Negative effect of flocculant (cationic acrylamide) on detectability of the nematode eggs in sewage sludge.

The use of sewage sludge in agriculture brings the risk of microbiological and parasitological contamination of soil, ground and surface water, as well as cultivated plants. Therefore prior the application to the soil, sewage sludge must be examined, among others, for the presence of live eggs of intestinal parasites. However, the efficiency of commonly used for this purpose parasitological methods is not satisfactory. This is probably due to the presence of flocculants in the sediments used in the dehydration process. The objective of the study was analysis of the effect of flocculant (cationic acrylamide) on the possibilities of isolation of parasite eggs from dehydrated sewage sludge. For this purpose 10 samples of sewage sludge were prepared: 5 containing flocculant and 5 without flocculant. Samples were tested by flotation method according to Quinn. From sewage sludge free of flocculant, 67.8 eggs were isolated, on average, whereas from sludge containing flocculant - only 2.8 eggs. The experiments confirmed that the isolation of eggs from sewage sludge containing flocculant (cationic acrylamide) is much more difficult than from sludge free from this substance and therefore the simple parasitological methods should not be used to examine the dehydrated sewage sludge.