METHOD OF TREATING PULP AND PAPER WASTE WATER VIA PRESSURE FLOATATION Russian patent published in 2011 - IPC C02F1/24 B03D1/18 C02F103/28 

FIELD: chemistry.

SUBSTANCE: method is meant for treating pulp and paper waste water containing suspended particles as well as organic dissolved pollutants, including substances which give water a colour which is difficult to rid of. The water treatment method involves adding floatation agents, saturation of part of the stream of the water to be treated and/or treated water with gas/air or mixture thereof with carbon dioxide in a saturator. The gas-saturated water is then throttled, while simultaneously mixing with the remaining portion of the water to undergo treatment or with its entire stream in an ejector to form at its outlet uniformly foamed water. Subsequent floatation of pollutants takes place in a floatation chamber with separate outlet of floatation foam and treated water from the chamber. A water stream is additionally fed into the separator, where the said stream is prepared by treatment with a dispersion of ash dust formed in a multifuel boiler when burning floatation sludge, excess activated sludge, bark and wood wastes, containing sulphuric acid, with residue from production of chlorine dioxide or mixture thereof with fresh sulphuric acid.

EFFECT: when implementing the method, the colour grade of the treated water falls below the allowable level, environmentally hazardous wastes are recycled - multifuel boiler ash, acidic remains from chlorine dioxide production, consumption of fresh floatation agents also drops.

2 cl, 3 ex