Optimizing Membrane Performance at a Hybrid NF Plant

Abstract

Low-fouling nanofiltration (NF) membranes are being used at a 10-mgd plant in Pompano Beach, Fla., to meet difficult treatment objectives for high-fouling, colored feedwater. Based on extensive pilot testing and process design considerations, a hybrid NF system was selected and installed. On recommissioning in summer 2009, the plant met required feed pressure and permeate quality targets during a 60-day performance acceptance test. Challenging permeate-quality targets required iron to be reduced to less than 0.2 ppm and disinfection by-product formation potential to low levels while maintaining calcium at 8–33 mg/L and alkalinity at 20–61 mg/L as calcium carbonate. To better restore membrane performance and prevent further fouling trends, fouling is being further analyzed.