AWWA WQTC69283

The Long Beach Water Department (LBWD) is aggressively pursuing seawater desalination as a new source of potable water for its service area. In addition to testing out the operational feasibility of various desalting membrane technologies, including the patented two-pass nanofiltration (NF²) process and traditional seawater reverse osmosis, LBWD is also researching other issues which will be important to address prior to commissioning a full-scale production seawater desalination plant. LBWD is pursuing an alternative intake and discharge system, which is based on using perforated laterals placed under the ocean floor to collect or expel the water through either natural media found on the ocean bed, or alternatively, filter media placed into an excavated area on the ocean floor (ocean floor system). The intake system is based on the concept of slow sand filtration (< 1 gallon/min-ft^2M, (gpm/ ft²)), which should mitigate any negative impacts associated with impingement and entrainment due to its slow intake rate. Additionally, the collection of seawater through the filter media may also offer some pretreatment benefits, including reducing organic and suspended solids. Includes 12 references, tables, figures.