Novel Hybrid PBR-UASB System for the Treatment of High Strength Pet Food Wastewater

Pet food industrial wastewater contains high concentration of oil and grease (O&G) which is difficult to treat using conventional biological systems. In this study, anaerobic treatability of pet food wastewater was evaluated in a hybrid packed bed reactor-upflow anaerobic sludge blanket (PBR-UASB) treatment system. The PBR was packed with sol-gel/alginate beads containing immobilized enzyme as media which hydrolyzes the O&G in the wastewater as a pretreatment step while the UASB reactor was seeded with anaerobic sludge. The PBR was operated at 4 L/d for 64 days (phase I) and 8 L/d for another 57 days (phase II). The UASB reactor was operated at an HRT of 2.5 d and 1.25 d with an OLR of 1.27 and 2.5 kgCOD/m3.d during phase I and II respectively. Overall COD and O&G removal efficiencies of about 90% were achieved without any sludge floatation and with methane to COD yield of 80%. Despite the loss of immobilized lipase, the performance of PBR was satisfactory at oil loading of 0.9 kgO&G/m3.d which hydrolyzed 41% of O&G. Moreover, there was no sludge flotation observed during the period of operation due to pre-hydrolysis of O&G in the PBR. Further studies on system performance at higher organic loading rate and lower HRT are in progress.