Olive Oil Mill Wastewater Research Articles

An Olive Oil Mill Wastewater Extract Improves Chemotherapeutic Activity Against Breast Cancer Cells While Protecting From Cardiotoxicity.

Cardiovascular toxicity in cancer patients receiving chemotherapy remains one of the most undesirable side effects, limiting the choice of the most efficient therapeutic regimen, including combinations of different anticancer agents. Anthracyclines (doxorubicin) and antimetabolites (5-fluorouracil (5-FU), capecitabine) are among the most known agents used in breast cancer and other neoplasms and are associated with cardiotoxic effects. Extra-virgin olive oil (EVOO) is rich in polyphenols endowed with antioxidant cardioprotective activities. Olive mill wastewater (OMWW), a waste product generated by EVOO processing, has been reported to be enriched in polyphenols. In this study, we investigated the activities of polyphenol-rich extract from OMWW, A009, in cooperation with chemotherapy on two breast cancer cell lines, namely, BT459 and MDA-MB-231, in a cardio-oncology perspective. The effects of A009 on cardiac cells were also investigated with and without chemotherapeutic agents. Cell viability was determined on BT459 and MDA-MB-231 (i.e., breast cancer cells) and H9C2 (i.e., rat cardiomyocytes) cells, using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. A spheroids assay was used as a 3D in vitro model on BT459 and MDA-MB-231 cells. For in vivo studies, the murine sponge assay of angiogenesis was used as a model of breast cancer-associated vascularization. The embryo of Danio rerio (zebrafish) was used to detect the cardioprotective activities of the OMWW. We found that the A009 extract exhibited antiangiogenic activities induced by breast cancer cell supernatants and increased T-cell recruitment in vivo. The combination of the OMWW extracts with doxorubicin or 5-FU limited BT459 and MDA-MB-231 cell viability and the diameter of 3D spheroids, while mitigating their toxic effects on the rat H9C2 cardiomyocytes. Cardioprotective effects were observed by the combination of OMWW extracts with doxorubicin in zebrafish embryos. Finally, in human cardio myocytes, we observed 5-FU-induced upregulation of the inflammatory, senescence-associated cytokine IL6 and p16 genes, which expression was reduced by OMWW treatment. Our study demonstrates that the polyphenol-rich purified OMWW extract A009 combined with cancer chemotherapy could represent a potential candidate for cardiovascular protection in breast cancer patients, while increasing the effects of breast cancer chemotherapy.

Biological activities and phenolic compounds of olive oil mill wastewater from Abani, endemic Algerian variety

The current study aimed to determination of cytotoxicity, antioxidant, anti-inflammatory, anti-hemolytic, and anticoagulant activities of phenolic compounds extracted from olive oil mill wastewater (OMW) issue from the cold extraction of olive oil from Khenchela eastern in Algeria. The LC–MS (liquid chromatography–mass spectrometry) results were revealed the presence of 20 phenolic compounds in the extract of OMW and mostly consisted of Kaempferol, 4,5-di-O-caffeoyquinic acid, quinic acid, and caffeic acid. The extracts possessed effective reducing power (FRAP) and high radical scavenging activity against DPPH (2,2-diphenyl-1-picrylhydrazyl), ABTS + (2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) free radicals, and it inhibited cytochrome c reduction in a dose-dependent manner. They exert a protective effect on red blood cells, and they were found to exhibit the highest inhibitory effect anti-inflammatory activity using inhibition of protein denaturation (IPD) and membrane stabilizing potential (MSP) tests (80.46 ± 3.81 µg/mL and 87.43 ± 0.66 µg/mL) more than the standard used. The extract also showed the greatest anticoagulant activity in both the endogenous and exogenous routes (44.77 ± 0.25 s and 15.84 ± 0.12 s, respectively). Based on these findings, it is reasonable to infer that OMW is a good source of natural phenolic compounds with potential antioxidant, anti-inflammatory, and anticoagulant properties.

