| The role of microbial consortia proximity, reactor configuration and nutrient supplementation, individually or in combination, on propionate degradation were investigated in this study. For the role of microbial consortia proximity, the results demonstrated that the unit rate of propionate consumption by whole granules was about 200% greater than that of homogenized granules. For the role of reactor configuration, the results indicated that, for propionate, staging and plug flow reactors performed better than the single-stage reactor. For acrylic acid, the two-stage UASB reactor showed superior performance over the single-stage UASB reactor. For glucose, the downflow and horizontal flow anaerobic granular sludge reactors performed better than the single- and two-stage UASB reactors under shock loading. Changing the operation mode from “upflow” to “horizontal flow” resulted in a reduction of the recovery period for an overloaded system. Addition of iron, cobalt, and nickel (10, 1, 1 mg/L, respectively) and/or yeast extract (100 mg/L) were required to double the propionate utilizing rate vs. the control. For the combined role of microbial consortia proximity, reactor configuration, and nutrient supplementation on propionate degradation, there were three reactor configurations (CSTR, homogenized granular UASB, and whole granular UASB) and seven types of nutrient supplementation, operated under mesophilic temperature. The maximum OLR and F/M ratio could be increased by enhancing microbial consortia proximity (up to 100% increase), reactor configuration (up to 600% increase), and nutrient supplementation (up to 270% increase) and all combinations (up to 2300% increase). The maximum OLR and F/M ratio were 34 g COD/L-d and 4.25 g COD/g VSS-d, respectively. The change in reactor configuration from a CSTR to a plug flow slurry reactor enhanced the reactor performance. The benefit of calcium supplementation was clearly demonstrated in terms of a higher OLR and F/M ratio. “Tap water + Ca + N + P” resulted in a maximum OLR of nearly 80% of that for the fully balanced Vanderbilt Media. |
