This is caused by the unchecked growth of micro-organisms which form a slimy biomass. The effect of the biomass is to restrict water flow, reduce system capacity, and inhibit heat transfer much the same as with deposition.
The types of organisms most often encountered in industrial water systems are:
- Bacteria
- Algae
- Fungi
- Protozoa
Some organisms trigger corrosive attack on metal surfaces as a result of their metabolism. Other problems created by micro-organisms include the deterioration of wood in cooling towers and the contamination of products such as paper mill products.
Micro-organisms thrive with moderate temperatures, nutrients and moisture – major factors that promote the growth of organisms.
Cooling water systems are particularly susceptible to biological fouling because conditions are ideal for growth of the micro-organisms.
- Water temperatures are warm enough to stimulate growth, but not hot enough to kill the organisms.
- Nutrients are often present in the water.
- Open recirculating systems permit large numbers of airborne organisms time to establish themselves on moist system surfaces.
Microbiocides are used to control organisms in order to curtail their damaging effects on the operation of industrial water systems.
Micro-organisms exhibit a remarkable tenacity for life. A portion of their population will often adapt to the presence of non-oxidising biocides, and will thrive in spite of continued use of the biocide. Adaptation to the toxic environment created by the biocide is called building biocide immunity.
To counteract this resistance to a particular biocide, many treatment programmes alternate between the use of two or more biocides.
For more information on microbiologicial control in cooling systems see our cooling water treatment page
For information on what chemicals are available see our cooling water treatment chemicals page
To see what chemicals we have available for purchase online in our shop visit our cooling water chemicals shop page
