Amount Of Olive Mill Wastewater Research Articles

Evaluation of the Effect of Incorporating Olive Mill Wastewater on Nutrients, Quality, and Bacterial Flora in Fermented Total Mixed Ration

Olive mill wastewater (OMW), a major by-product of the olive oil production industry, is rich in polyphenolic compounds that impart health benefits to several animals. Here, we evaluated the effects of OMW addition on the nutrients, quality, and bacterial composition of fermented total mixed ration (TMR). Different amounts of OMW (0%, 5%, 10%, and 20% in fresh matter) as a substitute for water were mixed with the formulated TMR and fermented for 4 weeks. At the initial stages of fermentation, OMW significantly altered the dry matter, pH, and lactic acid content; however, it had minor effects on most macronutrients, quality parameters, and bacterial flora in the final TMR product. OMW (10%) supplementation improved the polyphenolic compound content in the fermented TMR. However, OMW (10% and 20%) increased lipid levels beyond the recommended level of 3% in cow diets. OMW supplementation did not affect the microbial composition of TMR, except for an increased abundance of Weissella. These findings suggest that supplementation of 5–10% OMW improves the quality parameters of TMR without affecting the nutrient composition of fermented TMR. OMW can be used in cow feed; however, further studies involving feeding trials are needed to validate the effects of OMW on cows.

Catalytic pyrolysis of olive mill wastes towards advanced bio-fuels and bio-chemicals using metal oxide catalysts

Among the environmental challenges that Mediterranean countries have to address are the abundant amounts of olive mill wastewater (OMWW) produced by olive oil agro-industry, such as those found in Greece and Tunisia, which lead to significant land and water pollution. The most common disposal method of olive mill wastewater, includes storage ponds, where most of the water is evaporated, while the residual sludge (olive mill wastewater sludge, OMWWS) is sent to landfills. Fast pyrolysis of OMWWS was investigated as an alternative approach of valorizing this waste, leading to the production of high heating value biofuel (bio-oil). Extraction of polyphenolic compounds with bioactive properties from OMWWS was additionally explored in order to provide further added value to OMWWS, considered as a source of bioactively important polyphenolic compounds, prior its use as pyrolysis feedstock towards the production of green fuel. Pyrolysis of the treated OMWWS (after extraction) led to a considerable reduction of the bio-oil yield, however in both cases the bio-oil produced exhibits a very interesting composition (predominance of aliphatic hydrocarbons and small fractions of aromatic hydrocarbons and phenols) and sufficiently low oxygen content. Exploring the effect of either an acidic (ZSM-5) or a basic (MgO) catalyst on the yield and composition of the bio-oil produced during the catalytic pyrolysis of OMWWS we observed that yield and quality of the produced bio-oils strongly depended on the catalyst used. Thus, acidic ZSM-5 zeolite catalyzed cracking and aromatization reactions, resulting in a bio-oil enriched in aromatics, while basic MgO catalyzed decarboxylation of fatty acids yielding a bio-oil composed mostly of aliphatic hydrocarbons. In addition, Co-promoted catalysts (5% Co either on ZSM-5 or MgO) led to additional variation of bio-oil quality, mostly enhancing ketonization reactions. The effect of a series of Fe and Mn oxide catalysts, based on alumina, silica and magnesia supports, was also studied for the catalytic pyrolysis of OMWWS, mainly focusing on using low-cost catalytic materials. In addition, ferric oxide, aluminum oxide, magnesium oxide, and silicon oxide, are among the major components of red mud, an effective catalyst used in the pyrolysis of OMWWS. All of these Fe- or Mn- materials exhibit very promising in situ upgrading of pyrolysis vapors (retaining organics’ yield and improving produced bio-oil). Most of these materials also tend to favor ketonization reactions, a more or less preferred route among the studied catalysts, which seems to mainly relate with their multifunctional (both acidic and basic) character.

Mitigation of OMW toxicity toward Enchytraeus albidus with application of additives.

