Threats to Sources of Drinking Water and Aquatic Ecosystem Health in Canada
- Executive Summary
- 1. Waterborne Pathogens
- 2. Algal Toxins and Taste and Odour
- 3. Pesticides
- 4. Persistent Organic Pollutants and Mercury
- 5. Endocrine Disrupting Substances
- 6. Nutrients—Nitrogen and Phosphorus
- 7. Aquatic Acidification
- 8. Ecosystem Effects of Genetically Modified Organisms
- 9. Municipal Wastewater Effluents
- 10. Industrial Point Source Discharges
- 11. Urban Runoff
- 12. Landfills and Waste Disposal
- 13. Agricultural and Forestry Land Use Impacts
- 14. Natural Sources of Trace Element Contaminants
- 15. Impacts of Dams/Diversions and Climate Change
12. Landfills and Waste Disposal
Allan S. Crowe,1 Carol J. Ptacek,1 David L. Rudolph2 and Rick McGregor3
1Environment Canada, National Water Research Institute, Burlington, ON
2University of Waterloo, Department of Earth Sciences, Waterloo, ON
3J.R. Scientific, Suite 302, 285 Erb Street W., Waterloo, ON
Canada ranks among the highest producers of solid waste per capita in all of the industrialized world. Although Canada is viewed as a country of abundant fresh water resources, in reality we are facing a mounting threat as a result of improper waste management. Canadian citizens have been directly impacted by the consequences of improper waste disposal, and many of these have drawn widespread media attention. In the spring of 2000, seven people died and over 2000 took ill as a direct result of improper disposal of animal wastes in Walkerton, Ontario. Important drinking water sources at Elmira and Smithville, Ontario; Abottsford, B.C.; and Ville Mercier, Quebec, have been destroyed as a result of poor waste disposal practices. Hazardous waste from the Sydney tar ponds, Nova Scotia, have contaminated groundwater and surface water in highly populated areas, and has resulted in the release of pollutants to the ocean. Millions of litres of contaminated water flowing daily from the waste rock of Britannia Mine, near Squamish, B.C., have caused large areas downstream to become void of life. These incidences will become more frequent in the future, unless Canada immediately develops and implements a comprehensive waste management plan.
Wastes are a part of life. They are produced as by-products of agricultural, industrial, commercial and domestic activities. These wastes are recycled, incinerated or treated, or disposed. Disposal approaches range from the use of highly engineered facilities to simple landfilling and spreading operations to deep-well injection. Canada has a wide spectrum of approaches in managing wastes within primary waste streams. Canadians are one of the largest producers of waste in the world. 1988 statistics (Environment Canada 1991) show that Canada produced 30 million tonnes of solid waste annually, amounting to about 1.8 kg per day per person or twice as much produced per person in Sweden.
The main threat to water quality due to the disposal of wastes focuses on the groundwater environment. Surface water contamination also occurs as a result of direct runoff from waste sites to streams, lakes and wetlands, and indirectly as contaminated groundwater discharges to surface waters. The contamination of groundwater has many factors which makes it very different from surface water contamination. Because we cannot observe groundwater, we typically discover that the groundwater is contaminated once a well or surface water body becomes contaminated. Surface water contamination occurs quickly and can be stopped at the source. However, groundwater contamination may commence years after the waste source is in place. The slow release rate causes it to take years to thousands of years to move through the groundwater flow regime, and groundwater can be difficult, if not impossible to remediate, and prohibitively costly to remediate. Ultimately all contaminated groundwater will discharge to surface water. Thus, should serious groundwater contamination occur, the destruction of drinking water supplies and aquatic ecosystems occurs for decades to hundreds of years.
Municipal/Hazardous/Industrial Solid Waste
Solid waste is predominantly composed of domestic waste, hazardous waste, industrial waste, contaminated soils and building debris. It is estimated that hundreds of landfill sites are located within Canada. This estimate is considered low as it does not account for small landfills, landfills not registered with the appropriate agency, or abandoned landfills. Disposal options for municipal wastes range from disposal in engineered facilities to disposal in open excavations, with regulations and guidelines varying across Canada. The siting, design and monitoring of solid waste facilities is relatively well understood. It is now accepted that all landfills will eventually release leachate to the surrounding environment and therefore all landfills will have some impact on the water quality of the local ecosystem. Traditionally, solid waste landfills are monitored for nutrients, heavy metals, major ions and volatile organic compounds (VOCs). Many of these constituents have been observed in aquifers at distances up to several kilometres from the landfill source. As an example of the cost of containment failure, PCB waste which leaked to groundwater from a waste transfer facility at the town of Smithville, Ontario, between 1978 and 1985, forced the closure of the town's water supply wells. After spending over $55,000,000, the shallow contaminated soils have been removed, a new water supply system for the town of Smithville has been installed, and groundwater studies have been conducted. However, long-term threat from contaminated groundwater still exists and after 15 years of study we are just beginning to gain the knowledge necessary to understand how the waste is moving through the subsurface and what we can do to remove it (Novakowski et al. 1999).
