Reducing pipe corrosion during implementation of disinfectant by-products (DBPs) control practices

Corrosion is a serious problem affecting water utilities. Surveys distributed by AWWA showed that cast iron pipe corrosion was the leading problem for water utilities. There have been many speculations surrounding the use of orthophosphate with chloramines. Many utilities have switched from chlorine to chloramines in order to comply with Stage I of the Disinfectant By-Product (DBP) Rule.; The results of the Phase I of the DBPs Control Implementation Plan helped verify which corrosion inhibitor was best in controlling the rate of corrosion in the pipes, helped provide useful methodology, and identified transferable results to other supply systems. The study used a pipe loop to examine the effectiveness of corrosion control practices on 11 different water chemistry variations for two Birmingham Water Works Sewer Board (BWWSB) source waters, Carson Filter Plant (CFP) and Western Filter Plant (WFP). Each filter plant contained 11 different tanks with variations in disinfectant, inhibitor, and pH use. The project consisted of two periods, a baseline period to stabilize the pipes and a testing period. There were 29 parameters tested in both the field and the laboratory.; The data were analyzed using Systat Version 10 software and Microsoft Excel. Analysis of variance (ANOVA) and t-tests were among the many analyses used.; The results indicated that tanks given only chlorine with no inhibitor at a pH of 9.5 s.u. had some of the highest concentrations of metals at the end of the testing period. The tank with chlorine and no inhibitor addition at a pH of 8.5 s.u. proved to be the best condition for lowering metals in the system, especially lead and copper.; Results from CFP and WFP were not significantly different for lead, copper, nitrate, total iron, manganese, orthophosphate, total phosphate, dissolved oxygen (DO), and total chlorine. Results for these parameters seemed to be independent of supply water chemistry and may be applicable to other water utilities.; Results from the two filter plants were significantly different for majority of the parameters. Results from these parameters are closely linked to supply water chemistry and are not transferable to other water utilities without further investigation.