Table 3 Maximum and Minimum Concentration Values of Olive Oil Wastewater According to Applied Type of Technology

Technology type

Parameters

Centrifuge Traditional presses

0.4-7.1 0.3-6 43-426 0.4-12.5 15.2-199.2 140-966 42-495 18-124 630-2500 47-200 60-180

1.4-14.3 0.9-13.3 71-937 4-42.6 42.1-389.5 154-1106 157-915 38-285 1500-5000 58-408 90-337

• high content of polyphenols, up to 80 g/L; other references up to 10 g/L [28];

• high content of solid matter (total solids up to 102.5 g/L);

Table 4 compares the composition values of olive oil mill wastewater (A and B) with those of municipal wastewater (C). While the ratio COD/BOD5 in both types of wastewater is rather close (between 1.5 and 2.5), there is a big difference between the two for the ratio (BOD: N: P); olive oil wastewater (100:1:0.35) highly deviates from that in municipal wastewater (100:20:5).

Based on Tables 2 and 3, the phenols and the organic substances responsible for the high COD value must be considered as problematic for treatment of this wastewater, and the presence of inhibitory or toxic substances may seriously affect the overall treatment system. Therefore, the chemical oxygen demand (COD), the total aromatic content (A), and the total phenolic content (TPh) are mostly selected as representative parameters to follow the overall purification process [19,21,29].

The terms and definitions for the waste resulting from the different oil extraction processes are neither standardized nor country specific [30]. Table 5 shows the nominations found in the Mediterranean countries, while Table 6 shows the most common terminology used in these countries with descriptions.

Table 4 Comparison of Composition Values of Olive Oil Wastewater from a Small Mill (A) and a Big Mill (B) with Municipal Wastewater (C)

Source of liquid waste

Parameter

A

B

C

pH

4.5-5.3

5.3-5.7

7-8

BOD5 (g/L)

15-65

17-41

0.1-0.4

COD (g/L)

37-150

30-80

0.15-1

Total solids (g/L)

24-115

19-75

0.35-1.2

Volatile solids (g/L)

20-97

17-68

0.18-0.6

Suspended solids (g/L)

5.7-14

0.7-26

0.1-0.35

Fats and oils (g/L)

0.046-0.76

0.1-8.2

0.05-0.1

Total nitrogen (g/L)

0.27-0.51

0.3-0.48

0.02-0.08

Total phosphorus (g/L)

0.1-0.19

0.075-0.12

0.006-0.02

COD/BOD5

2.3-2.5

1.8-2

1.5-2.5

BOD5: N: P

100:0.98:0.37 100:1.3:0.34

100:20:5

Between 400 and 600 L of liquid waste are generated per ton of processed olives from the traditional presses used for olive oil extraction, which are operated discontinuously. Depending on its size, the capacity of such an olive oil mill is about 10 to 20 tons of olives per day. With a capacity of 20 tons of olives per day and a process-specific wastewater volume of 0.5 m3 per ton of olives, the daily wastewater can range up to 10 m3 per day.

Compared to the traditional presses, twice the quantity of wastewater (from 750 to 1200 L per ton of olives) is produced with the three-phase decanting method. Depending on their size, the capacities of the olive oil mills are also between 10 and 20 tons of olives per day. With a capacity of 20 ton of olives per day and a process specific wastewater volume of about 1 m3 per ton of olives, the daily wastewater volume from a continuous process is up to 20 m3 per day. The concentration of the constituents in wastewater from traditional presses is therefore twice as high as in the wastewater resulting from three-phase decanting. In general, the organic pollution

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