Measuring COD in Olive Oil Manufacturing Wastewater


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 semi-solid 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.


An olive mill was looking to update from BOD to COD methodology to characterise their wastewater influent and effluent.

HI83399-Angle-COD-Adapter_detailHanna Instruments recommended the HI83399 Water & Wastewater Multiparameter (with COD) Photometer and pH meter and HI839800 COD Reactor. As one of the most versatile photometers on the market, the HI83099 can measure 44 of the most important water quality parameters, in addition to COD. Using the optional HI92000 Windows® Compatible Software and USB cable, the meter can be connected to a PC to manage data. Equipped with a powerful interactive user support system, the user can enable the tutorial mode to guide them through each step of the analysis process. The HI83099 encompasses a broad spectrum of COD levels, from 0 to 150 mg/L for low range, 0 to 1500 mg/L for medium range, and 0 to 15000 mg/L for high range.

The customer was also supplied with the NIST traceable, range-specific COD reagents, developed in accordance with Standard Methods 5220D, USEPA 410.4, and ISO 15705:2002. The reagents come ready made in pre-dosed vials, requiring only a simple addition of deionized water for the blank measurement, and wastewater for the sample measurement. Furthermore, due to the hazardous nature of some of the reagent components, such as dichromate and strong acids, the customer appreciated the ready to use reagents that eliminated the need to handle them directly. Overall, the customer was more than happy with their experience with Hanna Instruments.


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