Heterogeneous catalysis based on photo-Fenton reaction for olive oil mill wastewater treatment

Motivation: The production of olive oil generates high volume of olive-oil mill wastewater (OMW), which is normally deposited at large build-evaporation ponds. This OMW are characterized by acidic pH, high organic load and phenolic compounds. The accumulation of this polluted wastewater does not represent an adequate solution becoming an important environmental issue. Advanced oxidation processes (POAs) are known for their efficiency in removing contaminants. The photo-Fenton process is one of the best known and is based on the combination of Fenton reaction (Fe/H2O2) with the presence of ultraviolet light. The photo-Fenton system can be carried out in homogeneous phase (liquid) as in heterogeneous phase (liquid-solid). The use of solid catalysts has its advantages, especially in the easy recovery and reduction in its consumption. In this work has been evaluated the use of iron oxide (III), HFeO2, as solid catalyst in the photooxidation (UV/HFeO2/H2O2) of OMW .Methods: All experiments were performed in a 1L reactor and commun operating conditions were: initial COD = 16586 g O2/L, pH = 3, T = 20°C, agitation rate = 700 rpm and UV-ligh. Different catalyst concentrations (HFeO2) were assayed 0.038; 0.263; 0.758; 5; 10; 20; 30 and 50 g/L. In addition, control experiments have been developed only with air, UV, H2O2 and the combinated system of UV/H2O2.Results: The removal percentages values recorded for the range of catalyst concentrations tested were: 46.8-62.8% and 76.4-88.8% of COD and total phenolic compounds 'TPCs', respectively. The removal percentages in control experiments registered in the case of air (%CODremoval = 11,1% and TPCs = 50,0%), UV (%CODremoval = 37,8% and TPCs = 56,97%), H2O2 (%CODremoval = 43,1% and TPCs = 70,4%) and UV/H2O2 system (%CODremoval = 46,7% and TPCs = 78,0%).Conclusions: The photo-Fenton oxidation has high efficiency in organic pollutant reduction. Catalyst concentration increase improves the oxidation capacity of UV/H2O2/HFeO2 system in the OMW treatment. The industrial application of this photooxidation system is depending to the final destination of the treated water and the quality requisite. Another operation units can be added if the final water quality requires it. On the other hand, for future it's interesting indicate the importante of the evaluation of catalytic capacity of recuperated HFeO

Influence of agitation rate on a semi-industrial photoreactor for olive mill wastewater treatment by photo-Fenton reaction

Motivation: Olive mill wastewaters (OMWs) generated in the Mediterranean countries present an environmental problem due to its high organic load and the presence of toxic and inhibition growth compounds such as residual oil matter and phenolic compounds. The various attempts to treat OMWs by conventional methods have not yielded satisfactory results due to the recalcitrant nature of the organic material contained in OMWs (Thanekar, Panda and Gogate, 2018). Advanced oxidation processes (AOPs) have the capacity to degrade biodegradable and non-biodegradable compounds, in addition to a wide number of persistent organic compounds (Oller, Malato and Sánchez-Pérez, 2011). Photo-degradation with artificial UV-irradiation lamps can accelerate the degradation of pollutants more than dark degradation (Fenton Reaction) (García and Hodaifa, 2017). Methods: In this work, experiments were performed in a semi-industrial batch stirred photo-reactor. The agitation rates were varied in each experiment (60, 150, 300, 400 and 500 rpm). The common operating conditions were initial pH = 3, hydrogen peroxide amount equal to that determined by the reaction stoichiometry, oxidant/catalyst ratio = 0.03, temperature = 20 ºC and artificial ultraviolet irradiation. Results: The highest photo-degradation percentage (90%) was registered in the experiment with 500 rpm. In all cases, the TOC removal percentages were increased throughout the reaction. The global removal percentages were decreased when the agitation rate exceeded 300 rpm. Conclusions: Finally, it can be concluded that at this scale the best agitation rate used is 300 rpm and the photo-degradation time needed is higher than 60 min. In these conditions, the TOC removal percentages expected are in the range from 76% to90%

Effect of FeCl3 fixed on silica-gel as catalyst on olives and olive-oil washing wastewaters treatment by photo-Fenton

