THE BIODEGRADATION OF OLIVE OIL AND THE TREATMENT OF LIPID-RICH WOOL SCOURING WASTEWATER UNDER AEROBIC THERMOPHILIC CONDITIONS

摘要

The biodegradation of olive oil and the treatment of the lipid-rich wool scouring wastewater were studied under aerobic thermophilic (65 deg C) conditions using the newly isolated strain Bacillus ther- nioleovorans IHI-gl. In a continuously operated laboratory-scale stirred-tank reactor olive oil was degradedto more than 90 at a residence time of 2 h with a maximum volumetric degradation rate of 900 mg l-1 h-1. A relatively high maximum biomass yield of l.05 g dry cell weight per g olive oil con- sumed was measured and a maintenance coefficient of 0.04 g olive oil (g DCW)-1`h-1' was calculated from steady-state data. A severe growth inhibition was observed when the feed olive oil concentration was increased to more than 4 g-l. Lipid removal from the highly loaded wool scouring wastewater (COD of 77000 mg l-1) was 20-30 at a residence time of 10-20 h while the COD removal was 15 20. GC-MS analysis revealed that longchain fatty acids up to C18 were efficiently degraded while degradation of the predominant sterol-fraction of the wool grease was not detected. The high concen- trations of volatile fatty acids (60 mM acetic acid, 13 mM propionic acid) present in the wastewater were completely removed even at residence times of 2 h. Compared with data from mesophilic processes the lipid degradation rates obtained under thermophilic conditions are extremely high.