reduces visibility, causes nasal and eye irritation, increases respiratory problems, and creates unpleasant odors.
1.4 Administrative aspects
In a community, one of the best indicators of health and quality of life is the cleanliness and beauty of the locality.
The management of solid wastes and its final sanitary disposal shows the quality of the local administration and the efficiency of its leaders, in particular, of the mayor. Through public cleaning services it is possible to evaluate political will, managerial capability, and responsibility toward public health and cleaning workers, as well as commitment to protect the environment.
It is important to emphasize that with appropriate technology and adequate planning and administration it is possible to reduce service costs, charging a tariff according to the payment capacity of the users.
"EVERYBODY TAKES PRIDE IN SHOWING A CLEAN CITY"
1.5 Public cleaning service
The public cleaning service consists of the following activities: separation, storage, in-house containerization, collection, sweeping, transportation, treatment, and final sanitary disposal of solid wastes, the latter one is indispensable in waste management. The user or waste producer is responsible for the first two activities, while the others are responsibility of the municipality or cleaning facility (Figure 1.3). In developing countries, refuse collection is one of the environmental sanitation problems that requires greater attention by governmental authorities and by research and financial agencies.
The following factors contribute to ill public cleaning services:
Currently, waste management entails the evaluation of local and regional conditions to face it as a sanitary engineering problem that requires the cooperation of other professionals. It is also important to point out the role played by mid-level technicians, operators, cleaning service supervisors, and promoters of sanitation in solving solid waste problems.
The first step, however, is in the hands of the government at all levels. The activities of international cooperation agencies are also of great importance.
At the national level it is necessary to take appropriate measures to regulate the management of solid wastes and also to promote the establishment of a national urban cleaning system.
At the regional level, plans, programs, and projects should be prepared to provide municipalities technical advisory services and support according to national sanitation policies.
At the local level, municipal governments should take action to improve cleaning service quality and to provide sanitary final disposal methods for their wastes. This should be one of the main concerns of local administrations, not only for sanitary reasons, but also to improve the beauty of the community. The old maxim: "Clean city, civilized city" should always be considered.
1.6 Waste treatment systems
The main objective of solid waste treatment is to decrease the risk of contamination and to protect the health of the population.
Among the alternatives considered, the best solution should be chosen according to local technical and socioeconomic conditions, bearing in mind contamination issues.
The main treatment methods to reduce waste volume are incineration, composting, and recovery. They are not considered, however, as final disposal methods since a sanitary landfill is required to dispose of the wastes produced.
The incineration of solid wastes reduces the volume to about 10%, it produces inert material (scoria and ashes) and releases gases during combustion. This reduction is completed in special furnaces that require combustion air, turbulence, retention periods, and suitable temperatures. Poor combustion will generate smoke, ashes, and undesirable odors.
Incineration, except for hospital wastes, is not recommended for developing countries, even less for small communities for the following reasons:
Composting is the process by which the organic content of the refuse is reduced by bacteriological action of the microorganisms contained in the refuse. The product of this process is the compost, which is a soil conditioner (not a fertilizer). Its commercial value, however, is less than the cost of production.
Composting could be an effective waste treatment method for developing countries because the organic content of the refuse is recovered. It also requires separation from other solid wastes, providing a good opportunity to initiate the recycling of other materials. Before deciding the construction of a composting plant, careful consideration should be given to whether there is a market for selling the product. Many plants in the world have failed because marketing issues were neglected.
In our Region, composting has had little success due to:
Composting of organic market wastes may be advisable in some small communities where solid wastes may be processed manually. Care should be taken with the distribution costs, since they may increase total production costs.
Up to now, the purpose of waste management systems has been to move materials from one place to another and dispose of them at the least cost. However, new ways to manage solid wastes are now under consideration due to the increasing generation of solid wastes, the complex treatment of new materials, the pressure to comply higher environmental standards, and the over exploitation of natural resources.
At the present time, in industrialized countries there is increasing awareness that the supply of raw materials is limited and that waste recovery may become an essential factor in natural resource conservation.
Recovery may be divided into three categories:
The materials found in refuse are traditionally separated manually at the place of origin, on the sidewalks, in the collector trucks, or at the final disposal site. In the Region, the latter practice is frequent in nearly all open dumps in large cities and even in small communities. Poor people working under risky conditions without sanitary protection and social security benefits usually perform this activity. For this reason, this practice should be avoided and an integral program with extended community participation should be promoted.
On the other hand, several countries in the world, especially in Europe, have a large number of facilities using mechanical separation with sophisticated equipment, however, operational and maintenance problems are common and efficiency is bellow the expected considering the high investment costs.
To date, the experience in developing countries with industrial plants for solid wastes has not been very encouraging and has often result in a complete failure.
Therefore, recovery at the source where wastes are generated is recommended for small communities. This offers the greatest benefits for manual labor and does not require large investment.
The municipality gains the following benefits from recovery or recycling of materials at the source:
The local administration and central government should foster the recovery of resources creating the market for recycled products through purchase centers or collecting points. Municipalities should increase public awareness on problems that stem from waste collection and should establish suitable ways to make such collection.
There must be environmental education campaigns aimed at the community to improve collection service and to facilitate the recovery of materials through waste separation. On the other hand, the market for recovered materials should be studied since no recovery system would be successful if the products can not be sold.
Worldwide, the trend is to maximize the recovery or recycling of refuse as the best solution to face this problem.
1.7 Waste final disposal
The main methods for waste final disposal are:
Sanitary landfill is considered the only environmentally sound alternative, since it does not involve major annoyance or hazards to public health.
The dumping of refuse into water streams, lakes, or oceans is unacceptable because it produces ecological imbalance and excessive nutrients and organic load to the water.
Open dumps are a serious public health problem because they favor the proliferation of insects and rodents that transmit diseases. Besides, the smoke produced by fires causes respiratory problems and the view of an open dump deteriorates the beauty of the surrounding area.
The feeding of animals with wastes should be prohibited due to the high risk of transmitting diseases to man. The feeding of animals with food wastes from hotels and restaurants may be allowed only if it is guaranteed that such wastes will be cooked at 100 oC for at least 30 minutes.
Sanitary landfills have been, technically and economically, the best-suited technique for sanitary disposal of wastes in our Region.
2.1 What is a sanitary landfill?
The sanitary landfill is a technique used for the final disposal of solid wastes that does not cause annoyance or threat to public health. It does not deteriorate the environment during its operation or after its closure. This technique uses engineering principles to deposit the waste in the smallest area possible, daily covering it with layers of soil, and compacting it to reduce its volume. Problems related to liquids and gases generated by the degradation of organic material are also dealt with in a landfill.
2.2 Sanitary landfill methods
The construction and the sequence of operation in a sanitary landfill are mainly based on the topography of the land. They also depend on the source of the covering material and the depth of the water table. There are two different ways to construct a sanitary landfill: the trench method and the area method.
2.2.1 Trench or ditch method
The trench or ditch method is used in flat regions and consists of periodically digging trenches two or three meters depth with an excavator or tracked dozers. It should be noted that there have been trenches dug up to seven meters depth. The soil taken out is stockpiled for later use as covering material for a subsequent trench. Wastes are placed in the trench, and then they are spread, compacted and covered with soil.
Care must be taken when it rains because the water may flood the ditches. Therefore, canals must be built on the perimeter to collect and divert the water and to provide internal drainage. In extreme cases, it may be necessary to pump out the accumulated water. The sidewalls of the ditches have to keep the slope of the excavated soil.
Ditch excavation requires favorable conditions regarding water table depth and adequate soil. Lands with a high water table or very close to the surface are not suitable because groundwater would be contaminated. Rocky soil is not adequate since excavation is very difficult. (Figure 2.1).
2.2.2 Area method
In flat areas where pits or trenches cannot be dug, refuse can be deposited directly on top of the original soil, elevating the level a few meters. Cover soil should be brought in or extracted from the surface layer. In both cases, the first cells are constructed with a smooth gradient to prevent slides and create stability as the landfill rises. Figure 2.2.
This method can be used for filling natural depressions or abandoned quarries a few meters depth. The cover material is dug from the slopes or from a nearby place to avoid increased transportation costs. The unloading operation and construction of the cells should be done from the bottom up.
The cells of the landfill are supported on the natural gradient of the land, the incoming refuse is spread and compacted at the base of the slope and covered daily with a layer of 0,10 m to 0,20 m of soil. The operation continues along the terrain maintaining a smooth gradient of about 30 degrees on the slope and 1 to 2 degrees on the surface.
