Improvement of rapid filtration performance with chemical precipitation at Gäddvik drinking water plant

Luleå Kommun has started a project of construction of a new plant in Gäddvik. In this framework, new ways of treatment for the raw water have been explored or currently used method have been improved. The most efficient method regarding the quality of the water, the costs and also other parameters is likely to be the method used in the future plant. This master thesis is a part of this project and is based on the will of improvement for the rapid filtration method. Its aim is to discuss the efficiency of a direct filtration on different kinds of waters with different qualities (river water, ground water), according to several filter materials (sand/anthracite, filtralite), and different coagulants (aluminium- and/or iron-based chloride, aluminium sulfate). To achieve this study, a filter pilot plant has been built in the water plant of Gäddvik to simulate the results we can obtain for each combination at different filtration rates. Many parameters have been taken into account to see if each combination is efficient or not. Thus, chemical analyses of the filtered water (turbidity, color, Al, Fe and Mn concentrations) but also studies of the hydraulic losses and of the backwashes have been made. The best solutions found have then been compared to each other to finally figure out which filter material is the most interesting and which coagulant is the most effective.Validerat; 20101217 (root