Oil Mill Wastewater Research Articles

Systematic screening for the biocatalytic hydration of fatty acids from different oily substrates by Elizabethkingia meningoseptica oleate hydratase through a Design-of-experiments approach

The edible plant oils production is associated with the release of different types of by-products. The latter represent cheap and available substrates to produce valuable compounds, such as flavours and fragrances, biologically active compounds and bio-based polymers. Elizabethkingia meningoseptica Oleate hydratases (Em_OhyA) can selectively catalyze the conversion of unsaturated fatty acids, specifically oleic acid, into hydroxy fatty acids, which find different industrial applications. In this study, Design-of-experiment (DoE) strategy was used to screen and identify conditions for reaching high yields in the reaction carried out by Escherichia coli whole-cell carrying the recombinant enzyme Em_OhyA using Waste Cooking Oils (WCO)-derived free fatty acids (FFA) as substrate. The identified reaction conditions for high oleic acid conversion were also tested on untreated triglycerides-containing substrates, such as pomace oil, sunflower oil, olive oil and oil mill wastewater (OMW), combining the triglyceride hydrolysis by the lipase from Candida rugosa and the E. coli whole-cell containing Em_OhyA for the production of hydroxy fatty acids. When WCO, sunflower oil and OMW were used as substrate, the one-pot bioconversion led to an increase of oleic acid conversion compared to the standard reaction. This work highlights the efficiency of the DoE approach to screen and identify conditions for an enzymatic reaction for the production of industrially-relevant products.

Wastewater and Grey Water Footprint Assessment of the Olive Oil Production Process in Northwest Argentina

Argentina stands as the leading producer and exporter of olive products in the Americas, with the province of La Rioja as its main productive area. Since the 1990s, the olive grove cultivated area and related agro-industry in La Rioja have expanded. However, the resulting wastewater has generally been neglected. The water footprint (WF) provides information about the water volume consumed and polluted by a production process. Since the 1990s, agricultural and agro-industrial activities in La Rioja have experienced substantial growth. This study aims to analyze the generation, quality, and management of Oil Mill Wastewater (OMWW) using the grey WF of chloride and nitrate as an indicator and focusing on two olive mills (OM) in La Rioja. Additionally, it seeks to examine the relationship between the international trade of provincial olive oil and the estimated grey WF. For the diagnosis of OMWW generation, a description of the production process was made coupled with flow and physico-chemical characterization. The total grey WF was 8.69 and 45.5 L water/L olive oil for OM 1 and OM 2, respectively. Nitrate was identified as the critical pollutant. The grey virtual water export related to the export of olive oil was 5569 m3 for OM 1 and 28,000 m3 for OM 2. The provincial grey virtual water export related to olive oil was 161,955 m3 with major trade destinations including Spain, the United States, and Brazil. The article analyses for the first time the grey WF of olive oil industries and assess the related grey virtual water exports. This research represents a step forward in the knowledge of wastewater management in the olive oil sector and facilitates the search for solutions to minimize negative environmental impacts while promoting cleaner production.

Treatment of Turbid Water Collected from Oil Mill Waste (OMW) Using Low Content of Gum Arabic polymer (GA)

Using synthetic polymers in clarifying of turbid wastewater is a very expensive method, in addition to their monomers toxicity produced from the polymerisation reaction. Those drawbacks encouraged several scientists who were interested in eco-friendly sustainable materials to discover an upright replacement to clarify turbid wastewater. The present study introduces Gum Arabic (GA) as a health-friendly natural polymer flocculant, which could be applied in the pre-filtration process of oil mill wastewaters (OMWW) treatment. GA-silica as a model work and GA-OMWW interaction was investigated experimentally by turbidimetric technique and mathematically by GraphPad Prism® software, since plateau followed by one phase decay was a good fit at adding 1250 and 12500 mg of polymer, while one phase decay was selected as a proper fit for 12.5 and 125 mg. Results supposed that the biopolymer improves markedly the sedimentation performance of suspended materials. Digital micrographs agreed with the turbidity results.

