Treatment of oil spill water by ozonation and sand filtration

Abstract

Increasing volumes of crude oil being produced and transported throughout the world in recent decades have resulted in increased risks of spill and high-profile spill incidents of significant environmental and ecological impacts over extended periods of time. While immediate in situ and ex situ responses have been implemented, none are available for onsite treatment of contaminated water for immediate release of the treated water. We demonstrate here a potential treatment scheme involving ozonation and sand filtration intended for immediate treatment and discharge of the impacted water. Waters of tap, Utah Lake, and Great Salt Lake sources were spiked with crude oil of the Great Natural Butte of Utah at 2.5% and 0.025% oil (v/v) and tested for treatment. The results showed near complete removal (100%) of both Chemical Oxygen Demand (COD) and oil and grease (O&G) from initially 20000 and 11000 mg L(-1), respectively, via flotation pretreatment, ozonation in pressure cycles, and sand filtration. At lower oil level of 0.025%, complete removal of COD and O&G from waters were achieved without floatation. The treated waters showed reduction of turbidity to <1 from 4000 NTU and high Biochemical Oxygen Demand/COD ratio of 0.3-0.5 that reflected highly biodegradable residual organics. The results showed synergistic oil removal when two well practiced methods, namely ozonation and sand filtration that either alone seems ineffective, are combined sequentially. It indicates a potential on-site treatment response for oil spill incidents where the collection and transport of a large amount of contaminated water may be avoided.