Feasibility study of applying dissolved air flotation to the treatment of barge cleaning waste



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Tank barges carrying petroleum products must be cleaned for three major reasons: 1) for inspection, 2) for hot work such as welding or burning, and 5) for a change of cargo. The use of hot water in washing the less volatile products creates a strong oil-water emulsion. This thesis studies the feasibility of treating barge cleaning wastewater with dissolved air flotation. Dissolved air flotation is a two-stage process. A coagulant is added to form floc particles which are then bouyed to the water surface through the entrapment of tiny air bubbles formed when a pressurized water stream is released to atmospheric pressure. Laboratory tests produced favorable results. The tests indicated that the wastewater pH must be controlled. Laboratory treatment of shipyard wastewater indicated the need for both alum and polyelectrolytes as coagulants. Alterations should also be made to the cleaning process to enhance effluent water quality.