The Importance of Constructed Wetlands in the Process of Mine Pollution Amelioration - Term Paper Example

Describe and Assess the Importance of Constructed Wetlands in the Process of Mine Pollution Amelioration Name: Course: Institution: Date: Describe and Assess the Importance of Constructed Wetlands in the Process of Mine Pollution Amelioration Introduction The major challenges facing the mining industry today include regulations from the government and negative criticism concerning their involvement in instances of environmental pollution. Since the development of the mining industry, mineral components that are perceived to be dangerous to the environment have been leaking into the environment (Sobolewski1997, 6). The mining industry has been accused of releasing these mineral components into the environment hence contaminating the soil, air and water. In addition, the mining industry has also been accused of creating vast lands that are largely infertile, and unproductive (Snyder & Aharrah. 1985, p. 6). The passing of the Surface Mining Control and Reclamation Act of 1977 introduced different measures that would ensure that the industry was involved in different initiatives of environmental conservation (Environmental Protection Agency 1985, p. 85). Through this Act, different standards that define the mining industry were developed and this explains why the industry is in the process of advancing towards the objective of ensuring higher levels of environmental sustainability. The main objective of this paper is to assess and describe the importance of constructed wetlands in the process of mine pollution amelioration. Constructed wetlands and Acid mine drainage Acid mine drainage (AMD) has been considered as one of the greatest environmental problem facing the mining industry. This is because most techniques that are involved in the process of treating water are timely and costly (Snyder & Aharrah. 1985, p. 8). This is often because since their implementation often involves years of water treatment. For the treatment of AMD to be effective, it is necessary that it is made are required to be continuous even after the mining companies abandon their activities (Perry, et al 1991, p. 20). Constructed wetlands have been perceived as the most appropriate long terms solutions to remediation of acid mine drainage. These wetlands treat AMD through a continuous process that is relatively affordable and effective to the ever growing problem of environmental protection (Snyder & Aharrah. 1985, p. 12). Acid mine drainage (AMD) AMD is perceived to have occurred when the sulfide oxidation component in rocks are exposed to react with water and air. This enables the creation of hydroxide, sulfate and hydrogen ions. Pyrite is the mineral that is responsible for the reaction in both coal and metal mining areas (Perry, et al 1991, p. 26). In the process of mining, minerals are exposed to air, water and other microbial processes hence the creation of AMD. When this occurs, the contaminated waters will increase in terms of their level of acidity, the concentration of heavy metals, sulfates and other solids that are dissolved in these waters (Snyder & Aharrah. 1985, p. 10). The contamination arising from AMD which are perceived to be of great concern to the environment, aquatic life and human life are those of acidity, iron, manganese and aluminum. There are other sources of AMD such as the chemosynthetic bacteria. This bacterium plays an important role in contamination considering tha it acts as a catalyst by oxidizing the pyrite (McHerron 1984, p. 25). AMD is perceived to be a relatively complicated issue in the mining industry because rain water that flows over unearthed sulfide mineral deposits risk becoming acidic. Acidic water often has the tendency of dissolving metals (McHerron 1984, p. 23). This means that failure to treat this acidity may generate highly contaminated water which in itself is considerd as an environmental hazard. In addition, it is often relatively complicated to predict the possibility that water will become acidic, the beginning of acid generation and the duration of acidity of the water. This is an indication that AMD can be a probable liability long after these mines cease to operate (McHerron 1984, p. 25). Wetlands and the removal of AMD Wetlands play numerous roles that help in the removal of heavy metals in the drainage system hence ameliorating AMD. Wetlands possess the ability eliminate metals from mine drainages. In addition, they also play the role of neutralizing the levels of acidity in water (Perry, et al 1991, p. 26). The ability of wetlands to be self-sustaining is an indication that they have the capacity to remediate any contamination in mine drainage as long as it is still being produced (Pascoe et al 1994, p. 8). It is often relatively complicated to demonstrate the uniformity of wetlands in ameliorating contaminated mines. However, there are selected instances from different sources which demonstrate this notion (Snyder & Aharrah. 