This chapter presents a review on limited studies that have been conducted using advanced oxidation processes (AOPs) in treating biologically treated palm oil mill effluent. Palm oil mill effluent is the byproducts of palm oil production that is normally treated using a series of biological processes. However, despite being treated for a long period of retention time, the effluent still possesses high concentration of organics, nutrients, and highly colored, and will pollute the environment if not treated further. Advanced oxidation processes that utilized hydroxyl radicals as their oxidizing agents have the potential of further treating the biologically treated POME. Fenton oxidation, photocatalysis, and cavitation are the main AOPs that have been studied in polishing the biologically treated POME. Depending on the experimental conditions, the removal of organics, in terms of COD, TOC, and color, could reach up to more than 90%. Nevertheless, each of this process has its own limitations and further studies are needed to overcome these limitations.
TopCharacteristics Of Palm Oil Mill Effluent
The characteristics of raw POME are dependent on several factors such as harvesting period, raw material quality (FFB) in terms of age and type, extent of the milling process, activities being conducted at the respective mill, processing technique, the discharge limit set by the factory as well as climate or weather (Irenosen et al., 2014). Besides, the wastewater quality may differ according to batch, day and mills (Madaki & Seng, 2013).
Fresh POME is usually a viscous brownish colloidal mixture of water, oil and fine cellulosic fruit residue (Mat Rani, 2014) with unpleasant odour (Azuar et al., 2015; Irenosen et al., 2014). Some physicochemical properties of raw POME are shown in Table 1. Generally, raw POME is high in temperature, organics, solids, oil and grease as well as nutrients. The high temperature of POME, ranging from 80 – 90 °C is mainly due to the use of large amounts of steam and hot water in sterilization process. The pH for raw POME is slightly acidic in nature because of the organic acids content in complex forms (Madaki & Seng, 2013).
An important characteristics of raw POME is that it has a high concentration of organics. This is due to the fact that POME has a high amount of protein, carbohydrate, nitrogenous compounds, lipids and minerals which partly contributed to organic contents of the wastewater (Rupani et al., 2010). Additionally, the high organic matters in POME is also contributed by the presence of different sugars such as arabinose, xylose, glucose, mannose and galactose (Ujang et al 2010). The solids in raw POME mainly come from oil-bearing cellulosic materials of the oil palm fruit (Ujang et al., 2010). A variety of suspended components ranging from cell walls, organelles, short fibres, a spectrum of carbohydrates and nitrogenous compounds, free organic acids as well as mineral constituents also can be found in POME (Kanu & Achi, 2011).