Using a Mobile Pilot Plant to Evaluate Need and Protocol for a Previously Failed Coagulant Changeover

Shades Mountain Filter Plant (SMFP), a traditional drinking water filter plant, needed treatment optimization testing performed by the Birmingham Water Works Board (BWWB) mobile pilot plant to indentify ways of further reducing Total Trihalomethane (TTHM) and Haloacetic Acids (HAA) precursors beyond current results with the use of Aluminum Sulfate (Alum) as a primary coagulant. TTHM and HAA's are a byproduct of the reaction between Chlorine disinfection and organics present in the water. Focus on reducing TTHM and HAA formation potential centered on removal of Disinfection By-Product (DBP) precursors in the form of Total Organic Carbon (TOC) with a target TOC level less than 2.0mg/l. The use of Ferric Sulfate (Ferric) had been investigated and attempted previously at SMFP but poor filter performance one week into the initial changeover required the reinstatement of Alum. The pilot plant identified that Ferric would be the best performing coagulant for treatment optimization at SMFP and also determined that the previous attempt of Alum to Ferric changeover failed most likely due to simultaneous implementation of a new polymer and removal of chlorine at the rapid mix. Results of pilot plant testing for the change to ferric resulted in recommending keeping all treatment conditions the same but change only the primary coagulant no later than March/April due to system demand.