Impact of enzymatic pre-hydrolysis on batch activated sludge systems dealing with oily wastewaters

Dairy wastewater containing different oil and grease contents was treated in batch activated sludge systems with and without (control) an enzymatic pre-hydrolysis stage [with 0.2% (w/v) of fermented babassu cake containing Penicillium restrictum lipases]. When the oil and grease concentration in the control bioreactor was increased (400, 600 and 800 mg l(-1)), the COD removal efficiency fell (86%, 75% and 0%). However, in the reactor fed with pre-hydrolysed wastewater, COD removal efficiency was maintained (93%, 92% and 82%). At an oil and grease concentration of 800 mg l(-1), the control bioreactor presented final volatile suspended solids (VSS) values ten times greater (2225 mg l(-1)) than those obtained for bioreactor fed with pre-hydrolysed wastewater (200 mg l(-1)).