AWWA WQTC65699

The Olivenhain Municipal Water District (Encinitas, CA) pioneered using ultrafiltration(UF) membranes for the treatment of drinking water. The Olivenhain Water Treatment Plant(OWTP), which began operation in 2002, utilizes immersed ultrafiltration (UF) to produce up to 34 mgd offinished water from the treatment of blends of State Project and Colorado River water, bothcharacterized by low and consistent levels of total organic carbon (TOC) and turbidity.In 2006, the District began evaluating an expansion of the OWTP, in response to projectedpopulation growth and increasing water demand. The District also faced the potentialintroduction of a new source water, Lake Hodges, into Olivenhain Reservoir. Lake Hodgeswater presents a significant change in water quality and new challenges for treatment,including higher levels of TOC, taste and odor (T&O), iron and manganese, and disinfectionbyproduct (DBP) formation. The existing OWTP, which utilizes UF and chloraminationdisinfection for treatment, is not equipped to adequately address these water qualitychallenges.The District's objective was to identify the optimum approach for expanding the OWTP,including addressing water quality changes from Lake Hodges, while continuing to use theexisting UF system. The evaluation considered 26 water treatment alternatives includingmembrane pre-treatment, UF, membrane post-treatment, and residuals handling anddisposal, with an emphasis on effective control of organics and taste and odors and onachieving a sustainable membrane flux and cleaning frequency interval, despite variationsin anticipated source water quality.Laboratory-scale treatability testing was conducted in support of the evaluation of treatmentapproaches to fill specific identified data gaps as part of the decision process. Prior totesting, a wide range of candidate treatment approaches were evaluated, and ozone andpowdered activated carbon (PAC) were identified as key unit processes for the bestpotential approaches to meet the District's treatment goals. The focus of the treatabilitytesting was on ozone and PAC, and the treatment implications with respect to a number ofspecific water quality and cost performance issues. The focused laboratory-scale testingserved as an efficient way to generate key data, understand the effectiveness of potentialtreatment approaches, and develop design criteria for potential project implementation. Includes 3 references, table, figures.

Product Details

Edition:

Vol. - No.

Published:

11/01/2007

Number of Pages:

14

File Size:

1 file , 810 KB