Parasitological Contamination of Urban Sludge Used for Agricultural Purposes

Abstract

Sludge re-use in agriculture has increased in many countries, but this practice must be associated with a knowledge of the pathogens present in these sludges. The aim of this study was to determine the parasitic contamination of helminths found in urban sludges. Parasitological analysis was then performed on 99 samples collected by the waste recycling mission for agricultural purposes: urban sludges (89), lagoon sediments (3) and composts (7). The results of 89 urban sludge analyses expressed per 100 g of dry matter showed a high proportion (47%) of samples presenting concentrations lower than 60 eggs. Thirty-eight per cent of the samples were with higher concentrations ranging from 60 to 240 eggs; only 15% of the analysis results indicated concentrations higher than 240 eggs with a maximum of 898 eggs. In lagooning sediments, the concentration observed ranged from 56 to 569 eggs and the analysis of compost samples yielded average concentration of 40.8 eggs. When the whole study is taken into account, Nematode eggs (Toxocara, Ascaris, Capillaria, Trichuris, Ascaridia, Enterobius) are mostly represented with 93.2%, whereas Cestode eggs (Tenia, Hymenelopis) are only detected in a proportion of 6.8%. The study of the lime treatment impact on 10 treatment plants showed a decrease in helminth eggs concentration in seven samples and no difference for the three others. For the egg viability, sludges from all types of treatment (mesophilic anaerobic and aerobic digestion, composting, liming) contained viable eggs in concentration higher than or equal to 10 eggs per 100 g of dry matter. © 1997 ISWA