The Effectiveness of Storm Water Wetland in Pollutant Removal Performance - Literature review Example

LITERATURE REVIEW By Name Course Instructor Institution City/State Date Understanding the effectiveness of storm water wetland in pollutant removal performance – Literature Review Storm Water Wetland Stormwater treatment as mentioned by Howitt et al. (2016, p.534) has become an important issue, because of the likelihood of urban run-off having high contaminant loads. Without a doubt, contaminants in the stormwater can negatively influence the receiving aquatic environments, and such impacts could be challenging to examine because the input is highly pulsed, which leads to the exposure of organisms to both short-term high concentrations of the contaminant as well as reduced level of chronic exposures to the contaminants that have accumulated. Therefore, stormwater wetlands are considered an important stormwater management tool because the successfully reduce contaminant levels in the stormwater runoff. A simple designed stormwater wetland includes wetland vegetation area as well as basin having a forebay. According to Hunt et al. (2007, p.1), there must be an adequate flow of water so as to facilitate permanent water pool. In addition, the length-to-width ratio of the wetlands must be no less than 5:1 in order to avert short-circuiting. Moreover, there should be a distance maximisation between outlet and inlet through utilisation of peninsulas and islands. Hunt et al. (2007, p.1) further posit that the drainage area of a stormwater must be over 5 hectares. In order to reduce the sediment loading and velocity, sediment forebays should be utilised. Basically, the levels of water during large storms can bring about extreme water fluctuations levels; therefore, a detention basin is utilised to protect the wetland from such fluctuations. Natural wetlands according to Greenway (2010, p.25) perform different social, ecological, and hydrological functions. Suspended Solid (Sediment) In Storm Water Wetland The suspended solids normally originate from the stormwater runoff, and are normally carried as fine articles. The sources of suspended solids are numerous: fine metals, air dust, and erosion within the construction sites, landfill areas, asphalt, and many others (Shammaa & Zhu, 2001, p.359). Suspended solids are associated with the level of urbanisation, and are the main contaminants in stormwater runoff; thus, making the receiving water turbid and reducing its quality, limiting the growth of the plants and decreasing species diversity. According to Shammaa and Zhu (2001, p.359) excess suspended solids can destroy the bottom-dwelling biota habitats and fish spawning beds. For this reason, scores of authorities have come up with different solutions so as to control suspended solids and reduce their effect on the receiving waters. Therefore, controlling storm water’s suspended solids is considered a crucial part of the Best Management Practices (BMP). The BMP is utilised to control suspended solids and improve the quality of water and can be grouped into structural as well as non-structural techniques. Structural techniques involve; detention, filtration and infiltration facilities while the non-structural techniques involve public education, effective housekeeping, pesticide use and fertiliser application controls, street sweeping controls, as well as management of solid wastes. The most common technique utilised to remove suspended solids from stormwater is detention basins (constructed wetlands, wet ponds and dry ponds). The detention basins as observed by Shammaa and Zhu (2001, p.365) offer stormwater runoff detention volume; therefore, reduces the peak runoff at the pre-development phase. In addition, the detention basins offer the residence adequate time so that the particles can settle; thus, making them the suitable devices for removing suspended solids in the stormwater. A dry pond includes a basin or reservoir, an outlet, an inlet and sometimes a spillway to facilitate the passing of high flows. It is also known as an extended detention dry pond when it is used for water quality control. The outlet invert of the dry pond is normally flushed with the floor of the basis in order to make sure that the pond is kept dry except for when there is a storm. Furthermore, the outlet size defines the period of time that the pool will exist while drawing down after the storm ends. In the dry ponds, Shammaa and Zhu (2001, p.365) assert that the removal of suspended solids takes place through sedimentation, but the rate of removal depends on the time of stormwater detention, which normally is measured by utilising the drawdown time. Earlier, Shammaa and Zhu had observed that the rate of removing the suspended solids increases by almost 60 per cent after increasing the drawdown time from 0 to almost 24 hours (Shammaa & Zhu, 2001, p.365). On the other hand, the wet detention ponds normally include three important components: a large storm control storage, a long detention storage as well as permanent pool,, which are designed with the objective of offering detention for the needed runoff volume. The main enhancement mechanism for improving the quality of water in the wet detention is the permanent pool. The wet ponds performance for the removal of suspended solids as mentioned by Shammaa and Zhu (2001, p.366) is a function of the ponds’ depth and time of detention. Therefore, the pond’s outlet must be created to facilitate a 24 hours detention, specifically for the design. Adequately sized wet ponds can help remove almost 90 per cent of the suspended solids in the water. In their study, Qasaimeh et al. (2015, p.715) observed that the metals available in the stormwater wetland in Northern Virginia were very high in the inlet as compared to the outlet; thus, demonstrating that wetlands are effective in the removal of metals from stormwater . Hashemi et al. (2013, p.11) point out that heavy metals are very toxic contaminants that threaten watery perimeters