Malcolm Pirnie has been involved in conducting several pipe loop studies to understand
the impacts of distribution system water quality on red water occurrences. The pipes
were retrieved from several areas of the distribution system from cities in Texas and
Arizona. The retrieved pipes were of different diameter and different types of materials
found in the distribution system. Care was taken to retrieve pipes with varying levels
of internal corrosion. Pipe segments with different degrees of internal corrosion were
coupled to form loops. The arrangement of various pipe segments is referred as "pipeloops".
Pipe loops were exposed to simulated distribution system water qualities. The extent of
of corrosion was measured by measuring changes (increase or decrease) in concentration
of corrosion byproducts (Fe, Zn, Ca) and water quality parameters (pH, alkalinity,
turbidity, dissolved oxygen).
Performance of corrosion inhibitors (polyp and orthophosphates, sodium silicate, and
stannous chloride) were evaluated as a part of red water control strategies. Corrosion
inhibitors interact with pipe scale and form a surface complex or a passive layer on the
pipe scale surface. Spectroscopic analysis was performed to understand the pipe scale
composition. Multiple phases of iron oxide/hydroxides were present in the pipe scale.
Composition of pipe scale is related to its potential to release the corrosion byproducts.
Based on findings from the study conducted in Arizona and Texas, recommendations
were developed inline with maintaining finished water quality goals at the treatment
plants, exploring the possibility of adding a corrosion inhibitor at the treatment plant,
managing flow velocities, pressure zones and, exploring the possibilities of long term
changes in treatment strategies to increase the chemical stability of finished water. Includes figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 180 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 6 |
| Published : | 11/01/2007 |