Concentration of phenolic compounds from olive washing wastewater by forward osmosis using table olive fermentation brine as draw solution

The olive industry has a considerable amount of process water consumption. As a result of the process, a large volume of oil mill wastewater (OMW) and table olive wastewater (TOW), both of them with high concentrations of organic matter, phenolic compounds and conductivity, are released. The appropriate management of these wastewaters is of paramount importance due to their toxic impacts on the environment. In this work, forward osmosis (FO) process is presented as an option to concentrate phenolic compounds for their further recovery. Two membranes, OsmoF2OTM (FTS, USA) and HFFO.6 (Aquaporin, Denmark) were evaluated with NaCl as draw solution (DS) and olive oil washing wastewater (OOWW) filtered at 5μm (5F) as feed solution (FS). Both membranes were able to concentrate the phenolic compounds with acceptable volume reduction (VR) values. The HFFO.6 membrane, which presented the lowest passage of phenolic compounds (TPhC) to the DS, was tested with fermentation brine from table olive processing (FTOP) as DS. As FS the same 5F-OOWW as well as an OOWW ultrafiltration permeate (UF-OOWW) were considered. Interestingly, greater percentages of TPhC concentration were observed compared to the tests with NaCl as DS (74.13–76.93% versus 62.6%, respectively). Although the tests with UF-OOWW presented greater flux, the recovery percentages of TPhC were similar, even slightly lower than those obtained with 5F-OOWW. Therefore, FO appears as a promising option to concentrate TPhC from OOWW and as well as to dilute FTOP. Thus both wastewaters from the olive industry could be treated at the same time.

Olive Oil Mill Wastewater Degradation: Storage Effect

AbstractOlive oil mill wastewater (OMW) is one of the pollutant sub‐products produced by the olive oil industry. Nowadays, to treat the effluent and decrease its environmental impact, several studies on different methods for degradation have been developed, e.g., wastewater valorization through the steam reforming process. This work aimed to analyze how physicochemical characteristics of OMW are modified under different storage conditions. Different conditions were applied to the effluent in terms of temperature, light, and storage time. Real and synthetic OMW samples were tested during this work. The results showed that the properties of the effluent changed when it was stored at high temperatures due to degradation of organic species during storage.

Screening of Chemical Composition, Antimicrobial and Antioxidant Activities of Essential Oil and Volatile Fraction from Olive Mill Wastewater

Oil mill wastewater is the main by-product of the olive oil industry resulting mainly from the treatment and pressing of olives in mills. It is a rich source of nutrients and phytochemicals with a wide spectrum of biological properties. The present study focuses on the chemical analysis and evaluation of the antimicrobial and antioxidant activity of the essential oil (EO) and the volatile fraction (VF) obtained, respectively, by hydrodistillation. Chemical analysis by gas chromatography coupled to mass spectrometry (GC/MS) and a flame ionisation detector (GC/FID) revealed the predominance of phenolic compounds (25.71%, 60.36%) and fatty acids (62.37%, 38.25%) for the VF and EO, respectively. It was also shown that the main compounds were oleic acid (24.9%) for the VF and 4-ethylphenol (28.5%) for the EO. The results of the antimicrobial activity in terms of MIC values against twelve microorganisms showed that, overall, the VF was more active than the EO. The antioxidant activity of the VF and EO was evaluated using the DPPH assay and expressed as half-maximal inhibitory concentration (IC50), where the EO (218 μg/mL) showed better antioxidant activity than the VF (244 μg/mL). The results also revealed that the antimicrobial activity and antioxidant activity values for both oils were significantly lower than the standards used.

Functional and Sustainable Application of Natural Antioxidant Extract Recovered from Olive Mill Wastewater on Shelf-Life Extension of “Basil Pesto”

A natural antioxidant extract obtained from oil mill wastewater was used for the formulation of basil pesto sauce, with the aim to improve quality and stability during storage. The antioxidant extract was added to traditional ingredients (basil, cheese, oil, etc.) and after preparation, packaging, and thermal treatment it was submitted to storage (monitored for 90 days). Fresh samples were stored at 4 °C and pasteurized samples were stored at room temperature. The effect of natural antioxidant addition on basil pesto sauce was evaluated for the main qualitative attributes, such as: physicochemical, microbiological, and antioxidant parameters. The principal results showed that the addition of a natural phenolic extract led to an evident reduction in pH, attaining food safety values under pH 4. The high oxidative stability observed in the basil pesto sauces fortified with the phenolic extract suggests that the incorporation of phenolic compounds delays the propagation phase of lipid oxidation.

