Desalination plants, open-loop cooling water intakes, seafood processing plants and other seawater users risk contaminating their process during an oil spill or other marine accident. Potential pollution sources include crude oil drilling and production, ships and barges with oily bilge wastewater or cargo spills, and other industrial plants with oil leaks in cooling water discharges.

Oil-in-water monitors provide an extra line of defense for these facilities. The monitors, such as those from Turner Designs Hydrocarbon Instruments, use fluorescence-based measurement technology. They provide good sensitivity to oil based hydrocarbons such as crude oil, fuels, lubricating and hydraulic oil, and aromatic chemicals.

Continuous online monitors can offer detection limits as low as 20 ppb, depending on the organic background of the water source. One Turner system, the TD-4100, was applied to river pollution monitoring in Austria more than 15 years ago. It is used to sense groundwater from monitoring wells under the influence of the Danube along its banks in Austria. Their viability was proven by detecting river spills above 20 ppb in the first weeks of operation.