In this study, we have investigated the effect of lagoon treatment on the elimination of helminth eggs. The Marrakech treatment lagoon receiving only part of the city sewage, consists of two connected ponds (total retention time from 8 days to 30 days). Water samples (surface and deep) and sediment samples were collected. In the surface water samples collected at the lagoon entrance there was an average of 11.7 eggs/l, while no helminth eggs could be recovered at the exit from the lagoon. In the two ponds very few eggs were found, both in surface and deep water samples (͌ 3/1). Helminth eggs were mostly found only in the sediment samples: 275 eggs/100 g sediment from the first basin and 158 eggs/100 g sediment from the second, on average. In conclusion, this study demonstrates that lagoon treatment is efficacious in removing helminth eggs. Nonetheless sediments from such treatment present a problem as they remain heavily contaminated with helminth eggs.

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