Biodegradation Of Olive Mill Wastewater Research Articles

Activity and elution profile of laccase during biological decolorization and dephenolization of olive mill wastewater

The performance and enzymatic strategy exhibited by basidiomycete Euc-1, a laccase producing strain, was investigated during the biodegradation of olive mill wastewater (OMW). This strain yielded better decolorization of solidified OMW than Phanerochaete chrysosporium and removed 90% of phenols (initial concentration=800 mg l −1), 73% of color (initial A 465=4.4), and 45% of chemical oxygen demand in batch cultures containing OMW. Since partial phenol removal occurred before the detection of enzymatic activity, no plausible correlation could be established between them. In contrast, decolorization occurred only after the detection of laccase activity and coincided with its production over time. Two laccase fractions (Lac1 and Lac2) were separated by chromatography. OMW strongly induced Lac2 that was almost absent in defined liquid medium. Furthermore, Lac2 was the main laccase fraction in the presence of OMW. This study pointed out that basidiomycete Euc-1 and its ligninolytic system could be a useful tool for the bioremediation of wastewater generated in the process of olive oil extraction.

Roles of two white-rot basidiomycete fungi in decolorisation and detoxification of olive mill waste water.

A Phanerochaete chrysosporium strain was isolated from Moroccan olive mill waste water (OMW) and its ability to degrade OMW in different culture conditions was investigated and compared to that of Pleurotus ostreatus. The results indicated that Ph. chrysosporium isolate is more efficient than Pl. ostreatus in decolorising and detoxifying OMW in the presence of added nutrients. Ph. chrysosporium is able to remove more than 50% of the colour and phenols from OMW within 6 days of incubation, whereas Pl. ostreatus needs more than 12 days to reach similar results in the same conditions. Many factors affecting the treatment of diluted OMW (20%) by Ph. chrysosporium were studied, including the effects of added nutrients, initial pH, temperature and inoculated biomass. Once the optimisation of 20% OMW biodegradation process had been set up, higher OMW concentrations (50%) were tested. The results show that the fungus is capable of reducing all parameters analysed (colour A395, phenol content and chemical oxygen demand) by at least 60%, after only 9 days of growth.

Biodegradation of olive mill wastewaters (OMW) by strains of Scopulariopsis spp. isolated from OMW‐contaminated habitats

Six strains of Scopulariopsis spp. isolated from olive mill wastewater (OMW) disposal ponds were tested for biodegradation of OMW. When growing on undiluted OMW, all strains produced relatively high amounts of biomass [from 19 to 32g (dry weight)/l], and conducted variable reductions of the chemical oxygen demand (34–54%), total phenols (41–71% and pigmentation (8–28%) of the effluent. Best results were obtained by cultivation of strain SC3 for 18 days without agitation or 10 days with agitation. This strain showed a biphasic growth, using the available carbohydrates during the first phase. Degradation of phenolic compounds and OMW decolourization occurred preferentially during the second phase of growth.

The biodegradation of recalcitrant effluents from an olive mill by a white-rot fungus

Biodegradation of olive-mill wastewater (OMW) was performed by the polyurethane-immobilized mycelium of Lentinula edodes. Throughout three consecutive treatment cycles of the effluent significant abatements of its polluting characteristics were observed. In fact, its contents in total organic carbon, total phenols, total ortho-diphenol were dramatically reduced. In addition, a significant effluent decolorization was evident.

Improvement of the anaerobic biodegradation of olive mill wastewaters by prior ozonation pretreatment

The purification of olive mill wastewaters (OMW) is investigated by a single anaerobic digestion in a batch reactor containing immobilized microorganisms, and by the combination of an ozonation pretreatment followed by an anaerobic digestion. In the single anaerobic digestion the removal of the COD is determined and the methane yield coefficient, which is the best measure of the extent of transformation of the biodegradable substrate, is also obtained, its value being 194 ml CH4/g COD. A kinetic study is performed by using the Monod model combined with the Levenspiel model, due to the presence of inhibition effects. Both models lead to the determination of the kinetic parameters of this anaerobic treatment: kinetic constants, critical substrate concentration of inhibition and inhibitory parameter. In the combined process, the ozonation pretreatment of OMW achieves a great reduction in the phenolic compounds, leading to a significant increase in the methane yield coefficient in the following anaerobic digestion, its value being 266 ml CH4/g COD.

Toxicity and biodegradability of olive mill wastewaters in batch anaerobic digestion

The anaerobic biodegradability and toxicity of olive mill waste-waters (OMW) were studied in batch anaerobic digestion experiments. Anaerobic digestion of OMW or the supernatant of its centrifugation, the methane production was achieved at up to 5–15% (V/V) dilution corresponding to only 5–20 g/L COD. The washed suspended solids of OMW were toxic at up to 80 g/L COD; however, the kinetic of biodegradability of OMW or the supernatant was faster than for suspended solids, which are constituted meanly of cellulose and lignin. The darkly colored polyphenols induce the problem of biodegradation of OMW, whereas the long chain fatty acids (LCFA), tannins and simple phenolic compounds are responsible its toxicity for methanogenic bacteria.

Decolourization of olive mill waste-waters by the white-rot fungus Phanerochaete chrysosporium: involvement of the lignin-degrading system

The decolourization of olive mill waste-waters (OMW) by Phanerochaete chrysosporium was investigated. OMW decolourization occurred during the primary phase of growth when glycerol was used as the carbon source, and during secondary metabolism in nitrogen-limited cultures. The decolourization was found to be extensive (74% of colour removal, 80% of chemical oxygen demand removal) when the cultures were supplement d with veratryl alcohol and flushed with O2. The biodegradation system was repressed with glutamate as a nitrogen source. These results suggest that all or part of the lignin-degrading system of P. chrysosporium played a role in biodegradation of OMW. The decolourization of OMW corresponds to depolymerization of high-molecular-mass aromatics combined with mineralization of a wide range of monoaromatic compounds.