Effectiveness of Stormwater 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 Metals in Storm Water Wetland Essentially, natural processes inspire constructed wetlands within the naturally occurring wetlands. According to Sahu (2014) natural wetlands bogs, swamps, marshes, everglades are extremely productive systems that store large water volumes, offer habitats supporting different animals and plants population, recalculate nutrients, and remove contaminants from the water. In natural conditions, Sahu (2014) posit that wetlands can significantly remove pollutants from the influent streams of contaminated waters such as urban runoff, municipal, storm water, landfill leachate, as well as industrial wastewater. In wetlands, treatment happens after photolysis, organic matter oxidation, the suspended particles have settled, and indigenous microorganisms’ metabolism. For many years, natural wetlands have been utilised to discharge treated wastewater runoffs mainly as a measure for disposal and a way of reducing concentrations of heavy metal, phosphorus, nitrogen, as well as the pathogen in the runoff. Heavy metals as mentioned by Sahu (2014) normally exist in mine drainages, industrial wastewater, and also municipal wastewaters. The heavy metals commonly found in the wastewater and generated by industries and mines include Zinc, Lead, Cadmium, Mercury, Iron, Chromium, and Copper. The removal of these heavy metals from constructed wetlands can be achieved through different techniques such as adsorption, filtration and sedimentation, as well as precipitation. The rates of removing heavy metals using the constructed wetland system as evidenced by a number of studies cited by Sahu (2014) is 100 per cent. Heavy metals as observed by Maddock and Lopes (1988) are toxic to aquatic systems and their concentrations in runoffs are attributed to their different uses in the industries. In aqueous effluents, heavy metals can bring about intolerable damage; for these reasons, they are recognised in scores of countries’ legislations. Heavy metals after being dissolved in the water, the sediments absorb them; thus, even after industrial emission cessation, the sediments will still have large amounts of absorbed metals that could be remobilised resulting in toxic effects to the biosystem. While monitoring the newly constructed wetlands in the Newbury Bypass in Berkshire, UK Pontier et al. (2003) observed that although the pollutant loadings had some variability, the newly constructed wetland system facilitates the accumulation and removal of sediments as well as the related metals. They further established that combining pollutant removal and flow balancing functions can be enhanced by preventing sediments from being transported and promoting processes that favour the retention of metals by the bed deposits. Heavy metals as described by Qasaimeh et al. (2015) are dangerous components related to industrial as well as agricultural wastewaters. They normally undergo different chemical and physical transformations, and they can be found in living species, air, water, and soils. They are considered hazardous because of the level of their carcinogenety, toxicity, and damage to the environment. Aquatic ecosystem as indicated by Ogoyi et al. (2011) receives nearly everything, which includes heavy metals. Heavy metals pollution in the aquatic systems has become a major issue globally and they have reached a disturbing rate. According to Ogoyi et al. (2011), heavy metals are sourced from different sourced from different sources, especially the anthropogenic activities such as hospital wastes discarding, sewerage draining as well as recreational activities. Equally, heavy metals occur naturally, but in small amounts and could enter the aquatic environment through rocks leaching, forest fires, airborne dust, as well as vegetation. Since degradation of heavy metals is impossible, they incorporated and deposited continuously in the aquatic organisms, sediment and water; as a result, causing pollution of, heavy metal in the water systems. In Lake Victoria, pollution is sourced from different industries like agro-processing factories mining, shipping, tanning, breweries and fish. These industrial effluents as observed by Ogoyi et al. (2011) put the lake together with its wetlands at risk since they are directly discharged into the surface water without or with minimal treatment. Besides that, metallic pollutants concentrations are very high in the nearby towns. Small-scale miners, especially in Tanzania, were using water with the aim of removing mercury, impurities, and mud so as to gather gold. The miners then dispose of the wastewater from their mining processes in the close by streams, which eventually end up in Lake Victoria basin. The lake is also polluted by urban stormwater effluent, domestic wastes, boating activities, and landfill leachate. The existence of these heavy metals has enormously affected the microalgae, which is the main source of food for zooplankton, bivalve mollusks in every stage of their growth, as well as for some fish species and crustacean larval stages. While examining the range of concentration and occurrence of different pollutants in urban stormwater in three