What is a cooling water treatment system?

A cooling tower is a heat exchange device that transfers heat from water to the surrounding air or atmosphere to remove or reduce heat from a process or facility.

It lowers water loss by reducing the amount of water that evaporates. They are created and constructed in various shapes and sizes, each with its own set of applications, benefits, and limitations.

open circuit closed circuit, and once-through systems are the main three types of it. The medium used in the cooling tower can be either air cooling or water cooling tower.

As water consider a high heat capacity medium, water cooling is the most common cooling tower.

A cooling tower water treatment system is frequently required to maintain an effective process and long equipment service life.

Organic growth, fouling, scaling, and corrosion are the main problems that affect plant productivity, plant downtime, and the cost of replacement equipment if the cooling tower water is left untreated.

What is a cooling water treatment system? Why is needed? What are their components? Will be covered in this article.

What is a cooling water treatment system?

It is a collection of technologies that remove harmful contaminants from the feed water, circulation water and/or blowdown water in it.

Many factors influence the configuration of the system such as:

1-Types of cooling tower

2-Quality of your feed water

3-Manufacturer- quality requirements for the cooling tower and equipment

4-Chemistry/makeup of circulatory water

5-Regulatory requirements for discharge

6-whether or not blowdown will be treated for reuse in the cooling tower

7-Type of heat exchanger

8-Cycle of concentration

Why cooling tower water treatment is needed?

Water treatment for cooling towers is subjected to various water-related operating problems which include:

Microbiological Deposits and Mud/Grime inside the cooling tower

 

Microbiological deposits such as fungi and algae can create slimes on the heat transfer surfaces of the cooling tower, resulting in severe cooling inefficiencies.

These deposits can build up in cooling systems to the point where they restrict the free flow of water and air, weighting down its structural members and perhaps causing them to break.

They also have an impact on cooling efficiencies, which raises the cost of energy to maintain performance. Any mud or grime that develops within the tower can cause similar problems.

Scale Deposits inside cooling tower

When the concentration of a dissolved substance exceeds its solubility in water, scaling can occur. This is a problem for materials whose solubility decreases as the temperature rises.

Scale is typically caused by calcium sulfate, calcium phosphate, other calcium salts, and excessive concentrations of specific minerals like silica or silicates.

Any scale that forms will affect heat transfer, reducing the cooling efficiency of the tower and, as a result, increasing the cost of operation.

Cooling tower Corrosion

The concentration of electrolytes caused by evaporation in open, recirculating cooling water systems can make the water more corrosive.

Foam

Foam can form in some systems due to cascading water in the cooling tower. however, it is not as common as other cooling tower problems.

As a result, its sump could overflow, or the fans may push foam out of the top of the tower. The foam also concentrates deposit-forming particles, causing system fouling to increase.

What are the components of a cooling water treatment system?

According to its needs and the quality of circulated and feed water requirements, the components of the cooling water treatment system can differ.

However, the basic water treatment system components include:

Makeup water intake

Makeup water means the water that is needed to overcome the deficiency in evaporated or leaked water in the cooling tower.

Depending on the source water quality, water softeners should be employed to remove hardness or silica as well as adjust the pH levels before being added to the system.

Filtration important for cooling tower

You can eliminate suspended particles and some forms of organic matter that can lead to scaling, corrosion and foaming by putting your cooling tower water through a filtration system.

Because eliminating suspended solids upstream can assist prevent ion-exchange resins and membranes from fouling downstream, filtration should be done first in the water treatment process.

Water softening/ion exchange

Water softening is needed to remove hardness from makeup water or source water. Water hardness encourages the development of rust and scale deposits which reduces the efficiency of cooling towers.

Chemical treatment inside the cooling tower

Chemically treated cooling tower water is necessary to balance the chemical properties of the water.

Chemical treatments include:

Corrosion inhibitors

Chemicals such as bicarbonates are added to neutralize acidity and protect metal components

Scale inhibitors

Chemicals such as phosphoric acid are added to prevent contaminants from forming scale deposits

Algaecides and biocide

Bromine is added to control and reduce the growth of microbes and biofilms.

PH adjusters

Low pH can accelerate corrosion that’s why a pH adjuster is needed to control corrosion inside it.

Side-Stream Filtration

Side-stream filtration units are used to remove any pollutants that enter inside it through leaks or drift contaminants.

The parameter that is needed to be controlled

A cooling tower water treatment system is necessary to control the level of:

1-Alkalinity: which determines the calcium carbonate scale potential

2-Chlorides: can be corrosive to metals; different levels will be tolerated based on the materials of the cooling tower and equipment

3-Hardness: leads to the formation of scale in cooling towers and heat exchangers

4-Iron: when iron can foul equipment if combined with phosphate,

5-Organic matter: promotes microorganism growth, which can lead to fouling, corrosion, and other system issues

6-Silica: hard-scale deposits causing

7-Sulfates: extremely corrosive to metals

8-Total dissolved solids (TDS): include a contribution to scaling, foaming and corrosion.

9-Totals suspended solids (TSS): include undissolved contaminants that can cause scaling, biofilms and/or corrosion.

10-Ammonia: Promotes the growth of biofilm in heat exchangers and cooling tower

11-Nitrates and Nitrites: Additional mild steel corrosion protection.

Cooling  water quality

The quality of the cooling water is determined by the type of heat exchanger or engine to be cooled.

Parameter limitation
Suspended solids None
Conductivity 50-600 uS/cm
Hardness 8o dH max
pH 7.8
CO2 aggressive   None
Chloride < 250 mg/L
COD < 40 mg/L
Bacteria < 1000 CFU/ml

References

[1] Basics of Water Treatment for Cooling Towers, Chem READY, [online] Available at: https://www.getchemready.com/water-facts/basics-of-water-treatment-cooling-towers/

[2] What Is a Cooling Tower Water Treatment System and How Does It Work? OCTOBER 26, 2016 [online] Available at: https://www.samcotech.com/cooling-tower-water-treatment-system-process/

[3] Cooling water quality, Lenntech [online] Available at: https://www.lenntech.com/applications/process/cooling/cooling-water-quality.htm

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