AWWA WQTC59028

The City of Wilmington's Brandywine Filtration Plant was originally built in the late 1800s. While upgrades have occurred over the years, the plant is in need of modernization to ensure a sustainable and reliable water treatment and delivery system. A study was undertaken to evaluate the existing treatment processes and condition of the plant infrastructure. Plant upgrade alternatives were then developed and evaluated based on their ability to increase reliable production capacity, while fully complying with all current regulations and providing flexibility to meet evolving future regulations. Results of the study indicated that an immersed ultrafiltration (UF) membrane process would be the most desirable alternative. The immersed UF system was compared to and selected over plate/tube settlers, dissolved air flotation, and Actiflo clarification because it could be located in the existing sedimentation basins in a historical treatment plant building and because of the enhanced pathogen removal offered by UF membranes. The UF process had the highest present worth capital and O&M costs of all the alternatives evaluated. The driving force behind the process selection, more than cost, was the the fact the process will not compromise pathogen removal if coagulation failure occurs, unlike the other alternatives and conventional treatment. Based on these results the City implemented a two-season pilot study to determine full-scale membrane operating conditions and design criteria. The pilot study was conducted for three months in the winter and two months in the summer to assess both cold water and warm water process performance of the membrane system. Membrane flux rates, chemical dosing of coagulant and acid, and recovery rates were varied to determine optimum operating conditions during both seasons. The UF system met all treated water quality goals of the piloting program, providing significant improvement in all areas when compared to the current plant. This report describes the piloting set-up and the results of the ultrafiltration membrane pilot study. The collaborative efforts of the city, engineer, and vendor made the program a success. The project is currently in the preliminary design phase and will include an immersed UF process sized to treat 20 million gallons per day (mgd). The plant will be the first municipal membrane plant in the state of Delaware and the largest operating enhanced coagulation membrane plant in the United States. Includes tables, figures.