by Derek Greedy and Jan Thrane
The purpose of this feature is to highlight the issues associated with open dumping, which is used as a waste disposal option in many developing countries. The International Solid Waste Association (ISWA) supports initiatives associated with moving away from open dumping to practices where the waste is better contained and covered, and where environmental impacts from waste disposal are progressively reduced.
Unfortunately, waste management is not considered to be a priority for developing countries unlike the provision of clean water. Some spend as much as 95% (The Guardian, 20 August 2008) of their available resources on clean water with the remainder being spent on sanitation, which has made open dumps an easier option. What is not recognized is the impact open dumping is potentially having on water resources, and the fact that some additional expenditure on waste management could make clean water provision cheaper.
Throughout history, mankind has used dumps to solve solid waste problems. In the past open dumping was used as an inexpensive and often appropriate solution. It served the purpose of keeping waste separated from the populace, hence limiting exposure to disease, vectors as well as odour. However, the introduction of more complex products into the waste stream, increased urbanization and population growth, have all resulted in a huge increase in the negative impacts of open dumps.
Open dump, Sierra Leone Click here to enlarge image
Today the use of open dumps does not conform with the increasing public awareness of environmental issues, including the current focus on sustainability and global climate change. Closing, or alternatively upgrading, open dumps is therefore a key issue for many communities. Such upgrading is an essential step in reducing future environmental and public health impacts, as well as avoiding future costs caused by the ongoing mismanagement of waste, evident at open dumps.
The visual characteristics of such sites are typically:
- widely dispersed uncovered waste
- open fires and/or waste periodically on fire
- no recording or inspection of incoming waste
- no control of waste placement
- no compaction of waste
- no application of cover soil, or minimal cover (often associated only with forming access roads)
- scavenging at site
- no security
- vermin, dogs, birds and other vectors often present
- poor or no leachate management
- no provision for the management of landfill gas.
In addition, it is typical for no planning or engineering measures (such as a liner system) to have been implemented prior to the placement of waste.
The impact of open dumps
There are many impacts from open dumps. The most important factors are those relative to location proximity to waterways, geological/hydrogeological conditions and climatic conditions. In addition, the solid waste composition, quantity, and the boundaries and age of the dump site will have their own particular impacts. The following are the most important potential impacts of open dumping on the environment and to public health and safety:
- contamination of water may occur when leachate from the dump, via flow paths (on or under the surface) reaches groundwater or surface water. Waste is sometimes deposited directly into water at dump sites resulting in the direct contamination of surface water. Furthermore, sites are often located in areas where the land quality is poor and marshy.
- many contaminants (especially heavy metals) are trapped in the soils beneath dump sites risking long-term contamination and restricting the potential after-use of the site.
- landfilled organic waste may contribute to the greenhouse effect via emissions of carbon dioxide and methane. However, in the case of the open dump, the predominate gas emitted is carbon dioxide as aerobic conditions prevail.
- uncontrolled burning of solid waste (particularly certain types of plastics) releases smoke and gaseous contaminants into the air. The smoke commonly contains particulates, carbon monoxide, carbon dioxide and other contaminant gases, including low levels of dioxins all of which can be hazardous to health. Odour from the generation of hydrogen sulphide may also be problematic.
- fauna in and around dump sites may be impacted, either by direct consumption of the solid waste, or by consumption of contaminated plants and/or animals, or as a result of leachate effects on groundwater and surface water.
- plants near open dump sites can be impacted directly by the waste, dust or smoke from burning.
- dumps tend to affect the type and number of plants in the area and the presence of dead vegetation is often associated with the zone of direct impact around them. Dead vegetation is normally due to trampling by foot, vehicle or animals, but may also be the result of direct contamination by waste or leachate, the migration of gasses, or as a result of burning or smoke.
Impacts on public health and safety
- the smoke from burning solid waste can result in respiratory complaints, dizziness and headaches in the short-term, as well as potentially more serious diseases, such as cancers and heart disease in the long term.
- direct or indirect contact with polluted soil or water by neighbouring water users.
- the potential for the spread of infection is large and is often related to direct contact with the waste by scavengers and other unauthorized persons. The other transmission pathway is by vectors such as foraging animals, rats, birds, flies and mosquitoes.
- site accidents frequently occur at dump sites, mostly involving scavengers. The greatest risk relates to cuts and wounds (and subsequent infection), but other types of accidents may involve fires, explosions, machine accidents and landslides of waste.
A poorly-sited open dump has the potential to severely impact quality of life for local residents so every effort should be made to cease the practice of open dumping, and to upgrade progressively to controlled dumping/basic landfilling, and then to sanitary landfilling with the associated environmental controls.
Problems encountered in closing open dumps
There are many potential problems related to the closure of open dumps. Several key questions typically arise: what method to use, who is going to pay, what new waste disposal method is best. There are many different approaches, some of which are outlined here.
It is difficult to close a site that continues to be used as a dump site. This can be addressed by providing a new waste disposal facility to accept the waste enabling the old site to be completely closed, and by educating waste generators and site users. Furthermore, it is essential to close off access to the existing open dump and enforce its complete closure once any new, upgraded site is available.
