Évolution des caractéristiques physico-chimiques, spectroscopiques et éco-toxicologiques des effluents d’huileries d’olive au cours de traitements biologique et chimique

Le premier volet de ce travail consiste à suivre les transformations des effluents d’huileries d’olives traités par un procédé biologique et chimique, en utilisant les différents paramètres physico-chimiques (pH, rapport C/N, phénols totaux, demande chimique en oxygènes (DCO), lipides) et spectroscopiques (UV-visible, IRTF, 13C-RMN). Les résultats du traitement biologique ont permis la mise en évidence des conditions optimales de traitement de ces effluents. Après 45 jours, les traitements ont permis la réduction de la pollution de ces effluents avec des abattements en DCO de 21.8% et 4.8% respectivement pour les traitements sans et avec chaux. La neutralisation du pH par ajout de chaux a montré un abattement de 75.9% en termes de phénols totaux. La spectroscopie IRTF et 13C-RMN ont montré qu’au cours du traitement avec chaux, les groupements aliphatiques diminuent et les structures aromatiques augmentent, ce qui indique la polymérisation de la matière organique. Le suivi de la fraction lipidique montre des variations pour les lipides totaux et pour les fractions lipidiques (lipides neutres, monoglycérides et phospholipides) en fonction du traitement choisi (sans ou avec chaux). Les lipides totaux augmentent pour le traitement sans chaux et diminuent pour le traitement avec chaux, correspondant à la variation des phospholipides. La spectroscopie 13C-RMN a confirmé ces variations et elle a montré la similitude entre le traitement des effluents à la chaux et le traitement au solvant (chloroforme/méthanol). Elle a aussi mis en évidence deux zones spectrales intéressantes C O-alkyle (50 -110 ppm) et C-carboxylique (160-200 ppm). Les résultats du traitement chimique sous UV/TiO2 ont montré une réduction du pouvoir polluant des effluents d’huileries d’olive. Les abattements après 24 heures de traitement sont de 22.2%, 57% et 94.3% respectivement pour la DCO, la coloration (UV à 330 nm) et les phénols totaux. La spectroscopie UV-visible et IRTF ont montré qu’il y a une attaque prioritaire des parties aromatiques et elle fait apparaître dans le processus de dégradation l’existence de trois phases successives qui peuvent correspondre à trois types différents de molécules dans les effluents d’huileries d’olive. Le deuxième volet de ce travail est consacré à l’étude de la toxicité et de la génotoxicité des effluents d’huileries d’olive après traitement biologique sur les plants de Vicia faba à l’aide du test des micronoyaux et d’un essai agronomique. Les résultats du test des micronoyaux ont montré que les effluents non traités sont génotoxiques à une concentration de 10%. Cette génotoxicité est liée à la présence de deux composés phénoliques : l’oleuropeine et l’acide gallique. Après traitement biologique, la génotoxicité de ces effluents a disparu même à une concentration de 20%. Ceci peut être expliqué par l’abattement important des phénols totaux au cours du traitement (75.9%). Le test agronomique a montré l’absence de toxicité des effluents traités par procédé biologique sur Vicia faba. En effet, les doses 5 t/ha et 10 t/ha ont donné des rendements respectivement supérieurs de 36.3% et de 29.9% par rapport au témoin. Les effluents d’huileries d’olive traités par un procédé biologique ne présentent alors aucun risque de toxicité ni de génotoxicité sur les plants de Vicia faba, ils peuvent alors être utilisé, sans risque, comme amendement organique sur les sols marocains. ABSTRACT : The first part of this work concerns the monitoring of treated olive mill waste water (OMWW) transformations during biological and chemical processes : different physico-chemical parameters (pH, C/N ratio, chemical oxygen demand (COD), level of total phenols and lipids) and spectroscopic analysis (UV-Visible, IRTF, 13C-NMR). The results of the biological treatment permitted us to determine the optimal conditions of OMWW treatment. After 45 days, the treatment decreased the COD, particularly for treatments without lime with a drop of 21.8% while the COD drop in treatments with lime only reached 4.8%. Neutralising the pH by the addition of lime had a positive effect on the degradation of total phenols, lowering their levels by 75.9%. The results of FTIR and 13C-NMR spectroscopy showed that during treatment with lime, the aliphatic groups decreased and the aromatic structures increased, indicating polymerisation of the organic matter. The lipid content showed an appreciable change in the relation to the applied treatment both for total lipids and for the lipidic fractions (neutral lipids, monoglycerides and phospholipids). Total lipid increased for treatment without lime and decreased for treatment with lime, corresponding to the variation in the level of phospholipids. 13C-NMR confirmed these variations and showed the likeness between the treatment of the OMWW with lime and the treatment with solvent (chloroform/methanol). The main spectral differences were observed in the C O-Alkyl region (50 -110 ppm) and in the C-carboxylic region (160-200 ppm). The results of the chemical treatment using TiO2 under UV showed depollution of the OMWW. Over 24 hours, the treatment degraded 22.2% of the pollutant COD, 57% of the coloured molecules (UV to 330 nm) and 94.3% of the total phenols. The UV-Visible and FTIR spectroscopy showed extensive attack of the aromatic structures and revealed the occurrence of three successive phases during the degradation process, thought to correspond to three different categories of molecules in the OMWW. The second part of this work concerns the study of the toxicity and the genotoxicity of OMWW after biological treatment, on Vicia faba plants, by micronucleus and agronomic tests. The results of the micronucleus test showed that raw OMWW was genotoxic at a 10% OMWW concentration. This genotoxicity was associated to two phenolic compounds: gallic acid and oleuropein. After biological treatment, the genotoxicity disappeared at a 20% OMWW concentration. This can be explained by the extensive degradation of phenols during the treatment (75.9%). The agronomic test showed the absence of toxicity of treated OMWW on Vicia faba plants. Indeed, at doses of 5 t/ha and 10 t/ha outputs were 36.3% and 29.9% greater than the negative control respectively. OMWW treated by a biological process do not present any risk of toxicity or genotoxicity on Vicia faba plants, the treated effluent can be used, without risk, as organic amendment on Moroccan soils

