Detection and removal of free-living amoebae in two different facilities for drinking water by culture and PCR

Document Type : Original Article

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Abstract

Conventional drinking water treatment plants (CDWTPs) and compact units (CUs) are the main 2 types of drinking water treatment using freshwater as a source for drinking water in Egypt. The Egyptian standards for drinking water denied the presence of any type of living protozoa in drinking water produced for human use.
In the present study, raw and finished water samples were separately collected from a CDWTP and a CU in Giza governorate, Egypt. Samples were separately concentrated through nitrocellulose membrane filters (0.45µm pore size). Potentially pathogenic free-living amoebae (FLAs) were detected in the concentrates by cultivation and PCR.
By culture and microscopy, five genera of free-living amoebae (Acanthamoeba, Vahlkampfia, Hartmannella, Naegleria and Vannella) were encountered from inlet water samples of the 2 treatment systems. Obtained data declared that 87.5% and 91.7% of inlet water from CDWTP and CU, respectively contained potentially pathogenic FLAs that were also isolated from 20.8% and 45.8% of finished water samples from CDWTP and CU, respectively. Of the isolated FLAs from inlet water samples, Acanthamoeba were detected in finished water samples of both CDWTP and CU, while Hartmannella were isolated from finished water of only CU. Removal of FLAs reached 76.2% in CDWTP, while it reached only 50% in CU. Molecularly, only three genera were encountered representing Acanth-amoeba, Hartmannella and Naegleria but with a lower incidence than that revealed by the culture method.
In conclusion, inlet water samples from both CDWTP and CU contained potentially pathogenic FLAs. Although CDWTP was more effective than CU in removing free-living amoebae, still some of these organisms could be detected in finished water and thus cause health risk hazards to consumers

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