Vegetable water: liquid waste produced after olive oil processing. It is reddish to black in color and has a strong, acrid smell.

Pomace: substance generated by pressing or crushing fruit such as olives. It essentially consists of the fruit pulp left after extracting the oil.

Olive pulp: residual paste produced when the whole olive stones are removed from the paste prior to processing. It has a very high water content and its storage and disposal are difficult.

Continuous three-phase extraction: system requiring the addition of water during olive oil extraction. Three products are separated in this system: olive oil, vegetable water (fruit vegetation water, diluting water and wash water) and olive pomace.

Continuous two-phase extraction: system requiring the addition of a small quantity of water during olive oil extraction. Two products are obtained: olive oil and wet (watery) olive pomace.

Wet olive pomace: olive pomace containing up to 70% vegetable water.

Vegetable water treatment: operation which reduces the pollutant nature and toxicity of this waste by chemical or biological processes.

Composting: aerobic breakdown of organic material into soil-like material called humus. Degradation occurs mainly through enzymatic digestion of the waste by soil micro-organisms, using the organic matter as substrate. Aerobic degradation of organic substances and mineralization into CO2 (carbon dioxide), water and inorganic salts is accompanied by a 40–50% reduction in mass. The organic waste is formed into heaps.

Due to intense biological activity of bacteria in the first degradation phase, exothermal reactions take place, leading to temperatures of 70 to 80 °C inside the heaps. This heating effect pasteurizes the waste material. Active or passive aeration of the heap has to be ensured to guarantee rapid, complete aerobic degradation of the biodegradable organic matter. The composting process is completed after three to four months.

BOD5: amount of dissolved oxygen consumed in five days by biological processes which break down organic matter.

COD: amount of oxygen in mg/l required to oxidize organic and oxidizable inorganic compounds.