Treatment of olive oil mill wastewater by Fenton's reagent

Wastewater from olive oil mills has been treated by means of the Fe(II)/H(2)O(2) system (Fenton's reagent). Typical operating variables such as reagent concentration (C(H(2)O(2)) = 1.0--0.2 M; C(Fe(II)) = 0.01--0.1 M) and temperature (T = 293--323 K) exerted a positive influence on the chemical oxygen demand and total carbon removal. The optimum working pH was found to be in the range 2.5--3.0. The exothermic nature of the process involved a significant increase of the temperature of the reaction media. The process was well simulated by a semiempirical reaction mechanism based on the classic Fenton chemistry. From the model, the reaction between ferric iron and hydrogen peroxide [k = 1.8 x 10(15) exp((-12,577 +/- 1248)/T)] was suggested to be the controlling step of the system. Also, the simultaneous inefficient decomposition of hydrogen peroxide [k = 6.3 x 10(12) exp((-11,987 +/- 2414)/T)] into water and oxygen was believed to play an important role in the process. On the basis of stoichiometric calculations for hydrogen peroxide consumption, an estimation of the process economy has been completed.     

Antioxidizing potency of phenol compounds in olive oil mill wastewater

The antioxidizing potency of phenol compounds contained in olive oil mill wastewater (OOMWW) has been elucidated. Commercially available phenol standards at varying concentrations and the Rancimat oxidation test have been used. Refined purified olive oil was utilized as an oxidation lipid substrate. Synthetic antioxidants, such as 2,3-tert-butyl-4-hydroxyanisole (BHA), 3,5-di-tert-butyl-4-hydroxytoluene (BHT), l-ascorbic acid, and gallates (commonly used as food preservatives), and other known chemicals endowed with antioxidizing properties have been employed as reference compounds. The OOMWW phenol compounds have been classified into different groups depending on their antioxidizing potency. This was significantly affected by the tested concentrations of the standards. Mixtures of phenol standards and other antioxidants (l-proline, chlorophyll a, chlorophyll b, and alpha-, gamma-, and delta-tocopherol) have also been tested. Many phenol compounds present in OOMWW showed antioxidizing potency higher compared to that of the less safe synthetic antioxidants and could therefore replace these in the industrial preservation of food items. They could also be used in combination with other natural antioxidants (e.g., tocopherols). In fact, some mixtures of antioxidants, owing also to the synergistic phenomena, showed strong antioxidizing potency.     

Chemical pretreatment of olive oil mill wastewater using a metal-organic framework catalyst

Olive oil mill wastewaters (OOMW) are not suited for direct biological treatment because of their nonbiodegradable and phytotoxic compound (such as polyphenols) content. Advanced technologies for treatment of OOMW consider mainly the use of solid catalysts in processes that can be operated at room conditions. A system based on combined actions of catalytic oxidations and microbial technologies was studied. The wet hydrogen peroxide catalytic oxidation (WHPCO) process is one of the new emerging oxidation processes particularly attractive for the pretreatment of highly polluted OOMW containing polyphenols that are not suited for classical treatments. In this work, the biodegradability of OOMW was evaluated before and after treating the wastewater samples by the WHPCO process using a metal-organic framework (MOF) as a catalyst. This material, containing Cu and prepared with benzene-1,3,5-tricarboxylic acid (BTC), is a robust metal-organic polymer with a microporous structure that is reminiscent of the topology of zeolite frameworks.     

Improved combined chemical and biological treatments of olive oil mill wastewaters

A novel system was investigated, finalized to reduce the impact of highly polluting wastewaters, and based on combined actions of catalytic oxidations and microbial biotechnologies. Olive oil mill wastewaters (COD 10,000-100,000 mg O(2)/L) were oxidized up to 80-90% by stoichiometric amounts of dilute hydrogen peroxide (35%) and in the presence of water soluble iron catalysts, either Fe(II) or Fe(III), at concentrations up to 1% w/w and more, i.e., much larger than those reported for conventional Fenton processes. In the combined action, the mineralization activity of a selected microbial consortium was used to degrade residual volatile and nonvolatile organic compounds into CO(2) and biomass. The results of this search could suggest an improved operational methodology capable to reduce the potential impact of wastewater.     

