Cooling Water Problems: Solutions and Treatments

Cooling Water Systems

• The main method of reducing deposition of solids in cooling water systems is to keep the cycles of concentration low.

Scale Formation and Prevention

• Maintaining a lower pH (6.5 to 7) helps keep solids in suspension.
• Polymers or phosphonates are added to cooling water systems to keep scale-forming salts in solution at high concentration levels.
• Plants that use source water with high hardness add sulfuric acid to remove carbonate alkalinity and reduce pH.
• The drawback of some compounds used to keep scale-forming salts in solution is that they can break down and lose efficacy over time.

Biological Growth Control

• Chlorine is added to control biological growth in cooling towers by oxidizing and breaking down microorganisms.
• The purpose of using crystal modification chemicals is to prevent scale formation by modifying the crystal structure of minerals.

Corrosion Control

• Applying protective coatings, such as paint or metal plating, prevents corrosion by creating a barrier between the metal and corrosive substances.
• Sacrificial anodes or induced electric currents are used in corrosion control to drive the corrosion reaction away from critical system components.
• Chemical inhibitors are used to prevent corrosion by forming a protective film on metal surfaces.

Inhibitor Characteristics

• Chromate was previously used as an inhibitor but is no longer used due to toxicity concerns.
• Phosphates and molybdates are alternative, nontoxic inhibitors that form a protective film in 30-90 days.
• Polysilicates and molybdates inhibitors take 30-90 days to form a protective film.

System Maintenance

• Installing a Y-strainer or equivalent upstream of the blowdown valve prevents debris from entering the blowdown line.
• Oxidizing chemicals like chlorine operate by oxidizing and breaking down microorganisms, preventing biological fouling.
• Biocides can be shock fed into the cooling system to control biological growth.
• An effective method to control wood deterioration is to treat cooling water systems with biocides.

Biocide Use

• Biocides should be used in a controlled manner to target specific microorganisms and prevent resistance development.