What is biocide?
A biocide controls bacteria, algae and fungi in cooling water. Untreated systems grow biofilm that insulates heat-exchange surfaces, shelters corrosion beneath it, and can harbour Legionella. Oxidising and non-oxidising biocides are normally alternated so organisms cannot adapt.
A cooling tower is close to an ideal incubator: warm water, sunlight, dissolved nutrients and continuous aeration. Biofilm forms within days on untreated systems, and it is a worse insulator than mineral scale at the same thickness.
Biocides split into two families. Oxidising types — chlorine, bromine — act fast and broadly but are consumed quickly and can be corrosive. Non-oxidising types are slower, persist longer, and reach into established biofilm more effectively. Alternating them prevents resistant populations establishing.
Biocide dosing also has a safety dimension that goes beyond plant efficiency: Legionella control in cooling towers is a genuine public-health obligation, not an optional efficiency measure.
