Environmental impacts relative to soil quality caused from the disposal of olive oil mills’ wastes

Case study : A municipality in Crete, Greece

M. Doula, V. Kavvadias, S. Theocharopoulos, P. Kouloumbis, NAGREF- Soil Science Institute of Athens

D. Ikonomou, D. ArapoglouNAGREF- Institute of Technology of Agricultural Products

The olive oil tree is amongst the oldest known cultivated trees inthe world while the consumption of olives and olive oil is believedto bring health, however, the side products (wastewaters-OOMWand solid wastes-SW) from their production and treatment couldimpact environment negatively if no precautions are taken.

It is estimated that there are 600 million productive olive trees onthe planet, occupying a surface area of 7 million ha. TheMediterranean region accounts for not less than 97% of the worldproduction Among European countries, but also worldwide, Spainand Italy are the two leaders in olive oil production, whereasGreece holds the third place.

The annual oil mills waste production of Mediterranean olive-growing countries is estimated to ranging from 7 million to over30 million m3, depending on annual olive production. The averagetotal production amounts approximately to 10x106-12x106

m3/year and occurs over a brief period of the year (November-March).

Annual olive oil Production in Mediterraneanfor the main olive oil-productive Countries

Country 2000(x103t)

2001 (x103t)

2002(x103t)

2003(x103t)

2004(x103t)

2005(x103t)

2006(x103t)

2007(x103t)

Spain 962,4 1.412 836,9 1.449 1.005 820,6 1.139 1.326

Italy 507,4 573,5 574,9 600,5 794,6 671,3 626,8 590,2

Greece 406,4 302,2 381,6 374,9 321,3 386,4 400,6 394,7

Tunisia 115,0 30,0 72,0 280,0 130,0 210,0 170,0 194,9

Portugal 26,0 35,0 31,0 36,5 50,1 31,8 51,8 39,0

1oo Kg olives

1oo-120 Kg wastewater

1 Kg olive oil

5 Kg wastewater

58% of mills dispose wastes in streams

11,5% of mills dispose wastes in sea and rivers

19,5% of mills dispose wastes on soil

It is estimated that :

Parameter Press 3-phase

Total solids, g/l 99,7 63,5Total Suspended Solids,g/l 4,51 2,80Total Volatile solids, g/l 87,2 57,4Ash, g/l 9,69 6,13Total Organic Carbon, g/l 64,1 39,8Total Kjeldahl Nitrogen, g/l 1,15 0,76Phosphorous (P2O5), g/l 0,87 0,53pH 4,50 4,80BOD5, mg/l 68.700 45.500COD, mg/l 158.000 92.500Specific Weight, g/cm3 1,05 1,05Conductivity, mmhos/cm 18,0 12,0Total Sugars, g/l 25,9 16,1Fats and Oils, g/l 2,80 1,64Polyalcohols, g/l 4,75 3,19Total Phenols, g/l 17,2 10,6Tannins, g/l 6,74 4,01Potassium (Κ2Ο), g/l 3,77 2,37Sodium (Na2O), mg/l 406 243Calcium (CaO), mg/l 382 271Fe (FeO), mg/l 48,3 32,0Magnesium (MgO), mg/l 74,0 50,0Silicon (SiO2), mg/l 28,6 18,0Total Sulfur, mg/l 101 63,0Total Chlorine, mg/l 219 124Mn, mg/l 18,2 12,0Zn, mg/l 19,7 12,0Cu, mg/l 10,50 6,00

Parameter (%) Press 3-phaseMoisture 27,21 50,23Fats and Oils 8,72 3,89Proteins 4,77 3,43Total Sugars 1,38 0,99Cellulose 24,14 17,37Ash 2,36 1,70Lignin 14,18 10,21Kjeldahl Nitrogen 0,71 0,51Phosphorous (P2O5) 0,07 0,05Total Phenols 1,146 0,326Potassium (Κ2Ο) 0,54 0,39Calcium (CaO) 0,61 0,44Total Carbon 42,90 29,03C/N ratio 60,79 57,17C/P ratio 588,0 552,9

