1687. Referring to the illustration, suppose while in the oil separation processing mode, the oil content detector display screen shows 17.9 ppm and the oily-water separator is discharging back to the bilge water holding tank for recirculation. What is most likely the cause

The oil content detector displays 17.9 ppm while the oily-water separator recirculates to the bilge water holding tank, indicating the tank contents are excessively contaminated with oil, preventing the separator from reducing oil levels below the 15 ppm discharge limit in a single pass.