Enhancing Copper Removal in Secondary Treatment by Chemical Addition

Chemical addition was tested for enhancing copper removal in the University of California, Davis (UCD) wastewater treatment plant (WWTP). Wastewater from the headworks and oxidation ditch were treated with ferric chloride and two organic precipitants in jar tests. Ferric chloride had little effect on residual dissolved copper, while the organic precipitants reduced it below 10 μg/L. In a full-scale trial, dose of 8 ppm to 13 ppm organic polymer effected a mean reduction in dissolved copper concentration of 2 μg/L, sufficient to maintain compliance with the WWTP's 13-μg/L water quality-based effluent limit for copper. Full-scale implementation required no additional solids separation or handling equipment.