Detection of Oil in Sewers

Methods capable of detecting oil present as a pollutant in waste water were selected which are capable of measuring quantities of oil from as small as those in a surface active film to massive accumulations. Detection techniques for both thick and thin oil deposits were studied, and systems incorporating the most promising ones were developed and tested. It was found that more techniques can be adapted to the thick oil than to the thin oil detection problem because thick oil can be measured by electrical- and thermal-conductivity devices that require little maintenance in sewer use, whereas detectors of small amounts are somewhat less suited to the sewer environment. The most promising techniques developed used RF and heat-conductivity sensors for the detection of massive oil accumulations from a few millimeters to several meters thick and used ultraviolet transmission sensors for the detection of dispersed oil over the range of 5 to 10 000 parts per million. The resulting instrumentation was tested in a sewer environment and found to be capable of unattended operation for periods ranging from a week to several months. The instrumentation was combined with telemetry to permit readout at a remote central location.