A cooling system is an ideal environment for microscopic organisms to live. They enter the system from the air or makeup water and survive with the help of different factors. Left uncontrolled, they multiply quickly and may completely foul a cooling system in a very short period of time. There are three types of microorganisms:
Bacteria form sticky slime masses that foul and cause reduced heat transfer. They produces acidic waste that lowers pH and cause corrosion. They also produce large volumes of Iron deposits that foul. Also, they produce acids from ammonia that increase corrosion and lower pH.
There are four classifications of bacteria.
Slime-forming bacteria are the sticky, jelly-like organisms that grow in tower basins and heat ex changers. They secrete jelly-like substance to protect their bacteria colony. This sticky layer makes them difficult to destroy and also provides an ideal spot for other materials to become trapped. These bacteria can cause serious fouling problems in a very short time.
Iron depositing bacteria use dissolved iron as their food turning them to reddish-brown deposits. The deposits may cause fouling problems.
Nitrifying Bacteria converts ammonia into nitric acid which lowers the pH of the cooling water and causes corrosion. They need a source for ammonia in the water and are most often found in ammonia plants or breweries.
Anaerobic corrosive bacteria are the most dangerous microorganisms. A popular place for them to grow is under deposits of slime forming bacteria. Anaerobic corrosive bacteria takes nutrients and convert these to acid that may eat right through cooling system metal.
Fungi cause either surface or internal rotting of the wood. Fungi are capable of collapsing an entire cooling tower as a result of deep wood rot. They plug distribution holes on tower deck and are food for other organisms. They also consume chlorine.
Algae requires sunlight. They form “Algae Mats” and cause fouling in equipment.
Once in the cooling water, the growth of the microorganisms is affected by the following factors:
The problems caused by bacteria, algae and fungi are different. Each one grows in a different area of the cooling water system. Microbiological growth can cause the other major cooling water problems: corrosion, scale, and fouling.
Scaling are affected by certain factors: mineral concentration, water temperature, water pH, suspended solids and water flow velocity. If there are more minerals in the water than the water can hold in solution, then scale will form. This condition is called supersaturation. As the water temperature increases, the common scale forming substances become less stable and may precipitate. As the pH of the water increases, the tendency for scale formation increases. Other suspended solids such as corrosion products or microorganisms, rough pipe surfaces or already formed crystalline deposits can seed the formation of new scale.
LCIPI offers three different biocides, a combination of non-oxidizing and biodispersant chemicals to ensure its compatibility with any material of construction of the cooling tower and heat exchanger system.
Combination of any two of these three available biocides are recommended depending on the condition of the cooling tower. The technical team critically and accurately determines the combination of biocides tailor-fit for the cooling tower condition, so that microorganisms do not become resistant to a single type of biocide. LCIPI Chemicals and Technical Services Division ensures proper monitoring and control for effective application of its biocide program.
