| Resumo: |
The effectiveness of a waste stabilization pond, to remove intestinal helminth eggs and protozoan cysts was studied in San Martin de Porres, Lima, Peru. From September to October 2000 four collections of samples were performed from raw domestic wastewater and from contends of primary, secondary and tertiary ponds. A comparative study of performance of the concentrations methods of Ritchie and Faust was also done. The overall average removal of parasitic forms was as follow: 69.37% from raw water and primary pond; 48.34% from primary to secondary pond; 85.45% from secondary to tertiary pond and 97.69% from raw water to tertiary pond. There was no significant difference in the quantitative performance of Ritchic and Faust methods. Giardia duodenalis (Lambl, 1859) Alexeieff, 1914, Entamoeba coli (Gras, 1879) Casagrandi & Barbagallo, 1895 and Ascaris lumbricoides (Linnaeus, 1758) were detected with both methods. Three other parasites were detected only by Ritchie method: Taenia sp., Rodentolepis nana (von Siebold, 1852) Spasskii, 1954 and Trichuris trichiura (Linnaeus, 1771) Stiles, 1901 and only Faust detected Isospora belli Wenyon, 1923. Overall number of protozoa cysts was higher than the number of helminth eggs. At the end, wastewater had a concentration of 1.5 parasitic forms L¹ what is considered inappropríate for ultimate use in agriculture by current standards.
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