Codigestion of olive oil mill wastewaters with manure, household waste or sewage sludge

Combined anaerobic digestion of oil mill effluent(OME) together with manure, household waste (HHW) orsewage sludge was investigated. In batch experimentsit was shown that OME could be degraded into biogaswhen codigested with manure. In codigestion with HHWor sewage sludge, OME dilution with water (1:5) wasrequired in order to degrade it. Using continuouslystirred lab-scale reactors it was shown thatcodigestion of OME with manure (50:50 and 75:25 OMEto manure ratios) was successful with a theoreticalOME utilization of 75% and with approx. 87%reduction of the lipids content in OME. An OMEutilization of approx. 55%, and lipid reduction of73% was reached in codigestion with HHW (50:50 and75:25 OME to HHW ratios). The results showed thatthe high buffering capacity contained in manure,together with the content of several essentialnutrients, make it possible to degrade OME withoutprevious dilution, without addition of externalalkalinity and without addition of external nitrogensource.     

Novel static composting method for bioremediation of olive mill waste

This paper presents results obtained on the evaluation of static composting process aimed at bioremediation of the hazardous solid olive mill waste (OMW). The static composting process carried out in gas-permeable polyethylene bags followed the fluctuating temperature and oxygen profiles similar to those seen in aerated composting systems. Static composting resulted in apparent increases and decreases in values for total nitrogen and C:N ratios respectively during the process. The amount of nitrogen (>3%) in the composting end product was in agreement with the Italian legislation (Decreto Legislativo 29 aprile 2010, n. 75) specification for nitrogen fertilizer. A gradual decrease in polyphenols during the storage of compost resulted in a non-phytotoxic composted organic matter high in humic substances. Different respirometric tests also stated high biological stability of the end compost product.     

Removal of low molecular weight phenols from olive oil mill wastewater using microalgae

The treatment of olive oil mill wastewater (OMW) with two phenol resistant algae, Ankistrodesmus braunii and Scenedesmus quadricauda, showed a limited reduction of phenol content after 5 d of treatment, irrespective of algal concentration. Otherwise, cultures of both algae, grown in the dark, degraded over 50% of the low molecular weight phenols contained in OMW, but they were not completely removed, but were biotransformed into other non-identified, aromatic compounds.     

Screening of fungal isolates and properties of Ganoderma applanatum intended for olive mill wastewater decolourization and dephenolization

AIMS: To investigate different autochthonous isolates of wood-rotting fungi for the removal of both colour and phenolic compounds from olive mill wastewaters (OMW). METHODS AND RESULTS: The isolates Bjerkandera adusta Ba-100, Fomes fomentarius Ff-106, Ganoderma applanatum Ga-20, Irpex lacteus Il-3, Trametes versicolor Tv-101 and Tv-103 were preliminarily screened for their OMW-decolourizing potential on potato dextrose agar supplemented with different OMW concentrations. A further screening of batch cultures under different agitation speeds, to test the effect of shear stress, resulted in the selection of isolate G. applanatum Ga-20. Batch cultures grown in OMW-based medium exhibited strong laccase induction and significant decrease in the values of phenols, colour and chemical oxygen demand. Concomitant onset of laccase activity and colour removal was observed, and apart from laccase, neither lignin peroxidase nor manganese-dependent peroxidase activities were detected. Moreover, the depletion of aromatic compounds with high and low apparent molecular mass was observed by chromatographic analysis. CONCLUSIONS: Isolate G. applanatum Ga-20 exhibited interesting properties for its use in bioremediation of OMW, namely high removal of recalcitrant phenolic compounds and strong colour abatement. SIGNIFICANCE AND IMPACT OF THE STUDY: For the first time, the white-rot fungus G. applanatum proves to be effective for the decolourization and dephenolization of OMW.     