Optimization of coagulation process for treatment of olive oil mill wastewater using Moringa oleifera as a natural coagulant, CCD combined with RSM for treatment optimization

Wastewater from olive oil mills (OMW) represents a major environmental problem that requires effective treatment to decrease pollution. In the present work, the treatment of olive oil mill wastewater by coagulation was studied using Moringa Oliefera as a natural coagulant. The processing is optimized using both Design of Experiments (DOE) methodology and a central composite design (CCD) combined with the response surface methodology (RSM). The optimization describes the relationship between 3 responses (turbidity, COD, and polyphenols) and 4 independent variables (Moringa Oliefera concentration, pH, agitation speed, and time). Analysis of variance ANOVA using Fisher's test indicated that the established models were significant. The study showed that the model was characterized by a good fit, justified by the very high adjusted coefficient of determination (R2Adj = 86.73%, R2Adj = 90.39% and R2Adj = 93.33% for the turbidity, COD, and polyphenols, respectively). Furthermore, the optimum conditions for a good purification performance of OMW using Moringa Oliefera are as follows [Mo] = Moringa Oliefera = 65 g/L, pH = 6, Agitation speed (Ss) = 35 rpm and Agitation time (St) = 25 min. Under these conditions, the turbidity, COD and polyphenol removal efficiencies are 96%, 88%, and 86% respectively. Finally, the proposed treatment process is a critical development in sustainable environmental technologies.

Anti-Inflammatory Activity Of Polyphenols From Olive Oil Mill Wastewaters

Olive oil mill wastewater (OMW) is a by-product of the olive oil industry. It is very polluting and causes serious environmental problems, but is very loaded with polyphenols, which have antioxidant and anti-inflammatory power. This study aimed to evaluate in vitro the anti-inflammatory potential of the phenolic extract of OMW from two varieties, Chemlal and Zlitni, extracted from a modern olive mill located in Khenchela, eastern Algeria. The maceration method did the extraction of the polyphenols. The dosage of total polyphenols and flavonoids content was determined by Folin-Ciocalteu and aluminum trichloride methods successively. Two tests made the anti-inflammatory activity, inhibition of protein denaturation (IPD) and membrane-stabilizing potential (MSP), comparing with sodium diclofenac. The results obtained showed that the phenolic extract of OMW of Chemlal was found to exhibit the highest inhibitory effect anti-inflammatory activity (IPD: IC50 = 91.27 ± 2.73 µg/mL, and MSP: IC50=98.41 ± 1.22 µg/mL) more than the phenolic extract of Zlitni and the standard used (sodium iclofenac). The in vitro assays carried out show that the phenolic extract of OMW has an important source of natural anti-inflammatory agents, which can be used in the pharmaceutical industry and on the other hand reducing its dangerous impact on the environment.

Potential use of olive oil mill wastewater for bacterial cellulose production

ABSTRACT In this study, olive oil mill wastewater (OOMW), an important waste in the Mediterranean basin, was evaluated to produce bacterial cellulose (BC). For this purpose, the effects of different ratios of OOMW fractions (25–100%) and some additional nutrients (yeast extract, peptone and Hestrin-Schramm medium (HS) components) on BC productions were investigated. Unsupplemented OOMW medium (75% and 100%) yielded as much as BC obtained in HS medium (0.65 g/L), while enrichment of OOMW medium (%100) with yeast extract (5 g/L) and peptone (5 g/L) increased the amount of BC by 5.5 times, reaching to 5.33 g/L. In addition, produced BCs were characterized by FT-IR, TGA, XRD and SEM analyses. BC from OOMW medium (100% OOMW with supplementation) has a high thermal decomposition temperature (316.8°C), whereas it has lower crystallinity index (57%). According to the FT-IR analysis, it was observed that the components of OOMW might be absorbed by BCs. Thus, higher yield productions of BCs from OOMW media compared to BC obtained from HS medium indicate that olive oil industry wastes can be integrated into BC production for industrial applications.

