ENZYME-ACTIVITIES AS INDICATORS OF THE STABILIZATION OF SEWAGE SLUDGES COMPOSTING WITH EISENIA-FOETIDA

Evolution of earthworm (Eisenia foetida, Savigny) biomass and changes in enzyme activities during 18 weeks of sewage sludge vermicomposting were studied. With time, hydrolase (P-glucosidase, urease, BAA-hydroly sing protease and phosphatase) and dehydrogenase (DH-ase) activities d ecreased as available organic compounds (water-soluble carbon) decreas ed. A high correlation among all enzyme activities and between each ac tivity and the water-soluble carbon (WSC) led to the conclusion that b oth hydrolytic and dehydrogenase activities could be feasible indicato rs of the state and evolution of the organic matter. The 'potential me tabolic index' (DH-ase/WSC) enabled distinguishing between hydrolytic and maturation phases in a sewage sludge vermicomposting process. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.