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Development of a Low-Cost Alternative for Metal Removal from Textile Wastewater
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Development of a Low-Cost Alternative for Metal Removal from Textile Wastewater
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Development of a Low-Cost Alternative for Metal Removal from Textile Wastewater
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Dissertation
Development of a Low-Cost Alternative for Metal Removal from Textile Wastewater
2012
نظرة عامة
Economic development, urbanization and population growth are three parameters that are influencing the quality of water nowadays. Textile wastewater is a typical industrial wastewater generated by human activities. This alkaline wastewater contains many pollutants and has high BOD and COD loads. Pollutants in textile effluents include suspended solids, mineral oils (e.g. antifoaming agents, grease, spinning lubricants, non-biodegradable or low biodegradable surfactants) and other organic compounds, including phenols from wet finishing processes (e.g. dyeing), and halogenated organics from solvent use in bleaching. Effluent from dyeing processes is colored and may contain significant concentrations of heavy metals (e.g. chromium, copper, zinc, lead, or nickel). The present study is focusing on heavy metal pollution found in textile wastewater because of their toxic effect in the environment and most studies on textile wastewater focus on the removal of organic pollutants.In Rwanda, textile wastewater contributes to heavy metal pollution in the swamps receiving that water. Chapter 3 presents the assessment of metal pollution in a swamp receiving textile wastewater from UTEXRWA in Kigali (Rwanda). The Nyabugogo swamp is a natural wetland located in Kigali City (Rwanda). This wetland receives all kinds of untreated wastewaters from the city. The assessment of heavy metal pollution (Cd, Cr, Cu, Pb and Zn) included all environmental compartments of the swamp: water and sediment, the dominant plant species Cyperus papyrus, fish (Clarias sp. and Oreochromis sp.) and Oligochaetes. Cr, Cu and Zn concentrations in the water were generally below the WHO (2008) drinking water quality guidelines, whereas Cd and Pb were consistently above these limits. Except Cd, all metal concentrations were below the threshold levels for irrigation. The highest metal accumulation occurred in the sediment with up to 4.2 mg/kg for Cd, 68 mg/kg for Cu, 58.3 mg/kg for Pb and 188.0 mg/kg for Zn, followed by accumulation in the roots of Cyperus papyrus with up to 4.2 mg/kg for Cd, 45.8 mg/kg for Cr, 29.7 mg/kg for Cu and 56.1 mg/kg for Pb. Except Cu and Zn, other heavy metal (Cd, Cr and Pb) concentrations were high in Clarias sp., the Oreochromissp. and the Oligochaetes. Therefore, there is a human health concern for people using water and products from the swamp.From the results of chapter 3, there is a need for the development of a cheap, reliable technology applicable in developing countries for heavy metal removal from polluted water bodies. This research aimed at improving the heavy metal removal from textile wastewater using an integrated system for wastewater treatment. The integrated system consists in a combination of an anaerobic reactor as the main treatment step, followed by a polishing step composed by a macrophyte stabilization pond. The main treatment step will remove a large quantity of heavy metals, mainly by adsorption combined to metal sulfide precipitation. The polishing step will be achieved by phytoremediation where removal will be conducted by algae and plants (duckweed and water hyacinth). The integrated system will show the complementary action of both systems in metal removal.