1985, p. 11). This is inclusive of the coal mines in the United States which have been active user of constructed wetlands for decades. Through these wetlands, the coal mines have witnessed progress in environmental protection (Pascoe et al 1994, p.9). The process of constructing wetlands requires the concerned parties to determine the type and level of contamination of the mine drainages as this is the only way through effective amelioration of mines can be realized (Perry, et al 1991, p. 28). For wetlands to have the capacity of eliminating these metals and reducing the levels of acidity, it would be important for specific characteristics to exist. These include adsorption, abiotic oxidation, and bacterial oxidation, and sedimentation, neutralization in the cases of acids, bioaccumulation and reduction (Perry, et al 1991, p. 23). The process entails detailed chemical processes through which different components of AMD must undergo considering their essence in neutralizing the possible effects of the contaminations. In addition, the contaminants that are of major concern in AMD include the sulfate, manages, aluminum and other heavy metals concentration (Snyder & Aharrah. 1985, p. 13). They are perceived to be dangerous due to adverse effects that they have on aquatic life, vegetation, plant and human life. There are different wetlands which play a role in ameliorating AMD and they must be designed in accordance to the role they are envisioned to play in the reduction of contamination levels (McHerron 1984, p. 23). Different processes within natural wetlands have been found to be important in the remediation of contaminants in AMD. The efficiency and effectiveness of constructed wetlands can only be realized through an imitation of the processes involved in the natural wetlands. Constructed wetlands operate effectively since they are rich in organic substrates which play the role of exchanging dissolved metals (Pascoe et al 1994, p. 10). The exchange often occurs between the dissolved metals and humic and fluvic acids that are contained in the substrates (Wildema et al 1991, p. 23). The sediments in wetlands are often anaerobic and they contain a thin layer of oxidized surface. In addition, the wetland sediments also contain organic carbon which is important for microbial growth (Pascoe et al 1994, p.12). These sediments have an oxidation zone which provides the most appropriate condition for microbial and reduction processes. These transform iron and sulfate components in AMD to hydrogen and sulfides (Fenessy and Mitsch 1989, p. 12). Construction and development of wetlands The development and the design of any constructed wetland varies form one mine field to another. This is largely depends on the characteristic of the site which include, the minerals that are mined, the distance of water masses, the level concentration of heavy metals and acids. In addition, the type of soil will also be an important determinant of the type of wetland to construct. Despite these considerations, Fennessy and Mitsch (1998) argue that the most essential variables to consider in the process of designing include; the biochemical processes involved, slope, substrate, loading rate, retention time, vegetation, sediment control, seasonality and the prevailing government regulations (Snyder & Aharrah. 1985, p. 16). It is important to consider the biochemical processes that define mining. These must be considerd in a careful manner especially in the planning and in the construction of wetlands. Biochemical processes in constructed wetlands often provide a plan on how to treats acid mine drainage (Perry, et al 1991, p. 28). Through such considerations it will be easier for the developers of the wetland to consider the favorable conditions for chemical and microbial processes. In addition these conditions will also aid in ensuring that the processes of adsorption, neutralization, and precipitation are incorporated into the soil. These will help in the protection of the vegetation and the environment (Fennessy & Mitsch, 1998). The loading rate is often used as an essential determinant of the maximum ability for constructed wetlands to treat acid mine drainage (Girts & Kleinmann 1986, p. 23). Through a consideration of the retention time, the wetland developers will be able to determine the capacity of the wetland in terms of volume and concentration of AMD. In addition, retention time is also perceived as a measure of the existing affluent standards, the rate of treatment, precipitation and evapotranspiration (Snyder & Aharrah. 1985, p. 14). All these variables are essential in the development of a constructed wetland since they can be used in the determination of the maximum level of contaminant reduction (Fennessy & Mitsch 1989, 40). An effective and highly performing constructed wetland has a hydrologic holding rate of 200m3/ha-day (Perry, et al 1991, p. 26). This is often reinforced by a seven day holding time which is perceived as the optimal requirements for constructed wetlands to treat waste water. This consideration will ensure that the developers of constructed wetlands understand the capacity of the se wetlands in terms of the level of concentration and the time required to treat AMD (Perry, et al 1991, p. 27). Slope is also an essential factor to consider in the construction of a wetland. A slope that is below 5% for instance is perceived to be maximizing the contact by wetland vegetation and substrate. This influences the rate at which iron and manganese are removed from AMD (Brooks 1984, p. 34). Despite this maximum level, the Environmental Protection Agency places its recommendation at a slope that is less than 1% considering its ability to optimize the efficiency in terms AMD remediation (FPA 1985, p. 4). There is a close association between substrate and vegetation. This link is often based on the assumption that the substrate that is used is often dependent on the vegetation that is desired (Fennessy & Mitch 1989, p. 67). In the design of the Typha wetlands, for instance, the developers often use composted hay and manure. This is spread on top of a layer of limestone (Snyder & Aharrah. 