Effect of Coconut Fiber as an Inert Media on Hybrid Upflow Anaerobic Sludge Blanket Reactor

The efficiency of a hybrid upflow anaerobic sludge blanket reactor (HUASB) where coconut fiber is used as an inert media was investigated under different hydraulic residence times (started with 6 h and then decreased to 2 h) with varied organic loading rates (ranged from 0.5 to 6.0 kg chemical oxygen demand (COD)/m(-3)day(-1)). The 3.5-L lab-scale reactor was used for sewage treatment under mesophilic conditions for 8 months. The COD reduction varied from 74% +/- 1.7% to 61% +/- 2.4%, the total suspended solids (TSS) reduction was in the range of 72% +/- 2.2% to 54% +/- 2.7%, and the methane content in the biogas was 65.1% +/- 0.3%. An attempt has been made to understand the performance of the lab-scale reactor for primary population of microorganisms using a microscopic technique. Different groups of anaerobic bacteria and granulation were visualized and quantified using unstained observations, Gram staining, ocular micrometry (granular size determination), Neubauer's chamber (counting of microorganisms), and scanning electron microscopy. Correlation analysis among the various operational parameters has also been prepared. Overall, the performance of the HUASB reactor using coconut fiber appears to be a cost-efficient sewage treatment alternative in developing nations. DOI: 10.1061/JOEEDU.EEENG-7325. (c) 2023 American Society of Civil Engineers.