2.2.3 Combination of both methods
Since these two methods of constructing sanitary landfill are similar, they may be combined to better use the land and cover material and to increase operation performance.
2.3 Basic principles of a sanitary landfill
It is important to emphasize some basic principles:
2.4 Advantages of a sanitary landfill
2.5 Disadvantages of a sanitary landfill
The degradation or natural putrefaction of wastes produces a black, foul-smelling liquid known as leachate which is similar to domestic wastewater, but much more concentrated. In addition, rainwater passing through the layers of refuse increases leachate in a proportion much larger than the waste moisture itself. Therefore, intercepting and diverting runoff before the beginning of the operation is important. If leachate increases too much it can cause problems not only in the operation of the landfill but will also contaminate nearby water streams, springs, and wells.
If we consider that in small communities the average area to be filled with solid wastes is not very large (see Annex I), the amount of leachate will also be small. We can then opt for its infiltration into the soil because along time, the leachate contaminant load diminishes once the landfill is completed and the soil acts as a natural filter (ref. 23). To protect surface and ground waters, however, the following measures should be taken:
A sanitary landfill is, indeed, an anaerobic digester that produces liquids, gases and other compounds due to the natural degradation or putrefaction of organic wastes. Degradation by microorganisms occurs in two stages: aerobic and anaerobic.
The aerobic stage occurs when the oxygen present in the interstices of the mass of buried wastes is rapidly consumed.
The anaerobic stage predominates in sanitary landfills and produces appreciable amounts of methane (CH4) and carbon dioxide (CO2), as well as traces of stinking gases such as hydrogen sulfide (H2S), ammonia (NH3), and mercaptans.
Methane gas is important, though odorless, it is flammable and explosive if the proportion of its concentration in the air ranges between 5% to 15%. Gases tend to accumulate in empty spaces within the landfill and escape through any fissure in the soil or cover material. High concentrations of methane may build up causing explosions in the surrounding areas. It is therefore necessary to adequately control the generation and migration of these gases.
Gases can be controlled by constructing a vertical system of gravel vents placed at different points of the sanitary landfill so that gases can be released into the atmosphere. Since methane is combustible, it can be burned simply by setting it afire at the exit of the vent once the sanitary landfill is closed. This gas can be used as energy for a small stove to heat food or to light the landfill. It should be noted that the recovery and use of methane gas for commercial purposes is only recommended for sanitary landfills that receive more than 200 tons of refuse per day (ref. 7) and when local conditions are favorable.
2.8 Cover material
One of the major differences between a sanitary landfill and an open dump is the use of cover material to separate the wastes from the external environment at the end of every working day.
Daily covering is of vital importance to the success of the sanitary landfill since it performs the following functions:
The manual sanitary landfills is a viable technical and economic alternative for urban and rural communities with less than 40,000 inhabitants and for urban marginal areas that generate less than 20 tons of refuse daily.
If the cost of transportation is low, a single manual sanitary landfill can be used for two or more communities.
When the manual operation technique is used, heavy equipment is required only to adapt the site, build internal roads, and to excavate trenches or cover material, in accordance with the landfill's method and advance.
Since all the remaining operations can be carried out manually, low-income communities unable to acquire and maintain heavy equipment can dispose of their refuse adequately using labor force easily available in developing countries.
Manual sanitary landfills can be used for up to 20 tons of refuse per day. A thorough analysis of the local conditions of each region is required to determine the most appropriate method to use. Depending upon the cost of labor, type of landfill, climatic conditions, etc., it may be better to use heavy equipment in the sanitary landfill in a partial or permanent way.
Based on previous experience, it is preferable to use such equipment when 40 or more tons of solid waste are produced per day.
A collection system using an agricultural tractor with a trailer (hydraulic tipping) and an agricultural tractor with a compactor trailer is being tested and evaluated in Antioquia (Colombia) to provide urban cleaning services in small communities.
This system offers collection and transportation services and supports the final disposal of refuse.
The agricultural tractor can work as an independent unit and accessories such as bulldozer blades, front loaders, backhoes, and rollers to compact solid wastes can be adapted to operate sanitary landfills. This increases the performance of the landfill because larger amounts of refuse can be disposed of daily. This more versatile device brings technical and economic benefits to the entire system of urban cleaning. In special cases, the tractor can also be used for other public works, taking advantage of the investment already made by the municipality. Figure 3.1.
In Mexico, after 18 months of experiments with prototype tractors, the Secretariat of Urban Development and Ecology concluded that an adapted 31 HP tractor can confine the waste of communities up to 80,000 population, i.e., approximately 40 tons of refuse per day, in eight hours of work with one day laborer. Ref. 25.
Although it is a small work, a manual sanitary landfill is an engineering project in which most potential problems are prevented through careful planning in the initial stages. It is simpler and more economical to plan well than to make corrections once it is in operation.
The initial planning lays the groundwork for site selection, design, construction, operation and maintenance. Basic information that should be examined includes the population served, the origin, quality, and amount of solid waste to be disposed of, possible available sites, future use of the land once the landfill is completed, resources for its financing, and the advisory of a competent professional.
It is important to have the advisory of a sanitary engineer with experience in landfill design, construction, and operation at the initial stage of a project.
Support of the public is needed, otherwise, it is quite probable that the project will not be successful. The initial planning should include a public information program that explains the pros and cons of establishing the landfill to the community. Every community should realize that a manual sanitary landfill, as any public work, requires resources for its financing, design, construction, operation, and maintenance.
3.2 Selection fo the site
Appropriate selection of the site for a sanitary landfill will eliminate many operational problems in the future. In selecting a site, places where the operation of the sanitary landfill will improve the land should be considered first.
3.2.1 Community participation
22.214.171.124 Local authorities
Local planners, health, and water protection authorities should be consulted when choosing a site. Figure 3.2.
Only on few occasions will a site meet the ideal conditions for building a sanitary landfill. The pros and cons should be analyzed according to the technical and financial resources available. The following steps are recommended:
126.96.36.199 Public opinion
Public relations are frequently neglected by municipal authorities and technicians during site selection. From the beginning of the selection process, the public should have an opportunity to participate in, comment on, and question the proposals made. It is essential to ensure that all sectors of the community give their support during all phases of the selection, design, construction, operation, maintenance, and future use of the sanitary landfill.
In many communities people believe that a sanitary landfill is an open dump. Because of this confusion, it is recommended that an educational and informational campaign be conducted in schools, associations, cultural centers, clubs, and through the local media.
3.2.2 Technical aspects
The sanitary engineer should consider the following aspects:
Location. The location of the site plays an important role in the system operation. The distance and even more the time it takes to reach the urban center affect the cost of solid waste transportation. It is recommended, thus, that the landfill be nearby (i.e. not more than 30 minutes for a round trip). This will reduce transportation costs and will allow the community to supervise that the landfill is being operated and maintained in the best possible way (figure 3.3).
Texto de la figura 3.3.
3.2.3 Methodology for site selection
188.8.131.52 Preliminary analysis
Field visits will be carried out with local authorities and those responsible for water and environmental protection. Topographic plans of the region on a scale of 1:10,000-1:25,000 should be available to locate possible access roads and exits from the urban area, the nearest streams, and the distribution of typical soils.
Back to the local planning office, land use and restrictions, as well as the future expansion of the urban area should be discussed to analyze whether or not the landfill is compatible to those sites.
184.108.40.206 Field research
For the sites selected, additional details should be analyzed such as the likelihood of groundwater contamination, soil and water table characteristics, and the identification of reference points, topographic irregularities, water springs, roads, and buildings.
With an urban map on a scale of 1:2,000-1:5,000, the advantages and disadvantages of each site, preliminary useful lifespan, and cost calculation can be evaluated. This information will be submitted to local authorities for the final decision.
3.3 Steps in design, construction and operation
3.3.2 Land preparation and construction of works
3.3.3 Operation and maintenance
3.4 Timetable of activities
The following timetable may be useful for programming the execution of activities of a manual sanitary landfill.
3.5 Basic project
3.5.1 Topography survey
Once the site has been defined and the municipality has acquired the land, a detailed topographic survey should be completed to make the calculations and prepare the final design of the sanitary landfill. Its scale should be of 1:250-1:500, with contour intervals at every meter and marked every 5 meters.
The topographic survey of the land and preparation of plans (drawings and sections) can be contracted out by the municipality. The Ministry or Secretariat of Public Works, Health, or Community Development may also be able to provide this service.