Influence of the microorganism support on the kinetics of anaerobic fermentation of condensation water from thermally concentrated olive mill wastewater

Two materials of different structure, sepiolite and bentonite, evaluated as supports for the microorganisms effecting anaerobic fermentation, behaved differently towards condensation water from thermally concentrated olive mill wastewater from a kinetic point of view. Assuming the overall anaerobic digestion process to conform to first-order kinetics, the apparent kinetic constant for the digester including sepiolite as support was 1.12 day^-1, while that of the digester using the bentonite support was 0.73 day^-1. Thus, the apparent kinetic constant of the process was increased by 35% with the use of sepiolite. The yield coefficient, Y_p/s, was 0.344 and 0.318 litres CH₄ STP/g COD for the sepiolite and bentonite supports respectively.     

Anaerobic digestion challenge of raw olive mill wastewater

Olive mill wastewater (OMW) was digested in its original composition (100% v/v) in an anaerobic hybrid. High concentrations (54–55 kg COD m⁻³), acid pH (5.0) and lack of alkalinity and nitrogen are some OMW adverse characteristics. Loads of 8 kg COD m⁻³ d⁻¹ provided 3.7–3.8 m³ biogas m⁻³ d⁻¹ (63–64% CH₄) and 81–82% COD removal. An effluent with basic pH (8.1) and high alkalinity was obtained. A good performance was also observed with weekly load shocks (2.7–4.1, 8.4–10.4 kg COD m⁻³ d⁻¹) by introducing piggery effluent and OMW alternately. Biogas of 3.0–3.4 m³ m⁻³ d⁻¹ (63–69% CH₄) was reached.Developed biomass (350 days) was neither affected by raw OMW nor by organic shocks. Through the effluents complementarity concept, a stable process able of degrading the original OMW alone was obtained. Unlike what is referred, OMW is an energy resource through anaerobiosis without additional expenses to correct it or decrease its concentration/toxicity.     

Composting of olive leaves and pomace from a three-phase olive mill plant

The composting of olive leaves and olive pomace from a three-phase olive mill was tested as a method for solid waste reuse. The process was carried out using a compost windrow and mixing olive leaves and pomace at a ratio of 1:2. Compost was retained in the windrow for 60 days during which thermophilic temperatures developed for the first 40 days. The compost was then placed into a closed area to mature for another 60 days. The final product proved to be high quality amendment with C/N 27.1 and high nutrient concentrations (N, 1.79%; P, 0.17%; K, 4.97%; Na, 2.8%). Mature compost presented the highest germination index (198%) reported to date, as the germination index in the majority of previous studies is under 80%. Furthermore, tests revealed that addition of 31.5 tons of compost per ha, could increase lettuce yield by 145%.     

Low-molecular-weight components of olive oil mill waste-waters

A new lignan 1-hydroxy-2-(4-hydroxy-3-methoxyphenyl)-6-(3-acetyl-4-hydroxy-5-methoxyphenyl)-3,7-dioxabicyclo[3.3.0]octane, the secoiridoid 2H-pyran-4-acetic acid,3-hydroxymethyl-2,3-dihydro-5-(methoxycarbonyl)-2-methyl-, methyl ester, the phenylglycoside 4-[beta-D-xylopyranosyl-(1-->6)]-beta-D-glucopyranosyl-1,4-dihydroxy-2-methoxybenzene and the lactone 3-[1-(hydroxymethyl)-1-propenyl] delta-glutarolactone were isolated and identified on the basis of spectroscopic data including two-dimensional NMR, as components of olive oil mill waste-waters. The known aromatic compounds catechol, 4-hydroxybenzoic acid, protocatechuic acid, vanillic acid, 4-hydroxy-3,5-dimethoxybenzoic acid, 4-hydroxyphenylacetic acid, 3,4-dihydroxyphenylacetic acid, tyrosol, hydroxytyrosol, 2-(4-hydroxy-3-methoxy)phenylethanol, 2-(3,4-dihydroxy)phenyl-1,2-ethandiol, p-coumaric acid, caffeic acid, ferulic acid, sinapic acid, 1-O-[2-(3,4-dihydroxy)phenylethyl]-(3,4-dihydroxy)phenyl-1,2-ethandiol, 1-O-[2-(4-hydroxy)phenylethyl]-(3,4-dihydroxy)phenyl-1,2-ethandiol, D(+)-erythro-1-(4-hydroxy-3-methoxy)-phenyl-1,2,3-propantriol, p-hydroxyphenethyl-beta-D-glucopyranoside,2(3,4-dihydroxyphenyl)ethanol 3beta-D-glucopyranoside, and 2(3,4-dihydroxyphenyl)ethanol 4beta-D-glucopyranoside were also confirmed as constituents of the waste-waters.     

