This invention is to a process for separating condensed water and entrained solids from an olefin stream so that fouling of the separation equipment by the entrained solids is reduced or eliminated. The process involves injecting an antifouling agent into a water condensing or quench system in an amount to maintain a zeta potential of fouling liquid and a zeta potential of the surface of the quench system both in a positive range or both in a negative range.