Ecotoxicological and fertilizing effects of dewatered, composted and dry sewage sludge on soil mesofauna: a TME experiment.

The effects of dewatered, composted and dry urban sewage sludge on the soil mesofauna were tested in mesocosms. PVC containers were filled with soil/sludge mixtures in a proportion to amount to 6% organic matter content and were colonized with soil fauna coming from undisturbed forest soils. Mesocosms were incubated under laboratory conditions for 7, 30, 60, 120 and 180 days, after which fauna was extracted in Berlese funnels. The animals were classified at different taxonomic levels. Acari were classified to the suborder level for Astigmata, to the family level for Mesostigmata and Prostigmata and to the species level for Cryptostigmata. Acute- and medium-term effects were determined on the faunal density, relative abundance of the main taxa and community structure. Prostigmata were sensitive to the acute effect of the sludge, whereas Mesostigmata and particularly Cryptostigmata were sensitive to its medium-term effect. The most negative effects were found for dry sludge, which caused acute and medium-term effects on the invertebrate communities and on the soil trophic structure.