Nanofiltration of wastewaters from olive oil production: Study of operating conditions and analysis of fouling by 2D fluorescence and FTIR spectroscopy

The presented work tries to solve the problem of the large volumes of oil mill wastewater (OMW). For this, nanofiltration is presented as a possible second stage of treatment. Different membranes were tested under different operating conditions, varying cross flow velocity (CFV) and transmembrane pressure (TMP), in order to obtain a concentrate rich in phenolic compounds and also an adequate permeate able to be returned to the process as machinery cleaning water. The NF270 membrane under the conditions of 1 ms−1 CFV and 10 bar of TMP was observed to be the best to concentrate the phenolic compounds, with high permeate flux and low fouling. Different types of tests were performed: membrane adsorption tests with different compounds, nanofiltration tests with a model solution (MS) to analyse fouling and check the effectiveness of the cleaning protocol and, finally, the selected NF270 membrane was tested with OMW. Also, for the first time, 2D fluorescence spectroscopy and Fourier-transform infrared spectroscopy (FTIR) were used together as tools to study membrane fouling. From the adsorption tests it was observed that all the considered compounds had an effect on the membrane surfaces, which was also confirmed from the nanofiltration tests (with the DM900 membrane the most affected). After cleaning, the membranes fouled with MS and OMW did not recover the spectra of the pristine membranes but, instead, matched the spectra presented by the new membranes subjected to the cleaning protocol. Finally, the following a suitable membrane for this purpose is selected In addition, it has been proved that the used spectroscopic techniques are a feasible option for the study of both fouling and efficiency of cleaning protocols.

Simultaneous adsorption behaviour of heavy metals from Oil Mill Wastewater onto natural clay

The present work reports the synergistic and inhibitory adsorption effects involved in the multicomponent adsorption of heavy metal ions (Fe (II), Pb (II)), and major elements from oil mill liquid waste (OMW) using natural bentonite as adsorbent cames from Nador (North-East Morocco). Morocco is one of the most olive oil producing Mediterranean countries. This industry, which is so beneficial to the national economy, leaves two toxic and non-biodegradable residues (liquid/solid). OMW or margin is a current liquid pollutant that has been listed by the United States Environmental Protection Agency (EPA). The classical methods used for phenol removal are expensive or limited to large-scale applications such as biological and thermal decomposition methods. The margins used in the studies were collected from a semimodern oil mill (Nador-Morocco). The results of the physicochemical analyses showed that the effluents of the oil mills showed that they are highly polluted, in particular the suspended solids, COD, and iron contents of around 154.82 (mg/l) and copper 31.72 (mg/l). Samples of OMW mixed with raw bentonites at different percentages vary between 10 % and 80 %. Different interactions between bentonite and metal ions dealing with the decrease of the concentrations. This study proves that this bentonite is an effective adsorbent for the elimination of heavy metals from OMW.

Removal of Phenolic Compounds from Synthetic Solution and Oil Mill Waste Water by Adsorption onto Nanoparticles Synthesized from Phosphate Rock

In this work, we studied the elimination of phenol compounds from phenolic solutions and Oil Mill Waste Water (OMWW) by adsorption method. The adsorbents used are natural phosphate rock coming from Khouribga phosphate mine (Morocco) and an Apatite synthesized from this phosphate by a dissolution–precipitation reactions. Results obtained showed that the structure of natural phosphate and synthesized apatite are respectively Ca9.55(PO4)4.96F1.96 (CO3)1.283 and (Ca10(OH)2(PO4)6). Synthesized apatite has a higher specific surface than natural phosphate (193.62m2/g). The adsorption study showed that the synthesized apatite can be used as an adsorbent to remove phenol from water with very fast reaction kinetics (about 10 min) and an adsorption capacity equal to 15mg/g. The optimal adsorption capacity was found in low values of temperature and in neutral pH. Adsorption kinetics of phenol solution on the two adsorbents can be described by an equation corresponding to a pseudo second order. Freundlich model fitted well with the adsorption isotherms more than the Langmuir model. Characterization of olive mill wastewater shows that, phenol index equal to 0.39 g/l and chemical oxygen demand COD equal to 158 g/l. The treatment of OMWW by adsorption method on the two adsorbents shows that the use of natural phosphate as adsorbent reduced phenol index by 23% and (COD) by 35% while using synthesized apatite reduced phenol index by 30% and COD by 38%.