distinct French towns, Gasperi et al. (2014) observed significant variations in numerous metals, Polycyclic aromatic hydrocarbons (PAHs), and Polybrominated diphenyl ethers (PBDEs). They established that the distributions of the pollutants between particulate and dissolved phases were same in all the experimental sites. They further established that the contributions of total atmospheric fallout (TAF) to the contamination of nonylphenol polyethoxylates (NPnEO), Bisphenol A (BPA) and PBDEs which are highly produced locally resulting in leaching of vehicles, buildings, and urban surfaces. In Victoria and other parts of Australia the utilisation of water resources is approaching the sustainability limits; therefore, improving urban water resources management as mentioned by Hatt et al. (2006) is very important. There is a need for integrated urban water management so that the expected population’ water requirement can be achieved devoid of compromising public health or deteriorating the environment further. Therefore, the using stormwater as the main source of urban water supply is considered the main focus of the proposed water conservation program. Hatt et al. (2006) cited that the heavy metals toxicity is determined by their bioavailability that relies on their speciation. In stormwater, the solubilities of the heavy metals at the pH range are normally low; for that reason, a small total concentration amount is deemed bioavailable. Still, altering the conditions could improve the bioavailable portion, and the toxic effect of heavy metals is still high even at extremely low levels. In his study, Keller (2011) quantifies the concentrations improvement of specific heavy metals in stormwater in the Greenway wetlands, North Carolina. Keller (2011) observed that the Greenway wetlands successfully remediated chromium, copper, iron, Selenium, and potentially zinc. Keller (2011) observed that the sediments close to the intake pipe has high levels of metals; therefore, this proves that wetland was somehow effective at retaining such metals through the capture of the sediments and facilitating the suspended metals sedimentation. In their study Howitt et al. (2014), found out that the utilisation of recreational wetland system such as Lake Pertobe wetland system as a basin to receive stormwater effectively helped in reducing the export of polycyclic aromatic hydrocarbons (PAHs) as well as numerous heavy metals in the close by Merri Marine Sanctuary. They also observed some improvements in water quality parameters as well as Escherichia coli loads, but the export of nutrient from the system was very high than expected. Howitt et al. (2014) suggest that increased plant biomass, as well as reduced area of open water, could facilitate in improving the contaminant retention. Mackintosh et al. (2016) while examining the constructed wetlands in the western basalt region, they observed that metal concentrations in fish tissues were very high, especially in the benthicspecies but reduced when the trophic level and size of the body were increased. This connotes that suggests that along the food chains in the examined constructed wetland systems, metals were not biomagnifying or bioaccumulating. Greenway (2010) observed that during wet weather the suspended solids reduced but they increased during dry weather because they were resuspended by the ducks. Greenway (2010) also found out that there was a reduction of NO3-N both during the dry and wet weather. The increase of Ammonium-N (NH4-N) was attributed to the organic matter ammonification. There were a slight increase in total suspended solids (TSS) concentrations in the wetland systems because of resuspension, but their concentrations were less in the ponds. In the wetlands, TSS increased during the dry weather because of resuspension attributed to water birds’ activities. Sedimentation as indicated in Walker and Hurl (2002) study is the main process used to remove heavy metals from stormwater in both constructed and natural wetlands. Still, heavy metal can be removed through other processes such as chemical transformation, biological assimilation, adsorption, filtration, decomposition, as well as volatilization (Walker & Hurl, 2002). Measurements Different studies have demonstrated how heavy metals in stormwater can be measured; for instance, in Chong et al. (2013) study they used heavy metals analysis technique. First, they filtered the stormwater samples using 1.2 μm and then utilised ICP/MS to analyse the sample. After calibrating with standard samples, they performed quantitative measurements. Chong et al. (2013) also utilised the three-dimensional (3D) fluorescence EEM (excitation–emission matrix) spectra with the objective of determining the organic substances’ nature through simultaneous alteration of the emission as well as excitation wavelengths. As mentioned by Chong et al. (2013), the EEM spectra offer crucial data regarding the organics’ chemical and physical properties of different origins in the stormwater. In their study, Chong et al. (2013) obtained the EEM spectra through utilisations of PerkinElmer LS 55 spectrofluorometer having an emission and excitation wavelength range of between 280 and 500 nm and 200 and 500 