Effects of untreated two‐phase olive mill pomace on potted olive plantlets

Two‐phase pomace represents an important environmental problem in Mediterranean areas. With its high organic content, direct application of two‐phase pomace in the field is recommended to improve soil organic carbon levels and fertility. However, this does not consider any antagonistic effects that this application might have on root proliferation and biomass partitioning. We studied the effects of untreated two‐phase pomace on properties of growth substrate, and on shoot and root growth and biomass allocation of potted olive plantlets. A pot experiment was carried out in a greenhouse over 90 days, with five levels of two‐phase pomace and using two olive cultivars. The effects on shoot growth, leaf pigment content and maximum quantum efficiency of photosystem II (ΦPSII) were assessed each month. After 90 days, the shoot and root biomass of the olive plants was quantified, along with total organic matter, and carbon, nitrogen and polyphenol contents of the growth substrate and shoots, and the fine root nutritional status. Two‐phase pomace increased the total organic matter, total nitrogen and polyphenol contents of the growth substrate. It significantly altered biomass partitioning in the olive plantlets, with reduced shoot dry mass and leaf area, and new shoot formation. It also increased fine and total root dry mass for all two‐phase pomace levels except 40%. There were no significant differences in leaf pigment content and ΦPSII across the treatment levels. Therefore, application of untreated two‐phase pomace at more than 4% induces a severe imbalance in olive plantlet biomass partitioning, and shoot and root growth.     

Treatment of olive mill wastewater in pilot-scale vertical flow constructed wetlands

Pilot-scale constructed wetlands (CW) were constructed and operated to treat pre-treated olive mill wastewater. Pilot-scale units comprising three identical series with four pilot-scale vertical flow CWs were operated for one harvest season in a Greek olive mill plant. The pilot-scale CWs were filled with various porous media (i.e., cobble, gravel, and sand) of different gradations. Two series of pilot-scale units were planted with common reeds and the third (control) was unplanted. Mean influent concentrations were 14,120 mg/L, 2841 mg/L, 95 mg/L, 123 mg/L and 506 mg/L for COD, phenols, ortho-phosphate, ammonia and TKN, respectively. Despite the rather high influent concentrations, the performance of the CW units was very effective since it achieved removals of about 70%, 70%, 75% and 87% for COD, phenols, TKN and ortho-phosphate, respectively. COD, phenol and TKN removal seems to be significantly higher in the planted series, while ortho-phosphate removal shows no significant differences among the three series. Temperature and pollutant surface load seem to affect the removal efficiency of all pollutants. Compared to previous studies, pollutant surface loads applied here were higher (by one or two orders of magnitude). Even though high removal efficiencies were achieved, effluent pollutant concentrations remained high, thus preventing their use for irrigation or immediate disposal into the environment.     

Phenolic removal in olive oil mill wastewater using loofah-immobilized Phanerochaete chrysosporium

Summary Olive oil mill wastewater (OMW) has a high organic load, and this is a serious concern of the olive industry. Conventional biological wastewater treatments, despite their simplicity and suitable performance are ineffective for OMW treatment since phenolics possess antimicrobial activity. In order to carry out a proper treatment of OMW, use of a microorganism able to degrade the phenolics is thus necessary. In this study the ability of Phanerochaete chrysosporium to degrade the phenolic compounds of OMW and to decrease the chemical oxygen demand (COD) using cells immobilized on loofah was examined. The basal mineral salt solution along with glucose, ammonium sulfate and yeast extract was used to dilute the OMW appropriately. The fungus did not grow on the concentrated OMW. The extent of removal in this bio-treatment, of total phenols (TP) and the COD were 90 and 50%, respectively, while the color and aromaticity decreased by 60 and 95%, respectively. The kinetic behavior of the loofah-immobilized fungus was found to follow the Monod equation. The maximum growth rate μ_max was 0.045 h⁻¹ while the Monod constant based on the consumed TP and COD were (mg/l) 370 and 6900, respectively.     

