Recently I visited a Sewage Treatment Plant (STP) and in the collection tank lots of oil was visible. This is because of high Fats, Oil and Grease (FOG) flowing down from Grease Trap. FOG is the cause of unhealthy working conditions like foul odor which is a health risk if exposed to, continuously. FOG reduces the efficiency of STP which will lead to higher BIO/COD levels, continuous foul odor, increase in Total Suspended Solids (TSS) and bottom solids and dirty water from the outlets.
Please find herewith attached file giving more detail on FOG.