Mining waste is generated through the processing of base metal and gold-bearing ore, coal, potash and tar sands. The waste is disposed of in piles, geographic depressions, or constructed impoundments which can cover thousands of hectares. It is estimated that mining activities in Canada have produced at least 350 million tonnes of waste rock, 510 million tonnes of sulphide tailings and more than 55 million tonnes of other wastes. More recent disposal methods include subaqueous disposal and as mine backfill. If the waste contains sulphide minerals, such as pyrite, sulphide oxidation reactions occur, releasing acidity and heavy metals to the groundwater and surface water. Currently the design of mine disposal sites is determined by geotechnical factors rather than water quality issues. Recent advances by Canadian researchers have shown that the disposal of mining waste may have a long-term detrimental impact on the surrounding ecosystem (Bain et al. 2000). These effects have been projected to last decades to centuries to even millenia due to the slow rate of oxidation and transport of oxidation by-products (i.e., acid, heavy metals, arsenic, etc.) through the underlying geologic media. Concentrations of contaminants can exceed drinking water and aquatic limits by several orders of magnitude.
On a national basis, the disposal of livestock waste associated with cattle, swine, and poultry farming, occurs over an extremely large area throughout Canada. The primary contaminants associated with manure include nitrate and ammonia, coliform bacteria, phosphorus, endocrine disrupters and other animal pharmaceuticals. Both the land use and waste management practices commonly employed on farms throughout Canada have impaired the quality of water resources on a regional basis (Rudolph et al. 1998). In a recent survey of farm drinking wells in Ontario, approximately one well in three was found to contain at least one contaminant commonly associated with agricultural activities, including nitrate or bacteria (Goss et al. 1998). Runoff of nutrients and microbes from manure have caused numerous incidents of serious contamination, for example, fish kills in PEI and Ontario, cases of eutrophication of surface water all across Canada, and the steady rise in nitrate levels in the tributaries of Great Lakes during the past 20 years. Environment Canada (1998) reported that eutrophication due to manure runoff was the principal cause of fish kills in Ontario. Current management practices throughout most of Canada involve the temporary storage of raw manure in open barnyards, earthen lagoons, or concrete tanks. Manure is subsequently spread on cultivated fields at different times of the year as a method of final disposal. Surface runoff from barnyards and storage facilities leads to direct release into surface water and groundwater. Once the contaminants have entered the groundwater system, they can be intercepted by local farm wells, municipal wells (as was the case at Walkerton, Ontario) and surface water courses.
Municipal Biosolids and Septic Systems
Urban sewage, consisting of a mixture of solid and liquid wastes, typically undergoes primary treatment in sewage treatment plants. The treatment plants are designed to remove biosolids and a fraction of dissolved components from the wastewater. The biosolids generated from the treatment process are typically disposed in landfills. However, huge quantities are still spread on agricultural land. It is estimated that 80% of Ontario's municipalities dispose of over 1.5 million tonnes of biosolid on 13,000 hectares of land each year by spreading it on agricultural land (Coote and Gregorich 2000). Biosolids contain elevated concentrations of nitrogen, phosphorus, metals, and other residues of often unknown composition. Depending on the degree of treatment, biosolids may also contain elevated concentrations of pathogens, including fecal coliform, E. coli, viruses and protozoa. There are a series of guidelines and regulations in Canada recommending best practices for land spreading of biosolids. These guidelines and regulations may not provide adequate protection to prevent exposure to humans, livestock, soil organisms, and crops to pathogens or undesirable uptake of metals and other constituents into food crops and other ecosystem impacts. When applied in tile-drained areas, pathogens may survive the downward transport to the drain (typically 40-50 cm below surface) and be discharged to adjacent streams or drainage ditches.