13C NMR study of the effect of aerobic treatment of olive mill wastewater (OMW) on its lipid-free content

Olive mill wastewater was treated by an aerobic bio-process at different values of pH (with or without addition of lime), for 45 days on a laboratory scale, to evaluate the reduction of the organic load. The lipid content showed an appreciable change in relation to the applied treatment both for total lipids and for the different fractions (neutral lipids, monoglycerides and phospholipids). 13C NMR spectroscopy was performed on initial and final samples both raw and after lipid extraction. The main spectral differences were observed in the C-alkyl region (0–50 ppm), in the C O-alkyl/N-alkyl region (50–110 ppm), and in the C-carboxylic (160–200 ppm) region, providing information on the alterations occurring in the different biochemical entities composing this complex biomatrix (e.g. lipids and carbohydrates) according to the treatment

Assessment of the genotoxicity of olive mill waste water (OMWW) with the Vicia faba micronucleus test

The present study concerns the genotoxicity of olive mill waste water (OMWW) generated in mills producing olive oil in Morocco. The Vicia faba micronucleus test was used to evaluate the genotoxicity of OMWW and the six major phenolic compounds identified by HPLC in this effluent. Five dilutions of OMWW were tested: 0.1, 1, 5, 10 and 20%. Maleic hydrazide was used as a positive control. The results showed that OMWW was genotoxic at 10% dilution. In order to investigate the components involved in this genotoxicity, the six major phenols present in this effluent, oleuropein, gallic acid, 4-hydroxyphenyl acetic acid, caffeic acid, paracoumaric acid and veratric acid, were studied at concentrations corresponding to the genotoxic concentration of the OMWW itself. Two phenols, gallic acid and oleuropein induced a significant increase in micronucleus frequency in Vicia faba; the four other phenols had no significant genotoxic effect. These results suggest that under the experimental conditions of our assay, OMWW genotoxicity was associated with gallic acid and oleuropein

Chemical and spectroscopic analysis of olive mill waste water during a biological treatment

The treatment of olive mill waste water was studied on the laboratory scale. Physico–chemical analyses showed the final products had a mean pH of 5.4 without neutralisation and 5.7 when lime was added to the process. Raising the pH by adding lime had a positive outcome on the degradation of phenols, whose levels were reduced by over 76%. The lime also changed the structure of the organic matter, as seen in the infra-red spectra. Combining the FT-IR and 13C NMR data showed that with addition of lime, the density of aliphatic groups decreased to the benefit of aromatic groups, indicating that polymerisation of the organic matter occurred during the bioprocess. Under our experimental conditions, the biotransformation of olive mill waste water appears to favour the stabilisation of the organic matter through mechanisms analogous to those that lead to the formation of humus in the soil

Photochemical UV/TiO2 treatment of olive mill wastewater (OMW)

Olive mill wastewater (OMW) was treated by photocatalysis using TiO2 under UV irradiation on the laboratory scale. The chemical oxygen demand, the coloration at 330 nm, and the level of phenols all showed decreases which, after a 24-h treatment, reached 22%, 57% and 94%, respectively. The differences between these three values indicate the persistence of colourless, non-phenolic compounds. Application of the novel Fictitious Atomic-Group Separation method showed an increase in carbon oxidation state and confirmed that the attack primarily concerns, aromatic moieties. A fine spectroscopic study revealed the occurrence of three successive phases during the degradation process, thought to correspond to three different categories of molecules in the OMW and the presence of pectin compounds

Treatment of table olive processing wastewaters using novel photomodified ultrafiltration membranes as first step for recovering phenolic compounds

