Olive oil mill wastewaters: phenolic content characterization during degradation by Coriolopsis gallica

Optimization of the Decolorization of the Reactive Black 5 by a Laccase-like Active Cell-Free Supernatant from Coriolopsis gallica

The textile industry generates huge volumes of colored wastewater that require multiple treatments to remove persistent toxic and carcinogenic dyes. Here we studied the decolorization of a recalcitrant azo dye, Reactive Black 5, using laccase-like active cell-free supernatant from Coriolopsis gallica. Decolorization was optimized in a 1 mL reaction mixture using the response surface methodology (RSM) to test the influence of five variables, i.e., laccase-like activity, dye concentration, redox mediator (HBT) concentration, pH, and temperature, on dye decolorization. Statistical tests were used to determine regression coefficients and the quality of the models used, as well as significant factors and/or factor interactions. Maximum decolorization was achieved at 120 min (82 ± 0.6%) with the optimized protocol, i.e., laccase-like activity at 0.5 U mL−1, dye at 25 mg L−1, HBT at 4.5 mM, pH at 4.2 and temperature at 55 °C. The model proved significant (ANOVA test with p < 0.001): coefficient of determination (R²) was 89.78%, adjusted coefficient of determination (R²A) was 87.85%, and root mean square error (RMSE) was 10.48%. The reaction conditions yielding maximum decolorization were tested in a larger volume of 500 mL reaction mixture. Under these conditions, the decolorization rate reached 77.6 ± 0.4%, which was in good agreement with the value found on the 1 mL scale. RB5 decolorization was further evaluated using the UV-visible spectra of the treated and untreated dyes.

Catalytic Steam Reforming of Biomass-Derived Oxygenates for H2 Production: A Review on Ni-Based Catalysts

The steam reforming of ethanol, methanol, and other oxygenates (e.g., bio-oil and olive mill wastewater) using Ni-based catalysts have been studied by the scientific community in the last few years. This process is already well studied over the last years, being the critical point, at this moment, the choice of a suitable catalyst. The utilization of these oxygenates for the production of “green” H2 is an interesting alternative to fuel fossils. For this application, Ni-based catalysts have been extensively studied since they are highly active and cheaper than noble metal-based materials. In this review, a comparison of several Ni-based catalysts reported in the literature for the different above-mentioned reactions is carried out. This study aims to understand if such catalysts demonstrate enough catalytic activity/stability for application in steam reforming of the oxygenated compounds and which preparation methods are most adequate to obtain these materials. In summary, it aims to provide insights into the performances reached and point out the best way to get better and improved catalysts for such applications (which depends on the feedstock used).

Potential of Halophilic Penicillium chrysogenum Isolated from Algerian Saline Soil to Produce Laccase on Olive Oil Wastes

Enzymes from halophilic fungi offer interesting biotechnological applications, which lead us to explore novel producing strains. 23 fungi were isolated from Algerian saline soil. Among the three strains presenting laccase activities, one exhibited the high decolourising capacity of olive mill wastewaters. Identification showed that the efficient isolate GS15 belongs to Penicillium chrysogenum. This strain achieves optimal growth at 15% NaCl, 25 °C, pH 5, dark, aerobic and static conditions. The selected fungus is capable of producing extracellular enzymes as follows: caseinase, tannase, esterase and lipase. The laccase activities produced by P. chrysogenum on raw olive wastes are being reported here for the first time. GS15 produced 183.0 and 203.0 U/L of laccase activities in 10% and 20% unsupplemented olive mill wastewaters, respectively. The significant enzymatic activities can be correlated to the high ability of GS15 to decolourise industrial wastewater from the olive oil extraction. In these conditions no pre-treatment of olive wastewaters was needed. On the untreated grinded and non-grinded olive pomace, the laccase activity was 5.78 U/g and 5.36 U/g, respectively. Because the halophilic fungus has basic requirement for growth, this fungal strain is promising for saline biotechnological applications.

Olive Mill Wastewater Valorization through Steam Reforming Using Multifunctional Reactors: Challenges of the Process Intensification

Olive oil mill wastewater (OMW) is a polluting stream derived from the production of olive oil and is a source of environmental pollution; this is relevant in many countries around the world, but particularly in all the Mediterranean region where major producers are located. In this effluent, several pollutants are present—namely, sugars, fatty acids, and polyphenols, among others. Nowadays, to reduce the pollutant load, several treatment techniques are applied, but these technologies have numerous cost and efficiency problems. For this reason, the steam reforming of the OMW (OMWSR) presents as a good alternative, because this process decreases the pollutant load of the OMW and simultaneously valorizes the waste with the production of green H2, which is consistent with the perspective of the circular economy. Currently, the OMWSR is an innovative treatment alternative in the scientific field and with high potential. In the last few years, some groups have studied the OMWSR and used innovative reactor configurations, aiming to improve the process’ effectiveness. In this review, the OMW treatment/valorization processes, the last developments on catalysis for OMWSR (or steam reforming of similar species present in the effluent), as well as the last advances on OMWSR performed in multi-functional reactors are addressed.