Determination of aerobic biodegradation kinetics of olive oil mill wastewater

Aerobic biological treatment was conducted for the treatment of high strength olive oil mill wastewater (OMW). Two different approaches were used for kinetic modeling of OMW biodegradation. TOC removal and CO₂–C evolution were monitored in an open and a closed bioreactor systems, respectively. Gompertz, Refractory organics plus first-order (RFO) and Chen–Hashimoto equations were applied to estimate the kinetic parameters by using the data from bioreactors. Furthermore, change in oxidation stage of carbon was monitored and temperature dependency of OMW biodegradation was investigated based on activation energy. At room temperature, 64% of TOC was removed in the open bioreactor while cumulative CO₂–C evolution was 6.32 g L⁻¹ in closed the bioreactor. Higher biodegradation efficiency and kinetic parameters were obtained at 25 °C rather than 10 °C. Gompertz and RFO equations provided better fitting with CO₂–C and TOC data, respectively. Experimental and kinetic estimations indicated that OMW constituted of approximately 30% refractory organics. The comparison of two different modeling approaches showed that kinetic modeling based on CO₂–C provided better correlation with the experimental data. Temperature coefficient indicated that biological degradation of OMW is slightly dependent on temperature.     

Two-phase olive mill waste composting: community dynamics and functional role of the resident microbiota

In this study, physico-chemical modifications and community dynamics and functional role of the resident microbiota during composting of humid husk from a two-phase extraction system (TPOMW) were investigated. High mineralization and humification of carbon, low loss of nitrogen and complete degradation of polyphenols led to the waste biotransformation into a high-quality compost. Viable cell counts and denaturing gradient gel electrophoresis (DGGE) profiling of the 16S rRNA genes showed that the thermophilic phase was characterized by the strongest variations of cell number, the highest biodiversity and the most variable community profiles. The isolation of tannin-degrading bacteria (e.g. Lysinibacillus fusiformis, Kocuria palustris, Tetrathiobacter kashmirensis and Rhodococcus rhodochrous) suggested a role of this enzymatic activity during the process. Taken together, the results indicated that the composting process, particularly the thermophilic phase, was characterized by a rapid succession of specialized bacterial populations with key roles in the organic matter biotransformation.     

Short-term impact of dry olive mill residue addition to soil on the resident microbiota

The short-term response of the resident soil bacterial and fungal communities to the addition of 5% (w/w) of either dry olive mill residue (DOR), DOR treated with Phlebia sp. (PTDOR) or DOR previously extracted with water (WEDOR) was investigated. As opposed to bacteria, the diversity of fungi increased upon the amendments as assessed by denaturing gradient gel electrophoresis of 18S rDNA. Over the first 30 days, phospholipid fatty acids analyses indicated a gradual decrease in the relative abundances of Gram⁺ bacteria (from 44.8% to 37.9%) and a concomitant increase of Gram⁻ bacteria (from 37.3% to 51.2%) in DOR-amended soil. A considerable increase in the fungal/bacterial ratio was observed after 7 days in DOR, WEDOR and PTDOR-amended soils with respect to the control (0.316, 0.165 and 0.265, respectively, vs. 0.011). The overall microbial activity was stimulated by the amendments as indicated by the higher activity levels of both dehydrogenase and fluorescein diacetate hydrolase. These results indicate that DOR at the application level examined is not toxic on soil microorganisms.     

Rhizosphere dynamics during phytoremediation of olive mill wastewater

The potential of phytoremediation as a treatment option for olive mill wastewater (OMW) was tested on five perennial tree species. Cupressus sempervirens and Quercus ilex proved tolerant to six-month OMW treatment followed by six-month water irrigation, whereas Salix sp. and Laurus nobilis and, later, Pinus mugo suffered from phytotoxic effects. Test plants were compared to controls after treatment and irrigation, by monitoring biochemical and microbiological variations in the rhizosphere soil. OMW-treated soils were exposed to 50-fold higher phenols concentrations, which, irrespective of whether the respective plants were OMW-resistant or susceptible, were reduced by more than 90% by the end of the irrigation cycle, owing to significantly increased laccase, peroxidase and β-glucosidase activities, recovery/acquisition of bacterial culturability and transitory development of specialized fungal communities sharing the presence of Geotrichum candidum. Of all results, the identification of Penicillium chrysogenum and Penicillium aurantiogriseum as dominant rhizosphere fungi was distinctive of OMW-tolerant species.     

