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Tue 7 Oct 2008 04:00 AM

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Chemical-free cooling

District cooling is already recognised as one of the major ways to increase the sustainability of a project, but how can it be improved further? A chemical-free technology recently installed on Palm Jumeirah provides some answers.

District cooling is already recognised as one of the major ways to increase the sustainability of a project, but how can it be improved further? A chemical-free technology recently installed on Palm Jumeirah provides some answers.

With sustainable building now top priority in the Middle East, consultants and contractors are seeking ways to improve all MEP systems used in developments.

Palm District Cooling (PDC) was looking for ways to save water, reduce energy consumption, eliminate condenser water chemicals, eliminate the need for employees to handle chemicals, and eliminate chemical discharge to the environment.

To achieve these goals, PDC has moved forward with awarding US Chiller Services (USCS) the turn-key, project of design, procurement, installation, and commissioning of the Clearwater Dolphin Chemical-Free Water Treatment System at its 15,000-ton Gardens Plant 3.

"USCS has been looking at chemical-free water treatment alternatives for the past 15 years, but was never satisfied with the many systems we evaluated," remarked Dan Mizesko, Managing Partner of USCS.

"However, about two years ago, our engineers identified the Clearwater Dolphin System as a chemical-free water treatment technology that truly outperforms any Non Chemical treatment system, as well as conventional Chemical water treatment.

We visited scores of sites in the USA and met with the Management and Engineers at Clearwater Systems Corporation over the past two years and performed extensive system evaluation. In April of 2008, we were confident in the performance of the Clearwater Dolphin System and decided to introduce this technology to the UAE."

USCS approached its partner customers regarding this technology and PDC were immediately interested in exploring the benefits of installing the Dolphin System at its District cooling plants.

After performing due diligence, PDC decided to move forward with installing the system on one of its plants. After a trial period PDC will move forward with installing the Dolphin System on all its plants.

Dan added "USCS will provide to PDC a comprehensive, plant-wide non-chemical water treatment technology that will completely eliminate any and all chemicals used in the condenser/cooling tower system at the Gardens Plant 3.

We are confident that PDC will move forward with the implementation of this technology at all its District Cooling Plants, as the technology not only benefits PDC, but also benefits the residents of the UAE, with substantial water savings, power savings, and the elimination of discharge chemicals to the UAE environment, while complying with H.H. Sheikh Mohammed's directive to Go Green."

Why the need for water treatment?

The primary goals of advanced water treatment in HVAC systems are to prevent mineral scale formation, control biological activity, and inhibit corrosion. These problems traditionally have been addressed by means of chemical additives.

Difficult to administer, monitor, and control, chemical additives are ultimately discharged to the environment where they can contaminate surface and ground waters, concentrate in water treatment plant residuals, and be directly aspirated by people exposed to the mist created by cooling tower drift.

To resolve these problems without using chemicals USCS is installing the Clearwater Dolphin non-chemical water treatment technology at PDC 3 Gardens.

In addition to eliminating all chemical usage, this technology will allow PDC to increase the cooling tower Cycles of Concentration (CoC), thus substantially reducing make-up and blow-down water requirements and associated water cost.

The technology will also reduce the carbon emissions associated with water production and distribution processes associated with water savings, allow PDC to earn points toward LEED Green Building Council certification, continue to demonstrate to the region that PDC is a leader in environmental stewardship, and comply with government mandates that all UAE buildings and industries move to a "greener" footprint.

Scale prevention

When evaporation occurs in a cooling tower, the water exits as water vapor and leaves the dissolved minerals behind, causing increased concentration. Upon sufficient concentration, the dissolved minerals such as calcium carbonate become solid in a process known as precipitation.

The Dolphin System changes the form of precipitated solids from "hard scale" to a harmless powder.

The Dolphin System accomplishes this change by "activating" naturally occurring, small-suspended particles in the water. These tiny suspended particles exist in large quantities in all city water or well water that is used as cooling tower water.Under Dolphin System treatment, the suspended particles (suspended meaning that they neither sink nor float because of their small size) act as seeds for precipitation of dissolved minerals. The Dolphin System activates the suspended particles by removing the static electric charge on their surface.

