Water-poor coastal regions of the world are turning increasingly to desalination
of seawater for supply. Tampa, Florida has a plant under construction and
San Diego, CA is considering one. In addition, the State of Texas is
evaluating a large-scale desalination demonstration project for several sites
along its Gulf Coast. While much of this desalination relies on membrane
process sites where electrical power is generated using steam are uniquely
suited to distillation processes.
The Water and Power Authority of the USVI (WAPA) has operated
hypobaric distillation desalination plants on the three major islands for over
10 years. The two major plants each provide potable water for populations
of about 50,000 persons. In the last two years one of the islands experienced
a sudden increase in TTHMs at the long-residence-time site (LRT). This
increase was roughly concomitant with changes in passivation for corrosion
control in the distribution system and a number of other changes, including
several in disinfection practices. Unlike most THMs in most systems, those
in the WAPA system were between 50% and 70% bromoform, with up to
90% brominated species.
Efforts of the Authority to address the problem are reviewed in this paper and the possible
contribution of electrolytic generation of mixed-oxidant disinfectants
is discussed, along with a review of the possibility of passivation chemical
addition contributing to the problem. A factor most likely to affect isolated
systems subject to severe interruptions in production, such as can
result from hurricane damage, is the large amount of finished water storage
required against such interruptions.
It was found that several factors contributed to the problem, including
automatic disinfectant rate control, operation of storage facilities, instantaneous
water supply demand changes and possibly application of mixedoxidants
generated on-site. For each contributing factor the corrective actions
taken by the Authority and their results are presented. At this point,
only a single, under-utilized part of the system does not comply with DBPR
Stage 2 requirements and proposed corrective action for this area is also
presented. [Pontius(1999)] Includes 13 references, tables, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 300 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 13 |
| Published : | 11/02/2003 |
