AWWA ACE63244

This slide presentation outlines a study on the comparative performance of high-rejection SWRO membranes. Specific study objectives included: evaluate performance of three commercially available, high rejection SWRO elements for boron and TTS removal; compare removal rates with projected data from supplier's software programs; and, estimate cost for feedwater alkalinization to meet WHO standard. Topics outlined include: regulatory limits for boron; boron speciation in water, seawater, temperature effect, and salinity effect. An SWRO pilot plant is outlined and includes: experimental protocol; pilot configuration; reverse osmosis (RO) system with pH adjustment; manufacturer element specifications; RO System Performance Permeate Boron Concentrations; manufacturer's projected permeate Boron versus Feed pH; manufacturer's projected permeate TDS versus Feed pH; SWRO TDS and Boron rejection; and, estimated cost of Boron compliance. Conclusions were: at ambient pH (8.0), only manufacturer A met permeate boron goal of 0.5 mg/L; feedwater alkalinization to pH 9.0 was required for all suppliers to comply boron goal; TTS rejection was poor predictor of pH impact on boron rejection, all supplier's products show constant TTS rejection over range of feedwater pH values evaluated; and, estimated cost of feedwater alkalinization to pH 9.0 is $0.12/kgals of permeate. This represents an additional operating expense of <10%. Includes figures.