Effect of continuous olive mill wastewater applications, in the presence and absence of nitrogen fertilization, on the structure of rhizosphere–soil fungal communities

Olive mill wastewater (OMW) is rich in potentially toxic organics precluding its disposal into water receptors. However, land application of diluted OMW may result in safe disposal and fertilization. In order to investigate the effects of OMW on the structure of soil fungal groups, OMW was applied daily to pepper plants growing in a loamy sand and a sandy loam at two doses for a period of 3 months (total OMW equivalents 900 and 1800 m³ ha⁻¹). Nitrogen (N) fertilization alleviated N scarcity and considerably enhanced plant biomass production; however, when applied in combination with the high OMW dose, it induced plant stress. OMW applications resulted in marked changes in the denaturing gradient gel electrophoresis patterns of soil basidiomycete communities, while concurrent N fertilization reduced these effects. In contrast, the ascomycete communities required N fertilization to respond to OMW addition. Cloning libraries for the basidiomycete communities showed that Cryptococcus yeasts and Ceratobasidium spp. dominated in the samples treated with OMW. In contrast, certain plant pathogenic basidiomycetes such as Thanatephorus cucumeris and Athelia rolfsii were suppressed. The observed changes may be reasonably explained by the capacity of OMW to enrich soils in organic substrates, to induce N immobilization and to directly introduce OMW-derived basidiomycetous yeasts.     

Optimisation of biodegradation conditions for the treatment of olive mill wastewater

The aim of the present paper was to optimise the conditions of aerobic treatment of olive mill wastewater. To do so, the waste was treated following the experimental optimal design methodology studying the set of factors susceptible to influence the treatment (pH, C/N ratio, aeration and temperature). The results of a first series of experiments showed a strong correlation between the reduction in the levels of polyphenols and three of the parameters studied, i.e. the C/N ratio, aeration and temperature. Optimised conditions led to a 94% drop in polyphenols.

Then, for a finer study of the conditions, just two parameters were varied, the pH and the C/N ratio. The results showed that the conditions of pH modification (addition of lime or sodium hydroxide) and the C/N ratio (urea or ammonium nitrate) allowed the microbiological activity to be very significantly improved. This led to polyphenol reductions of 51% and 76%.     

Plant growth hormone production from olive oil mill and alcohol factory wastewaters by white rot fungi

In this study, olive oil mill and alcohol factory wastewaters have been tested as growth media for the production of plant growth hormones. Funalia trogii ATCC 200800 and Trametes versicolor ATCC 200801 have been tested. Gibberellic acid (GA₃), abscisic acid (ABA), indole acetic acid (IAA), and cytokinin were determined in the culture media of these fungi. Both organisms produced enhanced levels of all three hormones in the presence of either of the wastewaters.     

Bioremediation of olive oil mill wastewater and production of microbial biomass

Olive oil mill wastewater (OMWW) was used as a substrate for the culture of a mixture of edible fungi in order to obtain a potentially useful microbial biomass and to induce a partial bioremediation of this fastidious waste. Before fermentation, the OMWW underwent an alkaline-oxidative treatment with the aim of decreasing the polyphenolic content which is the main cause of its toxicity. The fungal mixture grew fairly well in the treated OMWW and reached a maximum of biomass production within about 14 days of fermentation at room temperature. Up to 150–160 g of wet biomass was obtained per liter of OMWW. Analysis of the partially dehydrated biomass revealed a protein content of about 13 g% and 6 g% of row fiber. A relevant presence of unsaturated fatty acids was found, as well as the presence of significant amounts of vitamins A and E, nicotinic acid, calcium, potassium and iron. The possibility of using the microbial biomass produced from OMWW as an additive to animal feed is discussed.