Mitigation of olive mill wastewater toxicity

The toxicity of olive mill wastewaters (OMW) is commonly attributed to monomeric phenols. OMW were treated in an aerated, stirred reactor containing agricultural soil, where the oxidative polymerization of phenols took place. In 24 h, OMW monomeric phenols decreased by >90%. This resulted in a corresponding reduction in phytotoxicity, as measured by germination tests with tomato and English cress seeds, and in microbial toxicity, as measured by lag phase duration in Bacillus cereus batch growth. Soil germination capability after irrigation with OMW was assessed in long-term pot experiments. The relative germination percentage of tomato was higher when the soil was irrigated with treated OMW rather than with untreated ones, although it was lower than the control (e.g., soil irrigated with distilled water). At longer incubation times, a complete recovery of the soil germination capability was achieved with treated, but not with untreated, OMW.     

Quantification of phenolic compounds in olive oil mill wastewater by artificial neural network/laccase biosensor

In this paper is considered a new computerized approach to the determination of concentrations of phenolic compounds (caffeic acid and catechol). An integrated artificial neural network (ANN)/laccase biosensor is designed. The data collected (current signals) from amperometric detection of the laccase biosensor were transferred into an ANN trained computer for modeling and prediction of output. Such an integrated ANN/laccase biosensor system is capable of the prediction of caffeic acid and catechol concentrations of olive oil mill wastewater, based on the created models and patterns, without any previous knowledge of this phenomenon. The predicted results using the ANN were compared with the amperometric detection of phenolic compounds obtained at a laccase biosensor in olive oil wastewater of the 2004-2005 harvest season. The difference between the real and the predicted values was <0.5%. biosensor; olive oil mill wastewater; chemical analysis; phenolic compounds.     

Olive oil mill wastewater treatment using a chemical and biological approach

Olive oil mill wastewaters (OMW) are recalcitrant to biodegradation for their toxicity due to high values of chemical oxygen demand (COD), biological oxygen demand (BOD), and phenolic compounds. In the present study OMW, collected in southern Italy, were subjected first to a chemical oxidative procedure with FeCl3 and then to a biological treatment. The latter was performed in a pilot plant where mixed commercial selected bacteria, suitable for polyphenols and lipid degradation, were inoculated. The effect of treatments was assessed through COD removal, reduction of total phenols, and decrease of toxicity using primary consumers of the aquatic food chain (the rotifer Brachionus calyciflorus and the crustacean Daphnia magna). The results showed that the chemical oxidation was efficacious in reducing all parameters analyzed. A further decrease was found by combining chemical and biological treatments.     

Effects of olive oil mill wastewater on chemical,microbiological, and physical properties of soil incubated under four different climatic conditions

The objective of this study was to understand the degradation of the organic matter of olive mill wastewater (OMW) and its phytotoxic and water repellent effects in dependence on four different climatic conditions. We hypothesized that warm conditions with sufficient soil moisture ensure optimal biological activity and thus minimize negative effects of the OMW treatment. Therefore, OMW-treated soil was incubated for 60 days under four climatic conditions. During incubation, we monitored pH, contents of nitrate, manganese and phenolic compounds, soil respiration, soil water repellency, and δ¹³C. Additionally, calorific value and thermal stability of the soil organic matter at the beginning and end of incubation were determined. Soil samples of the wet-cold and moist-warm incubation were tested for phytotoxicity using a seed germination bioassay with Lepidium sativum. As a function of climatic conditions, positive and negative effects, e.g., addition of nutrients, phytotoxicity, and soil water repellency, were observed. Under dry-hot conditions, the soil was still water repellent after 60 days of incubation whereas the wet-hot, moist-warm, and wet-cold incubation show that soil would stay wettable if soil moisture before OMW treatment would be sufficient. Thus, the impact of OMW treatment on soil quality strongly depends on the environmental conditions which should favor an enhancement of microbial activity to minimize negative effects.     

