AWWA WQTC64058

To provide clear and quantifiable answers to water quality and O&M questionsrelated to the traditional seawater reverse osmosis (SWRO) versus dual-pass nanofiltration process, the Long Beach Water Department (LBWD)has formulated an aggressive research program and constructed a 300,000gallons per day permeate "Prototype" research facility using full-scale equipment.This paper presents LBWD's preliminary evaluation of SWRO and initialcomparisons against dual-pass nanofiltration.The prototype facility was constructed with the mindset to provide unbiasedaggressive process and water quality research. A process flow schematic of theprototype facility is provided in the paper. The prototype utilizes pressurizedmicrofiltration (MF) membranes as the pretreatment process. The MF unit isoperated in an outside-in configuration at a flux of approximately 35 gallons persquare foot per day (gfd). To extend the operation of the MF unit between each"clean-in-place", chlorine is added in the backwash process. Sodium bisulfite iscontinuously added to the MF filtrate to quench any residual chlorine remainingafter the backwash process. The MF effluent is collected in a main MF filtratetank, where it is then divided equally into two trains. This ensures that thepretreatment water quality is identical for both SWRO and dual-pass NF.Currently, train 1 is set up to test LBWD's patent-pending two-pass nanofiltration(NF²) process. Dow Filmtec NF90 membranes were selected for pass 1 and theSaehan NE90 seawater membranes were selected for pass 2. Train 2 isconfigured to evaluate traditional single-pass SWRO, where HydranauticsSWC3+ membranes were selected as the RO membrane. Identical EnergyRecovery Incorporated (ERI) pressure exchangers are used on both the SWROand NF² trains to allow for an "apples to apples" comparison on how much thesedevices aid in lowering energy consumption. The permeate and brine from bothtrains are recombined to reconstitute raw seawater and then discharged backinto the ocean. This allows for aggressive research without the risk ofendangering the public water supply. Power monitors for each process (MF,SWRO, and NF²) are incorporated to accurately determine actual power costs. Includes 10 references, tables, figures.

Product Details

Edition:

Vol. - No.

Published:

11/01/2006

Number of Pages:

12

File Size:

1 file , 370 KB