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2POMW (8,074,340 kg)

Water (57.47%) Olive oil (4.03%) Dry-extract (38.51%)

Olive oil (1,929,972 kg)

2POMW (8,074,340 kg)

Water (57.47%) Olive oil (4.03%) Dry-extract (38.51%)

Olive oil (204,990 kg)

Olive cake (6,123,708 kg)

Water (52.11%) Olive oil (1.5%) Dry-extract (46.39%)

Enzyme treatment

Pectinase and amylase

Enzyme treatment

Pectinase and amylase

Fig. 9.2. Purification of 2POMW by enzymatic treatment, filtration, and evaporation (ES2110912, 1998).

*The obtained concentrate is composed of; 24.0% humic extract; 2.7% total N; 6.7% K2O; 1.6% P2O5. Elements: Ca, Mg, Fe, Mn, Cu, Zn.

Fig. 9.2. Purification of 2POMW by enzymatic treatment, filtration, and evaporation (ES2110912, 1998).

*The obtained concentrate is composed of; 24.0% humic extract; 2.7% total N; 6.7% K2O; 1.6% P2O5. Elements: Ca, Mg, Fe, Mn, Cu, Zn.

the destoned effluent is collected and stirred in a special tank to prevent the physical separation of its liquid and solid elements, then fed into another tank where it is mixed with additives which:

a) reduce the moisture of the destoned effluent, so that the end product is non-percolating; suitable additives include wood shavings and sawdust from non-treated timber, straw from graminaceous plants, raw wool waste, etc.

b) allow good circulation of air in the end product; preferred additives are straw, olive leaves, and twigs obtained from trimming the olives in the olive-mill upstream of the oil extraction process.

c) reduce the C/N ratio of the initial effluent in order to cause more rapid microbial degradation in the soil and, minimize competition with agricultural crops for the nitrogen contained in the solution circulating in the soil; additives experimented comprise raw wool waste or raw wool itself, both readily available and inexpensive. Along with an organic nitrogen content that varies approximately between 4.5 and 6%, these materials present high hydroscopic capacity which derives, among other factors, from their low moisture content. Raw wool waste and wool have a content of organic matter of about 76% and about 9% ash (mainly composed of calcium, potassium, while iron is the principal constituent of micro-elements). The choice and quantity of additives depends on the type of the olive residue and the end product to be obtained.

The 3rd phase consists of the automatic packaging of the end product in sealed net bags (20-30 kg) to facilitate transport and storage. The bags are stored in static layered piles where the end product undergoes aerobic maturation due to the action of yeasts and bacteria, improving this way its chemical and physical properties. At the same time, the moisture level of the biomass falls, which in practical terms means less weight to be handled and increased agronomic efficiency due to the concentration of nutrients.

The end product can be used as a soil amendment and/or organic fertilizer in olive culture and crop cultivation in general — see Chapter 10: "Uses, section: Use as fertilizer/soil conditioner''. The so-called M.A.T.Re.F.O. technology (Method and Apparatus for the Treatment of Oil Mill Effluents) has been patented (application number: IT2004RM000084).

A treatment made up of physical and physico-chemical processes, the realization of which in a rational manner is claimed to achieve the maximum reduction in the organic load with lower energy costs is described in: ES2019830 (1991). According to this process OMWW is treated in a series of steps: (1) Primary reduction of organic load, "oil removal''. OMWW is thoroughly mixed with a solvent, so as to obtain: an aqueous phase olive wastewater-I with the oil removed, and another phase formed by a fatty phase — with a solvent, which is used again after distillation. (2) Secondary reduction of organic load, "flocculation". This consists of the separation of organic matter contained in the olive wastewater-I from the preceding process, by means of a coagulation or flocculation, and the flocculated matter is separated from the olive wastewater-II by sedimentation, filtration, or centrifugation. (3) Tertiary reduction of organic load, "formation of carbonated organic compounds''. The olive wastewater-II is subjected to the combined action of alkaline-earth hydroxides and carbon dioxide, so as to form organic carbonated compounds, which under certain conditions are insoluble and can be separated by filtration, sedimentation, or centrifugation.

A simultaneous combustion process — as described in: ES2032162 (1993) — is applied to the previous treatment (ES2019830, 1991). Such an improved system for the treatment of OMWW, comprising also biological and thermal processes, is described in: ES2024369 (1992). The combustion process generates the heat energy necessary for continuous regeneration of the reagents used in the process, eliminates contaminating organic matter, and provides the appropriate temperature for optimum operation of the biological process. Thermal dissociation, calcination, activation, and distillation units are included in the system, together with supplementary purification devices for the elimination of OMWW and sludges. The volatile products generated by biological processes, which produce additional calories, are used in the process as an additional fuel for joint thermal processing.