However, if such facilities are not available and the community lack topographic equipment to determine the area and capacity of the land, the topographic survey may be carried out with a measuring tape and hand level, or even a hose, since this small work does not require much precision.
3.5.2 Design of the sanitary landfill
The design embodies the conception of the landfill and planning of the construction. It is presented to the local authorities and the community for its promotion and financial analysis.
Whenever possible, the basic design should include the total space and land area to be filled, the construction method, the source of cover soil, and the layout of infrastructure works.
The report should also include the lifespan of the landfill, its future use and estimated cost of the project.
3.5.3 Details of the project
The design should be presented in maps with drawings and profiles of the project containing at least:
Basic information studies, estimations, and design of the manual sanitary landfill are presented in Chapter 5. The following chapter deals with landfill site preparation and infrastructure required for receiving solid wastes, as well as its construction, operation, and maintenance.
4.1 Preparation of the site
This stage includes engineering projects, landscaping, and construction details. They should fulfill sanitary requirements and be performed with simplicity and speed.
4.1.1 Construction of the perimeter
220.127.116.11 Access roads
The sanitary landfill should have access to a main public road that meets design standards whether or not it is paved. Figure 4.1.
It should be noted that the time it takes to transport refuse to and from the landfill site is more important than the actual distance.
18.104.22.168 Rainwater drainage
It is important to study the amount of rainfall to foresee drainage characteristics and the works required to lessen the production of leachate. By doing this, water contamination will be prevented and it will be possible to select the areas of operation and facilities for workers.
Rain falling nearby the sanitary landfill often drains into it, causing serious operational problems. Intercepting and diverting this runoff outside the sanitary landfill helps reduce the volume of leachate and improves the operation. A soil or soil-cement trapezoidal channel must then be constructed according to local precipitation pattern, the tributary area, soil, vegetation, and topographic characteristics. Figure 4.2.
Texto de la figura 4.2:
For a small basin, a channel with the dimensions shown in Figure 4.3 is recommended. However if greater precision is required and the engineer recommends it, the inflow can be calculated through the rational method and the dimensions of the channel.
The channel should be plotted along the maximum level curve of the landfill, and should guarantee an average maximum speed (0.5 m/sec) that does not cause excessive erosion. The size of the channel section can be calculated using the following equation:
Once the area of the section is determined, the dimensions are decided based on the previous recommendations.
4.1.2 Infrastructure of the landfill
Site preparation is important to improve its conditions, to facilitate the reception of solid wastes, to build the cells, and for the general operation of the sanitary landfill. The following activities should therefore be carried out:
22.214.171.124 Cleaning and clearance
A supporting base for the landfill should be prepared in the site. It is usually necessary to fell trees and shrubs because they could be an obstacle to the operation. This cleaning should be done in stages, in accordance with the progress of the operation to avoid soil erosion. Figure 4.4.
126.96.36.199 Solid base preparation
Before beginning the landfill, it should be decided whether to remove the bottom layers of soil. This will depend on the availability of cover material. In some cases, it may be advantageous to leave the land intact to use its absorption and filtration capacity to remove leachate contaminants.
To level the soil and slope sections, it is advisable to move the earth in stages so that the rain will not cause soil erosion and the earth can be used as cover material. On the other hand, topsoil should be stored and preserved to be used as final cover to support vegetation as some areas of the landfill are completed.
To level the soil and to excavate ditches, heavy equipment (a caterpillar tractor and/or backhoe) should be used because manual excavation is too inefficient. Similar equipment should be used for building internal roads or extracting and storing cover material (the latter is recommended only in dry periods). Figure 4.5.
Texto de la figura 4.5
A municipality may request heavy equipment as a loan or lease from a regional or national public works agency, a regional corporation, or even a nearby municipality. The municipality may defray the fuel costs and the wages and food of the operator. In general, earth movement will not take more than a week because the preparation for the manual sanitary landfill should be conducted in stages.
One of the greatest difficulties that small communities have to face, apart from acquiring the land for the sanitary landfill, is the loan or lease of heavy equipment to carry out the initial earth movement. This task challenges the managerial ability of the responsible staff member.
188.8.131.52 Lands with high water table
When only marshy or swampy lands are available, they can be used to construct a manual sanitary landfill by lowering the water table permanently through the following procedures:
Texto de la figura 4.6
Slopes are constructed to avoid erosion ant to provide landfill stability. Depending on the type of soil, slopes may range from vertical to 3:1 (H:V) and sections may range from one to three meters. Platforms should have a gradient of 2% toward the interior slopes to drain leachates and to prevent ponding when used as temporary access roads. This also provides a greater stability to the area. Figure 4.7.
Constructing a manual sanitary landfill over a small water stream or spring without first lowering its level, channeling it, and encasing it should be avoided to prevent direct contact with leachate.
184.108.40.206 Leachate drainage
Managing leachate is one of the greatest problems in a sanitary landfill. In many cases, despite the perimeter channels which intercept and divert runoff, the volume of leachate increases significantly by rain falling directly on the landfill surface (see operation in rainy seasons).
Texto de la figura 4.7
It is essential, therefore, to build a drainage system for the sanitary landfill before wastes are discharged. Whenever possible, this system should keep the leachate inside the landfill to allow more time for infiltration and reduce its appearance on the surface. This is to avoid leachate treatment as much as possible, which is complex and expensive for small localities.
To increase efficiency, it is recommended to build these drains at the base of the interior and exterior slopes of the landfill platforms or terraces to prevent runoff over the surface of the lower slopes and to connect them with vertical gas vents.
The drainage system consists of a horizontal network of gravel ditches that interrupts the continuous flow of leachate through screens made of mud and wood or even features of the land.
Drains can be constructed as follows:
Texto de la figura 4.8
Another way to build this drainage at the base of the site is to use discarded automobile tires. This takes advantage of a material that is difficult to manage in the landfill and creates a greater storage capacity for leachate. After tires have been buried vertically one against the other- a layer of 0.20-0.30 m of stone and dry branches (as in the previous example) is placed. It should be noted that the ditch should have a special shape for the tires. Figure 4.9.
Texto de la figura 4.9
During heavy rainfalls and when the amount of leachate exceeds the drainage capacity of the landfill, the drainage system should be extended by creating an infiltration field outside the landfill to store this fluid at least during rainy days. Figure 4.10.
Texto de la figura 4.10
In this drainage area outside the landfill, alternating sections without stones can be left between screens. This is done for several reasons:
However, there are regions with heavy rains (more than 3,000 mm/year) that create large amounts of leachate, which are difficult to handle. In such cases, according to calculations, the volume of leachate may be such that even the land available for leachate drainage, storage and infiltration may be insufficient or its construction may not be economically feasible.
In these cases, to manage and control the leachate production it is recommended:
Depending on the type of wastes and the field capacity, in regions where the annual precipitation does not exceed 300 mm and there is a channel for intercepting and diverting rainwater, no significant problems with leachate would appear. However, it is recommended to build drains in the bottom of the landfill and in the platforms or terraces. The size of the ditches will be smaller, though.
When the soil does not permit filtration or when the aquifer is being used as a water supply source, leachate will have must be treated.
Due to the high concentration of solid materials in leachate, treatment solely by chemical processes is too expensive. Since leachate from municipal solid wastes is similar to domestic wastewater (with a high proportion of biodegradable organic matter difficult to settle), treatability studies should be done to select the adequate biological treatments to improve leachate quality whenever possible.4 Among those processes that can be used to treat leachate are trickling filters and stabilization ponds.
220.127.116.11 Gas venting
Gas venting consists of a ventilation system in stone or perforated concrete pipe (lined with stone) which operates like a chimney or vent and passes through the entire landfill vertically from the bottom to the surface (figure 4.11). These vents are constructed vertically as landfill advances and a good compaction around it should be provided. The installation of vents every 20 or 50 m with a diameter of 0.30 and 0.50 m each, is recommended.
The method for constructing gas vents or chimneys is illustrated in Figure 4.11.
Texto de la figura a)
a. Vent construction using wooden stakes,
Texto de la figura b)
b. Vent construction using a plastic or
metal tube and stones.
Drains should be interconnected to increase the efficiency of fluid and gas drainage in the sanitary landfill. Figure 4.12.
Once the last cell is almost completed, two connected pipes must be placed. The first one should be perforated to facilitate gas capture and release; to avoid the obstruction by solid wastes or cover soil it must be filled with stones like a protective "sleeve". The second pipe should not be perforated so as to collect gas and burn it, eliminating odors produced by other gases. Figures 4.13 and 4.14.