Reinforced-concrete Bond with Brine and Olive Oil Mill Wastewater

Since the interaction between the steel reinforcement and concrete directly controls the bond strength between them, poor bond performance results in a direct negative effect on the existing state of reinforced concrete structures. This bond is one of the most important factors affecting the strength of reinforced concrete. The bond strength is measured using the pull-out test. The present paper discusses the effect of the addition of brine and olive oil mill wastewaters to the reinforced concrete mixes. The main objective of this study is to determine the effect of brine wastewaters and olive oil mill wastewaters on the bond strength between steel and concrete when adding each of the admixtures to the concrete components. Pull-out tests were conducted on concrete mixes with additive contents of 2.5, 5, 7.5, 10, and 15 % by weight of water for each. It was found that the bonding strength of reinforced concrete specimens with an olive oil mill and brine wastewater improved and decreased by approximately 6–10% and 2–5%, respectively, if compared to the reference samples. These values were observed for mixes with additive contents of 7.5% for olive oil mill wastewaters and 10% for brine wastewaters. Doi: 10.28991/CEJ-2022-08-02-010 Full Text: PDF

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.

Sequencing batch reactor efficiency to reduce pollutant in olive oil mill wastewater mixed with urban wastewater

Sequencing batch reactor efficiency to reduce pollutant in olive oil mill wastewater mixed with urban wastewater

Olive oil mill wastewater treatment by a combined process of freezing, sweating and thawing

Olive oil mill wastewater treatment by a combined process of freezing, sweating and thawing

Monitoring Olive Oil Mill Wastewater Disposal Sites Using Sentinel-2 and PlanetScope Satellite Images: Case Studies in Tunisia and Greece

Mediterranean countries are known worldwide for their significant contribution to olive oil production, which generates large amounts of olive mill wastewater (OMW) that degrades land and water environments near the disposal sites. OMW consists of organic substances with high concentrations of phenolic compounds along with inorganic particles. The aim of this study is to assess the effectiveness of satellite image analysis techniques using multispectral satellite data with high (PlanetScope, 3 × 3 m) and medium (Sentinel-2, 10 × 10 m) spatial resolution to detect Olive Mill Wastewater (OMW) disposal sites, both in the SidiBouzid region (Tunisia) and in the broader Rethymno region on the island of Crete, (Greece). Documentation of the sites was carried out by collecting spectral signatures of OMW at temporal periods. The study integrates the application of a variety of spectral vegetation indices (VIs), such as the Normalized Difference Vegetation Index (NDVI), in order to evaluate their efficiency in detecting OMW disposal areas. Furthermore, a set of image-processing methods was applied on satellite images to improve the monitoring of OMW ponds including the false-color composites (FCC), the Principal Component Analysis (PCA), and image fusion. Finally, different classification algorithms, such as the ISODATA, the maximum likelihood (ML), and the Support Vector Machine (SVM) were applied to both satellite images in order to assist in the overall approach to effectively detect the sites. The results obtained from different approaches were compared, evaluating the efficiency of Sentinel-2 and PlanetScope images to detect and monitor OMW disposal areas under different morphological environments.

Use of Ni-containing catalysts for synthetic olive mill wastewater steam reforming

The olive oil mill wastewater (OMW) is a by-product (with a high organic load) derived from the production of the olive oil. The OMW steam reforming (OMWSR) process was studied herein, aiming to decrease the environmental damage of such effluents; simultaneously, the waste is economically and energetically valorized with the H2 production. Several Ni-containing catalysts were prepared and tested to compare their performances for the OMWSR using a synthetic OMW effluent; still, stability tests were also carried out. The materials were extensively characterized: thermogravimetric analysis, temperature-programmed oxidation/reduction, temperature-programmed desorption of CO2/NH3, chemisorption of H2, inductively coupled plasma optical emission spectrometry and physical adsorption-desorption of N2 at −196 °C. Amongst the materials tested, the Ni–Ru/SiO2 sample stood out, exhibiting high catalytic performance: at 400 °C, the H2 yield (>8 molH2·molOMW-1) and conversion of total organic carbon (≈75%) were high during all the 24 h of the long-term test, with only a small deactivation being noticed.

