Continuous removal of copper from wastewater by the process consisting of ferric/limestone coagulation, polymer flocculation, and lamellar sedimentation

Removal of copper from wastewater by ferric/limestone coagulation and polymer flocculation followed by lamellar sedimentation was studied at laboratory scale. From jar test experiments, the optimum dosages of inorganic coagulant and polymer flocculant were Fe(III) 50 mg/L and 0.1% SA 407 solution 0.5 ∼ 1.0 mL/L, respectively. A novel process was developed for continuous copper removal, in which a limestone aeration bed, a rapid-mixing tank, a slow-mixing tank, and a sedimentation tank with lamellae were applied systematically. In the limestone aeration bed alkalization and coprecipitation of copper ion with Fe(III) were performed cocurrently. Flocculation of the ferric hydroxide/copper aggregates was performed efficiently with a minute quantity of the polymer flocculant in the mixing tank. The floes were settled down in the sedimentation tank with lamellae and were separated from treatment water. The pH was maintained around 7.6 during the whole process and the performance results of the process showed copper removal efficiency over 99%. Copper removal efficiency was dependent on hydraulic retention time (HRT) and especially the HRT in the limestone aeration bed was a limiting factor.