Reduction of Cryptosporidium and Giardia by sewage treatment processes

Lim, Y.A.L.; Wan Hafiz, W.I.; Nissapatom, V. (2007) Reduction of Cryptosporidium and Giardia by sewage treatment processes. Tropical Biomedicine, 24 (1). pp. 95-104. ISSN 0127-5720

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    Abstract

    Cryptosporidium and Giardia are two important pathogenic parasites that have caused many waterborne outbreaks which affected hundreds of thousands of people. Contamination from effluent discharged by sewage treatment plants have been implicated in previous waterborne outbreaks of Cryptosporidium and Giardia. This study evaluated the reduction of Cryptospotidium and Giardia (oo)cysts in two sewage treatment plants (STPA and STPB) in Malaysia which employed different treatment processes for a period of a year. Raw sewage influents and treated sewage effluents were concentrated by repeated centrifugation, subjected to sucrose density flotation and concentrated to a minimal volume depending upon the levels of contaminating debris. Cryptosporidium oocysts and Giardia cysts were enumerated using epifluorescence microscopy. The parasite concentrations in raw sewage were 18-8480 of Giardia cysts/litre and 1-80 of Cryptosporidium oocysts/litre. In treated sewage, the concentration of parasites ranged from 1-1462 cysts/litre and 20-80 oocysts/ litre for Giardia and Cryptosporidium respectively. Statistical analysis showed that sewage treatment process which employed extended aeration could reduce the concentration of Cryptosporidium and Giardia (oo)cysts significantly but treatment process which encompasses aerated lagoon could only reduce the concentration of Giardia cysts but not Cryptosporidium oocysts significantly. This phenomenon is of great concern in areas whereby effluent of sewage treatment plants is discharged into the upstream of rivers that are eventually used for abstraction of drinking water. Therefore, it is important that wastewater treatment authorities rethink the relevance of Cryptosporidium and Giardia contamination levels in wastewater and watersheds and to develop countermeasures in wastewater treatment plants. Further epidemiological studies on the occurrence and removal of pathogenic organisms from excreta and sewage are also recommended, in order that the public health risks can be defined and the most cost effective sewage treatment options developed.

    Item Type: Article
    Creators:
    1. Lim, Y.A.L.(Department of Parasitology, Faculty of Medicine University of Malaya, 50603 Kuala Lumpur, MALAYSIA)
    2. Wan Hafiz, W.I.
    3. Nissapatom, V.
    Journal or Publication Title: Tropical Biomedicine
    Additional Information: Lim, Y A L Wan Hafiz, W I Nissapatorn, V eng Malaysia 2007/06/15 09:00 Trop Biomed. 2007 Jun;24(1):95-104.
    Uncontrolled Keywords: Animals Cryptosporidium/*isolation & purification Giardia/*isolation & purification Humans Oocysts Sewage/*parasitology Water Purification/*methods
    Subjects: R Medicine
    Divisions: Faculty of Medicine
    Depositing User: Ms Johana Johari
    Date Deposited: 12 Dec 2012 12:10
    Last Modified: 12 Dec 2012 12:10
    URI: http://eprints.um.edu.my/id/eprint/4166

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