Grape pomace in equine nutrition: effect on antioxidant status

Grape pomace in equine nutrition: effect on antioxidant status

Fe3+- IDS as a new green catalyst for water treatment by photo-Fenton process at neutral pH

In this work, a new green and fully biodegradable (96% after 28 days) catalyst, Fe3+-iminodisuccinate complex (Fe-IDS), was prepared, characterized and applied in Fenton processes (dark and photo-Fenton) for water treatment, using phenol as model organic pollutant. Experiments were performed both in dark and under solar/UV-C radiation to evaluate the effect of the light source and [H2O2] (fixed at 5.3 mM)/[Fe-IDS] ratio on the catalytic degradation of phenol (50 mg L−1). Subsequently, photo-Fenton IDS supported process was compared to other advanced oxidation processes (AOPs) (namely, conventional Fenton at pH 3 and H2O2 photolysis, under solar and UV-C irradiation, respectively). The best results (54% and 49% COD removals for solar and UV-C based processes, respectively) were obtained using a [H2O2]/[Fe-IDS] molar ratio of 250 (R250), corresponding to 0.021 mM of Fe-IDS followed by R500 (0.01 mM of Fe-IDS) and R150 (0.035 mM of Fe-IDS). Process efficiency was in the order solar/Fe-IDS/H2O2 >UV-C/Fe-IDS/H2O2 >Fe-IDS/H2O2 (k = −0.0114, −0.0073 and −0.0018 min−1 respectively) for R250. A complete removal of phenol in terms of COD was obtained for solar/Fe-IDS/H2O2 and UV-C/Fe-IDS/H2O2. Furthermore, the application of Fe-IDS complex for real industrial (olive oil mill) wastewater treatment was also investigated (initial COD in diluted sample 2.4 g L−1). At constant H2O2 concentration (58.82mM), the best performance in terms of COD removal (55%, k = 0.0031 min−1) and biodegradability (BOD5/COD increased from 0.16 to 0.45) was obtained for the condition R150 (0.37 mM of Fe-IDS). Fe-IDS allows to overcome the main limitation (acidic pH) of conventional (photo)Fenton process, making the IDS supported (photo)Fenton an attractive option for water and wastewater treatment in a wide pH range.

Olive mill wastewater valorization through steam reforming using hybrid multifunctional reactors for high-purity H2 production

The main purpose of this study was to assess the benefits of different hybrid multifunctional reactors (sorption-enhanced reactor (SER), membrane reactor (MR) and sorption-enhanced membrane reactor (SEMR)) comparatively to a traditional reactor (TR) for H2 production through the steam reforming of olive oil mill wastewater (OMWSR). In all reactor configurations, an in-house prepared Ni-Ru/Ce-SiO2 catalyst was used, combined in the SERs with a potassium-promoted hydrotalcite-based sorbent to capture CO2. Additionally, in the MR and SEMR configurations, a commercial Pd-Ag membrane was utilized to separate H2 from the reaction medium.It was verified an increase in both the H2 production and catalyst stability using the SER (during the pre-breakthrough of CO2) in comparison with the TR. However, a higher enhancement of the H2 yield was observed using the SEMR (again during the pre–breakthrough period), which was less pronounced after the saturation of the sorbent (i.e., in the MR), due to the effect of the H2-selective membrane only. Furthermore, pure H2 can be obtained in the permeate side of the membrane reactors (in the absence of sweep gas).It was also demonstrated that the use of such multifunctional reactors (and particularly the SEMR) in the steam reforming of real olive mill effluents allows reducing drastically the pollutant load of these streams, while economically valorizing this waste with the production of green H2.

Effect of storage time on the biodegradability of olive oil mill wastewater from the cold extraction of olive oil system

Abstract The olive oil processing industry’s liquid effluents (OMW) have a polluting capacity for the ecosystems. This study aimed to evaluate the physicochemical quality of OMW of two varieties of separated and combined olives cultivated in Khenchela Eastern Algeria, from the cold extraction of the olive oil extraction system. These was to determine their degree of pollution and biodegradability during one year of storage at ambient temperature to recommend the correct treatment for each storage time. Results of the measured parameters pH, EC,TSS percent, H2O percent, lipids, DM, OM, MM, VM, COT percent, NTK percent, C/N, BOD5, COD, BI, TOM, BOD5/COD show that wastewater from olive oil mills has an acid pH, and they are very loaded with organic matter evaluated in terms of COD and BOD5, quite filled with minerals. The storage of olive mill waste can reduce progressively the pollution caused by this waste. Whereas during one year, the reduction rate of COD, BOD5, TOM, BI, is respectively 29.4%, 54.8%, 39.16%, 54.2%, but C/N, BOD5/COD continue to increase as well as pH that continues to decrease during the storage. Accordingly, storing olive mill waste during a year reduces its pollution rate, so it is slowly biodegradable. When disposing of it, an adequate treatment procedure must be required to protect the environment.

