The City of Brockton, Massachusetts, Advanced Water Reclamation Facility (AWRF) wanted to prepare for a proposed new phosphorus discharge limit set forth by the National Pollution Discharge Elimination System (NPDES) program of the United States Environmental Protection Agency (U.S. EPA).
The plant's existing treatment scheme included physical settling, activated sludge treatment and final filtration using two AquaDiamond® cloth media filters from Aqua-Aerobic Systems, Inc.
Even though the filters performed to a level well below the current phosphorus discharge limit, plant superintendent Dave Norton began looking for ways to meet the anticipated 0.1 mg/L limit with minimal equipment modification and without raising operating costs.The Brockton staff, working with Aqua-Aerobic Systems, conducted tests using OptiFiber PES-14® microfiber cloth media installed on one of the AquaDiamond filtration units and compared its performance to the unit using the existing OptiFiber PES-13® pile cloth media.
From December 2012 to April 2013, the two filters received common influent from the plant's secondary clarification system. Feed quality and discharge quality were monitored for phosphorus, as well as total suspended solids, turbidity, pH, iron and alkalinity.
The two filter units operated under identical flow and loading conditions during the study. The results show that the OptiFiber PES-14 microfiber media consistently reduced phosphorus levels to below the 0.1 mg/L target.
Additionally, the microfiber media outperformed the existing pile cloth media with respect to final total suspended solids, turbidity, particle size distribution and iron concentrations and fared extremely well during average design and peak HLR testing
The Brockton AWRF demonstrated it can meet the anticipated discharge standards. The plant also installed a third AquaDiamond CMF (with the OptiFiber PES-14 microfiber media) and a fourth is under construction and expected to be online soon. The AquaDiamond filter unit fitted with the original pile cloth media is also being retrofitted with the microfiber media.