The olive tree, Olea europaea is a species of small tree native to and naturalised in many locations around the world, such as the Mediterranean Basin and France. The tree bears the olive fruit, which can be consumed whole or used in the making of olive oil. Olive oil is the only commercially significant vegetable oil that is extracted from fruit rather than from seeds. Vegetable oils extracted from seeds, such as sunflower and canola oil, undergo significant processing to remove industrial solvents used during oil extraction, as well as compounds naturally present in most vegetable seeds that would otherwise result in unpleasant tastes and odours. Due to high levels of water in olives, olive oil can be extracted from the fruit by simpler, mechanical based methods, such as centrifugation or pressing; these methods produce a more flavorful and less processed product. Like most industries, olive oil manufacturing produces waste from unusable materials of both fruit and tree. The olive oil extraction process yields only 20% usable olive oil; the remaining 80% of byproducts consist of a semisolid waste (30%) and aqueous liquor (50%). The aqueous liquor, known as olive mill wastewater (OMWW), consists mostly of water from the vegetation and soft tissues of the olive fruits, as well as from usage in various stages of oil production, such as olive washing water. The OMWW may also contain upwards of 18% organic-based compounds. This high level of organic matter results in a polluting load 25 to 80 times greater than that of domestic sewage. To mitigate an overload into the municipal wastewater treatment plant from large levels of organic matter and other potential interferences, such as an acidic pH, OMWW requires pretreatment prior to discharge into the wastewater collection system. Pretreatment is monitored through the measurement of organic matter in the discharged wastewater, or effluent. Biological oxygen demand (BOD) or chemical oxygen demand (COD) are both useful measurements in quantifying organic matter in water, but due to its faster turnaround time, COD is becoming more commonly measured during wastewater treatment. In olive oil manufacturing, the maximum COD concentrations of untreated OMWW can reach values up to 220,000 mg/L.