Parameter Public sewernetwork

Streamsrivers

Sea Soil

pH 6-9 6-9 6-9 6-9Temperature (οC) 35 28 35 35Dissolved Oxygen(mg/l) - 3 - 3BOD5 (mg/l) 500 20 40 40COD (mg/l) 1000 120 150 120Suspended Solids (mg/l) 500 50 40 40Fats and Oils (mg/l) 40 5 20 2Kjeldahl Nitrogen (mg/l) 25 10 15 7Nitrates (mg/l) 20 4 20 5Phosphorous (mg/l) 10 0,2 2 2Total dissolved solids (mg/l)

3000 1000 1500 3000

Table 1 : Typical composition of wastewaters Table 2 : Characteristics of the olive oil processing solid wastes

Product Press 3-phase

2-phase

Olive oil 214 212 200

Wastewaters 920 1.670 -

Solid residues 323 462 800

Table 3 : Olive oil and wastes production per 1000 kg of olives processed

Table 4 : National Environmental Quality Standards for wastewater disposal in relation to each receptor apply

Source : Vlyssides et al., (1989-2002)

2009 - 2012

Co-funded by European Commission within the framework of LIFE+ Program.

Total Budget : 1.628.911 €

Beneficiaries

•NAGREF-Soil Science Institute of Athens•Technical University of Crete•Institute of Mediterranean Studies

•CERSAA-Centro Regionale diSperimentazione e Assistenza Agricola

•CEBAS- Centro de Edafologia y BiologiaAplicada del Segura

•Development and dissemination of innovative, environmentfriendly, low cost technologies for the protection of soil andwater pollution from olive oil mills’ wastes.

Project Objectives PROSODOL

•Establishment of an info-library/knowledge-base system toassess environmental impacts from olive oil mills’ wastes toMediterranean region.

•Facilitate the implementation of Soil Thematic Strategy in areas closeto olive oil mills.

•Design, implementation and support a monitoring system for theassessment of the soil and water quality affected directly or indirectlyfrom oil mills’ activities in relation to factors pressures and responses.

•Identification of potential safest uses in the agricultural sector ofolive oil mills’ wastes and its possible contribution to agriculturalproduction.

Design, implementation and support a monitoring system for theassessment of the soil and water quality affected directly or indirectly fromoil mills’ activities in relation to factors pressures and responses.

SOIL

Greek Implementation Area : Crete, Municipality of Nikiforos Fokas

Total area of 95m2, 21 Villages, 6600 residents

Geological formations are mainly identified as limestones, dolomites and marbles

Soils are slightly alkaline to alkaline (pH 7.3- 8.3) , clay or silty clay in texture and very rich in carbonates (50-60% CaCO3)

Three active olive oil mills (3-phase system with continuous centrifuge extraction systems) and two inactive for more than 5 years

Disposal areas contain ponds which were built by excavating the superfacial material of soil and by heaping excavating materials around the pond to form retaining walls. Protective impermeable membranes or other protective media were not used

From the five targeted areas, three will be presented.

NF1 : is a common disposal area, located in a field with slope of almost 10%. No surface disposal, the movement of wastes’ constituents is due to gravity

NF4 : is very large field with two ponds, of almost 5% slope. The owner disposes waste on soil through a pipe.

NF6 : is inactive for more than five years while it was used as disposal area for more than 20 years

Soil sampling took place 1 month after the completion of wastes disposal, between 6th and 9th May 2009.

Samples were collected from different distances from the ponds and depths of 0-25cm, 25-50cm, 50-75cm, 75-100cm, 100-125cm ,125-150cm and 150-175cm.

Samples were collected from inside the ponds at different depths (0m)

SAMPLING

The preparation of samples for analysis was performed according to ISO 11464:2006 method. Laboratory determinations were performed according to the methods usually used for soil characterization.

CHEMICAL ANALYSES

Particle size distribution, pH, Electrical Conductivity (EC) , organic matter (OM), total N, available phosphorous , Cation Exchange Capacity (CEC),exchangeable K, Ca, Na and Mg, water soluble Na, available Mn, Fe, Cu and Zn, Boron, Cl- , SO4

2-, PO43- ions by water extraction, Total

Polyphenols content.