Chemical characterization and adsorption of oil mill wastewater on Moroccan clay in order to be used in the agricultural field

Oil mill wastewater (OMW) is the main liquid discharge from oil mills, it is considered as a dangerous pollutant due to its toxic chemical compounds which are unloaded directly in the environment without any treatment. The aims of this study were to evaluate the effectiveness of OMW adsorption on clay as a good method for the elimination of toxic chemical compounds and to study the application of treated OMW as an irrigation source in agricultural field. For this, Clay was collected from the city of Agourai (Meknes region, Morocco) and characterized by X-ray diffraction, X-ray fluorescence spectrometry, BET and FTIR analysis. Moreover, the treated OMW was analyzed using UHPLC-ESI-MS and the determination of total phenolic content (TPC) was also performed. However, the application of the treated OMW in agricultural field was performed by the determination of its effect on the germination of Lepidium sativum seeds (in vitro) and as a source of irrigation of Vicia faba plants (in situ). The results of this study showed that OMW had the following physicochemical characteristics: average pH of 4.88, TPC of 4.75 g/l, COD of 80 g/l, BOD5 of 18.72 g/l, conductivity of 16.05 cm-1, dry matter of 135.7 g/l and volatile matter of 58.7 g/l. The adsorption on clay had increased the pH from 4.88 to 6.14 and reduced significantly the organic matter (42% of COD and 57.4% of phenolic compounds). UHPLC-ESI-MS analysis showed the presence of a wide variety of organic compounds in OMW, with the appearance of new compounds after adsorption. Moreover, the use of treated OMW as a source of irrigation showed a significant effect on the germination of Lepidium sativum seeds and the growth of Vicia faba plants. From this study, we can conclude that the adsorption on clay is a good method for the treatment of OMW, which became non-toxic for environment and can be used as a source of irrigation in agricultural field.

Study of Initial Adhesion of a Bacterium to Different Support Materials before and after Conditioning Film of Olive Oil-Mill Wastewater

To improve the start-up speed and efficiency of bioreactors, biofilm technology is sometimes used. This technology uses various types of materials to facilitate the adhesion of microorganisms. In this study, the surface characteristics of inert substrates and substrates after olive oil-mill wastewater (OMWW) conditioning film were evaluated to understand the impact of OMWW on adhesion as well as the most suitable material to optimize bacterial adhesion. Three common substrates made of different polymers were tested for bacterial adhesion before and after treatment with OMWW: PP (polypropylene), PET (Polyethylene terephthalate), and PVC (polyvinyl chloride). The surfaces’ physicochemical characteristics were studied by measuring the contact angle for the studied bacteria strain and the supports, before and after treatment with OMWW. Results of initial adhesion tests for untreated and treated supports showed differences in how bacterial cells adhered to substrates. Before treatment with OMWW, PVC and then PP showed a significant adhesion capacity, double that of PET [PVC: 1.58 × 105 CFU/cm2, PP: 1.48 × 105 CFU/cm2 and PET: 0.72 × 105 CFU/cm2]. After treatment with OMWW, initial bacterial adhesion increased by 106 (from 105 CFU/cm2 for untreated supports to 1011 CFU/cm2 for treated supports), and PET followed by PP demonstrated the highest adhesion capacity, 2 and 1.7 times more than PVC, respectively [PET: 1.39 × 1011 CFU/cm2, PP: 1.15 × 1011 CFU/cm2 and PVC: 0.67 × 1011 CFU/cm2]. OMWW conditioning film affects the physicochemical characteristics of plastic supports, especially the donor electron character, and improves the initial adhesion of bacteria to substrates (105 to 1011 CFU/cm2). Therefore, surfaces’ physicochemical characteristics were important in the initial adhesion of the bacteria onto the support before and after treatment.

