BACTERIAL NUTRIENTS AND BIOFILM FORMATION POTENTIAL WITHIN DRINKING WATER DISTRIBUTION SYSTEMS

摘要

The water supply companies in the Netherlands are aiming at distributingrnbiostable drinking water without a disinfectant residual. Growth promotingrncompounds may be present in drinking water and/or originate from materials inrncontact with drinking water and/or distribution line sediments. Oligotrophicrnbacteria are able to utilize substrates at concentrations of a few Fg C/l, but HPCrnvalues do not increase significantly in drinking water during distribution at AOCrnvalues below 10 Fg C/l. In most ground water supplies AOC concentrations arernbelow 10 Fg C/l but in a number of such systems regrowth of aeromonads hasrnbeen observed indicating a certain degree of instability. Regrowth was found to bernrelated with the biofilm formation rate (BFR) of drinking water as assessed with thernbiofilm monitor. This biofilm monitor also enables the assessment of iron andrnmanganese accumulation. Very low concentrations of easily assimilable organicrncompounds may cause a significant BFR value, and therefore no direct relationshiprnis observed between AOC and BFR values in a number of water types.rnConsequently both parameters are needed to assess the biostability of drinkingrnwater. Certain materials in distribution systems e.g. cast iron and synthetic materialsrnmay have a profound effect on biofilm formation. Materials in contact withrndrinking water are tested for their growth promoting properties. A Unified BiofilmrnApproach has been developed to evaluate the biostability of water and materials onrnthe basis of biofilm formation, using ATP as the biomass parameter.