If your intake is below the surface, how would oil be mixed with the water as it floats on the surface. I learned a lot about oil spills in the Navy and simple floating booms to keep oil away from the intakes should be sufficient. My ship actually spilled some fuel in Port Canaveral a few days after I reported aboard. Having just attended the school, I helped the port unscrew their boom system we needed because they deployed the thing upside down.
Tar balls under the surface.
Second and perhaps the most obvious reason oil threatens desalination plants is the
damage it can do to sea water intake filters and heat exchangers. Oil in sea water can
take the form of the well recognized slick, but it can also form large tarballs and “sunken
oil globs” that can be drawn into intake filters.5
Obviously, the oil can then foul the
filters limiting the amount of water intake as well as foul internal membranes disrupting
the reverse osmosis process if affecting a reverse osmosis facility.
The required clean-up and problems caused by oil affecting a multi-stage flash
facility are no less troublesome. “If oil enters a (multi-stage flash) desalination plant it
may be necessary to first use a solvent to loosen the oil particles. Next, the plant should
be flushed with soap and water and finally it should be flushed with fresh water. Oil
clings to heat transfer surfaces, disrupting the heat transfer process.”6