AWWA ACE62986

DeKalb County, Georgia, is responsible for potable water treatment and distribution for nearly700,000 citizens of the metro Atlanta region. Due to continued growth in the region, the countydecided to build a new potable water treatment plant and decommission their existing facility builtin the 1940s. The new facility, designed to be constructed on adjacent property to allow continueduse of existing clearwells and high-service pumping stations, is designed to be initially permittedat 150 million gallons per day (mgd). However, it is designed to operate at a hydraulic capacity of200 mgd, with an additional 30 mgd of redundant capacity.The new plant was designed to use advanced treatment technologies to achieve current and futureregulatory requirements and meet high standards for reliability and risk based redundancy. Thetreatment process for the new facility includes pre-ozonation, high-rate clarification with platesettlers, intermediate ozonation for microbial control and DBP precursor reduction followed bydeep-bed GAC biofilters, and finished water chemical application. To minimize water loss, theplant is designed to operate as a zero discharge facility with all filter backwash and solids streamsbeing equalized and clarified and ultimately being recycled. Key recycle streams are treatedthrough an ultraviolet disinfection system. Solids from the facility are treated at a new dewateringbuilding that houses centrifuges and sludge pumping equipment. Innovative approaches in design and construction, such as shared wallconstruction and utilizing an onsite concrete batching plant to supply more than 120,000 cubicyards of concrete, resulted in final construction costs for this facility of $1.02 /gal of capacity (thatincludes an additional 25% redundant capacity).Locating the new facility adjacent to the existing facility allowed for county operations andmaintenance staff to observe and participate in the construction of their facility, and provided theadvantage of being able to recycle water to the raw water reservoirs during startup phase withouthaving to send water to the distribution system. Transition from the existing plant to the newfacility included challenges associated with loss of key County staff due to retirement, schedulechallenges, and developing a transition plan to transfer operations from the existing facility to thenew plant.This paper presents the unique challenges in design, construction, and startup of the southeast'slargest and most advanced surface water treatment plant. Includes table, figures.

Product Details

Edition:

Vol. - No.

Published:

06/01/2006

Number of Pages:

15

File Size:

1 file , 3.3 MB