Sewage generated in non-urban settings is typically disposed using on-site treatment systems. Most commonly, the wastewater is released to septic tanks where anaerobic digestion processes take place, and the decant water is released to tile lines where infiltration to the subsurface is promoted. The solids slowly break down in the septic tank or are pumped out and spread on fields or treated in wastewater treatment plants. In Canada, there are a variety of alternative disposal practices followed which provide comparable or improved degrees of treatment to conventional practices. Most on-site wastewater disposal systems involving discharge to the subsurface result in the release of nutrients, metals, pathogens, surfactants, medications and other constituents to groundwater (Robertson et al. 1998). The resulting plumes can discharge to surface water bodies over time. Plumes of septic-system derived contaminants often contain concentrations of nitrate above drinking water guidelines, at times many hundreds of metres from the source (Ptacek 1998). On-site wastewater disposal represents the largest volume of wastewater discharged to the subsurface in Canada. As with agricultural waste, the short-term fate and transport of the traditional contaminants, such as nitrate and phosphate, are relatively well understood. However, the long-term impacts of these traditional contaminants are poorly understood as are the fate and transport of bacteria, viruses and other substances that have not been analyzed to date.
The petroleum industry can produce a variety of wastes. During the drilling of oil and gas wells, the sump pits typically contain brines with very high concentrations of salts and metals which leach to the underlying water table. There are hundreds of thousands of these sites located in Saskatchewan, Alberta and B.C. These have not emerged as a major threat because bentonite used in the drilling process will entrap the brine, and recent drilling techniques used above-ground tanks, from which the waste is disposed to landfills. Another by-product, sulphur, is extracted during the processing of natural gas and stored in large piles. Runoff which is not captured can cause elevated levels of sulphate in groundwater, however the groundwater near many of these sites typically has naturally high sulphate levels. Many wastes from the petrochemical industry are disposed through deep wells in Ontario and Alberta. Although this is generally a safe means of waste disposal, when improperly sited or constructed, extensive groundwater and surface water contamination occurs if the waste is able to migrate to the surface. Problems with corrosion of the well casing and seal in abandoned wells may produce a pathway for the upward migration of hazardous wastes and oilfield brines to shallow aquifers used as sources of drinking water. This was the case at Lambton County, Ontario, during the 1970s (Vandenberg et al. 1977). Processing plants also produce wastes at their flare pits. These wastes, which include produced water (brine), sludge, PAHs, metals, and oils, accumulate over time. Most of these pits have been found to leak and cause groundwater contamination.
Considerable waste sediment is generated during the dredging of harbours and channels. This sediment is generally used as fill along shorelines, but because some harbours are contaminated (e.g., Hamilton, Halifax, St. John's) special disposal facilities are required. Similarly, considerable fill is generated from the disposal of old buildings, roadways, and building excavations. If the material is uncontaminated it is used as shoreline fill or disposed in municipal landfills. If classified hazardous, it is disposed in hazardous landfills. The runoff of excess road salt has caused extensive contamination of surface and ground waters. Levels of road salt in the Waterloo Aquifer are rising and may eventually render the aquifer unfit as a source of drinking water. It is a common problem adjacent to just about every road in rural Canada. In urban areas storm sewers dramatically limit groundwater contamination, but discharge from the sewers causes extensive contamination of surface waters. High-level radioactive waste generated in nuclear reactors poses a very serious health risk and very long-term problem. Because of this, AECL is conducting an extensive program to manage and dispose of this type of waste.
The legacy of solid waste management in Canada has left a complex series of water quality problems, many of which we are just beginning to understand. The problems are not entirely due to poor management practices of the past, but are due to the evolving nature of the problem which causes us to look for new contaminants and institute new disposal practices. Many of the contaminants of the future currently exist, and perhaps have existed in water for years, we just have not begun to look for them yet (e.g., emerging POPs, pharmaceutical compounds). The contaminants which we currently know about, will also continue to cause major problems and numerous challenges. Predicting the significance of these contaminant releases on the long-term health of the aquatic environment, developing methods to minimize these future impacts, and formulating an effective regulatory framework that ensures effective management, represent the most immediate tasks at hand.
