Free-living amoebae have been detected in a large number of man-made water systems, includingdrinking water distribution systems. Some of these amoebae can harbor amoebae-resisting bacteria,and thus potentially act as reservoirs and vehicles for a number of pathogens. The objectives of thisstudy were to: quantify the free-living amoebae present at different steps of drinking water productionand distribution; assess their potential association with Legionella spp.; and, identify possible controlstrategies. Sampling campaigns were conducted in Europe on a series of drinking water treatmentplants supplied by different surface waters and applying different treatment technologies. The resultsof this study confirm the presence of free-living amoebae in surface waters used for drinking waterproduction. Although surface water treatment chains significantly reduce their numbers, they do noteliminate them totally. Moreover, when encysted, these microorganisms are highly resistant todisinfectants. Consequently, control strategies in drinking water production should be principallybased on physical removal processes such as clarification and granular or membrane filtration.Biofilms and sediments constitute ideal niches where they can feed on bacteria but also where theycan occasionally become infected by amoebae-resisting bacteria. Consequently, control strategies indrinking water production and distribution should also include good management of sludge fromclarifiers, of filter backwash, and biofilm and sediment control in distribution systems. Includes references, tables, figures.