Texto de la figura 4.13
Texto de la figura 4.14
18.104.22.168 Internal accesses and rain drainage
When planning a sanitary landfill, internal access roads within the site should be examined carefully since the continuos use of these roads may cause serious problems during the rainfall season.
A small road of 6 m width with drains should be built and kept in good conditions to unload wastes to the working face throughout the year. The maximum gradient can be between 7 to 10%, depending on the condition of the vehicle and whether they are going upward loaded or empty.
Although the access roads to the working face a manual sanitary landfill can be made of soil, stone and debris, such roads should be well maintained and drained.
4.1.3 Auxiliary structures
The proposed auxiliary structures are small and low-cost, although they must be compatible with the useful lifespan of the landfill and should meet sanitary requirements and intensive labor use in all its activities, while minimizing temporary investments.
22.214.171.124 Perimeter fence
A four-strand barbed wire fence with an entry gate should be built for safety. This will also stop livestock from entering the landfill, since it does not only hinder the operation but destroys cells, especially when workers leave at the end of the working day. Figure 4.15.
A live fence of trees and shrubs should be constructed to hide solid waste from neighbors and passersby, as an esthetic measure. It will also stops pieces of paper and plastic blown by the wind. Planting of fast-growing trees (pine, eucalyptus, laurel, bamboo, etc.) is recommended. Figure 4.16.
The construction of a booth (10-15 m2) is important to be used as a porter's lodge, a place to keep tools, for workers washing and changing (before and after work), a toilet facility, a kitchen for heating food on a burner, and as a shelter in case of heavy rain. A prefabricated booth can also be adapted and used for these purposes. The municipal administration can request it as a donation and give the company publicity in return. Figure 4.17.
126.96.36.199 Sanitary facilities
The landfill should have minimal sanitary facilities to ensure workers comfort and well-being. Water should be carried to the landfill for sanitary services and at the very least a latrine or cesspool must be built (Figure 4.17). During dry periods water should be sprinkled on the landfill surface with a hose to obtain better compaction and to prevent dust.
Information and advisory services about how to construct sanitary facilities can be obtained in the environmental sanitation offices of the municipality's health unit.
188.8.131.52 Maneuvering area
An area of approximately 200 m2 (10 x 20) should be prepared so that collection vehicles can maneuver and discharge refuse at the working face without problems.
A sign announcing the landfill must be placed to make it known by the community. The sign can be made of two sheets of tin and a wood frame. It will be painted first with anticorrosive, and then with a paint of the desired color; a brief description of the project and a civic legend must be written. A commercial company may also prepare this sign. Figure 4.18.
An official name for the sanitary landfill should be chosen at the beginning of the project. This name should then be used in all documents and relevant correspondence.
In order to integrate the sanitary landfill into the natural environment, not only the landfill's final surface but also the entrance and contour of the area should be landscaped.
For vegetation, the final compacted cover with a 0.40 to 0.60 meters as minimum, gas venting, and runoff drainage are needed. However, few species are recommended until the landfill stabilizes. Grasses and short-rooted plants, which do not exceed the cover, should be used on the whole area of the landfill. Pits filled with fertilized soil can also be used for planting.
To prevent erosion and leachate increase, it is important to plant grass while parts of the landfill are being completed rather than waiting until the operation is finished. This task is simpler if topsoil is stored when initial earth moving is done.
Construction begins immediately after designing the sanitary landfill. The best design will mean nothing if the administration does not have political will to execute it properly. The construction of a sanitary landfill is of great importance compared to other public work projects because of the time it requires for its execution and the continuous maintenance it demands.
To plan the progress of the operation, it is necessary to have topographic maps of the project with longitudinal profiles and cross sections profiles indicating the partial configuration of the areas filled at every stage. The advancement of the operation and of the working face is tracked by calculating the volumes and heights occupied according to the contour lines and elevations.
4.2.1 Construction method
The trenching or area construction method depends on topographic conditions, soil characteristics and water table. These factors will determine whether or not the cover soil can be extracted from the landfill; extraction from the landfill itself is the most economic alternative.
4.2.2 Cell construction
The daily cell is defined as the basic construction unit of a sanitary landfill. It is similar to a small block and is formed by the wastes buried in one day and the soil required to cover them.
184.108.40.206 Cell size
The size of the daily cell varies in each case and is theoretically defined as a parallelepiped. Its width is the working face required by collection vehicles (usually no more than two) to unload wastes. The length is determined by the amount of wastes that arrives at the landfill in a day and the height is limited to one meter or a meter and a half to facilitate compaction. Figure 4.19.
Texto de la figura 4.19
Wastes should be unloaded at the working face. The workers spread them over the slope of the cells already completed in successive layers of 0.20 to 0.30 m, using pitchforks (a three-pronged fork) or rakes (eight or ten prongs). The upper surface is leveled and compacted with a roller, while the lateral surfaces are compacted using manual tampers.
The spreading and compaction is done in horizontal or inclined layers with a 1:3 gradient (height: length). This provides more compaction, better surface drainage, less cover soil, better containment and landfill stability.
At the beginning of the construction, the landfill should always be contained by supporting every cell against the natural land slope or trench walls and, as the landfill increases in height, on the completed cells.
To complete the cell, it is covered with a layer of soil of 0.10 to 0.15 m. The layer is spread with a wheelbarrow, shovels and large hoes, and compacted with a roller and hand tampers. It is important to remember that the daily cover prevents the presence of insects, rodents, and buzzards, as well as fire, smoke, bad odors, moisture, and scattered garbage.
Cover should be applied at least once per every collection day. At the end of the working day, no solid wastes should be exposed to the air, much less on weekends.
There is no need to be demanding about the quality of a cover material for a manual sanitary landfill. It is recommended to use the available soil, since the basic objective is to cover wastes.
With regard to the amount of cover material required, 1 m3 of soil should be used for every 4 to 5 m3 of compacted solid waste, i.e., between 20% and 25%.
For the final cover, it is recommended to place two layers of 0.40 to 0.60 m each in two phases with an interval of approximately a month between layers to cover the settlements produced in the first layer.
If cover soil is dug at the site itself, the transportation cost for soil cover is minimal. It is recommended to extract it from the land slopes forming platforms to prevent erosion. It is advisable to expand the site's capacity and useful lifespan or take advantage of soil excavations for new buildings in the urban area. This can be done by publicizing that soil cover is needed at the landfill or through direct contact with builders who may assume the transportation cost.
In dry periods, extracting and accumulating the cover soil with a tractor or backhoe will generate better yields. The soil can be stored upon the finished cell and then be used for completing the other cell.
In rainy periods, the opposite will happen, since the accumulated material is dragged and is heavier because of moisture; hence, it will be more difficult to transport. Under these circumstances, it is necessary to extract the amount of soil needed to cover the cell on a daily basis.
When the trench method is used, cover material is readily available. It is recommended to accumulate it near the ditch being excavated or on the top of a completed cell.
Since the purpose of this basic sanitation operation is to use technology available at the region and to promote extensive labor force, cell formation and compaction will be made with masonry tools. Densities achieved in the manual sanitary landfill will therefore be relatively low (400-500 kg/m3) but sufficient for the proposed objectives. However, the following factors may affect solid waste compaction.
4.2.3 Landfill construction plan
Construction of the sanitary landfill should be guided and controlled, according to its design and future use. It is recommended to build the manual sanitary landfill in platforms of three meters high, which in turn will be formed by three one-meter cells. Each platform will correspond to a phase of the landfill's construction. Between each platform, a berm of about three to six meters wide should be left to give major stability to the operation.
When the trench and area methods are combined to take better advantage of the land, each construction phase will correspond to an operation method.
Figures 4.20 to 4.24 illustrate the operation plan for a sanitary landfill, depending on the method.
Texto de la fig. 4.20
Texto de la fig. 4.21
Texto de la fig. 4.22
Texto de la fig. 4.23
Texto de la fig. 4.24
Corte : Section
Once the site has been selected, the technician should complete several field studies. First, a thorough recognition of the site has to be done with a topographical map, notes, graphics, or tables showing the quantities of solid wastes and soil accumulated. This will be used to evaluate land depressions and slopes. The future use of the sanitary landfill has to be considered.
The field visit is essential for creating a good design. Thus, plans can be adapted to the land by identifying the area to be filled and its surroundings, internal access routes, drainages, construction method, and the source of cover soil.
