Effect of volatile fatty acid composition on upflow anaerobic sludge blanket (UASB) performance
Journal
Energy & Fuels
Journal Volume
22
Journal Issue
1
Pages
108-112
Date Issued
2008
Author(s)
Abstract
The effects of organic loading rates (OLRs) and volatile fatty acid (VFA) composition on upflow anaerobic sludge blanket (UASB) reactors were investigated. Four 2.5 L UASB reactors were fed by mixed VFA of 20 g of chemical oxygen demand (COD) L−1 initially and subsequently fed with different VFA compositions. In the initial stage of the experiment where the reactors were operated at an OLR between 0.82 and 10.4 g of COD L−1 day−1 with the substrate composed of a mixed acetate/propionate/butyrate composition, the COD removal efficiencies were in the range of 83 and 99% and the calculated methane yield ranged between 112 L of CH4 and 322 L of CH4 per g of COD removed. The result indicated that a higher methane yield corresponded with the increase of the OLR in the UASB treatment of the mixed VFA substrate. Mixed VFA-fed sludge showed a rather high activity in pure acetate and butyrate than pure propionate in a specific methanogenic activity (SMA) test. As the substrate composition changed from the mixed VFA (32:28:40 acetate/propionate/butyrate) to pure acetate, propionate, or butyrate at the OLR of 10.4 g of COD L−1 day−1, respectively, in the UASB reactors, the acetate- and butyrate-fed reactors showed higher gas production and COD removal than the pure propionate-fed reactor as expected. The result reviewed that the composition of VFAs has a significant influence on the reactor performance. The propionate substrate exhibited severe inhibition, leading to system failure at a feed concentration of 20 g of COD L−1, while the butyrate substrate can be efficiently degraded compared to the acetate substrate because of its high energy gain via degradation.
SDGs
Type
journal article