1985, p. 18). This generates the understanding that an increase in organic matter content of wetland sediments often influences an increase in metal adsorption. Limestone and sewage sludge are perceived as essential additives for the manipulation of soil conditions (Topper & sabey 1986, p. 56). The essence of vegetation is in its developmental attribute for wetland construction. This is often because of the role that vegetation plays in AMD remediation and its influence in other attributes of wetland. It is possible to establish perennial vegetation through a direct placement of rhizomes into a highly saturated subsurface zone (Fennessy & Mitsch 1989, p. 111). This is because rhizomes are local vegetation and their use is highly favored due to their ability to easily adapt to the prevailing environmental conditions. In addition, the use of vegetation can also be based on their ability to be tolerant to different levels of acidity and their capacity to thrive in harsh environmental conditions (Gerber et al 1985, p. 17). There are two main species of vegetation that are used in constructed wetland and they include Typha spp and Sphagnum spp. These are the most preferred type of species due to their versatility and hardiness. In addition their ability to easily adsorb manganese and iron makes them the most excellent choice of vegetation that can be used in constructed wetlands to remediate AMD (Snyder & Aharrah 1985, p. 78). Sphagnum ssp are also considered to be important vegetation species in constructed wetlands due to their ability to influence the reduction of the concentration of sulfates, iron and manganese. However, there are difficulties associated with the use of Sphagnum spp (Snyder & Aharrah. 1985, p. 16). This largely revolves around the attribute of high sensitivity and stresses that are associated with the process of transplanting and abrupt changes in the environment and water chemistry (Gerber et al 1985, p. 16). This complication along with it slow generating ability makes these of Sphagnum spp relatively low in constructed wetlands compared to the use of Typha spp. This however does not deny Sphagnum spp the excellent ability to facilitate AMD remediation (Perry, et al 1991, p. 20). High levels of sediments load in acid mine drainage often makes sediment accumulation an essential consideration in the design and construction of wetlands. It is possible to construct ponds designed to accumulate sediments as part of a wetland treatment system (Majer 1989, p. 60). This is however possible if the sediment ponds are constructed before the construction of the wetland treatment system (Fennessy & Mitsch 1989, 122). When this is realized it will be possible to dredge sediments from these ponds without interfering with the wetland habitat. Studies by Kadlec (1985, p. 56) indicate that seasonal harvesting of plant often reduces sediment accumulation in wetlands. Despite this reduction, it does not raise any concerns that would affect the level of essential organic components that accumulate in these sediments (Gambrell et al 1978, p. 45). The geometric configuration of the wetlands can be essential in influential in the ability of a constructed wetland to perform AMD remediation. This is possible through the development of designs which imitate natural wetlands. These include the shape, the slope, aesthetic nature, and the provision of wildlife habitat (Brooks 1984, p. 23). The placement of islands in the constructed wetlands for instances, increases their ability to embrace habitat diversity. This is because such islands often act as natural water flow breaks and diversions (Brooks 1984, p. 24). The establishments of islands that assume a more serpentine shape have been perceived to outperform rectangular shapes that in the reduction of contaminations of AMD (Wile et al 1985, p. 98). The seasonality of the locality in which the wetland is to be constructed is often perceived as an essential factor in the design of a constructed wetland. This is especially in areas that experience fluctuations in their climate (Gerber et al 1985, p. 10). The realization that the bacterium, which catalyzes AMD creation, is often very active in cold and warm seasons means that an effective wetland must have the capacity to accommodate large volumes of AMD in these seasons (Gambrell et al 1978, p. 48). It will also be important to consider the dormant seasons and the possible effect that the varied seasons might have on the ability of the vegetation to remediate AMD (Gerber et al 1985, p. 10). The process of deciding whether to use Typha spp or Sphagum spp often depends on the seasonality of the locality. Typha spp for instance are of low efficiency in localities the lower temperatures while Sphagnum spp does not face similar restrictions (Mcherran 1985, p. 45). Through the technology inspired by constructed wetlands, it has become a possibility to introduce additional measures that could be used in remediating AMD and reducing the hazardous effects of constructed wetlands (Gerber et al 1985, p. 14). This technique involves the treatment of the symptoms instead of focusing on the source of the problem (Majer 1989, p.57). The control in the level of concentration of AMD can be realized through the removal of one or more factors that are essential in AMD generation. The elimination of water, air or pyrite may only be realized through steps such as waste segregation, base