Ultrasonic extraction of phenols from olive mill wastewater: comparison with conventional methods

Recovery of phenols from olive mill wastewater (OMWW) was studied, comparing five sample preparation methods: filtration, solid-phase (SPE), liquid-liquid (LLE) and ultrasonic (US)-assisted extraction of liquid and solid (freeze-dried) OMWW. Results showed that ultrasonication is a good alternative to conventional solvent extractions, providing higher recoveries at both levels of individual and total phenol yields. Sonication of liquid OMWW in organic solvent was more efficient vs its nonassisted counterpart (agitation), but did not provide a representative phenol chromatogram due to ethyl acetate use. By contrast, the US-assisted extraction of freeze-dried OMWW (3 × 20 min) in 100% methanol (1.5 g/25 mL, w/v) offered the highest qualitative-quantitative phenol yields without any US-induced alterations. Moreover, freeze-drying is an excellent preservation of initial liquid OMWW, holding a great potential for delayed analysis. This study is also the first report that Slovenian OMWW may be utilized as a valuable source of phenols, especially hydroxytyrosol and tyrosol.     

The activity of healthy olive microbiota during virgin olive oil extraction influences oil chemical composition

The activity of olive microbiota during the oil extraction process could be a critical point for virgin olive oil quality. With the aim to evaluate the role of microbiological activity during the virgin olive oil extraction process, just before oil extraction freshly collected healthy olive fruits were immersed in contaminated water from an olive mill washing tank. The oils extracted were then compared with control samples from the same batch of hand-picked olives. The presence of lactic and enteric bacteria, fungi and Pseudomonas on the surface of olives was proved to be much higher in washed than in control olives, with increments in cfu/g between 2 and 3 orders of magnitude. The biogenesis of volatile compounds and the extraction of olive polyphenols and pigments were significantly influenced by the microbiological profile of olives even without any previous storage. In most cases the effect of olive microbiota on oil characteristics was greater than the effect exerted by malaxation time and temperature. Oils from microbiologically contaminated olives showed lower amounts of C5 volatiles and higher levels of C6 volatiles from the lipoxygenase pathway and some fermentation products. On the other hand, a decrease of chlorophylls, pheophytins, xanthophylls and the ratio chlorophyll/pheophytin was observed in these oils. Likewise, the microbiological activity during oil extraction led to significantly lower amounts of polyphenols, in particular of oleuropein derivatives. These differences in olive oil chemical composition were reflected in oil sensory characteristics by the decrease of the green and bitter attributes and by the modification of the oil color chromatic ordinates.     

Changes induced by UV radiation during virgin olive oil storage

The effects of UV radiation on the chemical and sensory characteristics of virgin olive oils (cv. Arbequina and Picual) were assessed. Even small doses of UV radiation induced oxidation of the virgin olive oil samples. Total phenols and fatty acids contents decreased during the process as well as the intensity of the bitter and fruity sensory attributes, while the intensity of the rancid sensory attribute notably increased. Acetaldehyde, 2-butenal, 2-pentenal, octane, octanal, hexanal, nonanal, and 2-decenal were the volatile compounds most affected, showing an important increase during the irradiation process. Nonanal, hexanal, and pentanal showed high correlation with the rancid sensory attribute (90%, 86%, and 86%, respectively). 2-Decenal and nonanal concentrations allowed us to predict the alteration level of the samples by mean of multiple Ridge regression.     

The fate of organic matter brought into soil by olive mill wastewater application at different seasons

Purpose

Application of olive mill wastewater (OMW) to soil may cause positive or negative effects. The present study aims at a better understanding of the fate of organic matter brought into soil by OMW application under different environmental conditions.

Materials and methods

Single OMW application to soil was conducted in spring, dry summer, summer with irrigation, and in winter. Two days and 18–24 months after the application, soil samples from two depths were analyzed for thermal soil organic matter (SOM) properties, total organic carbon, water-extractable dissolved soil organic carbon, and its specific ultraviolet absorbance at 254 nm.

Results and discussion

After winter and irrigated summer treatments, OMW was largely leached from the upper horizon within 2 days. Application in spring and summer dry initially increased the thermolabile fraction and the calorific value of SOM, however, in a different degree due to different transport, transformation, and immobilization mechanisms. At the long term, SOM content was still elevated after summer dry treatment. The reduction of the thermostable fraction in spring treatment indicates a priming effect of the labile OMW constituents.

