Full Description

A pipe loop system comprised of new ductile iron and lead pipes was operated for 13 months toinvestigate the effects of corrosion inhibitors on lead release and bacterial regrowth. Four pipeloops were treated with a corrosion inhibitor (orthophosphate, polyphosphate,orthophosphate/polyphosphate blend, and SnClsub2/sub) and one served as an untreated control. The pipeloop system received treated surface water from a full-scale lime softening plant and wasmonitored for total lead, dissolved lead, heterotrophic plate count (HPC), and coliformconcentrations. Total lead concentrations in each of the treated loops were significantly lower(95% confidence level) than in the untreated control, and orthophosphate (1 mg/L as P)consistently yielded the lowest lead concentrations of all of the inhibitors tested. Nevertheless,none of the corrosion inhibitors was able to consistently maintain total lead concentrations belowthe 15 mg/L maximum contaminant level for the 8-hour stagnation time sample in the new leadpipes used for this study. In addition, all of the phosphate-containing chemicals caused HPCconcentrations to exceed those in the untreated control loop during the warm summer months,raising concerns about regrowth and the potential for increased coliform detections. Conversely,HPC levels in the SnClsub2/sub loop were significantly lower than in the control during the same period.The microbiological results suggest that water utilities need to exercise caution when addingcorrosion inhibitors, so that reduced corrosion is not achieved at the expense of other water qualityindicators. Includes 12 references, tables, figures.

Product Details

Edition: Vol. - No. Published: 11/02/2003 Number of Pages: 12File Size: 1 file , 590 KB