AWWA MTC69693

The Town of Smyrna, Tennessee Water Treatment Plant experienced several challenges associated with treating water from the J. Percy Priest Reservoir, including extended periods of diminished water quality during seasonal turnovers in the lake. During these turnovers, elevated levels of hydrogen sulfide, carbon dioxide, iron and especially manganese have proven problematic for the plant operators. There have been additional complaints about the elevated hardness and algae levels inherent in the reservoir. In addition to these issues, the plant faces more stringent regulations associated with the Microbial/ Disinfection Byproduct Rules (M/DBP). In order to provide an effective and reliable means of alleviating the current issues experienced at the plant and meet the new drinking water standards, the Town considered adding lime softening and microfiltration to the treatment plant unit processes. A pilot scale treatability study was performed between July 30 and October 12, 2007 to demonstrate the ability of these unit processes to improve water quality for the town. The results of the treatability study indicate that lime softening and microfiltration can provide improved removal of iron, manganese, hardness and turbidity over the existing unit processes at the water treatment plant. The testing also demonstrated that the proposed unit processes could sustain treatment for these contaminants for extended periods of time during mechanical failures, unlike the current process. Finally, the testing indicated that decant from a solids holding pond could be returned to the treatment process for reclamation, improving the water usage efficiency of the plant to levels in excess of 99%. Includes tables, figures.