BIOREMEDIATION OF OLIVE-MILL WASTEWATERS BY COMPOSTING

Olive-mill wastewaters (O.M.W.) containing about 7% solids were compos ted with wheat straw in a forced aeration static pile. Two percent ure a was added to ensure a C/N ratio of about 35. To avoid overdosing wit h water, a fraction of the O.M.W. equal to the weight of the straw was added initially. When composting had reached the thermophilic phase, additional doses of O.M.W. were added every 3 days as water evaporated . The ratio of O.M.W. solids:straw approached 1:1 and the thermophilic phase was extended to 35 days. Temperature, oxygen consumption, pH, C /N, total organic carbon, total extractable carbon, humic and fulvic a cids and lignin degradation were followed during the process. The humi fication was assayed following the degree of humification, the humific ation rate and the humification index which respectively reached the v alues of 78%, 37.8% and 0.28 after 2 months. Humic acids were characte rized by their elemental composition and molecular weight. A lignin de gradation of about 70% was assayed at the end of the thermophilic phas e. No phytotoxicity was recorded on the end product, the chemical and physical properties of which suggest its possible use as fertilizer. ( C) 1995 ISWA