Depuration Performance of Aerated Tanks Simulating Lagoons to Treat Olive Oil Mill Wastewater under Different Airflow Rates, and Concentrations of Polyphenols and Nitrogen

The uncontrolled disposal of olive oil mill wastewater (OMW) is hazardous for the health of water and soil, since this wastewater shows low pH and high contents of organic matter and polyphenols (PP). Lagooning is one of the most common treatment systems for agro-industrial wastewater (such as OMW), due to its low cost and easy management. Aeration allows reducing the low depuration time, which is a constraint for this system. Despite this potential feasibility, literature about OMW lagooning is not abundant. Moreover, the effects of the aeration rates, concentration of polyphenols and nitrogen shortage on depuration performance of lagoons treating OMW have not been properly explored. This study analyzes the removal rates of COD and PP, and variations of pH in OMW treated in aerated tanks at the laboratory scale simulating lagooning systems. Compared to the non-aerated tanks, aeration of OMW increased the removal rates from 61% to 90% (for COD) and from 52% to 64% (for PP). Permanent aeration was more advisable compared to intermittent flow rates. Increasing concentrations of PP noticeably reduced the COD removal rates, which were halved at a 4-fold PP concentration. In contrast, the PP removal rate was constant at every concentration experimented. Compared to the COD:N value suggested by literature for aerobic processes (100:5), a shortage in nitrogen availability reduced both COD (by about 20–25%) and PP removal rates (by 25%), the latter only when COD:N was higher 400:5. The pH was less influenced by the variations in aeration rates, PP concentration and COD:N ratio compared to COD and PP removal. This investigation provides indications about the most suitable operation parameters (airflow rates, inhibiting PP concentration, and optimal COD:N) in aerated lagooning of OMW towards environmentally sound treatments of highly polluting wastewater.

Enzymatic oxidation of oleuropein and 3-hydroxytyrosol by laccase, peroxidase, and tyrosinase.

The oxidation of oleuropein and 3-hydroxytyrosol by oxidases laccase, tyrosinase, and peroxidase has been studied. The use of a spectrophotometric method and another spectrophotometric chronometric method has made it possible to determine the kinetic parameters Vmax and KM for each enzyme. The highest binding affinity was shown by laccase. The antioxidant capacities of these two molecules have been characterized, finding a very similar primary antioxidant capacity between them. Docking studies revealed the optimal binding position, which was the same for the two molecules and was a catalytically active position. PRACTICAL APPLICATIONS: One of the biggest environmental problems in the food industry comes from olive oil mill wastewater with a quantity of approximately 30 million tons per year worldwide. In addition, olive pomace, the solid residue obtained from the olive oil production, is rich in hydroxytyrosol and oleuropein and the action of enzymatic oxidases can give rise to products in their reactions that can lead to polymerization. This polymerization can have beneficial effects because it can increase the antioxidant capacity with potential application on new functional foods or as feed ingredients. Tyrosinase, peroxidase, and laccase are the enzymes degrading these important polyphenols. The application of a spectrophotometric method for laccase and a chronometric method, for tyrosinase and peroxidase, allowed us to obtain the kinetic information of their reactions on hydroxytyrosol and oleuropein. The kinetic information obtained could advance in the understanding of the mechanism of these important industrial enzymes.

Potential of Olive Oil Mill Wastewater as a Source of Polyphenols for the Treatment of Skin Disorders: A Review.