5.1 Basic information
5.1.1 Demographic aspects
The number of inhabitants to be served is required to define the quantity of solid waste that will be disposed of. A difference should be made between rural and urban production of solid wastes. Rural wastes present fewer requirements due to its low production, but its collection is more difficult. On the other hand, solid waste production in urban areas due to its concentration, population increase, and technological development is more complex and is the topic of these guidelines.
220.127.116.11 Population Projection
During the design process, it is extremely important to estimate waste future production to define the quantity of solid wastes that will be disposed of. As with any public service, population projection should be estimated. Table 5.1 summarizes the basic information needed.
Population growth can be estimated using mathematical methods or a curve projection using census data.
Among the mathematical methods, geometric growth (i.e., biological population expansion at a constant rate) is presented as a guide. The following expression shows its calculation:
(6) The SW
production in a week is disposed of in the SL in "x" collection days (7 days/x
Area/persons ------------- current (m2/persons)
However, it is recommended to compare the results obtained with other projection methods.
5.1.2 General aspects of solid wastes
Among the most important factors that should be considered for adequate handling of solid wastes are composition and quantity.
18.104.22.168 Waste Composition
Solid wastes in urban areas can differ according to its source: residential, commercial, industrial, street sweeping and markets, and institutional.Table 5.2.
a) Wastes from the Residential Sector
Domestic refuse consists mainly of paper, cardboard, tins, plastics, glasses, rags, and putrescent organic matter.
In studies carried out on refuse production in small localities (less than 40,000 persons) no larger differences were found among socioeconomic strata.
b) Wastes from the Commercial Sector
With some exceptions, businesses do not produce large amounts of solid waste. In small localities, they are not well developed and in general, commercial activity is combined with housing.
Wastes from the commercial sector are similar to domestic wastes but contain a higher quantity of packing material (paper, cardboard, glass, and plastics).
c) Wastes from the Industrial Sector
Industrial activities in small communities are usually low and labor-intensive, compatible with residential use. Therefore, its solid wastes do not have special characteristics and its influence in the general production of wastes is not significant. However, there are some exceptions.
d) Wastes from Markets
Wastes from markets have a defined character and are composed of rests of meat, fish, vegetables, fruits, and other food. Most are organic matter and packing materials. Compost production by manual methods is recommended for these wastes.
e) Wastes from Street Sweeping
Street sweeping and cleaning of public areas, such as central parks, fairgrounds and beaches contribute to waste production. These are composed mainly of leaves, grass, fruits, and peels, as well as paper, plastics, tins, glass, sticks, and a large amount of soil.
f) Wastes from the Institutional Sector
In case of special institutions, such as schools, it can be assumed that the amount of solid wastes produced is not significant compared to other sectors and its composition is similar to others.
Health centers and hospitals do not affect total waste production since in most cases bed capacity is generally low or medium. It is necessary, though, to distinguish between domestic wastes (cleaning, cooking, and common refuse) and those generated by specific activities that produce infectious or hazardous wastes, such as sharp materials, gauzes, bandages, cotton, and organs from operating rooms, called "pathogenic or infectious wastes".
These wastes should be stored separately in closed polyethylene bags (of a special color), avoiding spillage and contact with the collection personnel, even if they wear gloves and protective clothing. The final disposal of these wastes should be local whenever possible and by incineration or bury in a pit of appropriate depth, at least two meters above the water table to avoid groundwater contamination.
If the municipality collects hospital wastes, it should be handled as described and disposed of in the manual sanitary landfill. As soon as the wastes arrive at the site, they should be placed at the bottom of the slope and covered with other refuse and soil.
Wastes produced in small communities do not present significant differences in physical composition to deserve an exhaustive study and they can be considered as domestic wastes. To calculate production, the residential sector is the most significant; the others are so minor that they do not appreciably affect the quantity of total waste. The exception are market wastes.
For this type of solid waste and for such small quantities, chemical composition is not of great importance since they are disposed of in a sanitary landfill.
22.214.171.124 Per Capita Production of Wastes
126.96.36.199 Total Production of Wastes
188.8.131.52 Total Production Projection of Wastes
184.108.40.206 Density of Wastes
5.2 Calculation of the volume needed
5.2.1 Solid waste volume
5.2.2 LANDFILL VOLUME
5.3 Calculation of the area required
5.4 Selection of the construction method
Generally, the selected site should be prepared not only for the construction of the infrastructure but also to provide an adequate support base for the sanitary landfill and for obtaining cover material. This should accompany the topographical map to help the construction engineer in soil movement. Figure 5.2.
The final configuration of the landfill is the conformation of the land once its useful life is over. It is important to represent it in a topographical map to show the maximum levels of the landfill, according to the planner. Figure 5.3.
5.4.1 Trench or ditch method
220.127.116.11 Trench Volume (see Example 3 in Annex I)
18.104.22.168 Trench Size
22.214.171.124 Machinery Time
126.96.36.199 Lifespan of the landfill
5.4.2 Area Method
188.8.131.52 Volumetric Capacity of the Site/
184.108.40.206 Calculation of the Site Lifespan
5.5 Calculation of the cell
A height of 1.0 m, with a maximum of 1.5 m is recommended for the daily cell due to the low compaction of manual operations. This provide greater mechanical stability and the narrowest working face, which together with the cell length will be calculated depending on the daily waste volume as follows:
The quantity of refuse required for designing the daily cell can be calculated in two ways:
- The quantity of solid wastes produced daily:
SWsl = SW p x 7 [5-22]
It should be noted that the density used for recently compacted refuse is less than the stabilized refuse used for volume calculation.
Ac = Vc [5-24]
- Cell length (m)
Since the slope (perimeter) must also be covered with soil, the relation between the width and length of the cell that would require less cover material will be a square one. This measure would be the square root of the cell area:
When this is not possible because the width is too narrow for vehicle unloading, the width is set and the length is calculated using the equation [5-25].
5.6 Labor calculation
- Number of workers
The following calculations are presented to determine the number of workers required for the manual sanitary landfill, assuming eight-hours per day with an effective time of six hours. These figures are for normal working conditions and can vary according to the place and the factors already described.
(*) To be adapted according to the region.
Flintoff reports the following labor requirements for three sanitary landfills operated manually.
Site 1 30 tons/day 2 men/15 tons/man-day
The density of wastes found in these sites was between 250 and 400 kg/m3. For a given tonnage, the volume handled could be equal or greater than in developing countries.
The following table indicates the probable labor requirements and cover material for typical waste generation and density rates in Latin America.
In addition to the number of workers who will construct the manual sanitary landfill, it is necessary to have a supervisor to direct the operation.
Since hiring a professional trained in solid waste management is expensive, it is recommended to have a person with the following characteristics for the position of supervisor:
It should be noted that the presence of the supervisor in the sanitary landfill is important during almost all working hours, especially during the first months. As the work advances, it is possible to reduce the time on site to two hours per day: one hour in the morning and one in the afternoon. Thus, it will be possible to supervise urban cleaning in general and monitor the service quality.
Ultimately, supervisory tasks can be carried out by the chief of public works of the municipality with the support of sanitation promoters.
5.7 Cost analysis
As in every design, a cost evaluation or budget for the project should be included. The costs are divided into:
To determine capital costs, each item must be associated with the landfill lifespan as infrastructure works will be constructed for the design period.
5.7.1 Budget preparation
The planner or person who has designed the landfill should prepare a capital budget for the mayor or institution responsible for the work. The capital cost categories are listed in column (a) in Table 5.4, and its costs in columns (b) and (c). The total of column (c) will give the initial or capital investment required to initiate the work. Each work category is described below.
Column (c) contains the units in which the working volumes are measured. They can be changed if necessary.
In column (d) unit work costs are entered. Engineers, foremen, and persons related to the construction of public or private works usually know the local costs. Many ministries, development corporations, and other organizations have unit cost catalogs that are updated periodically. If such data are not available it will be necessary to calculate them using manuals or data from manufacturers.
Finally, in column (e) of Table 5.5 the cost of each component, which is equal to the product of columns (b) and (d), is introduced. The costs obtained are entered in column (b) of Table 5.4.
d) Closure of the garbage dump
Closing an open garbage dump is relatively easy if machinery and cover materials are available. However, to estimate the amount of work and prevent environmental damage or health risks, it is necessary to establish a plan including the future use of the site. In this case, Table 5.5 should be used and some categories may be added, if necessary.
Finally, once Table 5.5 is completed, its results should be transferred to Table 5.4 where the total of column (c) will give the initial investment required. This capital can be obtained through a loan including interest payments.
