Automation of an electrolytic cell for the treatment of oily wastewater

An automatic control system was installed and evaluated on a pilot plant for the electrolytic treatment of oily wastewater which was in operation at an automotive transmission plant. In this continuous process, the wastewater passes through a porous iron chip bed anode where the oil emulsion is demulsified by electrolytically dissolved iron, forming an oil‐rich floating sludge and oil‐free water. The control system maintains a low effluent oil concentration by adjusting the anode current—and hence the amount of iron dissolved—in response to deviations from a set‐point of effluent oil content, as sensed with an in‐line turbidimeter. The current automatically assumes the newly demanded value within about 6 to 10 minutes of a step increase or decrease in effluent turbidity. The system controlled the treatment of the widely varying plant wastewater continuously for 30 days, with no intervention or control adjustment and with a minimum of daily maintenance.