The olive oil industry generates considerable amounts of olive mill wastewater (OMW) which is treated and used in agriculture, energy production, or discharged into evaporating ponds where OMW contaminated soil (OMWS) is formed. Due to the extremely high phenol content, untreated OMWS is not suitable for plants and soil organisms. This study aimed to determine the adverse effects of OMWS on Enchytraeus albidus and whether the addition of clay and diatomaceous earth can reduce these effects. Without additives, reproduction was reduced up to 35%, with high number of unhatched cocoons, indicated hatching impairment. Furthermore, acetylcholinesterase (AChE) activity decreased significantly at the highest OMWS ratio (40%), as did glutathione-S-transferase (GST) activity at two ratios (40%), indicating neurotoxic effects and oxidative stress. The application of additives (clay and diatomaceous earth) decreased phenol concentration up to 35 and 45%, respectively. Consequently, the number of juveniles increased significantly compared to the control and AChE and GST activities were not affected. However, an increased number of unhatched cocoons and lipid peroxidation were observed after diatomaceous earth treatment, indicating the occurrence of stress. Although additives can bind phenols, neutralize harmful effects and allow the use of OMWS as a fertilizer in agriculture, they should be carefully selected taking into account soil organisms as well. The use of additives to reduce the adverse effects of OMWS can be a turning point in the remediation of olive contaminated soil.

Exploiting Olive Mill Wastewater via Thermal Conversion of the Organic Matter into Gaseous Biofuel—A Case Study

Olive oil is one excellence of the Italian food industry: around 300 kt yr−1 are produced, creating roughly the same amount of olive mill wastewater (OMW) to be disposed of. The present work describes a process to exploit OMW by converting its organic compounds to valuable gaseous biofuel. A sample OMW was characterized (COD, TOC, solids, and polyphenols) and submitted to membrane filtration tests to concentrate the organic compounds. Based on the results of the experiments, a treatment process was outlined: the retentate streams from microfiltration and ultrafiltration steps were fed to a cracking and a steam reforming reactor, respectively; the obtained syngas streams were then mixed and sent to a methanation reactor. The process was simulated with Aspen Plus (AspenTech©) software, assessing operating conditions and streams compositions: the final biofuel is around 81 mol.% methane, 4 mol.% hydrogen, and 11 mol.% carbon dioxide. The permeate stream cannot be directly disposed of, but both its amount and its polluting charge are greatly reduced. The heat needed by the process, mainly due to the endothermic reactions, can be obtained by burning an amount of olive pomaces, roughly corresponding to one-third of the amount left by olive treatments giving rise to the processed OMW feed.

Thermophilic Dark Fermentation of Olive Mill Wastewater in Batch Reactors: Effect of pH and Organic Loading

In recent decades, olive oil consumption has almost tripled worldwide. Olive oil production is linked with the production of enormous amounts of olive mill wastewater, the main by-product derived from three-phase olive mills. Due to the environmental risks of olive mill wastewater disposal, the management and valorization of the specific waste stream is of great importance. This work focuses on the thermophilic dark fermentation of olive mill wastewater in batch reactors, targeting pH optimization and the organic loading effect. A series of experiments were performed, during which the organic load of the substrate remained at 40 g/L after dilution with tap water, and the pH was tested in the range of 4.5 to 7.5. The maximum yield in terms of produced hydrogen was obtained at pH 6.0, and the yields were 0.7 mol H2/mol glucose or 0.5 L H2/Lreactor. At the same conditions, a reduction of 62% of the waste’s phenols was achieved. However, concerning the effect of organic loading at the optimized pH value (6.0), a further increase in the organic load minimized the hydrogen production, and the overall process was strongly inhibited.

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.

Increasing the Content of Olive Mill Wastewater in Biogas Reactors for a Sustainable Recovery: Methane Productivity and Life Cycle Analyses of the Process.

Anaerobic codigestion of olive mill wastewater for renewable energy production constitutes a promising process to overcome management and environmental issues due to their conventional disposal. The present study aims at assessing biogas and biomethane production from olive mill wastewater by performing biochemical methane potential tests. Hence, mixtures containing 0% (blank), 20% and 30% olive mill wastewater, in volume, were experimented on under mesophilic conditions. In addition, life cycle assessment and life cycle costing were performed for sustainability analysis. Particularly, life cycle assessment allowed assessing the potential environmental impact resulting from the tested process, while life cycle costing in conjunction with specific economic indicators allowed performing the economic feasibility analysis. The research highlighted reliable outcomes: higher amounts of biogas (80.22 ± 24.49 NL.kgSV−1) and methane (47.68 ± 17.55 NL.kgSV−1) were obtained when implementing a higher amount of olive mill wastewater (30%) (v/v) in the batch reactors. According to life cycle assessment, the biogas ecoprofile was better when using 20% (v/v) olive mill wastewater. Similarly, the economic results demonstrated the profitability of the process, with better performances when using 20% (v/v) olive mill wastewater. These findings confirm the advantages from using farm and food industry by-products for the production of renewable energy as well as organic fertilizers, which could be used in situ to enhance farm sustainability.