ES2108658 (1997) describes a process for the treatment of highly contaminated and/or toxic wastewaters including those from olive processing. The purification is carried out through bacteria adapted to the residue externally to the reactors involved in the process, said bacteria being fixed to support means which are immersed in the reactors. The process comprises: (a) first and second preliminary physical treatments including screening and/or centrifugation for the separation of solid matter; (b) physico-chemical treatment including sedimentation and/or flocculation and/or coagulation to remove suspended solids; (c) treatment in at least one aerobic biological reactor; (d) treatment in at least one anoxic biological reactor arranged upstream of the first aerobic reactor; (e) treatment in at least one clarification pool to separate the biomass; (f) at least one recirculation of a portion of the slurry generated in the biological reactors to at least one of them; (g) backfeeding from at least one of the aerobic biological reactors to the same; (h) a second refeeding phase from the outlet of the first aerobic reactor to the interior of the anoxic reactor, and (i) treatment in a refining reactor which operates alternatively in anoxic and aerobic conditions. The use of preadapted bacterial strains eliminates or reduces the adaptation time required in the reactor. COD and toxicity levels in the effluent water are reduced to well below acceptable levels for discharge into water-courses. This process is distinguished by a large number of process steps and by the addition of oxygen, which can be assessed as highly energy intensive and, depending on the application, as uneconomic.

ES2084564 (1996) describes an integrated process for the purification and total exploitation of liquid and solid waste product produced at an olive-mill through a combination of a set of physical, chemical, and thermal processes as shown in Fig. 9.3. OMWW is subjected to an accelerated separation of solids (Fig. 9.3, e), which may be done by coagulating and flocculating of the solids held in OMWW and/or by ultrasound emission. The resulting precipitate is isolated from the rest of the solution through decanting; and the obtained mud or solids are mixed with

13 n

1 Olive grove

2 Olive-mill

3 Accelerated solids separation

4 De-stoning

5 Boiler

6 Roughness elimination

7 Liquids conditioning

8 Solids conditioning

9 Evaporator

10 Liquid fertilizers preparation

11 Oil physical reclamation

12 Interchanging

13 Composting plant

14 Fodders manufacturing a) Irrigation b) Organic fertilizer c) Olives d) Oil e) OMWW

f) Olive cake g) Stones h) Ashes i) Liquids from OMWW j) Heal k) Solids

I) Liquid fertilizer m) Evaporation pools n) Vegetable waste from the area o) Hot water p) Concentrate q) Pulp r) Solids without oil

Integrated process for the purification of OMWW (adapted from ES2084564, 1996).

the solid waste product resulting from the process of obtaining olive oil at the olive-mill.

The liquid of OMWW (Fig. 9.3, i) may follow three ways: one to the evaporation pools (Fig. 9.3, m) where it is evaporated faster because it lacks solids and oils, the second one to a conditioning of liquids (Fig. 9.3, 7) to prepare liquid fertilizers (Fig. 9.3, 10), and the third one to an evaporation phase (Fig. 9.3, 9). The evaporation is under atmospheric pressure. Through a stage of sudden partial evaporation, previous to the evaporation itself, most of the organic volatiles from the water are removed. All the liquids coming into the evaporator (Fig. 9.3, 9) are subjected to roughness elimination (Fig. 9.3, 6) making them circulate inside an intense magnetic field, which polarize the salt molecules and avoid their deposition on the pipes and elements they circulate through. The calcium carbonate remains in suspension and is evacuated together with the solid waste, which has been removed at the accelerated solids separation stage.

Operating continuously allows to put away the concentrated dissolution (Fig. 9.3, p) formed at the evaporator, to use it as raw material for animal fodders, reclamation of polyphenols, and/or the extraction of chemical products. When the fumes are being condensed, the residual heat is used for the thermal necessities of the olive-mill (Fig. 9.3, 12) and, finally, it supplies hot water (Fig. 9.3, q) to the olive-mill. As for the olive cake (Fig. 9.3, f), the stones are separated (Fig. 9.3, g) from the pulp (Fig. 9.3, q), the stones are used as heater's fuel (Fig. 9.3, 5), the ashes (Fig. 9.3, h) come back to the ground as mineral fertilizer, the pulp (Fig. 9.3, q) is mixed with the solids from OMWW (Fig. 9.3, 8) and are subjected to a process of centrifugation (Fig. 9.3, 11) to extract the oil (Fig. 9.3, d), which has been kept almost completely in the OMWW-solids and in the olive cake. The solids without oil (Fig. 9.3, r) obtained at the oil reclamation stage (Fig. 9.3, 11), are useful in a process of composting (Fig. 9.3, 13), to make fodder (Fig. 9.3, 14), or as boiler fuel. The process is claiming to have zero waste and most of the oil lost in OMWW and solid waste from the mill is recuperated. No chemical additives are used and the oil is pure.

