Application of Different Lipases as Pretreatment in Anaerobic Treatment of Wastewater

Abstract

Wastewater from a swine and bovine meat industry with high content of oil and grease was treated in batch anaerobic reactors with and without an enzymatic pretreatment. Two different lipases were tested: a commercial lipase (Lipolase 100T, Novozymes) and a lipase obtained by solid state fermentation (Lipase SEP). Meat industry wastewater with different oil and grease concentrations (250 to 3,000 mg · L⁻¹) was treated with two amounts of enzyme preparations [0.1 and 5.0% (w/v)], in batch anaerobic bioreactors, corresponding to partial and complete hydrolysis of oil and grease. A control anaerobic bioreactor fed with raw wastewater was compared to an anaerobic reactor fed with prehydrolyzed effluent (test reactor). Although a high amount of enzyme maximizes hydrolysis of oil and grease, it decreases biodegradation, mainly when Lipolase 100T is used, probably due to inhibition caused by excess of free acids. However, the benefits of the enzymatic prehydrolysis became evident when the wastewater was treated with 0.1% (w/v) of lipase. The performance of Lipase SEP was better than Lipolase 100T, which could be related to the lower activity of Lipolase in the wastewater, when compared to Lipase SEP. When the wastewater containing 1,200 mg · L⁻¹ of oil and grease was pretreated with the lipase preparation obtained by SSF, removal of chemical oxygen demand (COD) increased 22%, compared to a control reactor fed with wastewater without any treatment. The results showed the potential of enzymatic pretreatment to improve the performance of a biological treatment system.