Wetland Pollution with Sources of the Contaminants - Coursework Example

Importance of Constructed Wetlands in Mine Pollution Amelioration Name Tutor Institution Course Date Table of Contents Importance of Constructed Wetlands in Mine Pollution Amelioration 1 Name 1 Tutor 1 Institution 1 Course 1 Date 1 Introduction 3 Water pollution 4 Wetland pollution 5 Human activities leading to wetland pollution 6 Altering the hydrologic conditions 7 Release of pollutants 7 Damage to vegetation 8 Mine pollution 8 Prevention of mine pollution 10 Constructed wetlands in mine pollution prevention 10 Design criteria for constructed wetlands 12 Types of constructed wetlands 13 Mechanisms for mine pollutants removal 14 Conclusion 15 References 16 Introduction 3 Water pollution 3 Wetland pollution 4 Human activities leading to wetland pollution 6 Altering the hydrologic conditions 6 Release of pollutants 6 Damage to vegetation 7 Mine pollution 7 Prevention of mine pollution 9 Constructed wetlands in mine pollution prevention 9 Design criteria for constructed wetlands 11 Types of constructed wetlands 13 Mechanisms for mine pollutants removal 13 Conclusion 14 References 15 Introduction Environmental pollution is the contamination of the natural environment with chemical and biological components, some which may result from natural activities or from human activities. This becomes a problem when it reaches an extent that the environment is unable to neutralize and process the contaminants thus interfering with its natural systems. Environmental pollution started many years back but it has recently been on the rise due to industrial revolution which has been facilitated by advancement in technology. There are three most important types of environmental pollution. That is, air pollution, water pollution and soil pollution. Air is mainly polluted by gases and radio active particles released form industries. Soil is mainly polluted by heavy metals, hydrocarbons and solvents released from human activities. Water pollutants includes all industrial wastes, wastes form livestock operations and other human activities including mining (Kill 2010). This report however focuses on water pollution, particularly wetland pollution with sources of the contaminants being mining activities. Water pollution Water pollution refers to biological, chemical or physical change in the water quality that may be harmful to people who consume that water or organisms that live in it. Therefore pollution makes water unfit for any use. The main source of water pollution is human activities. Human activities are classified into point and nonpoint sources of pollution. Point sources are those activities that discharge the pollutants directly into the water bodies through a sewer line or a pipeline. These include discharges from industries, oil wells and underground mines. Nonpoint sources are those activities that release pollutants whose source is difficult trace. These include acid deposits from air into the water and pollutants that get into the water bodies through ground water (Farmer 2013). Water pollution also results from destruction of wetlands by various human activities. Wetlands act as a natural way of filtering and cleaning water due to their ability to hold it and release it at a later time. Destruction of wetlands results in loss of the natural habitat for the various species of animals, birds and fish. The natural filters that help in storing and cleaning water are also removed therefore making the pollutants and toxins to remain in the water. Since wetlands also play a role in holding water, their destruction results in flooding since they hold water from overflowing river banks (Kill 2010). Wetland pollution Wetlands are defined as low lying water bodies where the water is at the surface or just below the surface. Examples of wetlands include swamps, streams and rivers. There is a growing concern over the growing incidences of wetland pollution which has affected sources of drinking water as well as natural biological diversity. A lot of pollutants some which are toxic are being released in the wetlands and this has caused their degradation and affected the aquatic lives. Wetlands are highly value as part of the environments for various purposes which include: Storage of flood water: they trap and absorb surface water which they later release. Their ability to absorb that water when there is heavy rainfall helps to prevent the rain from causing floods. According to Gulf restoration network (2015), an acre of a wetland can trap and hold about a million gallons of rain water although this also depends on the permeability of the soil at the area of the wetland. For example wetlands at the Mississippi river at one time stored at least 60 days of flood water. Their importance is can also be seen at the gulf region where most surrounding areas are low-lying and very prone to floods and hurricanes. The wetlands around the area help to diminish water surge that travels over them. Therefore conservation of wetlands is one of the flood control measures cheaper that construction of dykes and floodways (Gulf restoration network 2015). Water filtration: once surface run-ff passes by the wetland, all the sediments and other pollutants are filtered and this helps to improve the quality of that water. Natural habitat: wetlands act as a natural habitat to various animal and bird species that live in the waters. They are considered among the world’s most productive ecosystems (Comer et al., 2005). Some of the most endangered species of animals and birds such as wood stock and snail kite live in the wetlands (Gulf restoration network 2015). Cultural purpose: communities that live near the wetlands have made some of the wetland activities part of their culture. These include activities such as fishing, hunting and boat riding. Some have also made