(56c) Evaluating Changing the Primary Coagulant for a Drinking Water Filter Plant through the Use of a Mobile Pilot Plant and Determining the Correct Changeover Protocol

Pilot testing of Ferric Sulfate as a primary coagulant in the Birmingham Water Works Board's mobile pilot plant demonstrated significant improvement in all regulated EPA and stated drinking water parameters over the existing primary coagulant Aluminum Sulfate. After two years of plant optimization testing with a newly acquired state-of-the-art mobile Pilot Plant, Shades Mountain Filter Plant finally switched its primary coagulant from Aluminum Sulfate to Ferric Sulfate in March of 2009. The initial significance of this, was that this changeover was attempted in 2001 but resulted in poor filter performance leaving only 10 of the 52 filters in service three days after the initial changeover. The acquisition of the pilot plant facility allowed engineers and plant staff to evaluate the coagulant changeover process with great detail by using existing filter media from the Shades Mountain Filter Plant filters in the filter skids of the pilot plant. During this evaluation of the coagulant changeover a total of 6 filters (3 on each treatment skid) were used. Each skid contained 2 filters with existing media from SMFP (15? sand / 15? anthracite), and one filter on each skid was comprised of new media in the same configuration. The plan was to match existing performance through both treatment skids with alum and then change only the coagulant to Ferric on one skid. This allowed a direct comparison of Alum to Ferric accounting for any source water variations. Filter performance was monitored with headloss, runtimes, turbidity, metals residuals, TOC, pH, Disinfection By-Products formation (as regulated by the EPA Stage II regulations), and chlorine residuals. . From this testing a protocol was established for the changeover which took place without incident in March of 2009. The use of the pilot plant had initially established Ferric Sulfate dose ranges for various times of year and optimum coagulation and filter pH's. An evaluation of the accuracy of the dose ranges has been studied at the six month mark and in March of 2010 a 1 year evaluation will be conducted as well. Along with the dose evaluations; a cost analysis for the 6 month and 1 year evaluations have been and will be conducted.