"... it's summer again - summer in the city" The song by the Spider Murphy Gang from 1982 echoes in your head as you check the electroplating machine. The weather is finally nice again and there's the prospect of a weekend at the lake. A few more hours and it's time to switch off. But wait, what's there?
The high temperatures not only contribute to a positive mood. They also encourage the proliferation of a little troublemaker: the extracellular polymeric substance, or EPS for short. Over millions of years, nature has learned to settle in every niche and in the most unreal places. If the conditions change only slightly in the EPS's favor, the exponential growth quickly leads to visible changes. The speed at which this happens is always surprising. A doubling of the total bacterial count within 20 minutes leaves behind greasy walls and cloudy sinks. So far so good - I love nature at the quarry pond. I don't think a carpet of algae in the process baths is so appropriate! So let's take a closer look.
A doubling of the total bacterial count within 20 minutes leaves behind greasy walls and cloudy rinsing tanks
EPS goes through various stages of development. At the beginning, the microorganisms from which the EPS develops are often in a "viable but noncultarable" state. They are in hibernation and wait for suitable conditions. These are often so-called initial colonizers that occur everywhere and are difficult to determine via the total cell count even after disinfection measures.
Once the germs begin to multiply, the active proportion can be determined using culture media. It should be noted that the culture medium must provide the microorganisms with suitable food. In practice, DipSlide tests with a culture medium for bacteria and one for yeasts and fungi on the reverse side have proven successful. This covers a wide range of "troublemakers" and provides a rough orientation.
The result is a biofilm that works together in a highly complex way
Over time, the microorganisms continue to multiply and form the EPS more and more. The EPS is the supporting structure that holds the colony together. It consists of proteins, polysaccharides, glycoproteins, glycolipids and fragments of DNA. Hydrophobic ends lead to the formation of a skin which separates the EPS from the environment. The microorganisms are protected from environmental influences in the EPS that grows in this way. The waste products of one species are the food for others. The result is a biofilm that works together in a highly complex way.
Once the EPS has reached a certain size, parts of it break off again and again. The EPS tries to spread further and at this point at the latest, abnormalities can occur in coating processes. This is shown by inclusions, roughness, defects or pores on the components. As a result, extensive cleaning measures are now started. Although the defect is often gone afterwards, the exact cause has not been determined. If the fault reappears at a later date, the process starts from scratch again.
A general consideration of the complete processes can be a solution approach here. EPS occurs on surfaces, so it is worth taking a closer look. The living space and the retreats of the microorganisms can be a key to the solution. The food for the microorganisms must come from where. But even in highly pure, fully desalinated water, biofilms and microorganisms can be found. The food here is often the microorganisms themselves! Only system cleaning with suitable agents can help here - the biofilm must be removed from the processes.
