Pilot-Scale Investigation of Chemical Addition-Dissolved Air Flotation for the Treatment of an Oily Wastewater

Abstract

An investigation at the pilot scale of chemical addition-dissolved air flotation (CA-DAF) treatment of an oily wastewater was carried out comparing two chemical addition schemes [Grace Dearborn (GD) single cationic polymer; Calgon dual-polymer-cationic followed by anionic polymer]. The GD polymer produced a DAF effluent of higher quality (as measured by O/G and turbidity). The optimum dosage for GD polymer was much less variable than that required for the Calgon chemicals. Typically, alteration of the optimum GD dosage was not required for long periods of time, while the opposite was true for the Calgon dual-polymer scheme. However, the amount of sludge produced by the GD polymer was between two and three times greater than for Calgon chemicals, and the combined cost of chemicals and sludge disposal was almost twice as high for the GD chemical. Despite the lower cost associated with using the Calgon dual-polymer system, the use of the GD polymer with DAF was determined to be optimal for this system due to a better quality effluent and a more stable operation. Key words: oily wastewater; metalworking fluids; pilot scale; chemical addition; dissolved air flotation