some of the wetland animal species such as various types of fish part of their culture. Wetlands are also used as sites for conducting various cultural activities. For example the traditional Aboriginal owners of Coburg Peninsula still undertake traditional activities such as hunting and gathering at the costal wetland (Gulf restoration network 2015). Recreation purposes: various recreation activities are depends on wetlands. These include canoeing, fishing, swimming and bird watching among others. Human activities leading to wetland pollution Degradation of wetlands has been highly contributed to by human activities. This has led to change in the quality of water, its quantity and also the rate at which the water flows in the wetlands. The level of pollutants is high in the wetlands and this has destabilized the aquatic species of animals and birds living in the wetlands (United States Environmental Protection Agency 2001). All this has been as a result of common human activities which include: Altering the hydrologic conditions This involves the natural hydrologic cycle of the wetland causing saturation of the water table such that the wetland cannot hold much water. Changes in the hydrology also affect the composition of the soil and this can affect the animals and the plants which survive on the wetland waters. Hydrologic conditions can be altered by activities such as draining wetland waters for use in irrigation or other development projects, depositing materials in the wetland, diverting the flow of the water, and also construction of dams along the wetlands (United States Environmental Protection Agency 2001). Release of pollutants Even though wetlands have the ability to absorb and filter water off the pollutants, there is a limit to this capacity. The common pollutants that are deposited in wetlands include human sewage, pesticides, heavy metals, fertilizers and mining byproducts. Some of these pollutants originate from runoff from cities and towns, farms and mining areas. Dumpsites and old landfills sometimes leak toxic substances into the wetlands causing a poisonous impact into the waters and its inhabitants. Dirty air from factories, cars and power plants may also have its way into the wetlands causing pollution. Collapsed sewer lines may also have their way into the wetlands depositing there. Deposition of foreign materials in the wetlands may have effects such as altering the pH of water, changing the color of the water, increasing nutrients in water leading to eutrophication, changing the temperature, increasing the amount of minerals and salts which may have negative health effects on the people and animals who rely on the wetland waters (Earle, Robert & Adele 1996). Damage to vegetation Vegetation around the wetlands is also very susceptible to destruction by changes in hydrology as well as pollution of the waters. Other activities that can destroy the vegetation around the wetlands include grazing of domestic animals on the wetland vegetation, planting of foreign vegetation thus suppressing the native vegetation, cutting of the trees for commercial and domestic uses and also clearing the vegetation for mining purposes. Introduction of non-native plants and animals in a wetland can kill what was meant to be there and takeover the wetland. For example plant species of salvinia, mimosa and paragrass have caused a huge in the areas of tropical savannas. Wild animals such as buffaloes, pigs and wild horses trample the banks of the wetlands causing mudding and foul smell in the wetlands. They also disturb the natural fauna around the wetlands and bringing in weeds and undesired water plants into the wetlands (Kill 2010). Mine pollution Mining activities involves extraction of minerals and metals. All these materials range from some those are precious to others that are hazardous and also in different sizes. Mining becomes a source of pollution due to disposal of the generated mineral wastes, mainly the waste rocks and tailings. Waste rocks are those materials that arte removed to create access to the valuable minerals at the core. The rocks sometimes contain some pieces of the ore. Tailings are the waste materials that remain after the mineral is separated from the ore in the processing plant. These contain low concentrations of the ore and may also contain residues of the toxic chemicals used in the process of separating the rocks from the ore (Symposium Editors 2002). Pollution occurs where the metal sulfide minerals in the waste rocks come into contact with air resulting in formation of sulfuric acid solutions. Theses solutions find their ways into the ground water and other water bodies. The same can also happen to the tailings especially where the two are deposited in structures that can suffer catastrophes leading to their failure hence their way into the water bodies. This will affects the activities that take place in the water bodies as well as the living organisms that find habitat in those waters. Accumulation of these materials in the riverbeds makes the rivers to become shallow and this may lead to overflowing and incidences of flooding. The toxic chemicals that are found in mineral deposits pose great risk to people’s health as well as the environment. These substances are also found on the walls of the excavations where they can get leached by water or wind and spread to farther places. They can therefore gain entry into the human food chain. Windborne substances such as crystalline silica and asbestos can enter the human body through inhalation of contaminated air (Farmer 2013). Mine pollution results in various health effects which depend on the type and the concentration of substances that are present and those that find their ways into water, air, soil or even food. These effects are usually chronic in nature and may have adverse long term effects. Some