They are coolants that are not affected or eaten by bacteria. Many coolants that are labelled biostatic by producers require biocides and therefore are not truly biostatic. Some coolants may be pasteurized to kill bacteria. Another method is adjusting the pH to neutralize the effects of the bacteria. The effects of anaerobic bacteria can be reduced by maintaining an amount of oxygen in the coolant.
Anaerobic bacteria are most active over the weekend when no processes are running.
It is possible to prevent the growth of anaerobic bacteria by agitating or aerating the sump over periods of time when the process is not in operation, including weekends. Such aeration may cause problems in the coolant however and increase the foaming of some coolants. The coolant should be filtered and recycled regularly. The machines also should be broken down and cleaned at least once each year. A regular and systematic cleaning of the sump and coolant should also be completed.