Atanassova D. et al. (2005b) applied ultrasonic irradiation to reduce the anti-oxidant activity of OMWW and 2POMW. This process comprises cyclic formation, growth, and subsequent collapse of microbubbles occurring in extremely small intervals of tie, and release of large quantities of energy over a small location. Sonochemical degradation in aqueous phase involves several reaction pathways and zones such as pyrolysis inside the bubble and/or at the bubble-liquid interface and hydroxyl radical-mediated reactions at the bubble-liquid interface and/or in the liquid bulk. Sonication of diluted samples was conducted at ultrasonic frequencies of 24 and 80 kHz, an applied power varying between 75 and 150 W and liquid bulk temperatures varying between 25 and 60°C. At the specified conditions, the reduction in antioxidant activity was found to increase with decreasing temperature and increasing power and frequency. Addition of NaCl in the samples also appeared to enhance reduction.

A three-step process comprising adsorption-concentration, catalytic hydrogenation, and regeneration on a fixed bed of adsorbent-catalyst was investigated for the removal of polyphenols from OMWW (Richard D. and Delgado-Nunez M. de Lourdes, 2003). Tyrosol was taken as representative of the polyphenols present in OMWW. A ruthenium-activated carbon catalyst was used to evaluate the catalytic hydrogenation of the model phenol, tyrosol, under various temperatures (313-353 K) and pressure (0.4-4.0 MPa) conditions, and the Langmuir-Hinshelwood model was used to account for the results. At 353 K and 1 MPa, total hydrogenation of 0.042mol/kg tyrosol was achieved after 3 h.

WO03000601 (2003) describes a process for purifying several types of wastewater generating at the various stages of the olive processing comprising the following steps:

i. homogenization of the process waters such as OMWW, washing water, rinsing water, etc. (agitation or aeration);

ii. homogenization of waste lye-water and/or waste oxidation water used for debittering and blackening olives (agitation or aeration);

iii. degreasing of the homogenate;

iv. neutralization (optional addition of H2SO4, HCl, NaOH, etc.);

v. flotation (poly(aluminum chloride) and cationic polyelectrolyte);

vi. sand bed filtration;

vii. active carbon filtration;

viii. sand bed filtration;

ix. ozonation (50-500 g O3/m3 depending on the COD value the residue);

x. desalination.

The purification system claims to produce completely disinfected, clear, odorless water that complies with all legislative standards. Moreover, the proposed system is economical, fast, effective, easy to manage, and perfectly compatible with the environment.

Boari G. and Mancini I.M. (1990) studied the problem arising from OMWW in Apulia where, during the olive-milling season, organic pollution exceeds that from domestic use by a factor of three. Preliminary research allowed the estimation of organic load per ton of milled olives, and the comparison of the effectiveness of feasible treatment processes (in particular, the anaerobic process and the effect of sedimentation, coagulation followed by aeration). The results have been utilized in the Water Reclamation Plan of the Apulia Region (WRP). This Plan permits the discharge of OMWW into public sewers only when its contribution is less than 20% of municipal wastewater's organic load, or provides the transport of a controlled amount to treatment facilities, over a period ranging from 100 to 300 days. Results of full-scale and pilot biological treatment plants for combined municipal wastewater and OMWW are reported, together with the main project parameters. Anaerobic processes are more economical but their successful operation needs to be confirmed on full-scale plants.

A bleaching process combining clayey soil (7%) and hydrogen peroxide (0.5%) allows the decolorization of OMWW and the elimination of polyphenols. At pH = 6.7, the bleaching led to about 87% reduction of polyphenols and 66%

reduction of COD. The structure of clay and its concentration in iron salts has an effective adsorbent and catalytic effect on the removal of the majority of polyphenols (Oukili O. et al., 2001).

Tsonis S.P. (1997) used OMWW as carbon source in post-anoxic denitrification. A study was undertaken to evaluate the efficiency of applying OMWW as a non-nitrogenous external carbon source in the second anoxic stage of a five stage modified Bardenpho system for nutrients removal in order to assure consistently very low concentrations of total nitrogen (well below 3 mg/l) in the treated effluent. Addition of OMWW was found acceptable only up to 50 mg COD of mill waste/l of wastewater fed to the system because at higher additions color problems in the treated effluent were encountered. The required dosage of OMWW was found to be in the range 4.6-5.4 mg COD/mg N-NO3 removed. Operation with OMWW gives at the same time higher removal of phosphorus. Addition of physico-chemically pretreated OMWW with lime to the second anoxic tank at a rate of 22-45 mg COD/l of municipal type wastewater fed (ratio of volume of OMWW added to the volume of the municipal type wastewater fed 1:1000-1:2000) resulted in a treated effluent with total nitrogen below 3 mg/l and soluble phosphorus well below 1 mg/l.

Another minor process is cryogenesis (Franzione G., 1986). Except the high cost, cryogenesis has the problem that ice crystals of the water of OMWW trap the dissolved phenols and salts.

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Part III


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