5.7.2 Estimate of the unit capital costs
The unit capital costs and interests are calculated to be included in the total costs of the sanitary landfill and in the calculation of the user fee. Thus, it is necessary to calculate the annual or hour cost and afterwards the unit cost according to the production or performance:
Cn = Cost per year or hour according to n
Ctotal = Total cost of the concept
Cc = Ctotal (CRF) [5-30]
crf = i [5-31]
1 - 1
Once the capital cost is calculated by any of the above methods (column (g), Table 5.4), it is divided by the annual production or performance R (see column 5, Table 5.1) to obtain the unit cost in column (i) of Table 5.4. As it can be observed, annual performance or the number of tons received in the landfill will increase annually as the unit capital cost decreases. To avoid this, a performance "R" average can be assumed for all the lifespan of the landfill.
5.7.3 Estimation of operating costs
220.127.116.11 Annual Labor Cost
18.104.22.168 Tools and Protective Clothing
The tools used will depend on the landfill size and are described in Section 6.1.4. It is assumed that they have a lifespan of one year.
The protective clothing may include two uniforms per year, one pair of boots, spectacles, mask, and gloves. The costs will depend on local prices.
22.214.171.124 Drainages, roads, machinery, and others
Each year, an evaluation should be done according to the plans and progress of the work, costs of drainages and roads that should be constructed, number of hours that machines should be rented, materials, and temporary labor required.
The total of the three previous categories will give the annual cost or annual operation budget:
126.96.36.199 Unit Operation Costs
The unit operation cost will be the annual cost previously calculated divided by the number of tons buried during the year.
uoC = Unit operation cost ($/ton)
5.7.4 Total costs and rates
188.8.131.52 Total Costs
5.7.5 Tariff collection
6.1.1 Closure of the municpal dump.
For the successful operation of the system, all dumps in the municipal area should be closed.
To close a dump, the following steps should be taken whenever possible:
6.1.2 Operation control
The work of the sanitary landfill should be strictly organized and supervised to accomplish the proposed objectives. This is achieved through:
In a manual sanitary landfill all operations are based on the work performed by the municipality or community workers. The number of workers depends on the amount of solid waste to be buried, climatic conditions, and landfill construction method (see Chapter 5, item 6).
In addition, it is necessary to have a sanitation chief or supervisor to direct the operation.
The equipment used to operate a manual sanitary landfill are masonry tools such as wheelbarrows with pneumatic tires, shovels, pikes, large hoes, crowbars, wood tampers, as well as pitchforks or rakes and a compacting roller. Figures 6.2 to 6.4
- Llanta neumática = Pneumatic tire
The number of tools depends on the number of workers and the amount of solid waste buried in the landfill.
To carry cover material or refuse, it is recommended to place a few planks across the already constructed cells on the surface of the landfill to facilitate wheelbarrow movement, specifically in rainy periods to improve productivity (Figure 6.5).
6.1.5 Construction of a sanitary landfill
The manual sanitary landfill should be built according to a general plan. The supervisor, however, will be empowered to act according to his judgment when unexpected situations arise such as weather changes or emergencies.
The landfill infrastructure should be built before refuse is unloaded.
Unlike a landfill operated with mechanical equipment, in a manual sanitary landfill it is recommended to unload refuse and cover material from the upper part of the already completed cell. This will help the workers to form the cell and maintaining a narrow working face.
It is important to train all workers from the sanitation service in the construction, operation, and maintenance of the sanitary landfill, as well as in the entire process of waste management. The role of the personnel to achieve good results and the relevance of each activity should be emphasized.
The sanitation supervisor should remember that a worker would be more productive if there are good working conditions.
The steps for constructing the cells are the following:
Once the first cell basis is completed, a vehicle should drive over it during dry periods to achieve larger compaction. Waste is unloaded at the working face and spread downward maintaining a gradient of 3:1 (H:V).
Figures 6.6 to 6.24 show the construction method and manual operation of a landfill.
- UBICACIÓN PRIMERA CELDA = LOCATION FIRST CELL
Filling the daily cell
6.1.6 Operation in rainy periods
Most problems related to the operation of a sanitary landfill occur during rainy periods due to the following reasons:
These factors oblige the following precautions:
- MÓDULO TERMINADO = FINISHED MODULE
6.1.7 Work safety
The personnel working in urban cleaning services (collection, transportation, and final disposal of wastes) are constantly exposed to accidents on the road as well as to infectious diseases. Such accidents may have two causes: unsafe working conditions or worker negligence.
The main unsafe working conditions are:
Negligent workers usually commit the following:
All unsafe working conditions as well as the most common causes of occupational accidents and risks should be carefully identified to solve them adequately. Recommendations for minimizing these problems are indicated below:
Unlike other works, the construction of a sanitary landfill requires permanent supervision and maintenance. This implies expenses which, though minimal, should be made on a timely basis. These resources should be considered in the municipality's annual budget.
One of the most important persons at a sanitary landfill is the sanitation chief or supervisor, who should organize, direct, and control the operation on the site. He should have full support of the municipal administration.
If a manual sanitary landfill does not have good supervision or adequate technical and financial maintenance, it can easily become an open dump.
"A sanitary landfill requires constant supervision to prevent future deficiencies"
6.2.3 Access roads
Access roads, the working face, rain drainage networks, and completed landfill areas should be maintained in good working conditions.
The cost of maintaining access roads is lower than repairing a collection vehicle. Therefore, stones, debris, and soil should be stored for that purpose. The working face should be neat and clean.
6.2.4 Supply of material and tools
At the end of the workday tools should be cleaned. If they are damaged or broken, they should be repaired or replaced as soon as possible.
One of the greatest administrative problems is material supply, which must be planned. Spare parts and other materials should be kept in the municipality's warehouse. It is also important to monitor the supply of tools and implements to workers. This is done for two reasons; for inventory purposes and to determine when replacement is required because of damage. See Table 6.2.
6.2.5 Fly control
Fly control in the landfill should not be carried out with insecticides, since its excessive use not only causes environmental pollution, but builds up fly resistance. Instead, soil coverage should be the main method to control flies. However, flies come to the site in the collection vehicles and when their presence become annoying, it is recommended to fumigate the landfill area. Figure 6.29.
6.2.6 Spread material
It is important to keep clean the areas adjacent to the daily working face. Pieces of paper accumulated and blown out by the wind provide a poor aesthetic appearance to the landfill. One of the workers should collect all these scattered materials at the end of the workday using a sack or bag and deposit them at the site where the cell is constructed. Figure 6.30.
6.2.7 Fire control
Paper, cardboard, plastics, etc. should not be burned in the landfill area, because the decomposition of refuse produces methane, a combustible gas, which can start fires. Also, burning these materials makes the site look like an open dump.
6.2.8 Water control
Peripheral rain drainage (channels, culverts) and landfill surface should be kept in good conditions. In addition, the working face should have drains to facilitate vehicle movement.
6.2.9 Seepage drainage
The large amount of fine material in water clogs the drains progressively, making it necessary to clean them periodically. Such material should be extracted from the trench that conducts the leachate to the filtration field. Otherwise they will clog and overflow on the surface.
6.2.10 Gas drainage
Because of landfill settlements, motor vehicle transit on the cells, and other reasons, gas vents are deformed and inclined. It is necessary to keep them vertical as the level of the landfill rises to prevent their obstruction and loss.
6.2.11 Final finishing and settlement
The placement of the final cover and grass layer requires great care since it affects both the operation and final appearance of the completed landfill.
Solid waste decomposes (a part is transformed into gas and part into fluid) over time and the cover soil and moisture penetrate through its gaps, settling it. After two years there is less settlement and after five years there is practically none. Since the settlement is not uniform, depressions occur in the landfill surface, where rainwater accumulates. Therefore, the soil should be leveled and a drainage should be constructed.
The local administration should make sure that once the lifespan of the sanitary landfill is over, it should receive the final finishing and maintenance required, for its further use by the community. If this is not done, the community will not benefit from this basic sanitation work. This could be a cause for rejecting new sites. It could mean locations more distant from urban areas which will increase waste transportation and sanitation service costs.
It is recommended to place a sign with the name of the work, park, or sports field, indicating that it has been built on a sanitary landfill.
An administration is required to construct and operate a manual sanitary landfill according to the specifications and recommendations given in the study or final report of the project and to ensure that the objectives are fulfilled. Since the final disposal of solid wastes depends on a cleaning service, the landfill must be responsibility of the administrator of this public service. In our society, this administrator is usually a member of the cleaning service office or public works area of a municipality.