across the globe. The metals normally found in the stormwater are either naturally created or originate from industrial sewage, mines, oil leakage, and so forth. Therefore, if unchecked can indirectly or directly threaten people, especially through food chain. In their study, Ogoyi et al. (2011, p.156) observed that aquatic ecosystem is normally the last recipient of nearly all suspended solids, which includes heavy metals. The heavy metals pollutants in the aquatic environment have become a major concern not only in Australia, but also globally. Currently, the levels of heavy metals in the aquatic environments across the globe as mentioned by Ogoyi et al. (2011, p.156) is exceedingly high. There are various sources of heavy metals; some originates from anthropogenic activities like draining of sewerage, dumping of Hospital wastes and recreational activities. Given that heavy metals are not degradable, they are inclined to result in heavy metal pollution within the water bodies. In Wang et al. (2014, p.11), they observed that contamination factors in the sample sites were beyond one and the heavy metals’ contamination factors in west and east wetland were all exceeding one save for Cadmium (west wetland) and copper (east wetland). Wang et al. (2014) mention that the contamination factors exhibited that the plant-bed/ditch systems in one of the sampled wetland accumulated numerous heavy metals, especially Chromium, Chromium, Copper, Nickel, Lead, and Zinc. However, metals were removed by the small waterways in the plant-bed/ditch systems within the root-channel area from source water. Still, there was some accumulation of heavy metals in the source water, especially the root channel zones. Importantly, copper, nickel, zinc, and lead were effectively removed by the wetland. As observed by Brix et al. (2011, p.1831), the risk associated with Zinc in the stormwater runoff can be limited when issues of aquatic community composition, exposure duration, as well as bioavailability are taken into account. Measurements There are various that can be used to measure metals in sediment; for instance, the Atomic Absorption Spectrometry (AAS) may be utilised to measures the metal concentrations. The AAS can be utilised to analyse the concentration of more than 62 metals within a solution, such as stormwater and it sensitivity is very high to an extent that it can measure the samples down to parts (ug/dm–3). As mentioned by Gennaro et al. (2008, p.6), the AAS technique utilises the light wavelengths that the element has absorbed. They epitomise the energies required in order for the electrons to be promoted from an energy level to another. Another technique used to measure metals in sediment is the Inductively Coupled Plasma –Atomic Emission Spectrometry (ICP-AES), which is normally generated through radio frequency as well as maintained Argon Plasma, whose portions are 10,000 K, exciting the electrons. According to Gennaro et al. (2008, p.6), the Argon plasma is utilised with the aim of ionising and atomising the elements within the sample. Upon returning to the ground state, the electrons emit energy at certain wavelengths odd to the elemental composition of the sample. Therefore, the plasma emits the light and the lens focuses and passes the light into the spectrometer through an entrance slit. ICP-AES analysis uses two forms of spectrometers: simultaneous (polychromator) as well as sequential (monochromator). Besides, AAS and ICP-AES, the metals in sediment can be measured through Inductively Coupled Plasma Mass Spectrometry (ICP-MS), which according to Gennaro et al. (2008, p.18) is a extremely powerful tool for ultra-trace (ppq-ppb) as well as trace (ppb-ppm) elemental analysis. The resultant ions are subsequently transmitted through cones into a mass analyser (high vacuum). In addition, mass-to-charge ratio is used to identify the high elements’ isotopes. References Brix, K.V. et al., 2011. Ecological risk assessment of zinc from stormwater runoff to an aquatic ecosystem. Science of the Total Environment, vol. 408, pp.1824–32. Gennaro, G.d., Daresta, B.E., Ielpo, P. & Placentino, M., 2008. Analytical methods for determination of metals in environmental samples. Presentation. Molfetta BA, Italy: LEnviroS University of Bari. Greenway, M., 2010. Wetlands and Ponds for Stormwater Treatment in Subtropical Australia: Their Effectiveness in Enhancing Biodiversity and Improving Water Quality? Journal of Contemporary Water Research & Education, no. 146, pp.22-38. Hashemi, M.R., Ashournia, M., Rahimipour, M.A. & Modaberi, H., 2013. Survey of heavy metal (Copper, Iron, Lead, Cadmium, Zinc and Nickel) concentrations and their effects on the water quality of Anzali wetland. Caspian Journal of Environmental Sciences, vol. 11, no. 1, pp.11-18. Howitt, J.A. et al., 2016. Urban stormwater inputs to an adapted coastal wetland: Role in water treatment and impacts on wetland biota. Science of the Total Environment, vol. 485–486, pp.534–44. Hunt, W.F., Burchell, M.R., Wright, J.D. & Bass, K.L., 2007. Stormwater Wetland Design Update: Zones, Vegetation, Soil, and Outlet Guidance. In Urban Waterways Series. Search Results, 2007. North Carolina Cooperative Extension Service. Ogoyi, D.O., Mwita, C.J., Nguu, E.K. & Shiundu, P.M., 2011. Determination of Heavy Metal Content in Water, Sediment and Microalgae from Lake Victoria, East Africa. The Open Environmental Engineering Journal, vol. 4, pp.156-61. Qasaimeh, A., AlSharie, H. & Masoud, T., 2015. A Review on Constructed Wetlands Components and Heavy Metal Removal from Wastewater. Journal of Environmental Protection, vol. 6, pp.710-18. Shammaa, Y. & Zhu, D.Z., 2001. Techniques for Controlling Total Suspended Solids in Stormwater Runoff. Canadian Water Resources Journal, vol. 26, no. 3, pp.359-75. Wang, B., Wang, Y. & Wang, W., 2014. Retention and mitigation of metals in sediment, soil, water, and plant of a newly constructed root-channel wetland (China) from slightly polluted source water. SpringerPlus, vol. 4, pp.1-15. Read More