Effect of dewatering and composting on helminth eggs removal from lagooning sludge under semi-arid climate

Abstract

In this work, we assessed the drying and composting effectiveness of helminth eggs removal from sewage sludge of a lagoon wastewater treatment plant located in Chichaoua city. The composting was run after mixing sludge with green waste in different proportions: M1 (½ sludge + ½ green waste), M2 ( \( \raisebox{1ex}{\(2\)}\!\left/ \!\raisebox{-1ex}{\(3\)}\right. \) sludge + \( \raisebox{1ex}{\(1\)}\!\left/ \!\raisebox{-1ex}{\(3\)}\right. \) green waste), and M3 ( \( \raisebox{1ex}{\(1\)}\!\left/ \!\raisebox{-1ex}{\(3\)}\right. \) sludge + \( \raisebox{1ex}{\(2\)}\!\left/ \!\raisebox{-1ex}{\(3\)}\right. \) green waste) for 105 days. The analysis of the dewatered sewage sludge showed a load of 8–24 helminth eggs/g of fresh matter identified as Ascaris spp. eggs (5–19 eggs/g) followed by Toxocara spp. (0.2 to 2.4 eggs/g); Hookworm spp. and Capillaria spp. (0.4–1 egg/g); Trichuris spp., Taenia spp., and Shistosoma spp. (< 1 egg/g) in the untreated sludge. After 105 days of treatment by composting, we noted a total reduction of helminth eggs in the order of 97.5, 97.83, and 98.37% for mixtures M1, M2, and M3, respectively. The Ascaris spp. eggs were reduced by 98% for M1 and M3 treatments and by 97% for M₂ Treatment. Toxocara spp., Hookworm spp., Trichuris spp., Capillaria spp., and Shistosoma spp. eggs were totally eliminated (100% decrease) and the Taenia spp. was absent from the first stage of composting. These results confirm the effectiveness of both dehydrating and composting processes on the removal of helminth eggs.