Meeting New Demands: Treating Urban Runoff
Abstract:Dry weather runoff from urban creeks is a typical source of bacteria in coastal California. Beyond the Golden State, bacterial contamination of oceans, lakes and streams concerns many municipalities as well as they strive to reach increasingly stringent urban runoff and stormwater regulatory requirements. An innovative solution—ozone treatment for urban runoff—applied at two California beaches may inspire communities nationwide.
Just a few years ago, the popular Salt Creek and South Monarch Beaches in South Orange County, California were subject to public health postings when bacteria there exceeded State and Federal Beach Act standards. The source of the bacteria was Salt Creek, an urbanized creek that drains significant portions of the Cities of Dana Point and Laguna Niguel and discharges at the beaches. The creek conveyed a typical mix of urban pollutants including fertilizers, animal waste and detergents as it wound its way through primarily residential zones plus recreation spaces and light commercial uses.
The Salt Creek Urban Runoff Treatment Facility (URTF), an ozone treatment facility, was designed and constructed to bring the beaches into compliance with state and federal water quality standards. In spite of the challenge of treating low, dry season flow rates with a high variability of pollutant loading, the Salt Creek URTF has yielded excellent results since it began operation in October 2005. The project has received numerous awards including:
Public Works Project of the Year for 2006 awarded by the American Public Works Association (APWA)
An Honor Award in the 2006 Consulting Engineers and Land Surveyors of California (CELSOC) Engineering Excellence Award competition
A 2006 National Recognition Award 2006 from the American Council of Engineering Companies (ACEC)
A 2006 Project Achievement Award from the Orange County Section of the American Society of Civil Engineers (ASCE).
To further improve the water quality at Salt Creek, a second phase is under consideration. After additional treatment to remove salts and suspended solids, treated water from the facility may be recycled to irrigate a nearby golf course and other landscaped areas.
This paper will describe the ozone treatment system and components utilized at the Salt Creek URTF. Operating data as well as challenges and solutions for operating the URTF, with no similar facilities to pave a path, will be presented. In particular, designs for maximum operating flexibility and the use of automated systems will be presented. Facility start up challenges and solutions will be discussed as well.
An overview of the selection of ozone disinfection, versus UV light, will be provided. Design and permitting challenges successfully met, in particular, blending the new treatment building in a coastal resort setting, will be recounted. The status of plans to further treat water discharged from the URTF for irrigation will be presented along with costs/payback evaluations, permitting and regulatory challenges and solutions.
Disinfecting urban runoff is still relatively uncommon but is gaining interest as municipalities and districts nationwide work to meet increasingly demanding urban runoff regulatory requirements. The process used to design, construct and operate the Salt Creek URTF is adaptable to many communities concerned with the public health, environmental, financial and regulatory impacts of bacteria in dry weather urban runoff.
Of importance to communities just beginning to face more stringent water quality standards, the authors will provide a guide to selecting the best sites for investments in treatment facilities. A “blueprint for project success,” including team building, design, siting and construction considerations, plus means of leveraging public support through public education and research opportunities will be provided as well.
Document Type: Research Article
Publication date: January 1, 2006
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