Olive Mill Wastewater Treatment: A Recent Review

Olive oil-producing countries in the Mediterranean region generate a considerable amount of olive mill wastewater (OMW), contributing to a severe environmental polluting issue due to its high pollution load. This effluent is exceptionally toxic to the whole soil-air-water ecosystem, and the living organisms inhabiting it (i.e., plants, animals, aquatic organisms, microorganisms, etc.). Many researchers have assessed the efficiencies of different treatment techniques to find an environmentally friendly and economically viable solution to be generally adopted. In light of that, the present review article summarizes the state-of-the-art concerning the OMW treatment options, with their pros and cons when possible

Controlled Land Application of Olive Mill Wastewater (OMW): Enhance Soil Indices and Barley Growth Performance in Arid Environments

Olive oil industry generates a considerable amount of olive mill wastewater (OMW) each year, which increases the difficulties for successful processing and disposing. A possible and potential alternative is controlled application of OMW into the land. In these two fields’ experiments, we investigated a sustainable controlled land application of OMW to enhance soil properties and improve barley production under rainfed conditions. OMW was spread at five application rates (20, 40, 60, 80, and 120 m3 ha−1) in addition to the control at two sites, Rabba and Ghweer. The physicochemical characterizations of OMW were determined throughout the season. Physicochemical properties of soil were measured after 2 weeks of OMW spreading after planting and after barley harvest. Leaf nutrient content as well as other growth performance has been measured. The results of this study showed no harmful effect of OMW application for all application rates on growth parameters of barley as well as soil properties at both locations. Under all application rates, OMW has increased soil organic matter and nutrient contents, which could reduce the use of chemical fertilizer. There was a significant increase in barley growth in OMW treatments for dry weight (DM) (14 and 22%), biological yield (BYLD) (49 and 34%), grain yield (GYLD) (41 and 47%), and straw yield (SYLD) (55 and 31%) at Rabba and Ghweer sites, respectively. The results exhibited the benefit of controlled application of OMW. However, long-term effect of OMW application needs more study, and local legislative is necessary.

Microbiological and Chemical Modifications of Soil Cultivated with Grapevine Following Agronomic Application of Olive Mill Wastewater

The reuse of olive mill wastewater (OMW) by spreading on agricultural land is subject to a long-time debate since they supply to agricultural land both substances of undoubted positive influence on fertility and compounds that may adversely alter its chemical, physical and microbiological characteristics and/or cause negative effects on crops. In this study different amounts of OMW from 3-phases centrifugal decanter were spread in February on soil cultivated with grapevine in a research-farm located in central Italy for 11 consecutive years, with the aim to verify the long term effect on grape production, physico-chemical and microbiological characteristics of soil. In particular, the effect of the OMW spread in the largest amount (50 L m−2) was an increase of the weight of the grape-brunches and total grapes production and, in addition, an improvement of the soil characteristics due to the increase of the content of the organic reducing substances with humic-like properties. Moreover, it was also ascertained that in the short-medium period (2–8 months) the respiratory activity of the micro-organisms of the soil parcels, treated with different amount of OMW, was higher than that of the soil control parcels. The results obtained demonstrated that the controlled spreading of OMW helps to increase both the grapes crop and the fertility of the soil, recycling the organic matter and mineral nutrients, in this way allowing to reduce, or avoid, the use of chemical fertilisers.

Exploitation alternatives of olive mill wastewater: production of value-added compounds useful for industry and agriculture

Countries producing olive oil generate a considerable amount of olive mill wastewater (OMWW), one of the most harmful agro-industrial effluents with a powerful polluting capacity. In fact, owing to its high pollution load, this effluent is extremely toxic to the whole soil-air-water ecosystem as well as to the living organisms inhabiting it (i.e., plants, animals, aquatic organisms, microorganisms, etc.). Currently, OMWW is discarded but since it includes carbohydrates, organic acids and mineral nutrients, as well as elevated contents of phenolics and other natural antioxidants compounds, it could be considered as a potential source of high value-added natural products. Therefore, the valorization of different waste streams including OMWW into fine biochemicals and the recovery of valuable metabolites via biotechnological processes is probably the main challenge faced by the olive oil industry. In light of that, the aim of the present review article is to summarize the state-of-the-art in relation to the exploitation possibilities and the use of OMWW to generate added-value compounds of great significance for the biofuel, pharmaceutical, cosmetic, chemical, food, and agriculture industries. Valorization of this significant waste steam in particular through a biorefinery platform could substantially enhance the environmental sustainability aspects of the whole industry while simultaneously contributing to the improvement of its economic viability.