Municipal Solid Waste
As Canada's urban population grows, so does the amount of municipal waste produced. It was estimated that in 1995 Metropolitan Toronto, York, Durham and Peel regions disposed of 2.0 million tonnes of municipal waste, and another 0.95 million tonnes of private waste was exported from this area (Golder Assoc. Ltd. 1996). The lengths to which municipalities may have to go to dispose of their municipal waste was dramatically illustrated by the City of Toronto proposal last year to send its municipal garbage 600 km north to the abandoned Adams Mines near Kirkland Lake. The garbage would fill the mine's pen pits and rise another 35 m above ground surface, but the site would only have a life-span of 20 years (Golder Assoc. Ltd. 1996). Proposals to reduce wastes through recycling or at the source (e.g., less packaging) will only slightly reduce the rate of increase. Public pressure is causing the siting of landfills to become difficult. With the realization that all engineered facilities will likely fail, releasing leachate to the ecosystem, numerous issues have begun to emerge. Regulations (if any) on the siting, design and operation of facilities vary across the country thus creating a process that is vulnerable to political factors rather than a process that is based on technically sound criteria. Inevitably the leachate from the landfill will impact the water quality and thus require the installation of an expensive and often ineffective remedial system that requires long-term operation. The leachate may also change the conditions within the receiving aquifer or surface water body which may result in enhanced transport of contaminants. The potential influence of these changes on the mobility of these contaminants is not well understood. These factors along with the introduction of new chemicals and compounds will provide challenges for protecting water quality.
The number of feedlots in Canada increased dramatically between 1990 and 2000. As agricultural operations evolve, pressure to increase animal density on farms will lead to increasing volumes of manure wastes and the need for the development of appropriate management protocols to minimize future risks to water quality. Even if all sources are removed, the slow release and movement of associated contaminants from the existing mass in the subsurface will continue with increasing impacts on water quality over a very long time. As a result, significant degradation of regional water quality resulting from manure management practices may be anticipated regardless of the implementation of alternative management strategies. The occurrence of endocrine disrupting substances and animal pharmaceuticals in groundwater and surface waters in rural areas may be a significant issue. As yet, very little data exists to evaluate these risks. The increasing release of bacteria and viral species including pathogens may result in more frequent cases of microbial contamination, particularly in the groundwater environment. The development of alternative waste management practices, that will be both effective and inexpensive will be actively sought by the agricultural community. Both the development and implementation of these practices will require collaboration between government, researchers, and the private sector.
Although the number of mines in Canada has remained essentially constant during the last decade, there is a trend towards larger mining operations which produce larger volumes of waste. The emerging issues associated with mining waste are the need to develop and implement improved disposal techniques to reduce the oxidation of sulphide minerals within the waste and to develop cost-effective treatment methods for existing sites. Other emerging issues include the potential release of heavy metals and oxyanions (i.e., arsenic) from subaqueous disposed mine waste as well as geochemical reactions occurring at the surface water-groundwater interface. Abandoned mine sites represent long-term liabilities to various jurisdictions and further study is needed to fully understand the impact on future generations.
Canada and Ontario continue to undertake actions to reduce the levels of hazardous waste disposed within the Great Lakes region (COA 1997). Emerging issues associated with hazardous/industrial wastes are the issue of harmonization of regulations and guidelines between jurisdictions as well as the importation of hazardous waste from other countries such as the United States. Between 1998 and 1999, importation of hazardous wastes from the United States has increased by 18% to 663,000 tonnes prompting Minister Anderson to call for stricter standards (Judd 2000). Factors affecting the importation of hazardous wastes include liability issues, exchange rates and less restrictive regulations associated with the number and type of wastes allowed to be disposed of within landfills. Other issues include the effectiveness of barrier systems over a prolonged period of time (>50 years) and the influence of new chemicals and compounds on barrier integrity. Issues on the transport of dissolved and free-phase chemicals and compounds within a variety of geological materials have also been raised. The contamination of groundwater in Lambton County, Ontario, and the St. Clair River by hazardous waste injected into disposal wells (Vandenberg et al. 1977) is an excellent example of the extent of water quality problems which can result from a lack of knowledge. Disposal wells were constructed and waste injected following the regulations and best knowledge at the time. However, it was not realized that waste fluids would migrate to the surface through abandoned oil and groundwater wells, causing a major problem that still exists today.
