Investigation of sustainable methods to reduce water hardness in drinking water treatment plants

University essay from Lunds universitet/Miljövetenskaplig utbildning

Abstract: Water hardness is caused by magnesium and calcium ions (Mg2+ and Ca2+), and can result in formation of deposits, destruction of soap and increase of copper corrosion in old plumbing pipes. To soften the originally hard groundwater supplying 20% of Malmö’s drinking water, Bulltofta water treatment plant imports burned lime from Germany. Approximately 66 mg/L calcium is removed in the treatment plant, lowering hardness levels from around 17 °dH to 6 °dH. Previous experiments using plant biomass, pumice stone or plastic have demonstrated capacities for removal of Mg2+ and Ca2+ in water. As such, they were considered as sustainable options for reducing water hardness at Bulltofta. Theoretical calculations on the amounts required for each alternative, and their potential economical cost were made, and their environmental impact was investigated. All calculations are purely theoretical and should be experimentally validated, before definite conclusion can be drawn. Plant biomass showed most promise as an alternative, and further investigations on plant biomass common in Sweden could yield positive results. Rapeseed is such an example, as it has a similar composition to sugarcane bagasse, which has been proven to adsorb Mg2+ and Ca2+. Currently, the investigated alternatives are not economical nor environmentally friendly. Additionally, daily quantities required of each alternative makes them infeasible for Bulltofta.

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