The sanitary landfill administration should consider public relations as a priority during both the construction and landfill closure. Public opinion plays a definitive role in promoting and publicizing this basic sanitation work in areas where a new landfill is required.
To improve the cleaning service quality in small municipalities, a sanitation technician or promoter should be contracted as chief or supervisor of the urban cleaning service.This person will then be responsible for coordinating both the landfill and the entire cleaning service and will serve as liaison between users, workers, and the administration.
The administrators of the cleaning service should be informed about the quality of the sanitary landfill operations on a regular basis.
Among other functions, the cleaning supervisor will carry out the following specific activities:
When possible, it is recommended that the turnover of the staff trained in the different urban cleaning aspects especially construction and operation of sanitary landfills be the lowest possible, since this reduces efficiency and increases costs.
7.1.2 Productivity indicators
To manage the different activities adequately, the administrator of the cleaning service has to analyze two main factors: costs and productivity.
The sanitary landfill is under continuous construction and operation, thus, it is necessary to have comparative indicators with other sanitation service activities and similar works. With these indicators it is possible to evaluate productivity and costs, promoting maximum use of available resources.
It is necessary to implement several measures and controls to identify deficiencies, apply corrective measures, and evaluate their effectiveness. This is done to achieve the best productivity and provide an efficient service at the lowest possible cost.
A few indicators used to direct and manage a manual sanitary landfill (MSL) are indicated below
7.2 Control of the manual sanitary landfill
Despite the small size of this sanitation work, it represents an essential activity in the solid waste management for any community. It should, therefore, be carried out in the best possible manner.
It is important to make periodic evaluations to maintain appropriate control in the following areas:
7.2.1 Operation control
7.2.2 Construction control
By maintaining the alignment of the platforms and the height specified for the cells it is possible to control the construction of the manual sanitary landfill using the project's design plans or even by simple observation. The slope gradients should provide the stability required for the work according to the topography of the land.
7.2.3 Cost control
One of the aspects constantly neglected by municipal administrators is the cost analysis of urban cleaning service. This is one of the greatest problems because in general this service is subsidized by the municipality and consumes most of its budget.
The importance of collecting information related to the manual sanitary landfill cost during investment, construction, operation, and maintenance must be emphasized. The analysis of these costs increases productivity and provides more effective cost controls. The accounts of each public service must be dealt with separately.
It can be demonstrated that the overall cost of the manual sanitary landfill ranges between 10% and 20% of the municipal budget for cleaning services. This demonstration changes the wrong image of local administrators regarding the costs of this work. As well, the urban cleaning rate or tariff, essential for its sustainability, can be calculated more realistically optimizing quality and efficiency.
Among the factors to be considered as operational costs are:
7.2.4 Environmental control
Initially, the ground and surface water quality will be checked monthly. After confirming that there is no contamination by the landfill, it can be checked less frequently. The parameters to be analyzed will be those required by the local or regional water pollution control authority. Appendix III.
Gas vents should be checked.
Relative to life or to processes which occur in presence of oxygen.
A condition without free oxygen. Absence of air or oxygen for organic matter degradation.
Commercial solid waste
Waste generated in commercial facilities, such as warehouses, depots, hotels, restaurants, cafeterias, and market places.
Density of htre refuse
Relationship between the weight and the volume occupied (weight per volume unit). The density of the refuse depends on the compression. The following values can be adopted:
Dr = 150 - 300 kg/m3
= density in refuse container.
Domestic solid waste
Waste that by its nature, composition, quantity, and volume is generated in households or in any similar dwelling.
Moisture existing in a porous environment after the gravitational water has been eliminated.
Last operation of the urban cleaning service, by which waste reach final destination.
Industrial solid waste
Waste generated in the activities of the industrial sector as a result of production processes.
Institutional solid waste
Waste generated in educational, governmental, military, prison, and religious establishments, transportation terminals, and in office buildings, among others.
Liquid that percolated through solid wastes, carrying dissolved or suspended materials. The infiltration of a portion of the rain is the main generator of leachate in sanitary landfills and refuse dumps. Other factors are the water content of the refuse itself, water resulting from decomposition, and groundwater infiltration.
Pathogenic solid waste
Waste that by its characteristics and composition may serve as a reservoir or vehicle of infection.
This is defined as the velocity of the water in the soil under a unit hydraulic gradient. The dimension of permeability is that of the velocity, since the dimension is length divided by time.
Atmospheric water that falls on the soil in liquid or solid form, such as rain, snow, or hail. The intensity and frequency of the precipitation should be considered in the construction of the sanitary landfill to provide adequate drainage systems.
Obtaintion of secondary materials from solid wastes, either by separation, unpacking, collection, or any other way for recycling or reuse.
Process by which certain refuse materials are separated, collected, classified, and stored to incorporate them into the production cycle as raw material.
Refuse is understood to mean all solid or semisolid waste that lacks value for its immediate owner except excreta of human or animal origin. Included in the same definition are rubbish, wastes, ashes, street sweepings, and industrial wastes and those from hospital establishments and market places, among others.
Returning of a good or product to the economic flow to be used exactly in the same form as it was before, without any change in its shape or nature.
Water that does not penetrate the soil or does so slowly and runs on the surface of the land after a rain.
Control of the physical environmental factors that may have a harmful effect on man physical development, health, and survival.
Physical, chemical, or biological transformation of solid wastes to obtain health or economic benefits, or to reduce or eliminate harmful effects to man or the environment.
Any organism that carries the disease agent from a patient or a reservoir to a healthy person.
Period over which the sanitary landfill will be able to receive refuse on a continuous basis. The volume to be filled is the volume of refuse deposited between the original surface of the land after preparation of the site and the final surface of the landfill. The calculation of the useful spanlife involves a series of variables that should be evaluated to achieve a technically and economically
1. AIDIS. Vigilancia de rellenos
sanitarios, gestión ambiental en el caso del relleno La Feria. IV Congreso Chileno de
2. ASOCIACION DE INGENIEROS SANITARIOS DE
ANTIOQUIA (AINSA). Desechos sólidos: Generación, almacenamiento,
3. ARMSTRONG, Christian. Confección de
rellenos sanitarios con maquinaria agrícola y operación manual. Departamento de
4. CETESB. ORTH, María Elena de; KIYUSHI T., Celso. Aterros sanitários. Sao Paulo, Brazil. 1982.
5. CETESB. Aterro sanitário. Consejo Nacional de Desenvolvimento Urbano. Sao Paulo, Brazil. May, 1979.
6. CETESB. Manual de operaçao de resíduos sólidos No. 2, disposiçao de lixo em vala. Sao Paulo, Brazil. 1983.
7. CETESB. Recuperación de gas metano
de relleno sanitario. Módulo Programa Regional OPS/EHP/CEPIS de Mejoramiento de los
8. COLLAZOS, Héctor, and Leoncio HERNANDEZ. Relleno sanitario manual. Revista ACODAL No. 87. Bogotá, Colombia. April, 1979.
9. DEPARTAMENTO ADMINISTRATIVO DE
PLANEACION DE ANTIOQUIA. Diseño relleno sanitario manual "El Chagualo", I
10. DEPARTAMENTO ADMINISTRATIVO DE
PLANEACION DE ANTIOQUIA. Guía para el diseño, construcción y operación de un
11. EMPRESAS VARIAS DE MEDELLIN. Diseño
relleno sanitario "Plaza de Ferias", Informe Final. Compañía Colombiana de
12. ENVIRONMENTAL PROTECTION AGENCY. Sanitary
landfill design and operation. U.S. Government Printing Office. Washington
13. FLINTOFF, Frank. Management of solid wastes in developing countries. WHO. Regional Publications. Southeast Asia. 1984.
14. FOSTER, S., et al. Determinación del riesgo de contaminación de aguas subterráneas. CEPIS/OPS/OMS. Lima, Peru. 1988.
15. HADDAD, José. Módulo de disposición final de residuos sólidos. CEPIS/HPE/OPS. Lima, Peru. 1981.
16. HANSEN, Israelem. Principios y aplicaciones del riego. Editorial Reverté, S.A., 2nd edition. Barcelona, Spain. 1973.
17. IRVINE, William. Topography. Areas and Volumes. McGraw Hill. 1975.
18. MINISTERIO DE SALUD. Decreto 2104 de 1983, Residuos Sólidos. Bogotá, Colombia.
19. OROZCO, A. Desechos sólidos. Una
aproximación racional para su recolección, transporte y disposición. Universidad de
20. PENIDO, José. Recuperación
semi-mecanizada de materiales. Aspectos técnicos del servicio de aseo. Programa
21. RIVERO, F. J. Aterro sanitário.
Simposio Paranaense de Destinaçao Final das Resíduos Sólidos Urbanos em
Curitiba. Sao Paulo,
22. SAKURAI, K. Cálculo del volumen del relleno. Technical note. CEPIS. Lima, Peru. 1980.
23. SAKURAI, K. Diseño de zanja de intercepción. Technical note. CEPIS. Lima, Peru. 1980.
24. SAKURAI, K. Disposición final de residuos sólidos. CEPIS. Lima, Peru. 1980.
25. SECRETARIA DE DESARROLLO URBANO Y
ECOLOGIA, et al. Programa estatal de control de residuos sólidos municipales.
