| In this study, the feasibility of employing immobilized lipase for the hydrolysis of O&G from oily wastewaters was evaluated. A sequential treatment methodology for oily wastewater using a laboratory-scale packed bed reactor (PBR) packed with immobilized lipase followed by an upflow anaerobic sludge blanket (UASB) reactor was developed and tested. Inhibition of oleic acid biodegradation along with its impact of biodegradation intermediates on acetoclastic methanogens were also investigated.; The feasibility studies showed that the immobilized lipase from Candida rugosa could be used to hydrolyze fat in the oily wastewater at a bead concentration of 0.5-1.5 g beads/L of wastewater based on the bead capacity of 0.1 g lipase/g beads. The hydrolysis results showed that approximately 50% of the O&G was hydrolyzed due to enzyme activity. Anaerobic respirometric experiments confirmed the enhanced biodegradability of wastewater pretreated by immobilized lipase with COD and oil and grease (O&G) reductions of and 65% and 64% respectively versus 49% and 45% without pretreatment, while the maximum growth rate of 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 (∼2.7 g/L).; Comparative study of three different UASB reactors at different operating conditions revealed that although all three systems achieved O&G and COD removal efficiencies above 80% at an organic loading of 3 kg COD/m 3·d., system performance deteriorated sharply at higher loading rates, and the presence of high O&G caused a severe sludge flotation resulting in failure. The critical accumulated O&G loading was identified as 1.04 +/- 0.13 g O&G/g VSS for all the three reactors.; Inhibition studies of oleic acid and its biodegradation intermediates showed that the maximum biodegradation rates for oleic acid with caproic and caprylic acids increased with increasing initial concentration of one another. The maximum biomass-specific degradation rates (k) and Monod half-saturation concentration (Ks) of caproic acid, caprylic acid capric acid and oleic acid were found to be 21.2, 26.4, 19.8 and 13.4 mg COD/g VSS·d and 276, 317, 390 and 500 mg COD/L respectively. The observed synergism between the two substrates (oleic acid and MCFA) was modeled using correlation parameters alpha and beta while alpha (oleic acid on MCFA) was found to be 0.0017, 0.002 and 0 for caproic, caprylic and capric acids respectively with corresponding beta (MCFA on oleic acid) of 0.034, 0.033 and 0.0049.; Keywords. anaerobic digestion, enzyme treatment, food processing wastewater, high-rate anaerobic reactors, hydrolysis, immobilized lipase, oil and grease, oily wastewater treatment, oleic acid, UASB. |
