Over the years the Riverside Drive Water Treatment Plant in Gainesville, Ga., had been facing an increasingly difficult situation: trying to meet burgeoning water demand with a plant built in 1953. The plant was originally designed to produce 4 mgd and had grown to the point where it was producing 25 mgd in 1999.
Plant Superintendent Don Hall explained, ?With annual growth rates of 5 percent, we needed to boost water production with the least possible disruption to our operations. We were running at full capacity and looking for a quick but cost-effective solution.?
Plant officials commissioned a pilot study with Jordan, Jones and Goulding Inc. that called for increasing filter runs to 6 gpm/ft.2 on each of the six dual-bay filters. The filters had operated at 5 gpm/ft.2. The plan to increase flow was complicated by the original filter design. The old filters consisted of 12 inches of sand, 18 inches of anthracite coal, and 12 inches of gravel with concrete Wheeler bottoms. To cost-effectively achieve the new goals, the plant needed longer filter runs that in turn required deeper filter beds.
Working closely with Design Engineer Marshall Williams of JJ&G, Leopold determined its low-profile Type SL Underdrain with IMS Cap would be most effective in the Riverside Drive WTP situation.
Leopold and JJ&G needed to consider several factors as they implemented the new system. First, Georgia state regulations do not permit pipe penetration of media. To avoid this problem, JJ&G engineers designed an air header piping arrangement for the existing center flume located in a recessed concrete trough below the filter bed. The air feed piping was encased in the concrete floor to avoid penetrating the media. They also increased the media bed depth to 10 inches of sand and 27 inches of anthracite coal, and the media size to 0.65mm sand and 1.50mm anthracite. The new system required a combination air/water backwash to accommodate the larger, deeper media bed.
Timing was another important consideration. Since peak demand starts in the springtime, JJ&G started the project in the autumn along with Cajun Constructors, the project contractor. Although the first filter retrofit took 35 days, the next filters took only 151/2 days each. The total rehabilitation occurred without disruption to plant production.
Don Hall expressed his satisfaction with the project. ?Leopold was very conscientious throughout the entire process. First, they took the time to fully understand our situation, our goals, and our challenges, and explore the various options. Also important, they established a good working relationship with our contractor to ensure there was continuity between the design stages and actual installation.?
Today, the Riverside Water Treatment Plant is producing better water quality for its customers without a costly capital expenditure while adhering to state regulations prohibiting media penetration with air header piping.
About the Author: Thomas M. Getting is filtration product manager for the F.B. Leopold Company. He has over 25 years of experience in the design and startup of water and wastewater facilities. He holds a bachelor of science degree from the University of Pittsburgh.