Jet-loop reactor with cross-flow ultrafiltration membrane system for treatment of olive mill wastewater

AbstractOlive oil extraction is one of the ancient agricultural industries all over the Mediterranean area and even today it is of fundamental economic importance for many industries found over the whole Mediterranean. However, this industry generates large amounts of olive mill wastewater (OMW) and due to its physicochemical characteristics it causes severe environmental concerns and management problems in the Mediterranean area, which is facing water scarcity. Technologies to reuse this wastewater will have a high impact at the economic and environmental level. The work presented aims to improve the use of jet-loop reactors technology for the aerobic biotreatment of OMW. A jet-loop reactor (100 L) coupled with an ultrafiltration (UF) membrane (MBR) system (JACTO.MBR_100 L) were tested for the influence of hydraulic parameters on OMW degradation and scale-up to 1,000 L. Chemical oxygen demand and total phenols (TP) decreased notably (up to 85% and 80% removal efficiency, respectively) after the biological treatment. The treated OMW (UF permeate) was evaluated as a source for irrigation and its impact on the soil and plant growth and their quality parameters.

The impact of olive mill wastewater spreading on soils using integrated approach of proximal soil survey, spatial, and multivariate analyses.

Olive oil production generates a large amount of olive mill wastewater (OMW), the most difficult to treat of agro-industrial effluents. Spreading of OMW across the soilscape has become the most frequently used practice in several Mediterranean basin countries but is hotly debated because of its potential to impair soil environs. The research hypothesis states that soil deterioration is correlated strongly with the spatiotemporal rate of OMW application; thus, the spatial pattern of the soil attributes should be established in conjunction with the rate of OMW spreading. The spatial pattern was ascertained using proximal soil sensing that measures the apparent electrical conductance (ECa). Eight representative locations were identified using grouping analysis of the ECa data. The soils were analyzed for selected physical and chemical attributes known to be affected by OMW spreading as well as ancillary parameters needed for the calibration of the ECa. Discriminant analysis successfully categorized 76% of the ECa groups, selecting CEC, sand, pH, and ESP as the most powerful discriminatory variables in the grouping analysis. The correlation coefficients between the measured ECa, and the calculated ECa, and soil moisture were very high (r > 0.77, P < 0.05), suggesting that the proximal soil survey results are well calibrated. The spreading of untreated OMW over more than 7years did not impair the soils under study. No significant changes in soil chemo-physical properties such as pH (< 7.66), electrical conductivity in saturated paste (< 3.58dSm-1), sodium adsorption ratio (< 2.3), potassium adsorption ratio (< 0.33), exchangeable sodium percentage (< 3.85%), and unsaturated hydraulic conductivity (< 0.3cmh-1) were found in comparison with untreated soils. The results support the premise that moderate quantities of OMW (50-70m3ha-1year-1) equally spread over the soilscape will have little impact on soil health.

Long-Term Spreading of Olive Mill Wastewater on Olive Orchard: Effects on Olive Production, Oil Quality, and Soil Properties

ABSTRACTIn Italy, the law no 574 of 1996 permits and regulates the disposal of olive mill wastewater (OMW), the liquid by-product obtained in oil mill when olive fruits are processed to extract virgin olive oil, by its controlled spreading on cultivated soil. With the aim to verify the long-term effects of the practice on olive production, oil quality, and physical–chemical and microbiological characteristics of soil, different amounts of OMW were spread in February, for 9 years consecutively, on soil cultivated with olive trees. The results obtained confirmed that the controlled spreading of OMW is not harmful for the plant production. On the contrary, OMW spread on olive grove is useful for the fertility of soil and the growth of microflora for the important supply of nitrogen (N), phosphorus (P), potassium (K), and, above all, of organic matter. The evaluated biological properties indicated that OMW spreading stimulates the growth of soil fungal and fungus-like communities and aerobic N2 fix micro-organisms. With regard to the oil quality, the data indicate that no significant differences were ascertained on the analyzed parameters.

