Freeze-thaw treatment of membrane concentrates derived from Kraft pulp mill operations

Freeze thaw was studied as a waste treatment method for concentration and v olume reduction of contaminated waste concentrates that are derived from th e use of membrane technology in the treatment of high strength Kraft pulp m ill effluents. Unidirectional freezing experiments were conducted to simula te seminatural freezing, in which the independent variables-freezing rate, time frozen, storage temperature, concentration, liquid depth, thawing rate and method of thawing-were examined for their relative importance. Method of thawing followed by freezing rate, rate of thawing, storage temperature, and time frozen were identified as the most important independent variable s that contribute significantly to treatment performance. Under ideal condi tions. freeze thaw was shown to effectively concentrate and separate the co nstituent matter of alkaline. extraction-stage membrane concentrate to achi eve color removals as:high as 73% in the top 70% liquid fraction. The resul ts suggest a new held of use for freeze thaw as a waste treatment process f or the management of high strength liquid wastes amenable to mechanical coa gulation by freezing.