additives, collection and treatment of contaminants and bioremediation among other techniques (Gambrell et al 1978, p. 49). Discussion Concerns Constructed wetlands, which are an imitation of natural wetlands, in terms of their design have been found to be critical in the amelioration of AMD. Through these artificially constructed wetlands, it is possible for the mining industry to engage in processes that will ensure environmental safety hence enhancing the protection of different habitat within the environment (Girts and Kleinmann 1986, p. 9). Despite the outstanding benefits associated with constructed wetlands, there are concerns regarding metal accumulation of sediments and the uptake of this poisonous material by plants (Majer 1989, p.55). The possibility that vegetation may absorb heavy metals is a risk of the presence of these metals in the food chain. Despite these concerns there are is still no evidence that constructed wetlands introduce heavy metals into the systems of living organism such as plants, animal and the marine life (Kadlec 1985, p. 10). Additional findings have indicated that there are no negative health and life effects associated with constructed wetlands. Insects such as caddisfly have been found to have higher life expectancy in areas characterized by constructed wetlands (Kadlec 1985, p. 10). There is however need for more studies to be conducted on the possible effect of constructed wetlands prior to the conclusion that these areas have no adverse or life threatening effects on the environment (Joost et al 1987, p. 15). There are also concerns that constructed wetlands may be required to last forever without the anticipation that they would lead to the development of negative environmental impacts in the future. These concerns are related to the questions regarding the ability of wetlands to ensure constant remediation of AMD whenever they are emitted (Joost et al 1987, p. 15). This would mean that the process of constructing wetlands would require a monitoring system that would be used to ensure that these wetlands are not saturated to a level where they can leak toxic substances into the environment. It is therefore important for specific regulation to be ensuring that constructed wetlands for the treatment of AMD are protected from possible toxicities in the future (Kadlec 1985, p. 14). Critique The use of constructed wetlands in the remediation of acid mine drainage can be perceived as an essential technique for reclamation. It is important for constant examination of this technique to be conducted for the recognition of additional solutions for long term remediation. It would be important for environmental, mining and government agencies to put emphasis on the construction design specifications prior to its consideration as an ideal solution (Girts and Kleinmann 1986, p. 8). There are also additional areas of research that must be addressed in the process of improving on the efficiency and effectiveness of constructed wetlands. These include the possible environmental hazards and a better understanding of the natural wetlands to enable perfect mimicry. Such studies and conditions will provide best techniques for wetland AMD removal (Sobolewski 1997, p. 8). Conclusion Acid mine drainage (AMD) has been considered as one of the greatest environmental problem facing the mining industry. This is because most techniques that are involved in the process of treating water are timely and costly. The passing of the Surface Mining Control and Reclamation Act of 1977 introduced different measures that would ensure that the industry was involved in different initiatives of environmental conservation. Through this Act, different standards that define the mining industry were developed and this explains why the industry is in the process of advancing towards the objective of ensuring higher levels of environmental sustainability. Constructed wetlands, which are an imitation of natural wetlands, in terms of their design have been found to be critical in the amelioration of AMD. Despite the outstanding benefits associated with constructed wetlands, there are concerns regarding metal accumulation of sediments and the uptake of this poisonous material by plants. The possibility that vegetation may absorb heavy metals is a risk of the presence of these metals in the food chain. There are also additional areas of research that must be addressed in the process of improving on the efficiency and effectiveness of constructed wetlands References Brooks, R.P. 1984. Optimal designs for restored wetlands. IN Treatment of Mine Drainage by Wetlands. Contribution #264. Dept. of Biology, Pennsylvania State University. pp. 19-29. University Park, PA. Environmental Protection Agency. 1985. Freshwater wetlands for wastewater management handbook. EPA Region 4. Atlanta, GA. 904/9-85-135. Fennessy, S. and W.J. Mitsch. 1989. Design and use of wetlands for renovation of drainage from coal mines. IN Ecological Engineering: an introduction to ecotechnology. W.J. Mitsch and S.E. 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Natural Resources Forum 15: 178-184. Snyder, C,D. and E.C. Aharrah. 1985. The Typha community: a positive influence on mine drainage and mine restoration. IN Wetlands and Water Management on Mined Lands: Proc. of a Conf. 23-24 Oct. 1985 The Pennsylvania State University. pp. 187-188. University Park, PA. Sobolewski, A. 1997. Wetlands for treatment of mine drainage. Infomine website http://www.enviromine.com/wetlands/Welcome.htm Read More