Motivation: The high production of olive oil in Spain generates a large amount of wastewaters from washing of olives and oil which are currently stored in accumulation rafts for its evaporation. These wastewaters (OMWs) are an environmental problem because they have high organic load with inhibitory compounds as phenols. In this work, photo-Fenton reaction (chemical oxidation) has been used for OMWs treatment. Solid catalyst "FeCl3 fixed on silica-gel" has been used on the photo-Fenton reaction to test its effectiveness on the treatmeant of OMWs. Methods: In all experiments crude OMW (mixed of olives and olive-oil washing wastewaters) with initial COD 16500 g O2/L and TOC = 4942 mg/L are used. In all cases reactor capacity was 1 L. The development of the photo-Fenton experiments was carried out using a FeCl3 fixed on silica-gel as catalyst. Different catalyst concentrations (0.01, 0.1, 0.5, 5, 20 and 25 g/L) are tests. Commun operating conditions are: [H2O2] = 0.024 g/L, T = 20°C, pH = 3, and artificial UV-light. During experiments the quality of treated water was determined by measuring total carbon "TC", total organic carbon "TOC", total nitrogen "TN", chemical oxgen demand "COD", total phenol compounds "TFCs", total iron, turbidity and electrical conductivity. Control experiment has been carried in the same operating conditions but without iron catalyst. Results: In all experiments, the perecentages of organic load removal by photo-Fenton reaction (CODremoval = 48.3-73.5%, TOCremoval = 40.1-87.5%, TFCsremoval = 82.6-93.5% and turbidityremoval = 87.8-93.6%) were determined.Conclusions: The use of photo-Fenton shows high efficiency in the treatment of the olive oil mill wastewater. The photodegradation using the system of UV/H2O2 has a similar results to that obtained by UV/FeCl3/H2O2 system when use 0.01 g/L as catalys

Microalgal biomass production in bubble column using urban wastewater from secondary treatment

Motivation: Currently, urban wastewater treatment plants generate treated effluent, which contained pollutants that are discharged into aquatic resources. Microalgae for its growth could use these contaminants/nutrients. This use open the possibility to achieve three goals: i) Complete wastewater treatment, ii) The generation of algal biomass rich in energetic compounds, and iii) the incorporation of atmosphere or industrial carbon dioxide to the algal culture by its injection into the culture media with the aim to reduce the greenhouse effect (Malvis et al., 2019).  Methods: For the complete urban wastewater treatment, microalgal cultures in bubble columns were proposed. In this sense, all the experiments were performed under natural environmental conditions. The microalga Chlorella vulgaris was used under different aeration rates (varied from 1 L/min to 5 L/min). The common operating conditions were pH of the culture media 9.0, ambient temperature and solar light.  Results: The algal culture media in urban wastewater from secondary treatment registered variation in the values of maximum specific growth rate (0.00390-0.00942 1/h) and volumetric biomass productivity (0.0261-0.439 mg/(L h)) under different aeration rates. Both parameters were registered its highest value at aeration rate equal to 3 L/min. TOC removal was decreased with the aeration rate increase and varied in the range 14 % to 62.3 %.   Conclusions: The use of Chlorella vulgaris for its growth in urban wastewater from secondary treatment was verified. The highest values for maximum specific growth rate (0.00943 1/h) and biomass productivity (0.439 mg/(L h)) were determined in culture worked with aeration rate equal to 3 L/mi

Study of Catalysts’ Influence on Photocatalysis/ Photodegradation of Olive Oil MillWastewater. Determination of the OptimumWorking Conditions

The high production of raw olive oil mill wastewater (OMW) is a current environmental problem due to its high organic load and phenol compounds. In this work, photo-Fenton reaction as an advanced oxidation process has been chosen for OMW treatment. In this sense, different iron salts (FeCl3, Fe-2(SO4)(3), FeSO4 center dot 7H(2)O, and Fe(ClO4)(3)) as catalysts were used in order to compare their effects on treatment. For each catalyst, different H2O2 concentrations (2.5, 5.0, 7.5, 10.0, 15.0, 20.0, and 30.0%, w/v) as oxidizing agents were tested. The common experimental conditions were temperature 20 degrees C, the catalyst/H2O2 ratio = 0.03, pH = 3, and ultraviolet light. The Lagergren kinetic model, in cases of total organic carbon removal, for the best H2O2 concentration per catalyst was used. During the experiments, the water quality was determined by measuring the removal percentages on chemical oxygen demand, total carbon, total organic carbon, total nitrogen, total phenolic compounds, total iron, turbidity and electric conductivity. The best catalyst was FeCl3 and the optimum H2O2 concentration was 7.5% (w/v). At these optimal conditions, the removal percentages for chemical oxygen demand, total phenolic compounds, total carbon, total organic carbon and total nitrogen were 60.3%, 88.4%, 70.1%, 63.2% and 51.5%, respectively

Heterogeneous Photo-Fenton Reaction for Olive Mill Wastewater Treatment-Case of Reusable Catalyst

