AWWA ACE70797

This powerpoint presentation begins by providing a brief overview of a pilot study of a desalination study at Santa Cruz, California, from March 2008 through April 2009. Pilot-scale facilities treated up to 50 gpm and demonstrated technology to meet regulatory drinking water standards, establish optimal design and operating parameters, and compare pretreatment and reverse osmosis (RO) alternatives. The pilot plant process diagram of 4 pretreatment trains and 4 RO trains is presented, along with RO systems, single stage configuration, two-stage LPRO/SWRO, projected energy use before testing, water quality results - chloride, boron and bromide, relevant regulatory standards, impact on use for irrigation, and example of boron toxicity - mild and advanced necrosis. Conclusions indicate that: single stage ISD: achieves best balance of water quality and energy use (at 45-50% recovery); two-pass system: recommended to reduce impact on TTHM formation with free chlorine; two-stage LPRO/SWRO does not achieve boron regulation or bromide goal, provides lower energy use at high recovery (55 %), and may be feasible for lower boron source water (e.g., to reduce size of intake and pretreatment). Includes figures.