Parasite contamination of liquid sludge from urban wastewater treatment plants.

This study was performed on sludge samples from 20 wastewater treatment plants located in the north west of France with capacities of 1,000-20,000 inhabitant equivalents. The types of treatment studied were activated sludge low charge with and without denitrification. Respectively, 110 samples of fresh sludge and 84 samples of discharged sludge for spreading were analysed. Globally 78.6% of samples contained helminth eggs belonging to the cestodes (6.1%) and nematodes (93.9%). Most of the nematode eggs detected were viable with 135 positive samples. The distribution, according to genera, indicated a high prevalence of Toxocara eggs (77.4%) followed by Capillaria (13.2%), Trichuris (8.1%) and Ascaris (1.3%). For viable nematode eggs, the concentrations detected ranged from < 1 to 28/4 gDM for fresh sludge and from < 1 to 9.6/4 gDM for discharged sludge.