Studi Kinetika Produksi Biogas dari Limbah Cair Kelapa Sawit Menggunakan Reaktor Upflow Anaerobic Sludge Blanket – Hollow Centered Packed Bed (UASB-HCPB) Kombinasi Membran Ultrafiltrasi pada Suhu 45oC : Pengaruh Rasio Recycle

Abstract

Anaerobic digestion is one of the processes that can be used to produce biogas from palm oil mill effluent. This research studied biogas production from palm oil mill effluent using UASB-HCPB reactor combined with ultrafiltration membrane at 45oC. The effluent of ultrafiltration membrane will be recycled to reactor according to variation of recycle ratio. In addition, kinetics of biogas production and microbial growth from this research studied. The research began with loading up process, the reactor operated with gradually decreased HRT until reached of target HRT were from HRT 25, 15, 10, and 6 with pH control pH 7 ± 0,2 at 45oC. Furthermore, the effect of the recycle ratio studied by varying recycle ratio, which is 0, 15, dan 25%. The analysis parameters carried out include pH, alkalinity, TS, VS, TSS, VSS, SVI, COD, biogas volume and biogas composition. The analysis was carried out at three sampling points along the UASB-HCPB reactor and effluent of ultrafiltration membrane namely permeate and retentate. The results showed that the UASB-HCPB reactor operated stably where the pH and alkalinity values were 6.48-7.3 and 1800-4000 mg/L during the loading up process and 6.48-7.08 and 1800-2900 mg/L during the recycle ratio process, respectively. The highest biogas production was obtained at the 25% recycle ratio of 5,77 L/day or 36,35x10-5 L/mgVS.day with biogas composition of CH4, CO2, H2S were 81,25%, 17,25%, 0,078%, respectively. The average VS and COD reduction values were 72,81% and 77,53%. The use of ultrafiltration membrane was able to reduce the organic content in the effluent of anaerobic digestasion. The COD values of permeate and retentate end process were 6186 mg/L and 10825 mg/L, respectively. The modified Gompertz kinetic was able to represent the kinetics of biogas production in this research. The kinetic constant value for biogas production with modified Gompertz kinetic, namely B, Rb, and  were 36,469 L/mgVS, 1,305 L/mgVS.day, and 7,572 day, respectively. The Cone kinetic model and Chen & Hashimoto kinetic model have almost the same accuracy in representing the kinetic model of microbial growth rate in this research. The greatest microbial growth was obtained at sampling 2 of reactor. This is because there is HCPB in the middle of the reactor which can be maintain microbes along anaerobic digestion.