Hållbar vattenförsörjning i områden med vattenbrist : Sustainable water supply solutions for areas affected by water shortage

Sammanfattning: In some coastal areas in Sweden water shortage sometimes appears because the withdrawal of groundwater is greater than the groundwater recharge. It creates a situation where the available groundwater is insufficient to support residents and businesses with drinking water. The high withdrawal of groundwater also creates a risk for saltwater intrusion to drinking water wells. The problem most commonly occurs during the summer when the groundwater recharge is low, but the population is high, due to tourism and summer residents. The purpose of this study was to investigate how local water supply in areas affected by water shortage can be solved as sustainable as possible. The work was divided into three parts where the first part comprised of a literature review on water systems in which four different options were investigated: artificial groundwater recharge, rainwater harvesting, desalination and water reuse. The second part of the work consisted of developing a method for choosing the best water supply solution based on nature-given and social conditions. The method evaluated the quality of the supplied water and disease control, technical robustness, environmental impacts and resource use, liability and user aspects, the possibility for rebuilding and costs. Multi-criteria analysis (MCA) was used as a decision tool. The last part of the thesis was to test the method on a case study area, Grisslehamn in Norrtälje. Four systems alternatives were compared: desalination of sea water, building a surface water treatment plant supplied by water from two nearby fresh water ponds, rainwater harvesting at household level and collection and central treatment of greywater in combination with the construction of a surface water treatment plant. The results from the MCA showed that seawater desalination as a complement to the existing water plant was the best option for Grisslehamn followed by the surface water plant, collection of greywater and finally rainwater harvesting. Costs and possibility for rebuilding was shown to have a large impact on whether desalination or building of a surface water treatment plant was the best option. Therefore it is important in any future studies that detailed investigations of water quality and costs are done before decision is made on which one of the two alternatives that is the best solution for Grisslehamn.