Evaluation of commercial ultrafiltration systems for treating automotive oily wastewater

Currently at Ford Motor Company, oily wastewater is batch treated by chemic al deemulsification whose performance depends on determining optimum chemic al dosages and is occasionally inconsistent because of influent fluctuation s. Therefore, a pilot study was conducted at the Ford Romeo Engine Plant, R omeo, Michigan, to study treatment of raw oily wastewater and skim oil (fro m chemical deemulsification) using commercially available ultrafiltration ( CLIF) systems as an alternative to chemical demulsification. The study foun d that most UF membranes performed consistently and reliably, producing ave rage permeate oil and grease (O&G) concentrations of less than 100 mg/L, a typical discharge limit for an automotive plant. In addition, tubular membr anes typically outperformed spiral-wound membranes in permeate flux and was hing frequency. While all UF systems performed consistently well for removi ng O&G, the treated effluent still had a chemical oxygen demand (COD) of 10 0 to 2 000 mg/L, which is comparable to that found in typical chemically tr eated wastewater. This indicates that many dissolved organics are not remov ed by either chemical or UF treatment. Metals (such as copper and zinc) wer e found to be effectively removed by UF when the pH was greater than 8. Mos t membranes used as a second stage produced retentate with O&G of more than 40%. All attempts at UF skim oil treatment were unsuccessful because of hi gh oil viscosity, which made pumping it through a membrane system almost im possible. Chemical reactions during the chemical deemulsification process m ight have been responsible for the high viscosity.