Avskiljning av organiskt material vid konstgjord grundvattenbildning : Förändras reningen över tid?

A key function in the production of drinking water is to separate the organic matter pre-sent in the raw water as it has a great impact on the water quality; organic compounds con-tributes to a variety of hygienic and aesthetic water quality problems. The content of organic matter in Nordic watercourses has increased, most likely depend-ing on climate change, where the precipitation is an important factor. Increased precipita-tion results in more colored water containing more humus. Löfgren et al. (2002) estimated that the humus content in Swedish surface waters could increase with 26% in the future. According to the model estimated by Larsen et. al (2011), the median value of TOC in Nor-wegian lakes could increase by 65%. Waterworks that purifies raw water containing humus will be affected by these changes in the humus content. Svenskt Vatten AB (2007) predicted that the cost to separate the increasing humus levels caused by climate change in the years 2011 to 2040 will amount to about 400 millions.This study aimed to investigate the effectiveness of the separation of organic matter from surface waters by artificial groundwater recharge. Additional objectives were to study how the separation of organic matter changes over time, both in terms of retention time and the run time, and in relation to different types of plants.Three existing drinking water facilities with artificial groundwater recharge has been studied, Gäddvik, Forslunda and Wifsta, and also the startup of a new bank filtration facility in Rökebo was studied. This work was made by compiling several years of sampling series of water chemistry data from each existing facility, primarily the parameter CODMn. The com-piling has been done for both surface water (before infiltration) and raw water (after infiltra-tion). Through test-series of water chemistry from the plants as a basis, the report estimates on trends, seasonal variations, and comparisons between facilities. In addition, sampling at the startup of the infiltration facility at Rökebo was done, to see the development of treat-ment over time and in relation residence time.Based on the compilation made in this work it can be concluded that variations in con-tent of CODMn over short time intervals occurs, both in surface water and raw water. Studies of longer time series show weak trends that the amount of organic matter in the river water is slightly increasing. The raw water in the wells at Gäddvik and Wifsta also showed trends in increasing concentrations of CODMn with a low degree of explanation.The efficiency of the separation of organic material, measured as CODMn, did not change significantly over time and the average of the three surveyed plants in operation was at Gäddvik 87%, at Forslunda 90% and in Wifsta 68% with the bank filtration in Rökebo, Sandviken, a separation of 71% of the organic matter was achieved, during the sampling pe-riod. In Sandviken the water, however, requires further purification in terms of the organic material since the limit was exceeded in the raw water. However, it can be concluded that in comparison to using surface water directly as a source of raw water for drinking water pro-duction the need of purification reduced greatly to the use of artificial groundwater.Validerat; 20140824 (global_studentproject_submitter