Production of added-value metabolites by Yarrowia lipolytica growing in olive mill wastewater-based media under aseptic and non-aseptic conditions.

Yarrowia lipolytica ACA-YC 5033 was grown on glucose-based media in which high amounts of olive mill wastewaters (OMWs) had been added. Besides shake-flask aseptic cultures, trials were also performed in previously pasteurized media while batch bioreactor experiments were also done. Significant decolorization (∼58%) and remarkable removal of phenolic compounds (∼51% w/w) occurred, with the latter being amongst the highest ones reported in the international literature, as far as yeasts were concerned during their growth on phenol-containing media. In nitrogen-limited flask fermentations the microorganism produced maximum citric acid quantity ≈19.0 g/L [simultaneous yield of citric acid produced per unit of glucose consumed (YCit/Glc)≈0.74 g/g]. Dry cell weight (DCW) values decreased at high phenol-containing media, but, on the other hand, the addition of OMWs induced reserve lipid accumulation. Maximum citric acid concentration achieved (≈52.0 g/L; YCit/Glc≈0.64 g/g) occurred in OMW-based high sugar content media (initial glucose added at ≈80.0 g/L). The bioprocess was successfully simulated by a modified logistic growth equation. A satisfactory fitting on the experimental data occurred while the optimized parameter values were found to be similar to those experimentally measured. Finally, a non-aseptic (previously pasteurized) trial was performed and its comparison with the equivalent aseptic experiment revealed no significant differences. Yarrowia lipolytica hence can be considered as a satisfactory candidate for simultaneous OMWs bioremediation and the production of added-value compounds useful for the food industry.

Recovery of polyphenols from olive mill wastewater using drowning-out crystallization based separation process

Abstract Olive oil extraction generates a large amount of olive mill wastewater (OMW) (10 million ton/year), requiring specific management to minimize its potential negative impact on the environment. However, OMW is a rich source of polyphenols having a wide range of bioactivities. For that reason, the selective recovery of polyphenols from OMW provides the double opportunity to obtain bioactive compounds and to reduce its phytotoxicity. The present study relates to a highly efficient and novel method, using green technology, for obtaining a natural bioactive concentrate rich in polyphenols from OMW. The clean technology integrates centrifugation, batch evaporation and drowning-out crystallization-based separation process, for the separation of polyphenols from the different components present in OMW, based on the solubility behavior changing after addition of ethanol, accepted as food grade. Further, batch evaporation was applied for the regeneration of ethanol for sustainable process. Consequently, the proposed method provides a highly-concentrated polyphenols isolate (up to 75% ( w /w)), with up to (510 mg/g) of the polyphenols content being hydroxytyrosol. The recovered polyphenols can be of interest for the food industry, cosmetic industry, or pharmaceutical industry. Industrial relevance Drowning-out separation process by ethanol was found useful to achieve the main target for the recovery of polyphenols from OMW. Polyphenol concentration increased considerably by the proposed method based on the solubility behavior changing after addition of ethanol, a food grade solvent. Furthermore, batch evaporation was carried out for the regeneration of ethanol, which can be reused in the process. Polyphenols concentrate (up to 75% ( w /w)) developed in this study have the potential for application in food industry ( e.g. to develop a premium olive oil containing 1000 ppm of polyphenols, or developing e.g. grape juice with enhanced polyphenols content), or into cosmetics ( e.g. developing a lotion/hand cream with high antioxidant content), or into pharmaceutics ( e.g. developing capsules high polyphenols content; which could also be considered as food supplement).

