Running six vertical turbine pumps providing a total head of 100 feet, Gwinnett County (Ga.) Public Utilitys Lanier Filter Treatment Facility (FTF) approached its 22nd operating year with no accommodations for future growth. Gwinnett County expects a population increase from a 1995 level of 456,104 to around 546,565 by 2005.
In 1995, average daily use amounted to 66.95 mgd. Projections estimated the average daily usage to increase to 106.83 mgd by 2015. In 1996, to support growing water demands, Gwinnett County recognized the need to retrofit the high-service pumping facility at Lanier FTF.
A modeling test revealed three zones of pressure distribution within the county consisting of the northern, central and southern zones. The largest area, the central zone, also fed water to the southern area. The study recommended four pumps with 120-foot heads for the combined central and southern zones. The more elevated northern zone required three pumps able to handle 150 foot heads. Utility consultants recommended switching to low rpm, variable speed, horizontal split-case pumps to increase head and capacity, ensuring more efficient operation, mechanical dependability, low-cost maintenance and growth potential.
Of the several horizontal split-case pumps Gwinnett County reviewed, Patterson Pump Companys specifications more closely matched Lanier FTFs precise needs. Gwinnett County selected four 36x30 MAA pumps (35,415 GPM and 129 foot TDH), and three 20x18 MABS pumps (10,070 GPM and 159 foot TDH) for the Lanier Filter Treatment Facility.
Pattersons horizontal split-case pumps are designed to move clear water or low-viscosity, clear liquids at moderate heads. The pumps simple design extends service life, reduces maintenance costs, and minimizes power consumption. Patterson completed the retrofit installation in July 1997.
"Retrofitting our facility with the Patterson pumps was much easier than expected. There were no complications at all during installation. And, their variable speed has managed pressure exactly as we want it, during peak times and slow, middle-of-the-night periods. Our economy of operation was increased over the fixed speed pumps," said Reza Baniassad, Lanier Filter Treatment Facility Maintenance Superintendent.
Neal Spivey, Director of Water Production, said he is especially pleased with the current 150 mgd capacity of the facility. "It allows us to serve our 153,000 plus customers more efficiently, and gives Lanier assurance that we will meet our ... growth requirements well into the future," Spivey said.
