The principal cause of colored water is iron release
from corroded iron and steel pipes. In this
research, a pilot pipe-loop system was constructed
from 100-year-old unlined cast-iron pipes taken from
the Massachusetts Water Resources Authority in
Boston. The authors then evaluated the role played by
water quality factors - pH, alkalinity, and orthophosphates
- in controlling iron release.
Results from the experiments showed that iron
release was closely linked to turbidity, with turbidity
directly proportional to iron concentration. Iron release
was also found to be particularly sensitive to changes in
alkalinity. In the pH range of 7.6 to 9.5, higher alkalinities
(i.e., in the 10-60 mg/L as calcium carbonate
range) were associated with lower levels of iron release.
Overall, maintaining a stable water quality with constant
pH and alkalinity proved the most important
factors for reducing iron release.
The water industry has often based its control
strategies for iron release on information from corrosion
in new iron pipes. However, older corroded iron
pipes respond much differently to changes in water
quality parameters, and corrosion scale chemistry and
structure can dictate the iron release response in corroded
pipes. By focusing on the old, unlined pipes
prevalent in many distribution systems, this article
provides new insight into the causes of iron release and
the treatment options to control it. Includes 31 references, tables, figures.
| Edition : | Vol. 95 - No. 11 |
| File Size : | 1
file
, 320 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 12 |
| Published : | 11/01/2003 |