Table olive processing wastewaters (TOPW) have high salt concentration and total phenolic content (TPC) causing many environmental problems. To reduce them, ultrafiltration (UF) was applied for treating TOPW. However, NaCl, which is the main responsible of salinity in TOPW, and phenols are small molecules that cannot be separated by conventional UF membranes. They have serious problems caused by fouling, which can be overcome using membrane modification techniques. For these reasons, photomodification may be an effective technique to obtain a stream rich in TPC due to the changes in membrane surface properties. UV-modification in the presence of two hydrophilic compounds (polyethylene glycol and aluminium oxide) was performed to achieve membranes with high reductions of organic matter and to keep the TPC as high as possible. Commercial polyethersulfone (PES) membranes of 30 kDa were used. Surface modification was evaluated using FTIR-ATR spectroscopy and membrane performance was studied by calculating the rejection ratios of colour, chemical oxygen demand (COD) and TPC. Results demonstrated that UF is a useful pre-treatment to reduce organic matter from TOPW, obtaining a permeate rich in TPC. PES/Al2O3 membranes displayed superior antifouling properties and rejection values, keeping high the TPC (>95%). Therefore, UF using modified membranes is an appropriate and sustainable technique for treating TOPW.The authors thank the financial support of CDTI (Centre for Industrial Technological Development) depending on the Spanish Ministry of Science and Innovation. The authors also thank the Center for Biomaterials and Tissue Engineering (Universitat Politecnica de Valencia) for FTIR-ATR and contact angle measurements.García Ivars, J.; Iborra Clar, MI.; Alcaina Miranda, MI.; Mendoza Roca, JA.; Pastor Alcañiz, L. (2015). Treatment of table olive processing wastewaters using novel photomodified ultrafiltration membranes as first step for recovering phenolic compounds. Journal of Hazardous Materials. 290:51-59. doi:10.1016/j.jhazmat.2015.02.062S515929

Effect of fulvic acids on lead-induced oxidative stress to metal sensitive Vicia faba L. plant

Lead (Pb) is a ubiquitous environmental pollutant capable to induce various morphological, physiological, and biochemical functions in plants. Only few publications focus on the influence of Pb speciation both on its phytoavailability and phytotoxicity. Therefore, Pb toxicity (in terms of lipid peroxidation, hydrogen peroxide induction, and photosynthetic pigments contents) was studied in Vicia faba plants in relation with Pb uptake and speciation. V. faba seedlings were exposed to Pb supplied as Pb(NO3)2 or complexed by two fulvic acids (FAs), i.e. Suwannee River fulvic acid (SRFA) and Elliott Soil fulvic acid (ESFA), for 1, 12, and 24 h under controlled hydroponic conditions. For both FAs, Pb uptake and translocation by Vicia faba increased at low level (5 mg l−1), whereas decreased at high level of application (25 mg l−1). Despite the increased Pb uptake with FAs at low concentrations, there was no influence on the Pb toxicity to the plants. However, at high concentrations, FAs reduced Pb toxicity by reducing its uptake. These results highlighted the role of the dilution factor for FAs reactivity in relation with structure; SRFA was more effective than ESFA in reducing Pb uptake and alleviating Pb toxicity to V. faba due to comparatively strong binding affinity for the heavy metal

Posttreatment of olive mill wastewater by immobilized TiO2 photocatalysis

A photocatalytic reactor with UV/TiO2 was used for the post-treatment of olive mill wastewater after anaerobic digestion. A factorial experimental design was adopted to determine the statistical significance of each parameter tested, namely initial COD, pH, treatment time and recirculation flow, and possible interactions, in three response variables: phenols, colour, and COD removals. Removal efficiencies of 90.8 ± 2.7 %, 79.3 ± 1.9 %, and 50.3 ± 6.3 % were obtained for total phenols (TPh), colour, and COD, respectively. TPh and colour were almost completely removed after 24 h of treatment, while the COD removal was partial. Because increasing the treatment time is economically unfeasible a recirculation to the anaerobic reactor should be considered. Regarding the most significant variables, the TPh removal efficiency is dependent of the initial COD concentration; the colour removal efficiency decreased with increasing COD concentration and pH; and, the COD removal efficiency is directly linked with the treatment time. The interaction between the initial COD and treatment time affect negatively the response variables tested because of the inactivation of some active sites of the TiO2 paper.The Portuguese Science Foundation (FCT) and the European Social Fund (ESF, POPH-QREN) gave financial support through the Post-Doctoral grant attributed to Jose Carlos Costa (SFRH/BDP/48 962/2008) and through the project PTDC/ENR/69 755/2006. The authors thank Dr. M.N. Pons and Dr. O. Zahraa the offer of the reactor and Mr Ing. J. Dussaud from Alstrohm (Pont-Eveque, France) for the TiO2 paper