Conclusions

Application in winter or with irrigation cannot be recommended for the investigated site. Under hot and dry conditions, SOM content increased most persistently due to stronger mineral-organic interactions. Favorable conditions for biodegradation during OMW application in spring reduced the effects on SOM quantity in the long term. However, a possible priming effect and the persistence of changes in thermal properties need to be further investigated for repeated applications.

     

Hydroxytyrosol-rich olive mill wastewater extract protects brain cells in vitro and ex vivo

Elevated oxidative and nitrosative stress both impair the integrity and functioning of brain tissue, especially in aging. As long-term intake of plant foods rich in antioxidant phenolics, such as extra virgin olive oil, positively modulates surrogate markers of many human pathological alterations, the interest in cheap and abundant sources of such phenolics is rapidly growing. Olive mill wastewater is particularly rich in hydroxytyrosol, an o-diphenol with powerful antioxidant, anti-inflammatory, and antithrombotic activities. Due to the deleterious effect of oxidative stress on brain cell survival, the efficacy of a hydroxytyrosol-rich extract to attenuate Fe2+- and nitric oxide (NO)-induced cytotoxicity in murine-dissociated brain cells was investigated. The addition of either Fe2+ or SNP (an NO donor) caused both a severe loss of cellular ATP and a markedly depolarized mitochondrial membrane potential. Preincubation with hydroxytyrosol significantly attenuated the cytotoxic effect of both stressors, although with different efficiencies. Mice feeding studies were performed to assess the brain bioactivity of hydroxytyrosol ex vivo. Subchronic, but not acute, administration of 100 mg of hydroxytyrosol per kilogram body weight for 12 days enhanced resistance of dissociated brain cells to oxidative stress, as shown by reduced basal and stress-induced lipid peroxidation. Also, basal mitochondrial membrane potential was moderately hyperpolarized (P < 0.05), an effect suggestive of cytoprotection. In synthesis, the ex vivo data provide the first evidence of neuroprotective effects of oral hydroxytyrosol intake. Keywords: Hydroxytyrosol; olive mill wastewater; dissociated brain cells; oxidative stress; brain; Mediterranean diet.     

土壤微生物群落对高剂量的新鲜橄榄油厂废水的响应

An incubation experiment was designed in order to determine the further microbiological response to an addition (500 m³ ha^-1) of fresh olive mill wastewater (FOMWW) in a soil that has been frequently amended with uncontrolled doses of OMWW since 90s in an active disposal site (ADS soil). To achieve this aim, the phospholipid fatty acid (PLFA) profiles, microbial biomass C (C_mic), and dehydrogenase (DHA) and urease activities (URA) were monitored at the beginning (T₀), 3 h (T₁) and 97 d (T_f, i.e., the end) of incubation after FOMWW addition. After the FOMWW addition, an increase in the ratio of fungal to bacterial PLFAs was observed in ADS soil. Moreover, a relative increase of monounsaturated fatty acids (MUFAs) with respect to saturated fatty acids (SATFA) was found in the ADS soil. An increase of the Gram-positive to Gram-negative ratio was observed in this soil at the end of the incubation. While DHA and Cmic increased in the ADS soil after FOMWW addition, URA showed a decrease. Fungi and Gram-positive bacterial biomass experienced an increase after addition of a high dose of FOMWW in laboratory conditions.     

Changes in the content of bioactive polyphenolic compounds of olive mill wastewater by the action of exogenous enzymes

The aim behind the present research is to develop an enzymatic treatment for olive mill wastewater (OMW) to release high amounts of simple phenolics having high antioxidant value. OMW was hydrolyzed by a mixed enzyme preparation rich in β-glucosidase produced by Aspergillus niger . This research shows that A. niger β-glucosidase played a major role in the release of simple phenolic compounds from OMW. These compounds were recovered by ethyl acetate extraction and identified by HPLC and LC-MS. The main identified phenolic compound is hydroxytyrosol. The results of enzymatic hydrolysis of OMW under optimum conditions indicated a maximum hydroxytyrosol concentration of 2.9 g L(-1) compared to 0.015 g L(-1) contained in the control (test without added enzyme). The above results prove that OMW is a potential substrate for producing hydroxytyrosol through enzymatic hydrolysis of its glycosides.     