0

0,5

1

1,5

2

2,5

3

0m 1m 3m 4m 25m

50m

75m

90m

105m

Control

Surface Disposal

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

0m 15m

0-25cm25-50cm50-75cm75-100cm100-125cm125-150cm150-175cm

Former Disposal AreaNF6

Measured in paste extract

Electrical Conductivity, mS/cmActive Disposal Area

NF4

41,62

0

2

4

6

80m 1m 2m 4m 25

m

50m

75m

90m

105m

Cont

rol

0

0,5

1

1,5

2

2,5

3

3,5

0m 15m

0-25cm

25-50cm

50-75cm

75-100cm

100-125cm

125-150cm

Determined by dichromate oxidation

0

5

10

15

20

25

0m 2m 4m 10m

12m

Cont

rol

Organic Matter, %

Former Disposal Area, NF6

Active Disposal AreasNF4

NF1

Surface Disposal

0

1

2

3

4

5

6

7

0m 1m 3m 4m 25m

50m

75m

90m

105m

Cont

rol

0

1

2

3

4

0m 15m

0-25cm25-50cm50-75cm75-100cm100-125cm125-150cm150-175cm

Former Disposal Area, NF6

Total Nitrogen (Kjeldahl), mg/g Active Disposal Area

NF4

Surface Disposal

According to ISO 11261:1995

>2.5mg/g : very rich

0

50

100

150

200

250

300

350

0m 1m 3m 4m 25m

50m

75m

90m

105m

Cont

rol

0

40

80

120

160

200

0m 15m

0-25cm

25-50cm

50-75cm

75-100cm

100-125cm

125-150cm

150-175cm

Extracted with sodium hydrogen carbonate (ISO 11263: 1994)

Available Phosphorous , mg/kg

Active Disposal AreaNF4

Surface Disposal

Former Disposal Area, NF6

25-45 ppm : very much sufficient

0

2

4

6

8

10

12

0m 1m 3m 4m 25m

50m

75m

90m

105m

Cont

rol

0

2

4

6

8

10

0m 15m

0-25cm

25-50cm

50-75cm

75-100cm

100-125cm

125-150cm

150-175cm

Extracted with Barium Chloride (ISO 11260:1994)

Exchangeable Potassium , cmol/kg Active Disposal Area

NF4

Surface Disposal

Former Disposal Area, NF6

3.8-6.4 cmol/kg : sufficient

450

0

20

40

60

80

100

120

140

160

0m 1m 3m 4m 25m

50m

75m

90m

105m

Cont

rol

0

10

20

30

40

50

60

70

0m 15m

0-25cm

25-50cm

50-75cm

75-100cm

100-125cm

125-150cm

150-175cm

Extracted with Methonol

Total Polyphenols, mg/kg Active Disposal Area

NF4

Former Disposal AreaNF6

Surface Disposal

0

5

10

15

20

25

30

35

40

0m 1m 3m 4m 25m

50m

75m

90m

105m

Cont

rol

0

5

10

15

20

0m 15m

0-25cm25-50cm50-75cm75-100cm100-125cm125-150cm150-175cm

Extracted with DTPA(ISO 14870:2001)

Mn(IV) reduced to Mn2+

Available Mn, mg/kg Active Disposal Area

NF4

Surface Disposal

Former Disposal Area, NF6

0-5 ppm : very low5-15 ppm : low15-30 ppm : moderate30-50ppm large> 50 ppm : very large

0

50

100

150

200

250

300

350

0

50

100

150

0m 15m

0-25cm25-50cm50-75cm75-100cm100-125cm125-150cm150-175cm

Extracted with DTPA(ISO 14870:2001)

Fe(III) is reduced to Fe(II)

Fe(II) + quinones Fe3+

0

100

200

300

0m 2m 4m 10m

12m

Cont

rol

Available Fe, mg/kg Active Disposal AreasNF4

NF1

Former Disposal AreaNF6

Surface Disposal

> 50 ppm : very large

ConclusionsDisposal of untreated OOMW at evaporation ponds without using protective materials has significant effect on chemical properties of soil close to ponds

•Enhanced Nitrogen content

Soil samples collected one month after the completion of wastes disposal are characterized by :

•Enhanced Organic Matter content, but for the cases of direct disposal on soil

•Increased Electrical Conductivity

•Enhanced Polyphenols content

•Increased of available Fe and Mn contents

•Significant increase in exchangeable K content

Inactive disposal area is characterized by normal Organic Matter and Nitrogen contents while exchangeable K; available Mn and Fe, polyphenols, phosphorous and EC remain high

•Significantly large Phosphorous amounts