A powder of calcium carbonate grows by coating or adhering to the suspended seed particles.

The powder formation relieves the ever-growing pressure to form solids that occur from the increasing mineral concentration, before scale has a chance to form on equipment surfaces. Without Dolphin System treatment, the pressure to form solids is relieved by the formation of scale on equipment surfaces.

Biological control

The Dolphin System has two methods of controlling microbial populations in cooling systems: encapsulation and electroporation.

Encapsulation: The limestone-type powder previously described incorporates most of the free-floating (ie: planktonic) bacteria. Without Dolphin System treatment, the bacteria are repelled by the suspended particles due to the fact that nearly all tiny particles have similar negative static electric charges on their surfaces.

Once Dolphin System powder is growing, the repulsion to bacteria is eliminated; therefore, the bacteria are attracted to powder by other natural forces (ie: van der Waals forces) and become entrapped in the powder particle. The powder, in effect, sweeps the water clean of planktonic bacteria and renders them incapable of reproducing.

Electroporation: The high frequency, pulsing action of the Dolphin System's electric fields damages the membranes of planktonic bacteria by creating small "pores" in their outer membrane. The condition weakens the bacteria and inhibits their capability to reproduce.

Biofilm or slime

Normally bacteria form a biofilm or slime layer on equipment surfaces. A biofilm consists of a slimy bacterial secretion that forms a protective canopy to protect the bacteria beneath it from chemical biocides.

It is very slimy to the touch, four times more insulating to heat transfer than mineral scale, and is the primary cause of microbial influenced corrosion. The bacteria that live in a biofilm adhering to an equipment surface are called sessile bacteria and represent 99% of the total bacteria in a system. The Dolphin System eliminates the slime layer through the process of nutrient limitation.

Corrosion control

The most serious corrosion concerns in a cooling tower come from chemical additives. Removing chemicals and using the chemical-free Dolphin System eliminates this concern. Other serious concerns come from localized corrosive attack caused by biofilm or mineral scale. Under Dolphin System treatment, these conditions are absent and therefore these types of corrosion are eliminated.

The Dolphin System offers major advantages for District cooling facilities.

Exceptional system performance

The Dolphin System aims to improve the operational performance of the water-based system to which it is applied (chillers, towers, pumps). The Dolphin Pulsed-Power technology aims to make these systems more efficient and longer lasting by eliminating performance inhibitors such as: scale, corrosion, bacteria, biofilm, encrustation, and fouling.

Environmentally sustainable progress

Since it is chemical-free water treatment, the Dolphin System prevents exposure to and the migration of hazardous chemicals. The best way to prevent exposure to hazardous materials is not bring them into a facility. The Dolphin technology resolves more than 10 OSHA and EPA concerns associated with chemical treatment.

Energy savings

The Dolphin System creates significant energy savings because it eliminates scale and biofilm.

The following are the savings PDC will achieve at its Gardens Plant 3 with the Clearwater Dolphin System.

Blow-down/ bleed water increased from 5 CoC to 7 CoC. This increase equates to 13,129,600 Impg annual water savings in bleed/ blow-down water being discharged to the sewer system.

Energy Savings, a minimum 1.5% energy reduction on the chillers due to removing the bio-film and eliminating tube scale issues, equating to Over 1,200,000 Kwh per year.

Annual CO2 emissions savings/reduction 800 tons. These savings are directly related to the chillers energy savings associated with bio-film and scale abatement.

An additional savings/reduction of 356.35 tons, of CO2 Emissions will also be realized with the elimination of the associated production and delivery of the 13,129,600 IMPG that will no longer be required at DCP3 Gardens. These reductions are equivalent to removing 213 automobiles from the roads of Dubai for one full year.

Chemical savings, by completely eliminating all condenser water chemical usage.

With financial savings and the environmental benefits, Dubai's progressive district cooling industry seems set to follow Palm District Cooling's example and adopt a technology that is set to reshape the water treatment industry in the years to come.

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