The aqueous effluent from the wash cycle of a process for cleaning electronic circuit assemblies of rosin flux and other organic residues with an aqueous alkaline cleaning solution comprises treating the effluent with an alkaline earth metal compound which reacts with the rosin flux to cause precipitation of an alkaline earth metal rosinate. Alkali saponifiers such as alkali metal carbonates and bicarbonates and carboxylate organic adjuvants in the cleaning solution are also removed from the effluent by reaction with the alkaline earth metal compound to form water insoluble alkaline earth salts which are precipitated from solution.