Municipal Biosolids and Septic Systems
As the population in Canada increases, the mass of solid and liquid wastes generated will increase, resulting in larger volumes of wastewater released to the subsurface and the generation of larger volumes of biosolids from treatment plants. The number of septic systems will continue to increase dramatically with population increases in rural residential areas, recreational areas, and lakefront properties, and conversion of seasonal cottages to year-round homes, which are served by individual septic systems. Most regulations rely on the use of setback distances to prevent the uptake of bacteria in drinking water supplies, or the release of bacteria and nutrients to surface waters. These setback distances provide adequate protection in many geological materials to prevent large-scale disease outbreaks. There are, however, a number of aquifer types where the transport of viruses over long distances has been documented, and where infection of humans has occurred. Coarse-grained sand, gravel, and fractured bedrock aquifers are particularly susceptible to widespread transport of viruses and other pathogenic organisms. A number of physical, chemical and other aquifer properties have been identified as factors controlling the transport of viruses in aquifers. Information gained through research programs conducted outside of Canada can likely be transferred directly to evaluate the potential threat of pathogen transport in aquifers in Canada, however there are a few issues unique to the Canadian environment such as the much lower temperatures which might sustain the viability of pathogenic organisms over longer transport distances. Other information gaps relate to the transport of constituents that are newly recognized as being potential threats to human and ecosystem health. These include the unknown fate of medications, surfactants, food additives and natural hormones in the subsurface, and the uptake of these constituents in wells, or release to surface waters.
Considerable experience has been amassed over decades of waste management activity in Canada and elsewhere. The understanding of the complex array of issues associated with current management practices and historic activities has just begun to develop. This has been particularly true in Canada because of the enormous land and water resources available and the concept that these resources are essentially endless and not susceptible to environmental impacts of waste disposal as seen in the rest of the world. We can look back at many of our serious water contamination problems and identify poor disposal and management practices. However, many problems were not the result of bad management practices (in fact they followed existing regulations and engineering practices), but due to a lack of knowledge, which is now available. As such, several key areas require additional understanding and study.
Municipal Solid Waste
The major knowledge gaps in our understanding on municipal solid waste disposal include:
- Long-term integrity of liner, cover and leachate collection systems.
- Long-term aging reactions within the waste and receiving aquifer or surface water.
- Mobility and degradation of new chemicals and compounds, such as EDS, POPs, etc.
- Interaction between new chemicals and compounds.
- Methodological issues related to the detection and quantification of new chemicals.
- Effective implementation of aquifer remediation and leachate treatment systems.
- Role of changing geochemical environments on naturally occurring constituents.
The major knowledge gaps in our understanding on agricultural waste disposal include:
- Fate and transport of pathogens, EDS, and pharmaceuticals.
- Monitoring and inventory of existing contaminant mass in the subsurface.
- Development of best management practices, especially at a watershed scale.
- Slow release to the surface water courses through seasonal fluctuations.
- Investigation of alternative waste disposal methods (as being implemented in other parts of the world).
The major knowledge gaps in our understanding on mining waste disposal include:
- Release of contaminants from waste disposed of in underwater environments and as mine backfill.
- Attenuation and release mechanisms in aquifers impacted by mining waste.
- Long-term release of metals from waste-rock piles and tailings.
- Transport and fate of contaminants across the groundwater-surface interface.
- Effect of chemical additives on the mobility of heavy metals and other contaminants of concern.
- Long-term stability of engineered impoundments and piles.
The major knowledge gaps in our understanding on hazardous/industrial waste disposal include:
- Long-term integrity of liner/cover system.
- Co-disposal effects on transport and degradation processes.
- Degradation and transport properties of new chemicals and compounds.
- Availability of analytical chemistry methodology.
- Effects of waste types on barrier integrity.
- Influence of climate effects on disposal methods.
- Long-term integrity of steel casing and concrete plugs in abandoned disposal, oil and gas wells to maintain a seal which prevents upward migration of contaminants.
- Comprehensiveness of leachate treatment systems.
Municipal Biosolids and Septic Systems
The major knowledge gaps in our understanding on municipal biosolids and septic systems include:
- Long-term fate of accumulated nutrients and metal and release into drinking water supplies.
- Fate of pathogenic organisms in different soil types with particular attention to cold regions.
- Fate of pathogenic organisms applied to tile-drained fields.
- Transport and fate of EDS, pharmaceuticals and new chemicals as they are introduced.
- Development of alternative disposal methods to optimize removal of all undermined constituents.
- Research into long-term processes and reactions.
- Awareness of what to look for.
- Improved analytical and field methods.
- Close the gap between science and policy.
- New regulations, rather than guidelines.
- Harmonization of regulations and guidelines among all levels of government.
- Implementation of effective groundwater protection and watershed management practices.
- Improved monitoring procedures.
- Realistic bonding ($) to ensure funds available to deal with long-term problems and abandoned sites.
- Recognition of the extent of the problem.
- Need to deal with problems at the source rather than away from source.
- Focus on protection/prevention rather than remediation.
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