Purification of oily wastewater by ultrafiltration

Investigations have been carried out for purification of oily wastewater by a combination of ultrafiltration/reverse osmosis processes. A tubular ultrafiltration system using cellulosic and non-cellulosic membranes was tested with typical oily wastewater collected from harbour and simulated emulsion without any pretreatment. Both membrane types produced a permeate with an oil content generally less than 10 mg/dm³. Rejection of chemical oxygen demand (COD) is 80% for ultrafiltration treatment. The permeate is generally of acceptable quality for direct sewer discharge. For further treatment of UF permeate, reverse osmosis was applied with tubular B1 PCI modules using cellulose acetate membranes. The rejection of COD after ultrafiltration/reverse osmosis treatment increased up to 98.5% and total dissolved solids (TDS) to 95.7%. Reverse osmosis treatment will permit reuse of the treated water as process water.