Thomas Groundwater Treatment Facility
The city of Scottsdale is constructing a new Reverse Osmosis water treatment facility, the Thomas Groundwater Treatment Facility (TGTF), on Thomas Road adjacent to the existing Central Groundwater Treatment Facility (CGTF) at Pima Park. In addition to the new treatment plant, the CGTF will be undergoing operational improvements that will include the construction of a new building within the walls of the existing plant.
About the CGTF
The CGTF treats water pumped from groundwater aquifers in south Scottsdale that contain Trichloroethylene (TCE). The aquifers collectively make up the EPA-designated Superfund site North Indian Bend Wash.
Through airstripping technology, the CGTF removes the TCE from the groundwater to provide both a clean-up remedy for the aquifers and to allow the water to be used for the Scottsdale community. The facility removes TCE from the water to a level that is considered non-detect (less than 0.5 parts per billion), and is far below the EPA standard of 5 parts per billion.
The current operational improvements are not related to the superfund cleanup. Additional information is available on our North Indian Bend Wash Cleanup webpage.
Why is the new plant – the TGTF – necessary?
The CGTF treats water from four different wells in south Scottsdale, each of which presents a different water quality challenge. To meet Scottsdale’s high water quality standards, the treated water from the various sources must currently be blended together through a complex, operationally challenging blending scheme.
The TGTF will receive and treat a side stream of product water discharged from the CGTF. The treated side stream will then be blended with the remaining CGTF product water to achieve the desired finished water quality and eliminate the need for multiple blending plans.
Operational improvements to the CGTF
The Reverse Osmosis system that will be installed at the new TGTF will require a pH balancing of the water from the CGTF. To produce the required water quality, the CGTF will be undergoing operational improvements to reduce the pH. While the TGTF will not be online until 2019, the improvements to the CGTF will be in place by spring of 2017.
Reduced Water Hardness
The chemistry of the raw water treated at the CGTF – like most of the source water in the southwest – is characterized as very hard. This natural hardness, combined with the airstripping process, has resulted in scale formation within the CGTF and in the distribution system, which has created an ongoing operation and maintenance challenge and has been an ongoing customer concern. The TGTF and operational improvements to the CGTF will have the added benefit of reducing hardness in the finished water.
While the existing scale will remain in place, the operational improvements to the CGTF will greatly reduce the formation of additional scaling and significantly reduce future operation and maintenance costs for meter and service line replacement. Customers will also see a decrease in the hardness of their water and a reduction of future scaling.
What to expect of your water
The city is doing extensive testing and modeling of both the operational improvements to the CGTF and the new system that will be installed at the TGTF to ensure that there are no adverse impacts. Customers should expect to see a reduction in scaling and water hardness once the improvements are completed at the CGTF.
There is a chance that water cloudiness and temporary discoloration could occur when the new system comes online. If this occurs, it will be due to a temporary peeling off of existing scale in the distribution system or the home or business’s internal plumbing. It is important to note that scale is purely aesthetic. It is composed primarily of magnesium and calcium and does not present a health hazard.
If you experience cloudy or discolored water, flush the system for several minutes until the water returns to normal appearance. You can report the water cloudiness or discoloration to the project hotline at 480-657-7900.
General project questions
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