Hydrolytic pretreatment of oily wastewater by immobilized lipase

The purpose of this study was to evaluate the hydrolysis of wastewater with high oil and grease (O&G) concentration from a pet food industry using immobilized lipase (IL) as a pretreatment step for anaerobic treatment through batch and continuous-flow experiments. The intrinsic Michaelis constant (K-m) and maximum reaction rate (V-max) were estimated experimentally and the K-m, value of IL (22.5 g O&G/L) was six-folds higher than that of the free lipase (FL) (3.6 g O&G/L), whereas V-max of both FL (31.3 mM/g min) and IL (33.1 mM/g min) were similar. Preliminary batch anaerobic respirometric experiments showed that chemical oxygen demand (COD) and O&G reduction were 49 and 45% without pretreatment and 65 and 64% with IL pretreatment respectively, while the maximum growth rate (mu(max)) for pretreated wastewater (0. 17 d(-1)) was 3.4-folds higher than that of raw wastewater (0.05 d(-1)) with similar Monod half-saturation constants (K-S similar to 2.7 g COD/L). The continuous-flow experimental study showed the feasibility of employing the hybrid packed bed reactor (PBR)-upflow anaerobic sludge blanket (UASB) system for the treatment of high-strength oily wastewater, as reflected by its ability to operate at an oil loading rate (LR) of 4.9 kg O&G/m(3) d (to the PBR) without any problems for a period of 100 days. During pseudo- steady-state conditions, the hybrid UASB produced relatively higher biogas compared to the control UASB, The effluent COD and O&G concentrations of hybrid system were 100 mg/L lower than that of the control UASB reactor and no foam production was observed in the hybrid UASB compared to the control UASB reactor. (c) 2006 Elsevier B.V. All rights reserved.