AWWA WQTC50373

Cincinnati Water Works (CWW) performed a plant audit in association with Montgomery Watson Engineering at the Richard Miller Treatment Plant (RMTP). The audit concluded that changes to the current water treatment practices may be warranted to achieve compliance with pathogen removal/inactivation dictated by the Long Term Enhanced Surface Water Treatment Rule (LTESWTR). Proactive operational changes and modification of unit treatment processes were suggested. The audit also concluded that prior to the start of a full-scale demonstration study improvements to the current coagulant mix system needed to be made to show that the lamella/reservoir system is capable of providing the required levels of treatment at a rate of 220 MGD. Therefore, a new full-scale, flash mix system was installed to improve chemical mixing of both the alum and polymer feed system. Six in-line pump-diffusion mixers were installed. The first three of these mixers, which operate in parallel are dedicated to the mixing of alum. The other three mixers, which also operate in parallel, are dedicated to the mixing of polymer and are located approximately 1 minute (in terms of hydraulic detention time) downstream of the alum mixers. Impact to plant performance was evaluated before and after installation, and a pay back period was calculated. This paper summarizes a twelve-month full-scale high rate clarification demonstration study and an evaluation of new coagulant flash mixers. Includes 4 references, tables, figures.