Molecular methods

Untreated water contains many bacteria, protozoa, fungi and viruses. Some of them may pass into drinking water and become established in biofilm (a complex layer on the surface of the water distribution system).

Biofilms are a complex mixture of microbes, organic material accumulated amidst a microbially-produced organic polymer matrix attached to the inner surfaces of distribution systems, and likely to occur in all distribution systems (USEPA, 2002).

This picture can be found in a review article by Hall-Stoodley, Costerton and Stoodley (2004) “Bacterial biofilms: from the natural environment to infectious diseases” Nature Reviews Microbiology, 2, 95-108.

Attachment of organisms to surfaces has been shown to alter their physiology rendering them more active in absorbing nutrients as well as more resistant to environmental stress. The formation of biofilms in drinking water systems produce undesirable effects, such as contamination potential, resistance against disinfection and harboring of pathogens. The transfer of antibiotic-resistance genes provides an additional problem.

The ideal aim is to bring to the consumer potable water of an identical quality to that leaving the treatment plant. However, it has been well documented that water, which reaches the consumer’s tap, is often of inferior microbiological and sometimes chemical quality, when compared to that which left the waterworks. Thus in order to serve the consumer best the analytical systems used for monitoring of microflora in potable water/ water distribution system must be:

  • rapid to perform,
  • able to detect the major groups of concern,
  • reliable,
  • inexpensive and
  • preferably non-distructive, i.e. such that they do not disturb the sample composition.

Two main approaches for biofilm collection are used: (i) biofilm reactor Propella® which allows to produce biofilm and study the influence of certain factors (e.g. presence/absence of nutrients and/or disinfectants) on the behavior of cells and (ii) the installation of biofilm collectors in selected spots of the treatment train and water distribution system.

Biofilm collectors: coupons and a coupon holder. This is placed directly in the pipes/water distribution system.