Case Study

The Project

The replacement central utility plant (CUP) proj-ect was a design-build project involving construc-tion of a new CUP to replace the existing CUP at Los Angeles International Airport (LAX). The pur-pose of the project was to accommodate the in-creased utility demand associated with improve-ments to the Tom Bradley International Terminal (TBIT). The replacement 75,000 square-foot CUP was constructed between the existing CUP and the existing Federal Aviation Administration (FAA) air traffi c control tower. Upon completion of the replacement CUP, the existing CUP was demolished and used for the site of the thermal energy storage (TES) tank.

The project also included construction of new cooling towers with a 20,000-ton cooling capaci-ty. Systems and their components were designed and constructed to achieve LEED® Silver certifi -cation. Design began in January 2011 and the new CUP is expected to be completed for sum-mer 2014.

Clark/McCarthy, A Joint Venture, was awarded the design-build contract to replace the airport’s central utility plant (CUP). Murray Company was the installing contractor and ARUP were the con-sulting engineers.

The Challenge

Water from cooling towers attracts and absorbs airborne contaminants on a continuous basis. Typically, 85% of suspended solids in chilled water and even hot water loops are smaller than 5 micron in size. Scientifi c studies* have shown that these small particles (5 microns and less) are the adherent contaminants that lead to fouling of heat exchangers and a reduction in effi ciency.

A reduction in fouling was a key consideration in the design of the cooling system for this project. Not only would signifi cant savings in energy be realized, but a reduction in submicron particles also inhibits biological activity by removing a source of sustenance for bacteria.

In order to properly asses fi ltration requirements, an LPA (Laser Particle Analysis) test was con-ducted on existing LAX cooling tower systems, CHW and HHW circuits. The fi ltration challenge was clear: 95% of all system water TSS were smaller than 5 microns.

Cooling Tower WaterSize

(microns)Total

Counts/ccCounts %

< 1 40,040 751-5 12,991 24

5-15 93 < 1

Closed Loop Chilled WaterSize

(microns)Total

Counts/ccCounts %

< 1 34,770 841-5 6,050 14

5-15 318 1

*Muller-Steinhagen, H. (1999) Cooling-Water Fouling in Heat Exchangers. Advances in heat trasnfer. 33, 415-496.

Closed Loop Heating Hot WaterSize

(microns)Total

Counts/ccCounts %

< 1 15,144 651-5 7,389 32

5-15 512 2

Vortisand reduces LAX Central Utility Plant operating costs seven-fold and will save over $300,000 in the fi rst year

By selecting a Vortisand® system to fi lter their cooling water system, LAX CUP was able to lower capital costs, lower operational costs and increase the effi ciency of their cooling towers and heat exchangers

Sonitec-Vortisand Inc. | www.sonitec.com | info@sonitec.com | 866-876-9655 | 514-335-2200

The fi ltration challenge was clear: 95% of all system water TSS were

smaller than 5 microns.

The Solution

When designing the fi ltration system for the cooling system, the designers had initially looked at a system that combined a traditional sand fi lter with sweeper piping (typical fi ltration effi ciency 20 micron). Additionally, in order to fi lter particles less than 5 micron in size, a disposeable cartridge fi lter system needed to be added.

J.D. Sales Co. representing Sonitec-Vortisand was invited by the contractor to bid on this project. It was immediately apparent that conventional sand fi lters could not achieve this level of fi ltration, the use of cartridge fi lters would require frequent replacement (with additional labour and disposal costs) and the size of the particles made conventional centrifugal separators ineffective. A simple Total Operating Costs (TOC) calculation was performed for the cooling towers (see table at right) which clearly demonstrated that the Vortisand system would cost 7 times less to operate than the alternative solution!

Sonitec-Vortisand Inc. | www.sonitec.com | info@sonitec.com | 866-876-9655 | 514-335-2200

Selection of Vortisand®

By taking the time to properly asses fi ltration needs and perform a thorough TOC calculation for the cooling tower side-stream fi ltration, it was clear that the Vortisand® cross-fl ow microsand technology would solve their fi ltration challenge. With an ROI of less than 2 years, 7 times lower total operating cost and a smaller footprint than alternative technologies, the Vortisand® cross-fl ow microsand fi lter proved to be the best side-stream fi ltration system for LAX CUP.

Water Savings: $32,985Energy Savings: $171,900Chemical Savings: $30,000

Media Replacement Savings : $66,240

Estimated 1 year operating cost savings by selecting a Vortisand® cross-fl ow microsand

fi ltration system:

$301,125*

Selected Alternative DesignVortisand® Sand fi lter with

basin sweeper piping Cartridge fi lter

Flowrate 4 x 700 gpm (5%) 4 x 2,100 gpm (15%) 3,000 gpm (5%)

Filtration effi ciency < 1 micron 20 micron 2 micron

Technology Cross-fl ow Microsand Filter with Automatic

Backwash

Traditional Sand Filter with Automatic Backwash and Basin

Sweeper Piping

Disposable Cartridge Filter

Backwash Flowrate 70 gpm (5) 1,000 gpm n/a

Backwash Volume 5,250 gallons/day (1,870,000 gallons/year)

$8,415/year (1)

25,200 gallons/day9,200,000 gal/yr

$41,400 (1)

n/a

Filter Pump 4 x 15 HP (45 kW) 4 x 60 HP (180 kW) 75 HP (56 kW)

Electrical Usage (Based on 6,000 hrs)

270,000 kWh$40,500 (4)

1,080,000 kWh$162,000 (4)

336,000 kWh$50,400 (4)

Additional Cost of Chemicals (use of CT water for BW)

n/a $30,000 (2) n/a

Catridge Replacement Frequency

n/a n/a 1/week min. (3)

Cost Per Replacement $10,000 for 5 years or $2,000/

year (media)

$10,000 / year (media)

160 cartridges @ $7 ea.

($1,120/week $58,240/year)

Media Disposal Cost Once every 5 years (10 tons / 5

years)

1 every year (10-12 tons/year)

Once a week (10 - 12 tons/year)

Storage Cost n/a n/a Not estimated

Total Operating Costs Per Year (estimated)* $50,915

$243,400 $108,490

$ 352,040 combined

*Results may vary according to application and location. This TOC Analysis based on:

(1) Cost of water $0.0045 cents/gal. (2) Estimated additional cost of chemicals due to additional make up water required. (3) Estimated replacement frequency based on 2 micron effi ciency and side-stream fl ow of 3,000 gpm. (4) Cost of electricity: $0.15/kWh, (5) Backwash fl owrate per tank. Specifi cation required peak fl ow to sewer of no more than 100 gpm.

Vortisand® cross-fl ow microsand fi lters installed at LAX CUP

Total Operating Cost Analysis: Cooling Tower Side-Stream Filtration*

Contact us to learn more about how Vortisand® cross-fl ow microsand fi ltration systems can help you increase effi ciency, save water and increase your bottom line.

4 x 700 gpm (5%)