Reduction of phenolics content and COD in olive oil mill wastewaters by indigenous yeasts and fungi

Abstract

Olive oil mill wastewaters (OOMW) cause a recurrent environmental pollution problem. The large concentration of phenolic compounds in the organic fraction of OOMW is principally responsible for the phytotoxicity and microbial growth inhibitory effects of the effluent. Candida boidinii, Geotrichum candidum, a Penicillium sp. and Aspergillus niger HA37 were isolated from OOMW. When cultivated directly on an undiluted OOMW-based medium containing 82 g l -1 COD, these strains removed only 4-8% of chemical oxygen demand (COD) and phenolics. In contrast, reduction values attaining respectively 40-73% for phenolics and 45-78% for COD removal in the undiluted OOMW-based medium were obtained when using the strains gradually acclimated to high concentration of OOMW by successive stepwise transfer from media containing COD of 20.5 up to 82 g l -1 . Possibly, a sufficient production level of degradation and/or detoxification enzymes has to be attained to overcome the toxic effects of the phenolic fraction of concentrated OOMW. The present investigation calls attention to the necessity of acclimation for certain fungal and yeasts strains potentially useful for treating highly polluted effluents.

Lipase production by Aspergillus ibericus using olive mill wastewater

“…Regarding this aspect, the involved A. ibericus enzymatic system appears to be repressed when the organic load is high and easily degradable compounds are more available. This behavior was similarly reported for other filamentous fungi by Aissam et al [32]. According to the authors, the degradation of phenols can be adversely affected by media containing more than 20-25 % OMW.…”

Olive mill wastewater treatment using infiltration percolation in column followed by aerobic biological treatment

“…Thus, this COD and BOD 5 contents in the OMWW investigated is very high compared to that recorded in other types of discharges, these values are 200-400 times higher than those of municipal wastewater [32]. Indeed, the COD does not exceed 4.02 g/L in abattoir effluents, which are considered to be the main discharges of a dominant organic nature [33]. OMWW studied are very rich in suspended matter, their content is 29.25 g/L.…”

The Microbiology of Olive Mill Wastes

“…Moreover, the acidic pH of olive mill wastes may be advantageous for this microbial group to outcompete bacteria. Filamentous fungi, such as Aspergillus and Penicillium spp., are common habitants of olive mill wastes [43, 45], while white-rot fungi have been isolated to a lesser extent. It appears that the high salt and sugars concentrations of olive mill wastes as well as the acidic pH favor the growth of osmotolerant yeasts in olive mill wastes [46].…”