Effect of Volatile Fatty Acid Composition on Upflow Anaerobic Sludge Blanket (UASB) Performance super([dagger])

• Published in: Energy & fuels 2008-01, Vol.22 (1), p.108-112
• Main Authors: Wong, Biing-Teo, Show, Kuan-Yeow, Su, Ay, Wong, Rui-jyun, Lee, Duu-Jong
• Format: Article
• Language: English
• ISSN: 0887-0624; 1520-5029
• DOI: 10.1021/ef700282r

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 super(-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 super(-1) day super(-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 CH sub(4) and 322 L of CH sub(4) 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 super(-1) day super(-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 super(-1), while the butyrate substrate can be efficiently degraded compared to the acetate substrate because of its high energy gain via degradation.