Sorption of Chlorophenolic Compounds to Primary Clarifier Solids, 1995 Environmental Conference Proceedings

S. J. Severtson & S. Banerjee

IPST

An experimental study of the aqueous retention of chlorophenolic chemicals by wood fibers and sludge samples indicates the hydrophobic sorption to the lignin fraction of clarifier solids is responsible for the organic chemical retention by primary sludge. Measurements of the sludge/water distribution coefficient for a model system involving the aqueous sorption of 2,4- dichlorophenol and 2,4,5-trichlorophenol to kraft softwood fibers showed a strong dependency on the compound’s octanol-water distribution coefficient and on the kappa number of the fibers. Experiments also indicate chlorophenolic compounds do not bind to fiber-derived solids when they are in their conjugate base or ionized form. Through sorption measurements of model compounds using collected clarifier sludge and overflow samples, these findings are confirmed for the various fibrous components of primary sludge. The results indicate the sludge/water distribution for chlorophenolic molecules will be limited by their ionization under the alkaline conditions of primary treatment, but for compounds not possessing acidic groups, hydrophobic sorption can result in a strong magnification of concentrations in the sludge.