Correlation Of Elector-Noise To Iron, Copper And Lead Release In A Changing Distribution System Water Quality Environment With And Without Inhibitors

Abstract

This one year study focuses on the capability of corrosion inhibitors to mitigate the adverse effects of changing water quality in distribution systems that receive blended finished waters produced from ground, surface and saline sources. The inhibitors are Orthophosphate (OP), Blended ortho and polyphosphate (BOP), Zinc Orthophosphate (ZOP) and Silicate (Si). Data is collected from a large field facility, which includes 14 pilot distribution systems (PDS), 14 copper Corrosion Loops that contain one each Pb/Sn coupon, 14 Cradles that contain metal coupons that are used for chemical and biofilm studies, and 14 Nadles that are used to collect Electro-Noise (EN) data from Fe, Cu and Pb/Sn electrodes. The pipes used to construct the PDSs were taken from actual distribution systems. The samples collected from the PDSs, Corrosion Loops, Cradles and Nadles are paired by time and water quality. Metal release models using EN parameters are presented. The study began in February 2006 and data through October 17 2006 was used for model development. Corrosion monitoring is conducted by Linear Polarization, Electrochemical Impedance Spectroscopy and Electrochemical Noise techniques. The current data indicates that iron release correlates with localized corrosion (pitting) while copper release correlates with general corrosion. Inhibitors ranked by increasing effectiveness for reducing copper release are pH elevation, Si, ZOP, OP and BOP. © 2007 ASCE