26. SECRETARIA DE SALUBRIDAD Y ASISTENCIA. Instructivo sanitario. Ed. Limusa. Mexico. 1980.
27. STECH, Pedro José, et al. Aterro sanitário em valas. Divisao de Resíduos Sólidos Domésticos. Sao Paulo, Brazil.
28. UNIVERSIDAD DE ANTIOQUIA. Facultad de
Salud Pública. Estudio de aseo urbano (diagnóstico y proyecto). Municipio de
EXAMPLE 1. Calculation of Solid Waste Production per Day
EXAMPLE 2. Calculation of the Required Landfill Volume
The municipal administration of the city of Hierro is going to construct a sanitary landfill. It is necessary to know how much refuse is produced, the landfill volume, and the area required to start the selection of the site. The following information is available:
To handle the information more easily, use Table 5.3 where the results are summarized. The number of column referred to are those of that table (see it at the end of the problem).
A. Population Projection:
Geometric growth will be assumed for calculating population projections (see equation 5-1, column 1, for estimates of the needs for the next 15 years).
B. Production per Capita:
C. Quantity of Solid Wastes:
D. Volume of Solid Wastes:
E. Calculation of the Area Required
AT = 1.3 x 7,848 m2 = 10,203 m2 (1.02 ha*)
EXAMPLE 3. Calculation of the Trench Volume
In a municipality there is a flat land available for constructing a manual sanitary landfill by the trench method. To open the trenches, a backhoe with an an excavating capacity of 14 m3 per hour will be rented.
Quantity of solid wastes produced
If the cover material is estimated at 20%, lifespan at 60 days, and the density at 500 kg/m3, then:
EXAMPLE 4. Calculation of the Lifespan of the Site
For complementary works, 0.3 ha are reserved. Two hectares are left to filling wastes and each trench is separated 2.00 m from the other, then:
Since each trench occupies six m, plus two m of separation between them, i.e. eight m, the number of trenches in one hectare will be:
Number of trenches = 100/8 = 12.5 or 12
If each trench lasts two months, 12 trenches will last two years, and the total area required for the landfill will be 2.5 ha to have a lifespan of five years.
The trench method can be combined with the area method, i.e. raise the landfill a few meters above the original surface using cover material from the excavation (80% in case of the example) to use the land more efficiently.
EXAMPLE 5. Example of Volume Calculation for the Area Method
Assume a manual sanitary landfill project on an abandoned road which sections similar to those shown in the following figure and with horizontal axes at intervals of 100 m, yielding an average height of eight m.
The landfill will have a width "w" of six m at the base, a variable slope in each section, and the following data:
The larger base of the trapezoid will be:
Width of the landfill surface = (w + nc +
Therefore, the cross section area at every abscissa (trapezoid) will be:
EXAMPLE 6. Volume Calculation Using the Prismoid Rule
The figure shows a manual sanitary landfill project in a trench with the following data:
EXAMPLE 7. Volume based on the Extreme Areas
Using the same data as in the previous example we have:
Therefore the volume will be:
EXAMPLE 8. Volume Based on a Graticule
The figure shows a small part of the graticule. The area should be filled to 100.0 m height to obtain the final surface. The slope should be vertical.
The solid with a base in each square of the graticule is a vertical truncated prism, i.e. a prism which bases are not parallel.-
SUPERFICIE FINAL = FINAL SURFACE
- Volume of each prism = average height x base area
The average height of each truncated prism below the elevation of 100.0 m is:
The average height of the landfill is the average of the average heights of the prisms and not the height mean at the level points.
When analyzing this process, it can be noticed that level A was used only once to find the average height of the landfill, level B twice, and level E a total of four times. As a result, the average height, thus, the volume can be found more easily by tabulating the operations as in Table I.2.
The heights at the level points are tabulated in column 2 and the number of times that each one is used is entered in column 3; column 4 contains the products of the numbers in columns 2 and 3; the average height is found by dividing the sum of column 4 by that of column 3.
EXAMPLE 9. Volume Based on Contour Lines
If we take the volume between the contour lines of 105 and 115 m, which areas may be found by any of the methods described in Annex II, the mean section will be enclosed by the curve of 110 m, which area may also be found using any method. Then, the prismoid volume will be:
As well, the volume between the contour lines for 115 m and 125 m will be:
The sum of these results will give the volume between levels 105 m and 125 m.2h 2h
EXAMPLE 10. Calculation and Design of the Daily Cell
For the same population of 30,000 persons, with a production of 12 tons/day and a coverage of 90%, calculate and design the daily cell in a manual sanitary landfill that operates six days a week.
C. Cell dimensions
. The area, considering that the height is limited to one meters, is:
. The length or growth of the cell will depend on the normal variations of the refuse, while the width in this case can be maintained at three meters; thus:
EXAMPLE 11. Labor Force Calculation
For 12,600 kg/day, in each of the six days of operation of the sanitary landfill, with a workday of eight hours, and assuming six hours of effective work per day, how much labor is required, assuming the efficiency proposed in Chapter 5?
According to the different operations and efficiencies we have:
This means that this sanitary landfill could be operated with a total of approximately five men (performance of 2.5 tons/man-day). As it has been observed, the number of men depends on how near are the working face and cover material, on weather conditions (rainy season), and mainly on quantity variations of the refuse received at the landfill.
It is worth noting that supervision plays a primary role in the proper operation of the sanitary landfill as well as in the worker effectiveness.
EXAMPLE 12. Cost Calculation
The objective is to determine the operation and maintenance costs of a manual sanitary landfill and to establish, in addition, the user fee. The landfill, with an estimated lifespan of nine years, receives 12 tons of refuse daily (Monday through Saturday). The following information is available for the analysis:
1. Capital cost
2. Operation and maintenance expenses
SOLUTION TO THE PROBLEM:
(Uc) = annual amount of capital recovery
= _____ $ 4,713.5 per year
2. Calculation of the unit cost of operation and maintenance (Uco)
2.1 Labor cost (equation 5-32)
. Direct = 4 x 12 x 90 x 1.6 =
$6,912 per year
2.2 Other operation expenses (Ct + Cm)
. Materials and tools
$310 per year
TOTAL OPERATION AND MAINTENANCE
3. Calculation of fees
3.1 Fee with capital recovery plus operation and maintenance costs
TOTAL TO BE RECOVERED $3.54 per ton
Quantity of refuse
Monthly cost for tons
final disposal month
3.2 Fee based on operation and maintenance costs
4. Annual budget allotment from the municipality
1. Drawing to Scale
This is a measure relationship that represents real objects in exact proportions, in appropriate sizes, to facilitate the work of planners and builders.
"Drawing to scale" can be defined as the exact representation of something in a reduced size.
The establishment of proportional measures (ratios) that represent natural objects on appropriate scales, or the representation of the system chosen for a map scale, has the following nomenclature:
The first number represents the unit and the second, the number by which it has been divided to generate smaller proportional dimensions.
2. DRAWING AND MEASUREMENT OF LINES
This operation will be repeated as many times as necessary until reaching the other end.
3. Drawing a Perpendicular from a Point outside the Alignment
A person should be placed on the alignment with his arms extended, looking toward the point where the perpendicular is going to be drawn, making sure that his arms point toward each end of the alignment. Then he closes his arms and extends them forward; the perpendicular point should be in the direction indicated by the arms.
If a surveyor's square is available (Figure II.2), the observation is made simply by using the grooves.
- (ÁNGULO RECTO)= (RIGHT ANGLE)
4. Area calculation
4.1 Areas Deduced from Field Notes
Figure II.3 shows a simple survey with a tape measure, comprised by the triangle PQR with the following sides:
d. In Figure II.3 the area is calculated as follows:
Calculation of the Aarea by the Graphic Method