Removal of Phenolic Compounds from Olive Mill Wastewater by a Polydimethylsiloxane/oxMWCNTs Porous Nanocomposite

User-friendly and energy-efficient methods able to work in noncontinuous mode for in situ purification of olive mill wastewater (OMW) are necessary. Herein we determined the potential of oxidized multiwalled carbon nanotubes entrapped in a microporous polymeric matrix of polydimethylsiloxane in the removal and recovery of phenolic compounds (PCs) from OMW. The fabrication of the nanocomposite materials was straightforward and evidenced good adsorption capacity. The adsorption process is influenced by the pH of the OMW. Thermodynamic parameters evidenced the good affinity of the entrapped nanomaterial towards phenols. Furthermore, the kinetics and adsorption isotherms are studied in detail. The presence of oil inside the OMW can speed up the uptake process in batch adsorption experiments with respect to standard aqueous solutions, suggesting a possible use of the nanocomposite for fast processing of OMW directly in the tank where they are stored. Moreover, the prepared nanocomposite is safe and can be easily handled and disposed of, thus avoiding the presence of specialized personnel. After the adsorption process the surface of the nanomaterial can be easily regenerated by mild treatments with diluted acetic acid, thus permitting both the recyclability of the nanomaterial and the recovery of phenolic compounds for a possible use as additives in food and nutraceutical industries and the recovery of OMW for fertirrigation.

OMW spillage control tool based on tracking p-Coumaric acid degradation by HPLC

Olive mill wastewater (OMW) is a major watercourse pollutant agent with a high concentration of phenolic compounds. It is estimated that 30 million OMW m³ are released into rivers every year. Protecting the health of these courses against the uncontrolled discharges implies establishing an adequate legislation, where spillage control tools play a fundamental role. In this paper, a new tool for OMW spillage control is discussed. It is based on the use of a RP-HPLC-UV protocol to track p-Coumaric acid (pCA), a characteristic OMW phenolic compound, and its derivative compounds through their chemical oxidation and biological anaerobic degradation. Laboratory assays and real-life experiences allowed to determine degradation routes and apparition times for every pCA derivative, making it possible to detect an OMW spill and assess its age. Moreover, this RP-HPLC-UV introduces solid advantages over previous detection procedures, namely, quicker response times and smaller costs than HPLC methods and superior specificity than colorimetric methods. Finally, this tool was put to test in an actual OMW-polluted watercourse. In all scenarios, the tool demonstrated solid reliability.

Synthetic olive mill wastewater treatment by Fenton's process in batch and continuous reactors operation

Degradation of total phenol (TPh) and organic matter, (expressed as total organic carbon TOC), of a simulated olive mill wastewater was evaluated by the Fenton oxidation process under batch and continuous mode conditions. A mixture of six phenolic acids usually found in these agro-industrial wastewaters was used for this purpose. The study focused on the optimization of key operational parameters of the Fenton process in a batch reactor, namely Fe²⁺ dosage, hydrogen peroxide concentration, pH, and reaction temperature. On the assessment of the process efficiency, > 99% of TPh and > 56% of TOC removal were attained when [Fe²⁺] = 100 ppm, [H₂O₂] = 2.0 g/L, T = 30 °C, and initial pH = 5.0, after 300 min of reaction. Under those operational conditions, experiments on a continuous stirred-tank reactor (CSTR) were performed for different space-time values (τ). TOC and TPh removals of 47.5 and 96.9%, respectively, were reached at steady-state (for τ = 120 min). High removal of COD (> 75%) and BOD₅ (> 70%) was achieved for both batch and CSTR optimum conditions; analysis of the BOD₅/COD ratio also revealed an increase in the effluent's biodegradability. Despite the high removal of lumped parameters, the treated effluent did not met the Portuguese legal limits for direct discharge of wastewaters into water bodies, which indicates that coupled chemical-biological process may be the best solution for real olive mill wastewater treatment.

Assessment of Coriolopsis gallica-treated olive mill wastewater phytotoxicity on tomato plants

The aim of the present study was to evaluate the phytotoxicity of olive mill wastewater (OMW) after being treated by the white-rot fungus Coriolopsis gallica. For this, the effect of irrigation with treated OMW (TOMW) and untreated OMW (UOMW) on tomato plants (Lycopersicon esculentum) for 3 weeks was studied. The control plants were irrigated with distilled water. Agronomic tests were performed in pot experiments in a greenhouse using the randomized complete block (RCB) experimental design. The relative leaf height (RLH), as a morphological parameter, and the content of total phenols in the roots and total chlorophyll [Cha + Chb] and reducing sugars in the leaves, as physiological parameters, were selected as responses of the experimental design. The results obtained showed that [Cha + Chb] in the leaves of tomato growth under TOMW was enhanced by 36.3 and 19.4 % compared to the plant growth under UOMW and to the controls, respectively. Also, reducing sugar concentrations were closed to those of the control plants, ranging from 0.424 to 0.678 g/L for the different dilutions tested. However, the plants irrigated with UOMW showed lower reducing sugar concentrations ranging from 0.042 to 0.297g/L. The optimum RLH (0.537) was observed in the plants irrigated with TOMW diluted at (1:4), this value being higher than that observed in the controls (0.438). Our study proved that the irrigation with TOMW significantly improved tomato growth and photosynthesis activity over those irrigated with UOMW. Optimization of TOMW as a fertilizer was obtained for a dilution of 1:4. From the obtained results, it can be concluded that OMW treated by C. gallica holds potential to be used as a fertilizer for tomato plants. Graphical Abstract ᅟ Please provide a caption for the graphical abstract.The graphical abstract is improved and sent as attachment Please replace it.