Response Surface Modeling and Optimization of Microwave‐Activated Persulfate Oxidation of Olive Oil Mill Wastewater

AbstractOlive oil mill wastewater (OMW) is environmentally hazardous not only because it contains high recalcitrant and toxic compounds, but also due to its high organic load and turbidity. In this study, oxidation of OMW by microwave (MW)‐activated persulfate is investigated. Box–Behnken design is applied to investigate the effects of operating conditions on operating cost, organic matter, and color removal. Multi response optimization is performed according to minimum operating cost, maximum organic matter and color removal efficiencies. At optimum conditions (persulfate anion dose of 266 g L−1, oxidation duration of 23.58 min, MW power of 567 W, and initial pH 2), chemical oxygen demand (COD) removal of 63.38%, color removal of 94.85%, and operating cost of 0.0633 Euro/g total organic carbon (TOC) removal are found. The biochemical oxygen demand (BOD5)/COD ratio is increased from 0.144 to 0.285. Results of Pareto analysis show individual effect of MW power is 92.81% for TOC removal, 15.52% for color removal, 68.99% for operating cost, respectively. According to the results, it is not recommended to use this process as an ultimate treatment unit due to the high amount of oxidizing agent consumed. Instead, it is recommended to be used as a pre‐ or post‐treatment step.

Evaluation of enrichment with antioxidants from olive oil mill wastes in hydrophilic model system

Agro food industry generates significant amounts of by-products, as olive oil mill waste waters (OMWW), which could be valorize for their extraordinary content of bioactive compounds. The aim of this work was to evaluate the antioxidant stability of a hydrophilic model system with the possibility to create a functional beverage. The study was divided into different steps: extraction of phenolic compounds (PCs) from olive oil waste waters, formulation of enriched water fortified with phenolic extract (PE) (50 and 100 mg tyrosol/L), and evaluation of its physicochemical and antioxidant parameters during storage. Ultra-high performance liquid chromatography was used for the evaluation of single phenols present in the extract, and the highest content was observed for tyrosol (12.9 g/L). The results of this study showed that antioxidant capacity measured by diphenyl-1-picrylhydrazyl and ABTS assays is relatively stable during the storage in the samples enriched with lower concentration of PE (50 mg tyrosol/L). Practical applications The olive oil industry generates huge quantities of waste, with shown significant amounts of by-products that are discarded and can be a serious environmental problem. This food by-products are an extraordinary source of bioactive compounds, which can be recovered in order to produce valuable metabolites via chemical and biotechnological processes. The study demonstrated that the OMWW have a high concentration of PC and antioxidant activity. These antioxidant compounds can be used in the food industry for the production of beverages and/or enriched foods.

Oil Mill Wastewater and its Effects

Olive mill wastewater (OMW) is the liquid by-product generated during olive oil production. Different papers have discussed the effects of OMW discharge on soil characteristics, plant production and phytotoxicity.

Hydroxytyrosyl Oleate: Improved Extraction Procedure from Olive Oil and By-Products, and In Vitro Antioxidant and Skin Regenerative Properties.

Recently, we identified hydroxytyrosyl oleate (HtyOle) in the by-products of olive oil, pomace and olive mill waste water (OMWW). Herein, we report that HtyOle is more accurately quantified by extracting the phenolic fraction from both matrices by using aqueous methanol (80%). By applying this method, HtyOle was also detected in extra virgin olive oil (EVOO). Since olive oil is used in the preparation of many cosmetic formulations, we explored the antioxidant capacity of HtyOle in human keratinocytes. Formation of reactive oxygen species (ROS) and malondialdehyde (MDA), as well as activity of Glutathione-S-transferase (GST) and superoxide dismutase (SOD) were decreased by HtyOle. In addition to that, microRNAs (miRs) involved in both redox status balance and skin regeneration potential were also tested. The following miRs, hsa-miR-21 and hsa-miR-29a, were increased while has-miR-34a was not affected by HtyOle.

