Olive mill wastewater sludge from evaporation ponds: evolution of physico-chemical parameters during storage and composting process.

The evolution of analytical parameters of olive mill waste water sludge stored in evaporation ponds was investigated after one year and two years of storage. It was observed that some of the phenolic monomer compounds resisted removal and the fraction of water soluble phenols was only slightly polymerised. Co-composting of the sludge was carried out with yard trimming as bulking agent ratio and poultry manure to balance the C/N. Three turned piles with three proportions of 35%, 65% and 80% of olive mill waste water sludge were prepared. Co-composting of the sludge was possible in all the cases. Best results were obtained, however, at a proportion of 35% which permitted a shorter composting time, a higher degree of nitrification and a higher rate of total phenols decreasing. A high polymerisation of the fraction of water soluble phenols was observed at the end of composting in all the piles.