Oxidizing bactericides kill microorganisms mainly through oxidation. Such bactericides are usually strong oxidants (e.g., chlorine, chlorine dioxide, ozone, hydrogen peroxide). They oxidize enzymes closely related to metabolism in microorganisms by generating reactive oxygen species such as hypochlorous acid and atomic oxygen, thereby destroying the physiological activities of microorganisms to achieve bactericidal effect.

Advantages: Fast bactericidal speed, broad-spectrum effect, low treatment cost, low environmental pollution, and low likelihood of microbial resistance.

Disadvantages: Susceptible to the influence of organic matter and reducing substances in water, short agent duration, and great influence by pH value.

Non-oxidizing bactericides kill microorganisms through toxic effects. They do not rely on oxidation reactions but act on specific parts of microorganisms to destroy their cell structure or life activities. Common types include chlorophenols, isothiazolinones, quaternary ammonium salts, etc.

Advantages: Long-lasting bactericidal effect, permeation and stripping effect on sediments or slime, little influence by reducing substances such as hydrogen sulfide and ammonia, and little influence by pH value.

Disadvantages: Relatively high treatment cost, easy to cause environmental pollution, and possible microbial resistance in water.

Corrosion to system pipes and condenser copper tubes.

Ammonia promotes the reproduction of microorganisms in the circulating cooling water system, leading to a sharp increase in microbial slime in circulating water.

A large amount of acid produced by the nitrification of ammonia nitrogen in the circulating cooling water system causes a drop in system pH and aggravates corrosion.

It is simple to judge the main composition of the scale in the circulating water system by using the acid solution method.

Main components of scale                                 The apperance of acid dissolved by acid

Carbonate scale                            After adding acid, large number of bubbles are formed.

Silicate scale                                Slowly dissolved in hot HCl and HNO₃ , produces white insoluble deposit.

Iron oxide scale                           Dissolve with HNO₃ , it generates a yellow solution.

Copper scale                                Dissolve with HNO₃ , it generates blue and yellowish green solutions.

Phosphate scale                         The solution with ammonium molybdate plus HNO₃ generates  a yellow precipitate.

                                                     Then adding ammonia to this deposit:  phosphate scale is formed.