A mathematical model was developed for continuous electrokinetic dewatering of phosphatic clay, a clay-water suspension generated as an effluent from processing of phosphate ores. The model, accounting for compressibility of the cake and for both electro-osmotic and hydraulic permeability, provided good agreement with experimental data obtained from a prototype that separated a 10 wt% phosphatic clay slurry into clear water and a cake with a solids content up to 35 wt%. A constrained optimization strategy was developed to identify optimal operation parameters for an industrial-scale electrokinetic dewatering process for processing the effluent generated by a typical phosphate mine. (C) 2019 Elsevier Ltd. All rights reserved.