Enzymatic cleaning of ultrafiltration membranes fouled by abattoir effluent

Proteins and lipids are the major membrane foulants present in abattoir process effluent. The successful use of ultrafiltration (UF) to treat such effluent streams depends on the effective removal of these foulants, which are mostly hydrophobic fouling species, from the membrane surface. Lipases and proteases were used in this study to clean flat-sheet polysulphone membranes (PSMs) fouled in abattoir effluent. The lipases from Candida cylindracea, Pseudomonas mendocina and Aspergillus oryzea were used alone, as well as in combination with the proteases from Bacillus licheniformis, Protease A (a protein engineered protease specific for low temperature wash conditions) and Aspergillus oryzea. Enzyme assays were first performed to identify active bacterial proteases and lipases. The parameters used to determine the cleaning efficiencies of the enzymes used were: (i) lipid content adsorbed onto the membranes; (ii) protein content adsorbed onto the membranes; and (iii) pure-water flux (PWF) after enzymatic cleaning. The results show the ability of enzymes to remove adsorptive fouling, and indicate their usefulness in enzyme-based cleaning regimes for membranes operating on abattoir effluents.