nm, respectively. They took the spectra at an incremental wavelength of 2 nm in emission as well as 5 nm in excitation and they subtracted the blank sample EEM value from the stormwater samples being analysed in order to facilitate blank correction. Microsoft Excel® was used to analyse the EEM. In their study, Brix et al. (2010) used the plasma emission spectrometry that was inductively coupled to measure sodium, calcium, magnesium and zinc in the stormwater runoff. Furthermore, they measured alkalinity by means of titrimetric techniques and also used total organic carbon analyser to measure dissolved organic carbon. The measurement of stormwater sample pH was achieved through a combination electrode and the total suspended solids were gravimetrically measured. In the sediment samples, Brix et al. (2010) analysed the acid-volatile sulfide/simultaneously extracted metals using gravimetrically determined sulfide. The Walkey–Black method was used to determine the content of total organic carbon while the size of sediment grain size was measured according to ASTM D422 standards. Keller (2011) used inductively coupled plasma optical emission spectrometry (ICP-OES) while Dumčius et al. (2011) used Inductively Coupled Plasma Atomic Absorption Spectroscopy ICP-AAS to measure heavy metal in the stormwater. In Dumčius et al. (2011) study, they analysed the stormwater sample using ICP-AAS, DC Arc ES, and AAS with the objective of registering an intensive radiation from the atomic emission. Atoms in the ICP-AAS occur in the high frequency plasma (inductively excited) while in DC Arc ES they are excited in the electric field plasma. Dumčius et al. (2011) used the AAS to register the atomic emission spectrum’s absorption size. Presently, LA-ICP-MS and ICP-MS are commonly are widely used to analyse bottom sediment and soil. Both techniques rely on microplasma extraction from the stormwater sample. The interruption of the chemical links in the microplasma results in the occurrence of ions and atoms that are analysed using mass spectroscopy. X-ray fluorescence analysers can also be used to determine the samples’ microelement composition. In this technique, chemical elements’ dispersion and fluorescence excited by the X-ray are measured. During the analysis of the samples, Dumčius et al. (2011) posit that the chemical elements concentrations are measured using the basic characteristics that have been identified physically. When analysing the stormwater samples using the standardised ICP-MS and AAS techniques, Dumčius et al. (2011) assert that all procedures for sample preparation are needed. The LA-ICP-MS technique is considered simpler since the analysis of the sample does need microelements to be extracted chemically. The LA-ICP-MS technique facilitates the measurement of microelement composition even when the sample amounts are very small. When using the analysis XRF method, Dumčius et al. (2011) suggest that the samples must be finely ground. References Brix, K.V. et al., 2010. Ecological risk assessment of zinc from stormwater runoff to an aquatic ecosystem. Science of the Total Environment, vol. 408, pp.1824–32. Chong, M.N. et al., 2013. Urban stormwater harvesting and reuse: a probe. Environmental Monitoring and Assessment, vol. 185, pp.6645–52. Dumčius, A., Paliulis, D. & Kozlovska-Kędziora, J., 2011. Selection of investigation methods for heavy metal pollution on soil and sediments of water basins and river bottoms: a review. EKOLOGIJA, vol. 57, no. 1, pp.30–38. Gasperi, J. et al., 2014. Micropollutants in urban stormwater: occurrence, concentrations, and atmospheric contributions for a wide range of contaminants in three French catchments. Environmental Science and Pollution Research, vol. 21, pp.5267–81. 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, (146), pp.22-38. Hatt, B.E., Flander, L. & Mitchell, V.G., 2006. Quantifying Stormwater Recycling Risks and Benefits: Heavy Metals Review. ISWR Report. Clayton VIC: Institute for Sustainable Water Resources. Howitt, J.A. et al., 2014. 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. Keller, J., 2011. Effectiveness of wetland remediation on heavy metals in storm water runoff. Journal of Student Research in Environmental Science at Appalachian, vol. 1, no. 1, pp.36-43. Mackintosh, T.J., Davis, J.A. & Thompson, R.M., 2016. Tracing metals through urban wetland food webs. Ecological Engineering, vol. 94, pp.200–13. Maddock, J.E.L. & Lopes, C.E.A., 1988. Metals in Coastal Environments of Latin America. In Behaviour of Pollutant Metals in Aquatic Sediments. r Berlin : Springer Berlin Heidelberg. pp.100-05. Ogoyi, D.O., Mwita, C.J., Nguu, E.K. & Shiundu3=, 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. Pontier, H., Williams, J. & May, E., 2003. Behaviour of metals associated with sediments in a wetland based system for road runoff control. Water Sci Technol, vol. 48, no. 5, pp.291-98. 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. Sahu, O., 2014. Reduction of Heavy Metals from Waste Water by Wetland. International Letters of Natural Sciences, vol. 12, pp.35-43. Walker, D.J. & Hurl, S., 2002. The reduction of heavy metals in a stormwater wetland. Ecological Engineering, vol. 18, pp.407–14. Read More