Haloacetic acids, formed in drinking water during disinfection by chlorination, pose significant risks to human health. Semiequilibrium dialysis and ultrafiltration experiments were used to examine the partitioning. of the five regulated haloacetic acids (HAA(5)) viz. chloro-, dichloro-, trichloro-, bromo-, and dibromoacetic acids into cetylpyridinium chloride (CPC) micelles across a range of micellar mole fraction, surfactant concentration, and added NaCl conditions. The results of these experiments were successfully correlated using a nonlinear three-site equilibrium model, which combines thermodynamic relations with the Oosawa two-state binding theory, incorporates allowances for nonideality, and includes a parameter to account for haloacetate solubilization. Micellar-enhanced ultrafiltration using CPC provided excellent HAA(5) removal efficiencies of over 98%. (C) 2012 Elsevier Inc. All rights reserved.