Accumulation, Inhibation And Recovery Of Volatile Fatty Acid In Anaerobic Sequencing Batch Reactor Under Loading Disturbance

The set-up and steady state of the Anaerobic Sequencing Batch Reactor (ASBR) treating synthetic wastewater containing sucrose as the sole carbon source at a constant temperature of 35℃ were studied in this paper. Basing on the steady state, acidification experimentation was following to study the rules of the accumulation of the VFA in the ASBR.The reactor was operated on a 8-hour cycle. Changing water rate was 1/3, and the hydraulic retention time was 1 day. After operating 172 days, the reactor reached a steady state and a series of the technics index were got. The organic loading rate was SkgCODm^-3d^-1, and the soluble COD removal efficiencies exceeding 92% in the effluent. The total volatile fatty acid (VFA) concentration of the effluent was lower than 250mg/l as acetate. The gas production rate was steady and 14.4L gas more or less was produced in one day. The content of methane in the biogas is from 60% to 70%. The MLSS and MLVSS went to stable at 13.189g/L and 12.006g/L and the ratio of the MLVSS and MLSS was 91%. The sludge volume index was 41.7mL/g. The specific methanogenic activity (SMA) of formate, acetate, propionate, and butyrate was 0.3348gCOD-CH₄/gVSS·d, 1.2580gCOD-CH₄/gVSS·d, 1.094gCOD-CH₄/gVSS·d and 40gCOD-CH₄/gVSS·d, respectively.The organic loading was increased to 10kgCODm^-3d^-1, and the volatile fatty acid was accumulated to study the laws of the VFA accumulation. The results showed that: under the same condition, the VFAs have the different average accumulation rates and reached different accumulated maximum. The acetate was accumulated to the maximum at the cycle 7, and its biggest accumulation concentration value was 396.6mgCOD/L, and its average accumulation rate was 131.2mgCOD/( L ·d). The propionate, butyrate, valeric were at the cycle 25, and theirs biggest accumulation concentration value were 1629.2mgCOD/L, 85.9mgCOD/L, 198.9mgCOD/L respectively, and theirs average accumulation rate were 181mgC0D/( L · d), 9.5mgCOD/( L · d), 22.1mgCOD/( L · d). The isobutyrate and the isovaleric were at the cycle 13, and theirs biggest accumulation concentration value were 42.4mgCOD/L, 90.4mgCOD/L, and theirs average accumulation rate were 8.5mgCOD/( L ·d), 18.1mgCOD/( L ·d). As showed above, during the acidogenesis, the acetate had the fast speed to reach the maximum of accumulation concentration; the biggest accumulation concentration value and the average accumulation rate of the propionate was the biggest above the VFAs; and the iso-acids were faster than the acids to reach the maximum of accumulation concentration.