John Libbey Eurotext

Environnement, Risques & Santé


Evaluation of the parasite prevalence of sewage and sludge samples in Tunisia Volume 6, issue 6, Novembre-Décembre 2007


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Laboratoire Sciences et techniques de l’eau, Institut agronomique de Tunisie (Inat), 43, avenue Charles Nicolle, 1082 Tunis- Mahrajène Tunisie, Laboratoire de parasitologie des eaux usées et des boues résiduaires, Institut national de recherche en génie rural, eaux, et forêts (INRGREF), Rue Hédi Karray, BP n o 10, Ariana 2080, Tunis, Tunisie
  • Key words: helminths, parasitololgy, protozoa, sewage, Tunisia, waste management
  • DOI : 10.1684/ers.2007.0116
  • Page(s) : 433-42
  • Published in: 2007

Parasites were studied in sewage and sludge samples from seven sewage treatment plants in Tunisia from September through December 2005. All 28 samples were positive. Protozoan cysts were more frequent than helminth ova. The results allowed us to evaluate the detection technique (Bailenger method) and the effectiveness of the treatment processes (lagooning and activated sludge). Cysts of Entamoeba coli, Entamoeba histolytica/dispar and Giardia were found in all raw sewage samples, at concentrations ranging respectively from 333 to 856, from 160 to 720 and finally from 120 to 653 cysts/L. The frequency of helminths varied: 42% for Ascaris sp., 25% for Enterobius vermicularis, 14% for Taenia spp, and 3% for Hymenolepis nana (3%). During treatment, most cysts and all ova were eliminated. In the treated sewage samples, the elimination rate of helminths ova was 100% and between 82 and 100% for protozoan cysts depending on the treatment process and the month. Both lagooning and activated sludge eliminated protozoan cysts relatively effectively.