Presence of Acanthamoeba spp. in water purification plants in southern England

Objective To identify the prevalence of Acanthamoeba in drinking water treatment plants during the course of the purification processes. Methods Samples were taken from two drinking water purification plants and monitored for the presence of Acanthamoeba in order to estimate the removal capacity of treatment methods employed. Water samples were collected at each step in the purification, during the one year survey, and analysed for the presence of Acanthamoeba spp. by plating on bacterial-seeded plates. Results : The results showed that amoebae were present in surface raw waters in 100% of the samples tested. Acanthamoeba spp. were isolated from 71% and 57% of the water samples collected from post flat-bottom clarifier 1 and post-sedimentation plant respectively. Considering the outflow drinking waters, the removal capacity was 100% in both purification plants monitored. The occurrence of Acanthamoeba was not associated with seasonality. Conclusion : These findings confirm that water purification plants employing methods of flocculation, sedimentation, and filtration in combination with activated charcoal filtration, ozonisation and chlorination exhibited sufficient Acanthamoeba removal capacity and the presence of amoebae in the tap water may be due to older plumbing, water storage tanks, tap water hygiene, and/or environmental settings.