of the health effects include damage to the nervous system, birth defects, various types of cancers, diseases of the digestive system, and irritation of the throat, eyes and nose. These health hazards mostly affects people living near mines and this can make life unbearable for them (Kampa & Castanas 2008). One of the most complicated problems caused by mine pollution is Acid Mine Drainage. This occurs due to sulfide oxidation in the rocks reacts which air producing hydroxide, hydrogen and sulfate ions. In coal and metal mines, it is caused by a mineral known as pyrite (Wildeman et al. 1991). This mineral is exposed to air, water and microbial activities by mining activities. This causes those waters to become more acidic and to increase in the level of heavy metals and other dissolved substances. Acid mine drainage can also be caused by chemosynthetic bacteria that are known to cause catalysis of oxidation of pyrite. Chemosynthetic bacteria are those that convert carbon molecules and nutrients into organic matter. These bacteria include Ferrobacillus ferroxidans, T. thooxidans and Thiobacillus ferooxidans (Hilson 2000). Prevention of mine pollution Since mining is a very important economic activity, it must be made environmental friendly by developing sustainable practices that will reduce its environmental impact. Technological advancements have however come up with various strategies that can help reduce the negative effects caused by mining and make it more environmentally sustainable. Constructed wetlands are one of the sustainable strategies that can be used to control environmental pollution caused by mines (Wiseman 2002). Constructed wetlands in mine pollution prevention Wetlands are among the world’s most biologically productive ecosystems. This is due to their ability to filter water making it safe for use by humans and also a safe habitat for animals and birds. This is achieved where as water flows through the wetland, its rate of flow slows down and then any particles that were suspended in it get trapped by wetland vegetation settling it out. Any pollutants in that water is absorbed by the wetland plants and gets transformed to less soluble forms or even deactivated. The plants also create an environment with the necessary conditions that supports growth of microorganisms. These microorganisms make use of various complex processes that transform the pollutants removing them from the water. The wetlands plants and microorganisms survive on nutrients such as phosphorous and nitrogen that is deposited in the waters by water runoff from areas where manure and fertilizers are used (Tanner 2001). Constructed wetlands are water treatment systems that make use of the natural processes of water filtration by use of wetland vegetation, soil and microbial organisms that live within them to improve the quality of water. They are usually built on floodways and uplands so that they do not interfere with the natural wetlands. The process of constructing wetlands involve excavating, diking, grading and backfilling and then installing structures for controlling water to ensure proper hydraulic flow patters. For areas with soils that are highly permeable, a clay liner that is impervious is usually compacted and the original soil placed on top of it. Wetland vegetation is then planted on the liner, or sometimes it is allowed to grow naturally (Shutes 2001). Below is an example of a constructed wetland:  Figure 1. An example of a constructed wetland. (Source: White & Oki, UCNFPA News). Design criteria for constructed wetlands The design criteria for constructed wetlands involve putting into consideration three main factors. These include the substrate types, the pollutants loading rate and the retention time and the size of the wetland. The role of substrate is to provide a suitable medium that will promote growth of wetland plants and also facilitate proper infiltration and movement of wastewater that contains the pollutants. Some of the mechanisms used by the substrate include ion exchange, precipitation and complexion. When choosing the substrate, the things to consider include their hydraulic permeability and also their ability to absorb pollutants and nutrients. The most desirable substrate should have a hydraulic permeability of about 10-3 to 10-4 . In regard to nutrients, soils that are poor in nutrient promote better ability to uptake nutrients from the wastewater by the plants. For example soils with low content of Iron and Aluminium are very effective in promoting uptake f phosphorous from the affluent therefore lowering its concentration. Soils that contains a mixture of clay, gravel sand and crushed stones area also very effective in promoting growth of wetland plants (Wiseman 2002). The pollutant loading rate is determined by the flow of wastewater through the created bend. The flow must be slowed down to ensure longer retention time which will allow longer time for pollutants to be removed. Retention time of about five days allows better reduction efficiency that will achieve a balance between Nitrogen and Phosphorous in the wastewater. Shorter retention time does not allow enough time for the pollutants to be degraded (Shutes 2003). The size of the constructed wetland determines the level of pollutant that would be removed. However, most of the wetlands are designed for a minimum size due to cost considerations. This does not however reduce the wetland maintenance cost. The most appropriate surface area for the wetland should be calculated using the following empirical formula that will be appropriate for reduction of Biological Oxygen Demand in the wastewater (U S Environmental Protection Agency 2004): Ah= KQd (InC0 – In Ct) Where Ah is the surface area of the bed in square meters K is the constant for rate Qd is the average rate of wastewater flow per day C0 is the average biological