Scott Ahlstrom, P.E., with BW Primoris, discusses the water supply and treatment system that uses brackish groundwater in Seminole.

1. BW Primoris
(Gaines County Water Company)
Water Supply and Treatment System
Seminole, TX

2. Primoris Services Corporation
3/22/2016
• Provides construction, fabrication, maintenance, and product
engineering services for public utilities, energy companies,
municipalities, and others.
• Publicly traded – PRIM
• $2 billion/year of revenues
• BW Primoris is the PSC subsidiary that partners with
municipal and industrial customers, addressing their water
needs by providing services to advance their water projects
• Definition and development
• Construction
• Financing and ownership
• Operations
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3. Seminole, TX Project
Services provided:
• Increase water supply; reduce TDS, As, and F in drinking water
Infrastructure installed to date:
• Design, build, own, and operate three reverse osmosis plants
• Design, build, own, and City operates 2 new wells
Status:
• Full operations started January 1, 2016
Service Commitment:
• 40 years
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4. Seminole Water Supply System
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5. Osmosis
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A solution that is less
concentrated has a
natural tendency to
migrate to a solution
with a higher
concentration, thus
weakening it.

6. Reverse Osmosis (RO)
3/22/2016 6
In RO, pressure is
applied to cause
water to move the
other direction.

7. 3/22/2016 7From ESP Water Products

8. 8
Reverse Osmosis Plant Tour
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3/22/2016

9. 9
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3/22/2016

10. Challenges affecting the system
3/22/2016
• Silt Density Index (SDI)
• The silt density index is a measure for the fouling capacity of water in
reverse osmosis systems.
• The guideline is to maintain SDI at less than or equal to 5.
• Multi-media filtration followed by microfiltration is provided to help
keep the SDI below 5. SDI is measured daily.
• Silica (silicon dioxide or SiO2)
• A hard, glassy mineral substance which occurs in a variety of forms
such as sand, quartz, sandstone, and granite.
• As water moves through soil and rock, silica is picked up by the water.
• Silica can readily foul RO membranes. It can also collect in the RO
concentrate stream and exceed saturation.
• Preventative measures
• pH adjustment
• Anti-scalant
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11. 11
New Groundwater Wells
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3/22/2016

12. Improvements to System
3/22/2016
• RO concentrate management alternatives
• Arsenic removal via filtration without RO
• Additional raw water supply
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13. For more information . . .
3/22/2016
Scott Ahlstrom
BW Primoris
2100 McKinney Ave, Suite 1500
Dallas, TX 75201
214-740-5614
sahlstrom@prim.com
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