Abstract
Oily wastewater discharge to water bodies can have many negative consequences, especially on the marine ecological environment. Although there are numerous techniques for treating oily wastewater, this paper aims to introduce and evaluate the potential of the fractional freezing (FF) process as a new oil–water separation technique to overcome the several weaknesses found in the conventional oil–water separation methods. FF separates two liquid compounds based on their freezing point difference. In this study, two oily wastewater samples were used: oily bilgewater and oily kitchen wastewater. The effects of coolant temperature, freezing time, and stirring rate on the FF process efficiency were studied, and the significance of the data was supported by statistical analysis. The results show that a low coolant temperature is essential for allowing crystal nucleation formation and inducing crystal growth for an efficient separation process. However, the higher crystal growth rate that occurs at an even lower temperature might entrap the impurities inside the growing crystal. Consequently, continuing the crystallization for a longer time may yield a less efficient separation process. Furthermore, a too high stirring rate will rupture the solid formation, hence reducing the process efficiency. The final values of oil/grease and free fatty acids (FFA) obtained after the FF process of both samples were found to comply with the standard permitted by the International Maritime Organization (IMO) and Palm Oil Refiners Association of Malaysia (PORAM). Moreover, the p-values obtained for both of the above-mentioned samples were below 0.05 for all experiments. It can be concluded that this method has the potential to separate oil from the oily bilgewater and kitchen wastewater.
Highlights
Water pollution is one of the most significant issues worldwide [1] caused primarily by human activities [2]
The actual bilge water samples were collected from PETRONAS ULG95 Arwen tanker located at Lumut Maritime Terminal, Lumut, Perak, Malaysia, and used vegetable oil samples were collected from a drainage nearby Sri Nava Johthi Restaurant at Ipoh, Perak, Malaysia
The phenomenon was explained in an experiment conducted by Jusoh et al (2008) for assessing the effect of coolant temperature on a new progressive concentration system [39]
Summary
Water pollution is one of the most significant issues worldwide [1] caused primarily by human activities [2]. Sources of pollutions can be categorized in point-source and non-point source pollution. A pollutant that originates from an identifiable spot and single source is known as point-source pollution. Non-point source pollution cannot be identified from a specific time or location and typically comes from diffuse sources [3,4]. Wastewater effluent, which includes municipal and industrial, and storm sewer discharge are examples of point-source pollution [5], whereas the water drainage from urban and agricultural areas are the examples of non-point-source pollution [4,5]. Wastewater released by marine and food services industries is considered as point-source pollution, since the origins of these pollutants are identifiable
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