Heterogeneous catalysts can be an efficient and economical option for olive mill wastewater (OMW) treatment by an advanced oxidation process if they could be reused. In this work, OMW was treated using a heterogeneous photo-Fenton reaction (artificial ultraviolet light/H2O2/HFeO2). For this purpose, different concentrations of HFeO2 were tested: 0.04; 0.3; 0.8; 5.0; 10.0; 20.0; 30.0, and 50.0 g/L. The following operational conditions were chosen: pH = 3.0, temperature = 20 degrees C, agitation rate = 700 rpm. The experimental results showed high removal percentages of the main OMW characterization parameters at 50 g/L of HFeO2: %CODremoval = 62.8%; %total phenolic compounds (TPCs) = 88.9%. These results were also compared with those of other control oxidation systems, i.e., UV, H2O2, and UV/H2O2, which provided 35.5 and 56.1%; 46.2 and 74.0%; 48.0 and 76.8% removal, respectively. In addition, the catalyst was reused three times, recovering more than 90.5% of it.This research was funded by Junta of Andalusia and Ministry of Economy and Competitiveness (Spain) "Project: Application of advanced oxidation technologies for treating of washing wastewaters of olive oil and olives, grant number AGR-7092"

Elección del catalizador para el tratamiento por Fotofenton de aguas de lavado de aceite y aceitunas

Motivación:La elevada producción de aceite de oliva en España genera cantidades ingentes de aguas residuales de lavado de aceite y aceitunas que se almacenan en balsas de evaporación sin ser tratadas. Estas aguas son un problema medioambiental ya que no pueden reutilizarse debido a su elevada carga orgánica y su contenido en fenoles. En este trabajo se ha utilizado la reacción FotoFenton (oxidación química) para su tratamiento. En este sentido, se han empleado diferentes sales de hierro para la elección del mejor catalizador.Métodos:En el desarrollo de los experimentos se han utilizado cuatro sales de hierro diferentes (FeCl3, Fe2O12S3, FeO4S•H2O, y Cl3FeO12). La eficacia de cada catalizador se ha determinado a diferentes concentraciones de agua oxigenada (2,5; 5,0; 7,5; 10,0; 15,0; 20.0; y 30,0 %, p/v). Todos los experimentos se han realizado en un reactor discontinuo de 1 L de capacidad. Las condiciones de operación empleadas han sido: temperatura 20 ºC, relación [catalizador]/[H2O2] = 0,03, pH = 3, y luz ultravioleta. Al final de cada experimento se ha determinado la calidad del agua tratada (Carbono total "TC", carbono orgánico total "TOC", nitrógeno total "TN", DQO, compuestos fenólicos totales "FT", hierro total, turbidez y conductividad eléctrica). Como control se han llevado a cabo experimentos (sin catalizador) con luz UV y UV/H2O2 a las mismas concentraciones de agua oxigenada .Resultados:Los porcentajes de eliminación en los experimentos de control con UV en términos de TC, DQO, FT y turbidez  han sido 40,86%, 15,6%, 56% y 69%, respectivamente.Los porcentajes de eliminación más altosdeteminados en los experimentos de control UV/H2O2 han sido 52%, 48,3%; 29% y 66,8% para TC, DQO, FT y turbidez, respectivamente,a una concentración del 2,5 % (p/v) H2O2. En los experimentos de FotoFenton el mejor catalizador fue el FeCl3 con unos porcentajes de eliminación: TC = 70,1%, DQO = 60,3%, FT = 88,4%,  y turbidez = 69% a una concentración de H2O2 del 7,5% (p/v).Conclusiones:La utilización de FotoFenton muestra alta eficacia en el tratamiento de las aguas residuales de las almazara. La luz ultravioleta como el uso conjunto de la luz UV/H2O2 no es suficiente para alcanzar altos porcentajes de eliminación. El FeCl3 es el mejor catalizador a utilizar desde los puntos de vista de la degradación y del económic

New methods of mass cultivation of nematodes

Motivation:  Caenorhabditis elegans is a model organism used in biomedical research whose genome is completely sequenced, moreover, the physiology and development is well known [1]. C. elegans are usually fed with a bacterial-based medium [2].  Thanks to its rapid development by self-fertilization and its ability to be cultivated in both solid and liquid medium, C. elegans can be growth using liquid fermenters.  We want to explore new methods of massive production to use this nematode in different industrial processes.  Methods: In the laboratory, C. elegans is fed with E. coli OP50 on plate and with E. coli X1666 in liquid culture [2]. We have optimized the culture of nematodes with the bacterial strain PV333 in NGM plates. Then, they were transferred to liquid culture with S-Medium with 3% PV333. Finally, for the nematodes to be used in certain processes where high saline concentrations are required, we used an adapted strain to salt in liquid cultures with several NaCl concentrations (5 gr/L, 20 gr/L and 35gr/L).Results: Nematodes fed on PV333 showed a faster development compared to the E. coli control strain in both plate and liquid. The adaptation to salt of the nematodes was satisfactory up to the concentration of 20 gr/L and it is expected to achieve a good growth of the population at the concentration 35 gr/L NaCl. We expect to have a better nematode production yield using PV333 in liquid fermenters than using regular E. coli.Conclusions: Strain PV333 is a good substrate to produce nematodes massively and fast. In addition, the used of high concentration of salt will allow C. elegans to survive adverse conditions and to be used in diverse industrial procedures

