ABSTRACT
For several years Baird-Atomic has been involved in the design, construction and testing of a breadboard oil-in-water content monitor for use with bilge and ballast wastewater. This work has been supported by the Coast Guard, the Navy, and Baird-Atomic. The basis of the monitor is the luminescence (fluorescence) of the aromatics present in all petroleum oils. The advantages of this approach include high sensitivity, real time output, fast response time, insensitivity to many interferences, and reduced sensitivity to particulates. The chief problem is the unequal luminescence response of oils. The general approach involves simultaneous excitation and monitoring at a number of wavelengths, selected to give a net response almost independent of oil type.
A first approach involved a novel optical scheme involving two polychromators. The first provided excitation at different wave-lengths along a flowing sample. The second, operated in reverse, summed selected emission from different portions of the sample. This approach, called “synchronous scan,” while successful, was supplanted by a more general approach which utilized the total luminescence of the sample: i.e., all possible emissions resulting from all possible excitation. In this case, the second polychromator was used to disperse emission from the sample at right angles to the excitation dispersion. The total luminescence was then imaged at the exit plane of the second monochromator where a computer-designed mask selected those spectral regions equalizing response of various oil types. Results of tests are discussed, together with progress on a shipboard prototype.
