Control of Distribution System Water Quality in a Changing Water Quality Environment Using Inhibitors
Project Proposal Abstract

This document is a tailored collaboration proposal for evaluating control opportunities for distribution system water quality in a changing water quality environment using inhibitors. Tampa Bay Water (TBW), and its member governments of Pinellas, Hillsborough and Pasco Counties and the Cities of New Port Richey, St. Petersburg, and Tampa, are the participating utilities in this proposal. TBW provides wholesale drinking water to these member governments. J. S. Taylor will be the principal investigator (PI), J. D. Dietz and A. A. Randall will be Co-PIs from UCF. Chris Owen, Water Quality Assurance Officer for Tampa Bay Water (TBW) Operations, will be the TBW and MG project coordinator. The total budget for this project is $1,668,548. The project will require two years to complete. Periodic reports will be published every four months.

This TCP will determine the capabilities of corrosion inhibitors to offset the adverse effects of changing finished water quality on distribution system water quality. Previous work funded by a recently completed TCP has shown adverse effects of variable finished water quality on distribution system water quality (a) including release of apparent color, total iron and turbidity, (b) copper corrosion in excess of the LCR action level in high alkalinity environments, (c) nitrification resulting from residual loss and available ammonia and (d) biologically unstable conditions in unlined pipe and high AOC environments. Degradation in quality was caused by film exposure to varying water quality including alkalinity and temperature. This project will investigate using inhibitors to maintain a constant surface film in a varying water quality environment to offset adverse water quality effects. This research will be conducted in an existing facility that was constructed for a previous AwwaRF TCP and has eighteen 80' pilot distribution systems (PDSs) built from actual MG PVC, lined cement, cast iron and galvanized MG distribution system pipe in a 8500 square-ft roofed research facility. Three different doses of orthophosphate, zinc orthophosphate, blended ortho-polyphosphate and silicate inhibitors will be added to finished ground, surface, desalinated and a blend of the three TBW finished waters, which will be input to existing PDSs over a three month period. PDS input water quality will be changed every three months for one year. Inhibitor and inhibitor dose will be held constant. Water quality parameters necessary to evaluation release of apparent color, turbidity, total iron, biological stability of biofilms and bulk water, Cu-Fe-Pb corrosion, residual maintenance and nitrification will be monitored for one year. The capability of corrosion inhibitors to control distribution system water quality and stabilize chemical and biological films in a changing water quality environment will be evaluated by process, pipe material, bulk water quality and season.