Olive oil mill wastewater treatment and algal biomass production by combined process based on flocculation, UV light and Scenedesmus obliquus growth

Motivation:Olive mill industry uses different techniques to extract olive oil and the most common processes are traditional pressing (mainly employed by small producers) and centrifugation continuous processes which using 'Decanter' with two or three exits. The two-exits system is mainly used in Spain. Spain is the first producer of olive oil in the world with 1.40 millon tonnes in the 2015/2016 campaign (AICA, 2015) . Olive oil mill wastewater (OMW) generated has a huge organic load, phenolic compounds and long-chain fatty acids wich makes it phytotoxic and microbial inhibitor, becoming an important pollutant of both terrestrial and aquatic ecosystems (Hachicha et al., 2009). Methods:OMW used was obtained from an olive oil extraction plant, which uses the centrifugation method with two-phase separation.Two differents experimental series were carried out with OMW. For the first one flocculated water was used and for the second one we used an UV lamp after flocculation. For both of them OMW was centrifuged, filtered and sterilized by through a membrane of 0.2-µm pore size. In the first experimental series, culture media were prepared by mixing OMW and ultrapure water for a 5%, 10%, 25%, 50%, 75% and 100% (v/v) OMW final concentration. Undiluted urban wastewater (UWW) was used for a third experiment just filtered and sterilized, as shown in Hodaifa et. al (2012). S. obliquus was inoculated into a batch photobioreactor. Conductivity, turbidity, COD, total phenolic compounds, TOC, TC, IC, TN, ammonium, chloride, phosphates, iron and others were determined after each pretreatment and at the end of each experiment. Microalgal growth during culture was calculated indirectly by measurement of the absorbance. Protein and lipid contents in biomass was measured at the end of the experiments. Results and Conclusions:Reductions in the concentrations of total phenols, COD, TOC and TN and the other chemical parameters have been found after the experiments. The variation of the maximum specific growth rate values with the initial concentration of OMW may indicate an inhibitory effect of wastewater, but the highest volumetric biomass productivity is reachid in 100% OMW (v/v). The protein concentration of the biomass increased over the course of the experiment

Pretratamiento de las aguas residuales industriales de lavado de aceite y aceitunas

Motivación: España es el mayor productor de aceite de oliva del mundo, lo que implica la generación de grandes volúmenes de aguas residuales (aguas de lavado de aceite y aceitunas). Estas aguas se caracerizan por su alta carga orgánica con presencia de compuestos fenólicos, etc. Este problema ambiental que se encuentra en via de solución aplicando diferentes tecnologías entre las cuáles se encuenta la oxidación química (Fenton y FotoFenton). Independientemente de la tecnología a aplicar un pretratamiento (floculación-sedimentación) mejoraría la calidad de estas aguas reduciendo así los parámetros de DQO, compuestos fenólicos, turbidez, etc.Métodos: se han probado diferentes floculantes (Bentonita, Flocudex CS49, QG2001, etc.) a diferentes concentraciones (0-30 g/L) con el objetivo de determinar la concentración óptima para cada uno de estos. En estos test se ha determinado el volumen de sedimento formado a lo largo del tiempo y la calidad de las aguas. Tras esto se ha estudiado la influencia del pH, y una vez encontrado el mejor floculante, se propone la realización de un ensayo de FotoFenton para testar la eliminación de DQO, fenoles, turbidez, etc.Resultados:  Los porcentajes de eliminación de compuestos fenólicos, DQO, carbono total (TC), carbono orgánico total (TOC) y nitrógeno total (TN) varían según el floculante empleado entre el 11.3-25.1%, 5.6-20.4%, 2.3-26.5%, 1.50-23.8%, y 1.45-24.8%, respectivamente. Sin embargo, el pH y la conductividad eléctrica no varían. Los resultados mejoran aún más al corregir el pH, alcanzando porcentajes de eliminación en compuestos fenólicos, DQO, TC, TOC y TN de hasta el 44.9%, 41.1%, 43.6%, 37.6% y 47.3% respectivamente. Finalmente, los mejores floculantes para el pretratamiento de las aguas residuales ensayados han sido QG2001 y Flocudex CS49.Conclusiones: La aplicación de un pretratamiento es esencial para el tratamiento de las aguas de almazaras independientemente de la tecnología a aplicar. Los mejores floculantes comerciales entre los aplicados han sido QG2001 y Flocudex CS49. La utilización de FotoFenton muestra alta eficacia en el tratamiento de las aguas residuales de las almazara