Controlled landfill in Greece Click here to enlarge image
Another key problem relates to the cost involved in closing down an old dump. Invariably no money will have been set aside for this. However, the long-term costs (including costs related to the impact on the environment and on public health and safety) of not closing down an open dump may far exceed the closure costs. This means that closing open dumps should not be a cost issue but an environmental/human health issue. In reality, many countries with scarce resources have difficulty raising the required closure costs as other basic infrastructure costs (such as water supply and wastewater treatment) are always prioritized.
There is also the potential impact on the local economy and income for the scavengers, should an alternative source of income not be identified.
Closure is undertaken on a stepped approach which should follow the stages below:
- investigate potential impacts
- reduce risks (no-cost to medium-cost options)
- plan new sustainable disposal option
- develop a workable financial and information strategy
- secure dump users’ commitment to closure (using consultation)
- choose a closure method (using risk-based assessment)
- choose a new waste disposal method (using cost-benefit analysis)
- write a closure plan
- inform, train and educate users
- start a new facility
- close up the open dump.
There are three principle methods to close an open dump:
- closing by covering the waste (in-place closure)
- closing by removing the waste from the site
- closing by upgrading the dump to a controlled dumping site or sanitary landfill.
When choosing a closure/upgrading method the most technically advanced solution is not always the most appropriate. Depending on the situation, simple improvements of operational aspects (such as applying cover soil and eliminating open burning) can often result in marked site performance and greatly reduced environmental impacts. The key should always be to keep things simple and sustainable in a local context, while maximizing actual improvement in environmental performance.
Controlled landfill in Turkey Click here to enlarge image
In-place closure is the most commonly used option. The solid waste is left at the site and covered with a layer of local soil and re-vegetated. This approach will:
- reduce waste exposure to wind and vectors
- prevent people and animals from scavenging
- control odour
- minimize the risk of fires
- stop people from using the site
- control infiltration of rainwater/surface water
- reduce leachate generation
- control migration of landfill gas
- serve as a growth medium for vegetation
- support suitable post-closure activities.
The second option is to remove the solid waste from the open dump and to dispose of it off-site (typically to a sanitary landfill or a waste incineration plant). The removal can be combined with sorting the waste for recovery of recyclables. This may or may not lead to the release of odours, gasses and leachate, as well as the potential for generating windblown litter all of which can have an impact locally. This will need to be carefully managed to reduce the impact on the local community.
A further option is to to upgrade the open dump and to make it aesthetically acceptable this may only be feasible if the dump is in an area where groundwater pollution is not critical as the dump is not installed with a bottom liner to provide groundwater protection. This option requires implementation of sound design, operation and management of the landfill at all levels, and is effectively a move towards a sanitary landfill operation.
Sanitary landfill in Portugal Click here to enlarge image
Upgrading will include the provision of a low permeability cap over the existing waste mass which can then be soiled and vegetated. It will also be necessary to install a basic landfill gas collection system, as sealing of the waste will inevitably create the anaerobic conditions conducive to the generation of methane. Capping and grading will also reduce the potential for the waste to generate leachate.
New waste can then be deposited in properly engineered cells providing full containment and leachate collection. However, it needs to be recognized that this will increase the cost of disposal considerably, as there will be construction costs, costs to manage leachate and landfill gas, and long-term environmental controls.
Even though the closure of an open dump may pose short-term technical or financial difficulties, it is an objective that should be aspired to. The on-going operation of open dumps should be discontinued and care taken to prevent future contamination.
It is recognized that there are locations where a lack of resources precludes the immediate closure of open dumps. In these cases a controlled approach, where the principle is to keep it simple and sustainable without compromising public health or the environment, is appropriate, but this should only be an interim step to proper sanitary landfill practices. A staged approach can be taken, but ultimately the goal must be to achieve sustainable waste management with the sanitary landfill providing just a part of the overall solution. Recycling and composting will both have a role to play and must be integrated into the plan.
Where legislation does not exist consideration should be given to introducing legislative control for the management of waste. Some developing countries have already done so with positive effect boosted by the provision of guidelines on good operational practice to assist operators.
Derek Greedy is Chair of the ISWA Landfill Working Group
Jan Thrane is Vice Chair of the ISWA Landfill Working Group
Case Study Bo City, Sierra Leone
Bo City in Sierra Leone currently has two landfill sites. The first is an unofficial site in the centre of the city adjacent to a swamp area. This dump is continually on fire and is home to scavengers.
The second site, which is regarded as the official landfill site, is five miles (eight kilometres) out of Bo City, approximately eight acres (3.2 hectares) in extent, and is presently used for both solid household waste and liquid waste from latrines. No purpose-built facilities have been made available on site except for two tanks for liquid waste.
Bo City Council, Warwick District Council, Warwickshire County Council, United Nations Development Programme and One World Link are working jointly to improve the waste management infrastructure in Bo City. This will include the closure of the unofficial dump in the city, improved management of the official landfill site, improved waste collection and central composting of garden waste.
The protocol for the closure of the unofficial dump is still to be determined but will be in line with the closure methods outlined in this article. The official dump on the outskirts of the city will be upgraded operationally, but it is unlikely that resources to upgrade to a sanitary landfill will be available. In the first instance it is likely that waste will be deposited into excavated trenches and daily cover applied. Further improvements will take place on a progressive basis as resources become available.