Comparison of ceramic and polymeric ultrafiltration membranes for treating wastewater from metalworking industry

• It was found that the ceramic membrane operated effectively (i.e. higher fluxes).
• Fouling was reversible with ceramic membrane and irreversible with polymeric one.
• COD and lipophilic compounds were successfully removed by ceramic membrane (43% and 70%, respectively).
• Oil droplets did not coalesce in the permeate when the feed was in alkaline medium.
• The zeta potential of permeates was more negative than feeds in all cases.

Oily wastewater is one of the major pollutants that occur in the metal industry and is very harmful to the environment, especially to aquatic life. All conventional methods such as dissolved air flotation, coagulation, adsorption, used during oily wastewater treatment have their advantages but none is as effective as membrane technology, which offers many possibilities regarding the applications of different materials, modules and pressures. The aim of this study was a comparison between the ceramic and polymeric membrane modules for model solutions (1%, 2% and 4% solutions of hydraulic fluid Ultra Safe 620 in acidic and alkaline mediums). The model solution was filtered on a laboratory scale by using two plants equipped with ceramic (Al2O3/ZrO2) and polymeric (PVC) membrane modules. The best result was obtained when using ceramic membranes where reversible membrane fouling was mainly presented, whilst in the case of polymeric membranes the irreversible membrane fouling was dominant. The physico-chemical analyses were performed by measuring pH, conductivity, turbidity, particle size and zeta potential, chemical oxygen demand, and lipophilic substances. Regarding substances’ removals, the ceramic membranes were more efficient compared to the polymeric ones.