Oil and Grease Removal by Floating Sorbent in a CDS Device

Executive Summary A series of experiments were performed in a small but full-scale CDS device to determine its ability to remove free oil and grease from polluted waters using sorbents. Nine experiments were performed using five different sorbents. One control experiment was performed without a sorbent. The sorbents were allowed to float on the surface of the separation chamber of the CDS device. The CDS unit was not modified to accept the sorbents. Different amounts of each sorbent were used because of the varying properties of the sorbents (density and surface area). Tests were performed using a 2400-micron screen over 30 minutes at 125 GPM (approximately 50% of the CDS unit's nominal flow capacity). Used motor oil was introduced into the feed of the CDS at approximately 25 mgIL, which is generally the upper limit of oil and grease concentrations found in stormwaters. Oil and grease was measured at various times to determine the removal efficiency. Background oil and grease was measured as well as oil and grease released from the sorbents after the influent oil and grease was reduced to zero. Removal efficiencies for most sorbents varied from 63 to 96% depending upon conditions. One sorbent removed only 18%. Sorbent saturation was not achieved in any of the experiments. Very little oil and grease (generally less than I to 2 mg/L) was released from sorbents when the influent oil and 2rease was reduced to zero. Without a sorbent, the CDS unit removed 80% of the influent oil and grease, but released it after the oil and-grease in the influent was reduced to zero. This suggests that the CDS unit might be effective in capturing a spill, if the unit could be isolated after the spill to allow oil and grease recovery.