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Let examine how the microbial population is increased into our system.

We are considering a very limited starting population, introducing nutrients that will improve growth.

Under such conditions, a certain category of microorganisms, start to multiply. As it is shown in the video to the left, the population of this category (A') is increased, increasing also the figure of the total population.

The increase in A's population is leading to the increase of its physical enemies (Category B' ) which are being fed by them.

The population of A' rises to a maximum and starts to decrease, due to the lack of additional nutrients, plus the increase of the Category B'.

But  the population of the category C' starts to increase, being the physical enemies of category B', and the cycle is continuing till a final equilibrium, related to the system's characteristics and the nutrients available.

Normally this equilibrium status is well outside the operational limits of our system.

If we try to control the population by adding a dispersant toxicant (biocide), the total population growth will present the graphs of the video on the left.

The total population level will decrease for a small time period, but then it will expand to the untreated level, because organisms find the way to overpass the toxicity, creating mutagenic, more resistant species.

Those pore resistant species, can also be dangerous to human.

In open recirculating cooling water systems, the existing blow down is removing the toxicants from the system,  resetting the initial living conditions.

This cannot be done automatically in closed systems, so if the system has not significant leaks, it is mandatory either to replace the entire water volume every three months, either to use a self-detoxified biodispersant, like BDS^® 6950