Remediation of Oil Spills on Beaches


Bioremediation is an emerging technology for restoration of oil-contaminated beaches. One implementation of bioremediation involves the addition of nutrients (nitrogen and phosphorus) to enhance the growth of indigenous hydrocarbon-degrading bacteria. Recent biodegradation studies demonstrated that a nitrogen (N) concentration of about 2-10 mg/L is sufficient for the maximum growth of hydrocarbon-degrading microorganisms.

 

The effectiveness of biostimulation depends on prolonged contact between the added nutrients and the oil in the contamination zone (the bioremediation zone), which is usually less than about 25 cm below the beach surface.

 

 

Ideally, nutrient concentrations in contact with the oil should be sufficient to support near maximal growth rate of the oil-degrading bacteria, and this concentration must be maintained for the longest possible time. Therefore, maximizing the residence time of the nutrients in the contaminated zone of the beach is an important goal for effective bioremediation.

 

 

 

Movement of freshwater (blue) and saltwater (red) in a beach subjected to tide. Note the "pinching" of the freshwater to sea at low tide.

Our goal has been to select the best nutrient application strategy. For this purpose, we focused our attention on the mechanisms affecting the transport of dissolved nutrients in beaches. These are: Waves, tide, and buoyancy.

Movement of a tracer plume applied on the beach surface at low tide. a) total time=22 minutes, (two minutes into application), WL=92.7 cm, b) total time twenty four minutes (four minutes into application), wl=93.4 cm, c) total time thirty one (eleven minutes into application), wl=94.9 cm, d) total time thirty six (16 minutes into application), end of application time total time, WL=95.6 cm, e) total time (51 minutes), 15 minutes after end of application WL=95.7 cm, f) total time is fifty seven, high tide, WL=109.96 cm. The top of the Ubar is 70 cm, and the rectangles on the plexiglass side are 20 cm X 10 cm.