The seasonal influence of olive mill wastewater applications on an orchard soil under semi‐arid conditions

AbstractOlive oil production generates large amounts of olive mill wastewater (OMW). OMW has a high nutrient content and could serve as fertilizer, but its fatty and phenolic constituents induce soil water repellency, phytotoxicity, and acidification. An appropriate season of OMW application may mitigate negative consequences while preserving beneficial effects. In order to investigate this, a field study was conducted, in which OMW was applied to an olive orchard in Israel either in winter or summer. Soil–water interactions (water drop penetration time, hydraulic conductivity), soil physicochemical parameters, phenolic compounds, and soil biological activity (bait‐lamina test) were determined 12 to 18 months after OMW application. The results showed elevated K+ contents in all treatments, but all other soil properties of winter treatments were comparable to the control, which suggested a certain recovery potential of the soil when OMW is applied in winter. By contrast, summer treatments revealed a ten‐fold higher soil water repellency, a three‐times lower biological activity, and a four‐fold higher content of phenolic compounds, independently of whether the soil was kept moist by irrigation or not. Thus, the OMW constituents were neither degraded nor leached by winter rain when applied during the hot season. Further research is needed to distinguish leaching and biodegradation effects, and to understand the development of the composition and degradation kinetics of organic OMW constituents.

Integrated membranes for the recovery and concentration of antioxidant from olive mill wastewater

AbstractDuring olive oil production a great amount of olive mill wastewater (OMW) is produced that is potentially a rich source of bio-phenols with wide array of biological activity. The purpose of the present work is to recover and concentrate the valuable polyphenols from the OMW using integrated membrane systems. Further study was conducted by employing enzymatic hydrolysis using β-glucosidase followed by acid hydrolysis in order to release higher concentration of pure hydroxytyrosol (HT). Meanwhile, efficient treatment of OMW could be achieved for water reuse as well as protecting the environment. The OMW was directly subjected to a microfiltration (MF) where 77.6 and 34.8% reduction of total suspended solids (TSS) and chemical oxygen demand (COD), respectively, were achieved. The Permeate of MF was further subjected to ultra-filtration (UF), where the removal was 44.9% and 100% for the COD and TSS, respectively. Another portion of the MF permeate was also subjected to nano-filtration (NF), where COD ...

Influence of Olive Mill Wastewater (OMW) Spread on Carbon and Nitrogen Dynamics and Biology of an Arid Sandy Soil

Olive mill wastewater (OMW) contains large amounts of organic substances, including phenols, that can have negative environmental consequences when applied to soil. Because of the high concentrations of organic matter and mineral nutrients, OMW holds promise as a fertilizer source for cropping systems. The effects of the addition of 0.5, 1, or 2% OMW to a soil on carbon (C) and nitrogen (N) dynamics and microbiological characteristics of the soil were investigated. Mineral N presented a significant negative correlation with the amount of OMW. The total number of soil bacteria and fungi increased. However, the nitrifying population was sensitive to 2% OMW during the first month. The increase in microbiological activity accelerated the loss of soil organic carbon (SOC). However, the treated soil recovered the SOC, and the total C gains were 2.1, 1.9, and 2.4 g kg−1 for the three doses, whereas the SOC loss was 1.1 g kg−1 for the control.

Changes Induced by Olive Mill Wastewaters Used as Organic Fertilizer on Polyphenol Content, pH and Salinity of an Alkaline Soil

Aims: The main objective of this paper is to determine the recommended amounts of olive mill wastewaters (OMW) that should be applied as a fertilizer in alkaline soil, based on evolution of its pH, salinity and polyphenol content. Study Design: Randomized complete block design with three replications where the variable factor was amount of OMW. Place and Duration of Study: The trial was carried in an open glass greenhouse in the Regional Agricultural Research Center of Meknes Morocco, between February and March 2012. Methodology: Four amounts of OMW (50, 75, 100 and 150 m/ha) were tested as organic fertilizer on an alkaline soil in comparison with water treatment based on measurement of soil pH, electrical conductivity and polyphenol content using fenugreek as an indicator plant. The Indicators of stress measured on plants were leaf chlorophyll content, stomatal conductance and leaf temperature. Results and Discussion: The application of the four amounts of OMW induced a decrease of soil pH and an increase of its electrical conductivity whereas soil polyphenol Research Article Razouk et al.; JSRR, Article no. JSRR.2013.007 560 content following significant regression models. Soil pH and electrical conductivity changed slightly under all treatments with a maximal values under the treatment 150 m/ha. However, soil polyphenol content increased widely under different treatments of OMW. The physiological parameters of the fenugreek showed a certain stress under 150 m/ha. Conclusion: OMW may be used as organic fertilizer up to 100 m/ha on alkaline soil without adversely affecting its quality in the arable layer. Beyond this amount, a particular attention should be paid, to soil polyphenols as far as their phytotoxicity is concerned, since a high concentration of polyphenols may exert an allelochemical effect.