Biofilm exists from bacteria who attach by a self-produced slime. They create a layer which is very hard to remove. On this layer, even more, bacteria, as well as micro-organisms and ferments, can attach and develop.
A fully functioning biofilm is like a vivid fabric on the inside wall of pipes, storage tanks, water wells, etc. It is a complex cooperation of different types of micro-organisms who live each in their favourable climate. Even in the system of our drink water, more than 99% of the bacteria are part of the biofilm attached on the inner side of the pipes.
Glycocalyx, also called Extracellular matrix or EPS (Extracellular polymer substance), can include 90 or even 95% of the biomass of the biofilm, the rest are bacteria. As glycocalyx contains a lot of water, a surface which is covered by his biofilm as very slippery and gelatinous. Afterwards, the glycocalyx can capture other bacteria which will multiply and start building their glycocalyx.
A biofilm can contain different bacteria who produce corrosive chemicals. E.g. anaerobic sulphate reducing bacteria. These bacteria produce sulfuric acid which leads to corrosion of metal pipes. Also, the so-called iron-oxidizing can cause corrosion of metal which results in expensive reparations of the leaking pipes.
Biofilm also narrows the diameter of pipes and creates more resistance so less liquid can be pumped through. The result is a higher cost of energy.