Vessels produce oily wastewater during evolutions including engine room operations and maintenance, cargo operations, deck machinery operations, washdown, and runoff. Currently, technologies require effluent be gathered in a central tank for treatment or managed through best management practices. Technologies to remove oil include gravity separation, filtration, absorption, coalescing, centrifuging, and flocculation. The majority of the technologies require periodic replacement of treatment materials associated with oil removal. These technologies may lose efficiency due to vessel motion. In this article we introduce a simple, efficient, eco-friendly procedure using readily available materials and equipment for fabricating high-performance magnetic polydimethylsiloxane (PDMS) nanocomposite sponges for oil-water separation. The magnetic sponges are resistant to corrosive chemicals, exhibit high sorption capacities for oils and cleaning agents, and selective sorption for oil from oil-water emulsions. The sponges can be reused multiple times with no signs of deterioration. They are magnetically controllable and will hold position when magnetized, allowing for separations not compromised by vessel motion. The magnetic PDMS nanocomposite sponge(s) provide a promising technology for removing oil from vessel water discharges.
The removal of oil from water discharges is a concern for all vessels. Oil comingling with water discharges may occur at various locations on the vessel during operations and repair evolutions. These occurrences include the following:
Engine room repairs and operations
Engine room and other bilge accumulations
Cargo pumping operations
Deck washdown and drainage
Cargo gear and deck equipment leakages
Cargo and portable cargo handling equipment leakages
Scrubber effluent discharges for vessels equipped with SOx scrubbing equipment
Accidental oil discharges
Increasing environmental regulations and awareness have resulted in more stringent regulations regarding oil in vessel discharges.
Challenges to oil removal from water discharges include a wide variation in oil grades, chemicals used for treatment and maintenance, solids entrainment, and biologic contaminants. Effective treatment of water to reduce onboard quantities may be a challenge depending on the mixture and location of the effluent on board. Use of a common and simple-to-use technology for removal of oil from water discharges is advantageous to the vessel owner. Although one size does not fit all, a simple design with good efficiency and reusability is desirable. Magnetic nanocomposite sponges (MNSs) meet these requirements.