Wang, LK, Wang, MHS, and Kolodziej, PJ (2022). Removal of Trihalomethane Precursors and Coliform Bacteria by Lenox Flotation-Filtration Plant. In: “Environmental Science, Technology, Engineering, and Mathematics (STEM)”, Wang, LK, Wang, MHS, and Pankivskyi, YI (editors). Volume 2022, Number 5, May 2022; pp.23. Lenox Institute Press, MA, USA. ………ABSTRACT: Lenox Water Treatment Plant in Lenox, MA, USA, consists of mainly dissolved air flotation, sand filtration and chlorination processes, and is the first potable water flotation plant built in America. Before installation of the plant, the total trihalomethane (THM) in Lenox tap water ranged from 19.7 to 88.5 ppb. After placement of the plant on-line, the total THM of Lenox tap water was reduced by more than 50%. Even before using any disinfectant, the innovative Lenox flotation-filtration system was extremely efficient for separation of 80-100% coliform bacteria from raw water. The plant’s post-chlorination was used as a final safe-guard for providing residual chlorine in the distribution system. The chlorine requirement was significantly reduced by 10-40 percent during normal operations. ………… KEYWORDS: Memoir, Lenox Institute of Water Technology, Krofta Engineering Corporation, Historical data, First potable water flotation filtration plant in America, Lenox Water Treatment Plant, Trihalomethane precursor removal, Coliform bacteria removal.