Magnetically Enhanced Coagulation Minimizes System Size Needed for Industrial Wastewater Treatment

Many industries look to coagulation, flocculation and sedimentation processes to meet stringent new wastewater treatment limits on solids, metals and nutrients. Traditional systems require large clarifiers to settle the light floc and sometimes polish the effluent with space-consuming filters. These processes can pose problems for plants that have limited open space and lack the budget for large capital improvements. A United States kraft pulp and paper mill faces such issues at its 1,752 liters per second (40 million gallon per day) treatment facility. Regulators issued a new draft permit that requires reductions in biochemical oxygen demand (BOD), total phosphorus, ortho-phosphorus and suspended solids (TSS). The plant considered substantial modifications to its biological treatment system and the addition of large tertiary process, but it needed a solution that was less expensive, smaller, and more reliable. Engineers found that a combination of the CoMag™ treatment process and upstream waste minimization could reliably meet the new permit with a modest investment. CoMag™ is a "magneto-chemical" wastewater treatment process that combines the principles of ballasted flocculation, solids contact and magnetic separation. Bench scale tests of the CoMag process determined the mill could meet its proposed limits with an 18-meter (60-foot) diameter clarifier and a small amount of chemical addition. The treatment could be further enhanced by reducing the waste load from a concentrated coating stream. These modifications would be less expensive and more reliable than the other options being considered.