Biological Control Instead of Biocides: How Cooling Water Systems Can be Operated More Efficiently

Cooling water systems influence energy requirements, system availability and compliance. Biofilms reduce heat transfer and significantly increase OPEX. Biological control concepts, supported by the updated VDI 2047 Sheet 2 and stricter environmental requirements, enable stable processes without conventional biocides and improve efficiency as well as water and energy balance.

Cooling water systems are the backbone of industrial heat dissipation. But while companies invest millions in process optimization, cooling water often remains an invisible cost centre. Just 1 mm of biofilm build-up on heat exchanger surfaces can reduce heat transfer by 10 - 40 % - in typical systems this means additional costs of EUR 100,000 - 800,000 per year.
The standard answer for decades has been: more chemicals. But conventional biocides take a "kill" approach, which inevitably generates selective pressure, resistance formation and wastewater pollution:

• Resistance formation: Microorganisms adapt, dosing rates increase, efficacy decreases.
• AOX pollution: Biocides containing chlorine and bromine generate AOX concentrations that reach up to 1.5 mg/L - and thus exceed the possible future limit value of 0.3 mg/L (trend until 2030) many times over.
• Hidden costs: Contaminated heat exchangers increase condensation temperatures and energy consumption. Added to this are heavy polluter surcharges and rising wastewater levies.