AWWA JAW59057

The principal cause of colored water is iron releasefrom corroded iron and steel pipes. In thisresearch, a pilot pipe-loop system was constructedfrom 100-year-old unlined cast-iron pipes taken fromthe Massachusetts Water Resources Authority inBoston. The authors then evaluated the role played bywater quality factors - pH, alkalinity, and orthophosphates- in controlling iron release.Results from the experiments showed that ironrelease was closely linked to turbidity, with turbiditydirectly proportional to iron concentration. Iron releasewas also found to be particularly sensitive to changes inalkalinity. In the pH range of 7.6 to 9.5, higher alkalinities(i.e., in the 10-60 mg/L as calcium carbonaterange) were associated with lower levels of iron release.Overall, maintaining a stable water quality with constantpH and alkalinity proved the most importantfactors for reducing iron release.The water industry has often based its controlstrategies for iron release on information from corrosionin new iron pipes. However, older corroded ironpipes respond much differently to changes in waterquality parameters, and corrosion scale chemistry andstructure can dictate the iron release response in corrodedpipes. By focusing on the old, unlined pipesprevalent in many distribution systems, this articleprovides new insight into the causes of iron release andthe treatment options to control it. Includes 31 references, tables, figures.

Product Details

Edition:

Vol. 95 - No. 11

Published:

11/01/2003

Number of Pages:

12

File Size:

1 file , 320 KB