Olive mill wastewater composting: microbiological aspects.

Oxygen consumption, microbial growth, lignin and phenol degradation, urease, protease and nitrogenase activity were determined during the composting of an olive-mill wastewaters (OMW)-wheat straw mixture. Oxygen consumption, microbial growth and urease activity were greatly enhanced during the thermophilic phase, reaching their maximum in about three weeks. Casein-hydrolysing protease showed a high initial activity which sharply decreased after 2 weeks. At the end of the thermophilic phase both phenols and lignin were reduced by about 70%. Composting enhanced diazotrophic microflora as indicated by nitrogenase activity which increased at the end of the thermophilic phase