Chloramination and corrosion: Case studies, utility experience, and statistical comparisons with chlorinatio

The United States Environmental Protection Agency (EPA) began implementing the Stage 2 Disinfectant By-products (DBP) Rule (Stage 2) in 2012. The purpose of this regulation is to protect water utility customers from potentially harmful DBP's, most importantly, total trihalomethanes (TTHM) and haloacetic acids (HAA). DBP's have been directly linked to health problems, especially bladder cancer. Regulated DBP's are formed by the chemical reaction of chlorine and naturally occurring organic matter. Chloramines do not produce TTHM's and HAA's and water utilities have used chloramines in place of chlorine in an attempt to meet Stage 2 rules. However, a possible problem of introducing chloramines to a distribution system is a potential increase of metal residuals, particularly lead. Any process or chemical that increases lead corrosion could raise lead concentrations in drinking water supplies leading to health concerns.;The following dissertation examines iron and lead corrosion data collected from a study performed for the Birmingham Water Works Board (BWWB); Birmingham, Alabama. The study was conducted to determine if the BWWB could switch their primary disinfectant from chlorine to chloramines, in an effort to combat DBP's, without contamination of drinking water from increased lead and iron residuals. Statistical comparisons are made between chloraminated and chlorinated drinking water collected from a flow-through rack constructed by the BWWB. This rack was comprised of lead pipes, cast iron pipes, and brass fixtures. Statistical analyses are performed on the data to compare and contrast corrosion potential of chlorinated and chloraminated drinking water treated with corrosion inhibitors.;The results of this study showed that chloramines, coupled with an orthophosphate based corrosion inhibitor did not increase metal residuals in cast iron pipes, lead pipes, and brass fixtures. Prolonged use of orthophosphates in the flow-through resulted in the continued drop of lead and cast iron residuals. However, one of the most important findings of this study was that corrosion inhibitors, which contain polyphosphates, do not reduce but actually increase water corrosivity in lead bearing features. Utilities with distribution systems that contain any lead bearing features run great risks for high lead residuals when using polyphosphates or polyphosphate blends for corrosion control.