Researchers at Purdue University have...
When potable water demands increased at the Ft. Stewart army base in Savannah, Ga., the U.S. Army Corps of Engineers enlisted WaterProfessionals to handle the design and installation of a complete potable water treatment system.
Due to the limited data that was available about the area’s underground aquifer at the time, the initial parameters for the system were 1,500 to 2,000 ppm TDS — well above the secondary EPA drinking water limit of 500 ppm — 20 to 25 ppm silica, 100 to 175 ppm alkalinity and 290 to 320 ppm sulfate.
To bring the system into compliance with EPA standards, the contractors initially decided to replace the old system with RO systems to treat 75% to 85% of the well water, which would then be blended with 15% to 25% untreated well water.
But once the well was drilled, the unanticipated hardness levels proved to be a challenge for the RO systems, resulting in TDS levels well above EPA standards. Also, minerals with low solubility, such as sulfates, precipitated and formed scale on the membranes. Scale minimization using chemical antiscalants resulted in frequent membrane cleanings and reduced membrane life.
WaterProfessionals' solution was to soften 50% of the raw water stream, while lowering hardness concentrations to a level that made antiscalants effective. A triplex system, utilizing three 84-in.-diameter softeners, each containing 120 cu ft of cation exchange resin and a brine silo, were delivered and installed. In order to treat the required 300-gal per minute (gpm) continuous and 600 gpm peak flow of RO water, and to allow for some redundancy for the potable water plant, two 300-gpm RO units were installed.
After working under severe time constraints — a pressing 12-week delivery deadline — and with a challenging raw water supply, WaterProfessionals provided a treatment system that created finished well water meeting EPA and state of Georgia standards.