Effect of Volatile Fatty Acid on Upflow Anaerobic Sludge Blanket Digester Performance
Date Issued
2007
Date
2007
Author(s)
Wong, Biing-Teo
DOI
en-US
Abstract
Volatile fatty acid (VFA) is the most important intermediate product in the bioconversion of organic matter to CH4 and CO2. This study investigated the effect of VFA on the UASB digester performance based on the organic loading rates (OLRs) and the VFA composition.
UASB digesters fed by similar VFA of 20 g COD L-1 were operated at OLR between 0.82 and 10.4 g COD L-1 day-1. The chemical oxygen demand (COD) removal efficiencies were between 83% and 99%, and methane yield increased from 38.6% to 86.5% of the theoretical value. The results showed an elevated effectiveness in converting mixed-VFA substrate to methane at the increased OLRs.
By feeding pure acetate, propionate or butyrate substrate in the same COD to the UASB digesters, the acetate- and butyrate-fed digesters showed higher biogas production (9940 and 9730 mL day-1), methane composition (90% and 77.5%) and COD removal (78.6% and 97%) than pure propionate-fed reactor. Propionate substrate exhibited severe inhibition leading to system failure at a feed concentration of 20 g COD L-1. Carbon balance showed higher amount of carbon in acetate substrate fed to digester than butyrate substrate. 10.5% of carbon fed to butyrate-fed digester was converted to biomass and made an 13.1% increase of VSS concentration in butyrate-fed sludge compared with acetate-fed sludge. High purity of methane in acetate-fed digester was due to dissolution of carbon dioxide in high pH effluent.
Specific methanogenic activity test proved that the acetate-fed sludge was lacking of acetogen to degrade butyrate. Degradation of propionate is feasible while combined with the degradation of acetate and butyrate. Methane production of the digesters can be further increased from 2.4 to 4.2 times. The COD removal of digesters can be predicted well by SMA test except for the mixed acid-fed digester.
Subjects
厭氧消化
揮發性脂肪酸
上流式厭氣污泥床反應器
anaerobic digestion
volatile fatty acid
upflow anaerobic sludge blanket
Type
thesis
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