Current trends toward naturally occurring compounds of therapeutic interest have contributed to an increasing number of studies on olive oil phenolics in the treatment of diseases with oxidative and inflammatory origins. Recent focus has been on olive oil wastewater, which is richer in phenolic compounds than olive oil itself. In this review, we present findings demonstrating the potential use of olive mill wastewater in dermatology. Particular attention is given to compounds with proven benefits in topical pharmacology: caffeic and ferulic acids, tyrosol and hydroxytyrosol, verbascoside, and oleuropein. The review is divided into different sections: inflammatory skin diseases, microbial effects, wound healing in addition to the antimelanoma properties of olive mill waste phenolics, and their potential in sun protection agents. There is strong evidence to support further studies into the valorization of this abundant and sustainable source of phenolic compounds for use in dermatology and dermo-cosmetic preparations.

Optimisation of COD removal from the olive oil mill wastewater by combined electrocoagulation and peroxone process: modelling and determination of kinetic coefficients

ABSTRACT The olive oil extraction industry is one of the most extensive industries, especially in the Mediterranean region. The wastewater produced in this industry contains high concentrations of organic pollutants, resistant and toxic compounds that, if not treated, can threaten the health of the environment. In the present study, the optimisation of the combined process of electrocoagulation and peroxone using central composite design of the response surface methodology with the help of Design-Expert V.11 The parameters of current density (0.06–0.73 A dm−2) and reaction time (5–45 min) in the process of electrocoagulation and the parameters of hydrogen peroxide concentration (4–12 ml) and reaction time (10–90 minutes) in the peroxone process were investigated on the COD removal efficiency. The design results showed that the quadratic model was significant for both processes and was determined as the selected model. The optimal conditions determined by the software in the process of electrocoagulation were 0.5 A dm−2 and 34 minutes and in the peroxone process, concentration of hydrogen peroxide and the time were obtained 12 ml and 62 minutes, respectively. In these conditions, the COD removal efficiency of the processes was determined 79.8% and 52.8%, respectively. Under optimal conditions, in peroxone process ozone consumption was reduced to 0.88 mg per mg of removed COD. Also, according to the results of Pseudo-first-order kinetics, constant rate increases with increasing of hydrogen peroxide concentration. The results obtained in this study were confirmed the application of electrocoagulation process along with advanced oxidation of proxone for effective treatment of effluents of this industry and similar industries.

Bioactive Compounds in Waste By-Products from Olive Oil Production: Applications and Structural Characterization by Mass Spectrometry Techniques.

In recent years, a remarkable increase in olive oil consumption has occurred worldwide, favoured by its organoleptic properties and the growing awareness of its health benefits. Currently, olive oil production represents an important economic income for Mediterranean countries, where roughly 98% of the world production is located. Both the cultivation of olive trees and the production of industrial and table olive oil generate huge amounts of solid wastes and dark liquid effluents, including olive leaves and pomace and olive oil mill wastewaters. Besides representing an economic problem for producers, these by-products also pose serious environmental concerns, thus their partial reuse, like that of all agronomical production residues, represents a goal to pursue. This aspect is particularly important since the cited by-products are rich in bioactive compounds, which, once extracted, may represent ingredients with remarkable added value for food, cosmetic and nutraceutical industries. Indeed, they contain considerable amounts of valuable organic acids, carbohydrates, proteins, fibers, and above all, phenolic compounds, that are variably distributed among the different wastes, depending on the employed production process of olive oils and table olives and agronomical practices. Yet, extraction and recovery of bioactive components from selected by-products constitute a critical issue for their rational valorization and detailed identification and quantification are mandatory. The most used analytical methods adopted to identify and quantify bioactive compounds in olive oil by-products are based on the coupling between gas- (GC) or liquid chromatography (LC) and mass spectrometry (MS), with MS being the most useful and successful detection tool for providing structural information. Without derivatization, LC-MS with electrospray (ESI) or atmospheric pressure chemical (APCI) ionization sources has become one of the most relevant and versatile instrumental platforms for identifying phenolic bioactive compounds. In this review, the major LC-MS accomplishments reported in the literature over the last two decades to investigate olive oil processing by-products, specifically olive leaves and pomace and olive oil mill wastewaters, are described, focusing on phenolics and related compounds.