Paper Mill Wastewater Treatment

DAF Dissolved Air Flotation for Paper Mill Wastewater Treatment
Papermaking consumes a great amount of water and is with heavy pollution, the generated papermaking wastewater must be properly treated before it is allowed for safe discharging. Many paper mills use waste paper as raw material to make new paper, will generate deinking wastewater, with high pollution level of ink and short fiber(pulp). Paper mill wastewater is mainly composed of the below 3 parts:

1.
Black Liquor:
From pulping process, generally 1/3 is inorganic matters;
2/3 is organic matters, including alkali lignin, hemicellulose, fatty aid, resin acid, etc.

2.
White Liquor:
From paper machine and beater, with low pollution level.

3.
Mid-stage Effluent:
From the washing, screening and bleaching process, including biorefractory pollutants.

Feed papermaking wastewater to dissolved air flotation by pump. And dose flocculant and coagulant into and thoroughly mix with wastewater for flocculation reaction to coagulate the oil & grease, colloidal particles and micro suspended solids to conglomerate the particles into bigger clusters.

Dissolved air flotation will release millions of tiny bubbles into water, these bubbles attach to, and form within, the solids or chemical flocculants entering the vessel, causing them to float to water surface where they are retained and forms scum layer, which is then subsequently removed by DAF skimmer.

Dissolved air flotation removes the most part of color and suspended solids(TSS), also will remove part of BOD and COD, greatly reduce the pollution loads for the subsequent biological treatment process.