GB622282A - Method of and apparatus for purifying raw water from humic substances - Google Patents

Abstract

622,282. Purifying water. KARLSTROM. A. M. R. April 12, 1946, No: 11302. [Class 46] In a process for removing colloidal humic substances from raw water, the water is aerated and a water-soluble salt with a trivalent positive ion is added, the water is slowly agitated to effect the coagulation of the humic substance, and the air bubbles are enclosed in and securely bound to the flocs formed, which are then separated from the water by flotation. The raw water enters under pressure through a conduit 1, air being sucked in at 3 and a solution of a salt, e.g. aluminium sulphate, sprayed in at 4. Superfluous air escapes from a box 5. Alkali may be added-at 6, and aluminium sulphate and alkali at points 9 and 10 respectively. The water next passes to a flocculation tank 8, where platforms 29 rotating with a shaft 28. and spaced from the wall, alternate with fixed platforms'26 attached to the outer wall and having central openings 27. Both sets of platforms carry sets of pins 31, 32 respectively. The water flows generally upwardly, passing between adjacent platforms from the centre of the tank to the periphery and vice versa, 10 to 30 minutes being allowed for the water to pass through the tank. The water now intermingled with floes passes along a pipe 14 to the bottom of a flotation tank 17. Negatively-charged colloids such as animal glue or other protein substances; entirely saponified resin glue, soap solution, or sulphonated fatty and resin acids may be added to the water at some point between 14 and the bottom 15 of the flotation tank. In this tank the water during its upward flow is subjected to slow agitation between rotating arms 33 and fixed arms 34, the size of the flocs being thereby increased. A reduced pressure corresponding to a water column of 2.5 to 3 metres is maintained in the tank, causing the air dissolved in the water to be separated in the form of small bubbles on and in the humic flocs whereby these flocs are raised to the water surface, where they are removed by a scraper and a rotary suction nozzle 18. Purified water escapes through a plurality of openings 19 to a discharge tube 22. The tank 17 may be filled before starting through a conduit 24, and water for cleansing the tank and nozzle may be admitted through a conduit 25.