The EGS separates heavy solids and oil from industrial wastewater and storm water using traditional gravity separation. Heavy settleable solids drop out of oily wastewater in the inlet chamber. In the separating chamber, the oil rises and lighter settleable solids fall. Free oils floating in the separating chamber are collected by a rotary pipe skimmer for collection and disposal. A sheen baffle retains residual floating oil as the treated effluent discharges through the outlet. Flow rates of 100 gpm to 700 gpm are handled in a single tank.