PURIFICATION OF BILGE WATER BY HYBRID ULTRAFILTRATION AND PHOTOCATALYTIC PROCESSES

Investigations have been performed on the purification of bilge water by a combination of ultrafiltration and photocatalytic processes. The separation of oil from bilge water obtained from Szczecin-Swinoujscie harbour was performed on a laboratory-scale ultrafiltration pilot plan t with tubular membranes made from poly(vinyl chloride) (PVC), polyacr ylonitrile (PAN) and polyvinylidene fluoride (PVDF). The examined memb ranes with MWCO of 70 kD for PVC and PAN and 100 kD for PVDF produced a permeate with an oil content less than 15 ppm. Rejection of chemical oxygen demand (COD) was in the range 92-96% for the ultrafiltration t reatment. The permeate is generally of acceptable quality for direct d ischarge into the Baltic Sea district in accordance with present legis lation. Further treatment of UF permeate has been performed by heterog eneous photocatalytic oxidation in order to remove the residual oil. T he photocatalytic process was carried out using titanium dioxide based catalyst. The complete decomposition of oil was achieved after 2 h of UV illumination using a K-TiO2 photocatalyst with content amounting t o 0.8 g/dm(3) and after 3 h of UV illumination using 0.8 g/dm3 of KOH/ TiO2 photocatalyst. The photocatalytic process was found to be very ef fective for the permeate reclamation. (C) 1998 Elsevier Science B.V. A ll rights reserved.