Availability of triazine herbicides in aged soils amended with olive oil mill waste

Amendments are frequently added to agricultural soils to increase organic matter content. In this study, we examined the influence of alperujo, an olive oil mill waste, on the availability of two triazine herbicides, terbuthylazine and atrazine, in two different sandy soils, one from Sevilla, Spain, and the other from Minnesota. The effect of aging on herbicide sorption and bioavailability was also studied. Soils were amended with alperujo at a rate of 3-5% (w:w) in laboratory studies. Apparent sorption coefficients for the triazine herbicides were calculated as the ratio of the concentrations of each herbicide sequentially extracted with water, followed by aqueous methanol, at each sampling time. These data showed greater sorption of terbuthylazine and atrazine in amended soils as compared to nonamended soils, and an increase in the amount of herbicide sorbed with increasing aging time in nonamended soils. The triazine-mineralizing bacterium Pseudomonas sp. strain ADP was used to characterize triazine bioavailability. Less mineralization of the herbicides by Pseudomonas sp. strain ADP was observed in soils amended with alperujo, as compared to the unamended soils, and, despite the increase in sorption with aging in unamended soils, herbicide mineralization also increased in this case. This has been attributed to Pseudomonas sp. strain ADP first using alperujo as a more readily available source of N as compared to the parent triazines. In summary, addition of alperujo to the soils studied was shown to increase triazine herbicides sorption and hence to reduce its availability and potential to leach.     

Fate of diuron and terbuthylazine in soils amended with two-phase olive oil mill waste

The addition of organic amendments to soil increases soil organic matter content and stimulates soil microbial activity. Thus, processes affecting herbicide fate in the soil should be affected. The objective of this work was to investigate the effect of olive oil production industry organic waste (alperujo) on soil sorption-desorption, degradation, and leaching of diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea] and terbuthylazine [N2-tert-butyl-6-chloro-N4-ethyl-1,3,5-triazine-2,4-diamine], two herbicides widely used in olive crops. The soils used in this study were a sandy soil and a silty clay soil from two different olive groves. The sandy soil was amended in the laboratory with fresh (uncomposted) alperujo at the rate of 10% w/w, and the silty clay soil was amended in the field with fresh alperujo at the rate of 256 kg per tree during 4 years and in the laboratory with fresh or composted alperujo. Sorption of both herbicides increased in laboratory-amended soils as compared to unamended or field-amended soils, and this process was less reversible in laboratory-amended soils, except for diuron in amended sandy soil. Addition of alperujo to soils increased half-lives of the herbicides in most of the soils. Diuron and terbuthylazine leached through unamended sandy soil, but no herbicide was detected in laboratory-amended soil. Diuron did not leach through amended or unamended silty clay soil, whereas small amounts of terbuthylazine were detected in leachates from unamended soil. Despite their higher sorption capacity, greater amounts of terbuthylazine were found in the leachates from amended silty clay soils. The amounts of dissolved organic matter from alperujo and the degree of humification can affect sorption, degradation, and leaching of these two classes of herbicides in soils. It appears that adding alperujo to soil would not have adverse impacts on the behavior of herbicides in olive production.     

Evolution of organic matter and nitrogen during co-composting of olive mill wastewater with solid organic wastes

 Four olive mill wastewater (OMW) composts, prepared with three N-rich organic wastes and two different bulking agents, were studied in a pilot plant using the Rutgers system. Organic matter (OM) losses during composting followed a first-order kinetic equation in all the piles, the slowest being the OM mineralisation rate in the pile using maize straw (MS). The highest N losses through NH₃ volatilisation occurred in the mixtures which had a low initial C/N ratio and high pH values during the process. Such losses were reduced considerably when MS was used as the bulking agent instead of cotton waste (CW). N fixation activity increased during the bio-oxidative phase before falling during maturation. This N fixation capacity was higher in piles with a lower NH₄ ⁺-N concentration. Only the composts prepared with OMW, CW and poultry manure or sewage sludge reached water-soluble organic C (C_W) and NH₄ ⁺-N concentrations and C_W/N_org and NH₄ ⁺/NO₃ ^– ratios within the established limits which indicate a good degree of compost maturity. Increases in the cation-exchange capacity, the percentage of humic acid-like C and the polymerisation ratio revealed that the OM had been humified during composting. The germination index indicated the reduction of phytotoxicity during composting. Received: 14 June 1999