Process and assembly to supply drinking water from cold water public supply using two-stage single semi-permeable membrane

摘要

In a process to prepare drinking water from cold water, water taken from the public supply is subjected to reverse osmosis at higher feed pressure to form soft water and hard water. The semi-permeable membrane (3, 6) which removes calcium from the drinking water operates within a two-stage process (2, 5) division. Effluent water (C) arising from the first separation stage (2) is used as feed for the second stage (3) where it is subjected to further concentration of the Calcium content. Water (F) yielded by the first stage is used as drinking water. Secondary water (E) arising from the second stage (5) is returned to the primary feed flow (A), thereby diluting the calcium concentration in the feed (B) supply to the first stage (2). Both separation stages (2, 5) contribute to the water yield by further concentration in the second stage. Scaling is prevented in the second stage on the membrane by dosed introduction of a hardness stabilizer. also claimed is a suitable assembly.