A study on acetification process to produce olive vinegar from oil mill wastewaters

In this study, two different acetification procedures to produce olive vinegar (OV) from oil mill wastewaters (OMW) were assayed. Specifically, (i) alcoholic-acetous double fermentation with addition of Saccharomyces cerevisiae starter was compared with (ii) spontaneous acetification, without addition of any starter. Within few days from their production, the OMWs were diluted with distilled water (40:60, v/v) and supplemented with sucrose (100 g L−1) and yeast nutrients (0.5 g L−1). Both the procedures gave a satisfactory acidification, leaving a final acetic acid concentration of around 4% on average. Significant amount of residual sugars, especially fructose, was found in the OV by spontaneous acetification. Therefore, in relation to the consumed sugars, spontaneous acetification has been more performing in terms of acetic acid formation; in addition, the acetogenesis appeared to occur bypassing the alcoholic fermentation. Finally, both spontaneous and starter-driven OVs were permanently clear, with a vinous red color and without any abnormal smell.

Bioplastic recovery from wastewater: A new protocol for polyhydroxyalkanoates (PHA) extraction from mixed microbial cultures

A new protocol for polyhydroxyalkanoates (PHA) extraction from mixed microbial cultures (MMCs) is proposed. PHA-accumulating capacity of the MMC was selected in a sequencing batch reactor (SBR) fed with a synthetic effluent emulating a fermented oil mill wastewater (OMW). The highest recovery yield and purity (74 ± 8% and 100 ± 5%, respectively) was obtained when using NH4-Laurate for which operating conditions of the extraction process such as temperature, concentration and contact time were optimized. Best conditions for PHA extraction from MMC turned to be: i) a pre-treatment with NaClO at 85 °C with 1 h of contact time, followed by ii) a treatment with lauric acid in a ratio acid lauric to biomass of 2:1 and 3 h of contact time.

Effect of compost tea containing phosphogypsum on potato plant growth and protection against Fusarium solani infection.

Three composts made of industrial wastes were prepared by mixing olive oil mill waste water (OMW), olive pomace, coffee grounds, and phosphogypsum (0, 10, and 30%). Potato plants (Solanum tuberosum) cultivated in a greenhouse were used to screen compost tea suppressive ability. All compost tea treatments inhibited Fusarium solani growth and improved plant growth and response to F. solani infection. The antagonistic effects of the different treatments were associated with a marked increase of the antioxidant enzymes and PR (pathogenesis related) protein expression and a decrease of disease severity. These results also showed that plant growth and disease suppression were improved by application of phosphogypsum-supplemented compost teas (A10 and A30). This enhancement can be attributed to the influence of phosphogypsum on nutrient elements and microbial diversity in the resulting compost teas.

Chemical composition, antioxidant potential and phenolic profile of oil mill waste water from Tunisian olive varieties (Chetoui and Chemlali)

Oil mill waste water (OMWW) is of great interest due to the presence of valuable resources such as biophenols that can be recovered as food additives and pharmaceuticals. The aim of this study is to investigate the variation of physicochemical composition of OMWW from Chetoui and Chemlali varieties, to evaluate phenolic composition, antioxidant potential and phenolic profile of OMWW extracts under native and acidified conditions. Liquid-liquid extraction was performed for the extraction of polyphenols. Antioxidant activity was investigated by DPPH•, ABTS•+ and FRAP tests. Phenolic compounds content was determined by HPLC-DAD method. OMWW from Chetoui variety has been shown to contain an important amount of K, Ca and Na whereas Chemlali cultivar was rich in Mg. Phenolic extract from Chetoui fruit (COCt) has been shown to contain the highest amount of polyphenols (2.48 ± 0.21 g L-1) as well as an appreciable content of flavonoids (9.39 ± 0.32 g L-1). However, phenolic extract from Chemlali fruit (COCm) has been shown to have the highest content of proanthocyanidins (0.39 ± 0.00 g L-1). Acidification treatment improved polyphenol recovery of extracts from both varieties. COCt was more active using DPPH (EC50 of 7.5 mg L-1) and FRAP tests. However, COCt and COCm exhibited the same activity using ABTS test. In general, acidification treatment decreased antioxidant activity of extracts. COCt has been shown to contain higher amount of hydroxytyrosol when compared to COCm (157.16 ± 0.820 and 23.440 ± 0.440 mg g-1 D.W. of extract, respectively) as revealed by HPLC-DAD analysis.Â