Ecotoxicity of sewage sludge

Sewage sludge produced by various technological treatment processes within the EU-funded project ROUTES are assessed for their ecotoxicity with standard laboratory tests. The tests were selected among a number of test systems recommended by testing guidelines for waste. They encompass aquatic organisms (freshwater green algae and freshwater crustaceans) and terrestrial organisms (soil bacteria and earthworms). The test methods are described here and typical problems encountered with the testing of such organic material are illustrated by presenting results for one example batch of sludge samples. For this example, some evidence for a toxicity-reducing effect of the digestion treatment was observed only in the soil bacteria contact test with Arthrobacter globiformis.