The Providence Water Supply Board's Water Purification Plant in Scituate, Rhode Island provides water
to more than half the population of the state of Rhode Island. Clarification is provided by two
very large uncovered sedimentation basins. The plant's North and South Sedimentation
Basins, with a combined capacity of 161 million gallons, provide several treatment and supply
functions. They are used to remove suspended particulate matter, to achieve adequate
chlorine contact time during winter months to comply with the Surface Water Treatment Rule
(SWTR) CT requirements for Giardia inactivation, and for flow balancing and meeting
variable water demand. MWH conducted an evaluation of the existing sedimentation
treatment process to determine whether future capital improvements should include concrete
repair of existing facilities or more extensive upgrades or modifications to achieve other
treatment benefits. The existing sedimentation basins were found to provide sufficient
sedimentation prior to filtration and result in stable and excellent finished water quality.
Thus, improvements to the basins focused on reducing short-circuiting and minimizing
recirculation zones particularly because the South Sedimentation Basin is chlorinated in the
winter months to meet SWTR CT requirements for Giardia disinfection. Flow Science
developed a three-dimensional computer model of the basins using Computational Fluid
Dynamic (CFD) modeling. The model considered the intricate basin geometries and predicted
the detailed flow and velocity distribution in the basins. The modeling results were used to
evaluate both the existing configuration and flow conditions as well as prospective design
changes that would: reduce short-circuiting by rerouting the flow into portions of the basins
that were previously dead water zones; and, create a more uniform flow pattern to improve
settling performance. Recommended improvements include installing additional baffles to the
sedimentation basins to modify the existing flow path and achieve more uniform flow
velocities.
Includes 2 references, tables, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 640 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 15 |
| Published : | 11/01/2002 |