oxygen demand for the influent Ct is the expected biological oxygen demand per day. Types of constructed wetlands There are two types of constructed wetlands. That is surface flow constructed wetland and subsurface flow constructed wetlands. Surface flow constructed wetlands are where the biological activities usually take place at the top layer of the soil where the stems of the plans are sinking in water. Subsurface flow constructed wetland is filled with gravel and crushed rocks above the waters such that the waste water is not exposed to the surface. The surface is covered with concrete, compacted clay or polythene geomembranes. These are designed with a vertical flow where the pipes containing the wastewater lie on top of a gravel-filled bed, and horizontal flow where the wastewater passes in between the grave and moves horizontally (Arnold, Allen & Morgan 2001). Mechanisms for mine pollutants removal Mine pollutants are non-point sources of pollutants that can be effectively removed by constructed wetlands. The main principle applied in constructed wetlands is to maximize the contact time between the microbial species contained in the substrate and the wastewater. The main objective is usually to ensure bioconversion of the pollutants to water, carbon dioxide and biomass. This involves three main mechanisms: 1. Biological processes: generally, there are six biological processes involved in constructed wetlands. These are photosynthesis which is done by wetland plants and adds carbon and oxygen to the wetland. These drive the second biological process of nitrification. The other process is respiration which involves carbon dioxide by the living organisms. Fermentation is another process where the organic carbon is decomposed through microbial activity into energy-rich compounds in the absence of oxygen. This is followed by the process of nitrification or denitrification which involves removal of nitrogen. The last process phosphorous removal which involves adsorption, filtration and sedimentation. Wetlands should be constructed in such a away that they allow sedimentation of suspended materials as well as extensive uptake of nutrients by plants (Koottatep & Polprasert 1997). 2. Chemical processes: this process uses the pH of water and soils in the wetland to influence the direction of various chemical processes involving breakdown of organic compounds. Such chemical processes include cation exchange, biological transformation, solubility of solids and gases and also partitioning of acids and bases in both ionized and un-ionized forms (United States Environmental Protection Agency 2000). 3. Physical processes: the two physical processes involved in removal of mine pollutants in waste water are filtration and sedimentation. However, the effectiveness of all these processes depends on the retention time since the longer the water stays in the wetland, the more contaminants are removed (United States Environmental Protection Agency 2000). Conclusion Mining is one of the important commercial activities will very crucial effect to the economy. However, its effects on the environment are very unfriendly and do great harm to the ecosystem. Various technologies therefore need to be considered to make this undertaking environment friendly. Constructed wetlands have been considered to offer an environmental friendly solution to mine pollution. Constructed wetlands employ various processes that degrade the pollutants that are contained in the waters released form mine until they are rendered harmless. It is a sustainable and less costly technology that needs to be embraced to minimize the harmful effects of this important commercial undertaking. References Tanner, C 2001, Plants as ecosystem engineers in subsurface-flow treatment wetlands, Water Science and Technology 44(11-12): 9-17. Shutes, R 2001, Artificial wetlands and water quality improvement, Environment International 26: 441-447. Koottatep, T& Polprasert, C 1997, Role of plant uptake on Nitrogen removal in constructed wetlands located in the tropics, Water Science and Technology 36(12):1-8 Arnold, J, Allen, P, & Morgan, D 2001, Hydrological model for design and constructed wetlands, Wetlands 21(2): 167-178. Wiseman, I 2002, Constructed Wetlands for Mine water Treatment, R&D Technical Report P2-181/TR, Environment Agency Wales. Shutes, B 2003, The use of constructed wetlands for wastewater treatment, Wetlands International, Selangor, Malaysia. U S Environmental Protection Agency, 2004, Constructed treatment wetlands, retrieved from http://www.epa.gov/owow/wetlands/pdf/ConstructedW.pdf Hilson, G 2000, Pollution prevention and cleaner production in the mining industry: an analysis of the current issues, Journal of Cleaner Production 8, (119–126). Kampa, M & Castanas, E 2008, Human health effects of air pollution, Environemntal Pollution, vol. 151 (2), 362-7. Farmer, A 2013, Managing Environmental Pollution, London, Routledge. Kill, M 2010, Understanding environmental pollution, Cambridge University Press. Kadlec, R & Knight, R 2004, Treatment Wetlands, Lewis Publishers, Boca Raton, Fl. United States Environmental Protection Agency 2000, Guiding Principles for Constructed Treatment Wetlands: Providing for Water Quality and Wildlife Habitat ,EPA 843-B-00-003, retrieved from www.epa.gov/owow/wetlands/constructed/guide.html Symposium Editors 2002, Tailings and Mine Waste 2002: Proceedings of the 9th International Conference, Fort Collins, Colorado, CRC press. Earle, R, Robert R & Adele C 1996, Environmental Effects of Mining, Delray Beach FL, St. Lucie Press. United States Environmental Protection Agency, 2001, Threats to wetlands, retrieved from http://water.epa.gov/type/wetlands/outreach/upload/threats.pdf Gulf restoration network 2015,Wetland Importance, retrieved from http://healthygulf.org/our-work/wetlands/wetland-importance Read More