Study On The Accumulation And Recovery Of The Volatile Fatty Acid In The Anaerobic Sequencing Batch Reactor

Anaerobic sequencing batch reactor (ASBR) is paid more attention because of its many advantages such as low investment, flexibility of the operation and the ability of enduring perturbation and so on. However ASBR is less applied than the other high efficient reactors such as upflow anaerobic sludge blanket, upflow granular sludge blanket and so on, there are two main reasons. One is that there is pressure fluctuation in the ASBR because of the batch-fed and batch-decanted and the airhight reactor; the other is that the volatile fatty acid can accumulate in the ASBR because of the batch operation, in this article the accumulation and recovery of the volatile fatty acid in the ASBR were studied under the condition of the organic loading perturbation.Glucose was used as the influent substrate. The operation temperature was 35±1 °C. After 172 days'operation, a steady state was established. Its HRT and operation cycle are 24 days and 8h respectively, the influent, effluent, sedimentation and reaction time are 30 min, 10 min, 30 min and 410 min respectively, its organic loading is 5kgCOD/m~3/d. The effluent chemical oxygen demand (COD), volatile fatty acid concentration and pH were 100 mg/L, 95 mg/Land 6.56 respectively, COD removal reached 97.5%. The specific methanogenic activity (SMA) of acetate, propionate and butyrate were 1.70, 1.43 and 1.74 times of the domesticated sludge respectively. The maximum organic gas rate reached 15 L/d.Perturbation started at the base of the steady state. The influent organic loading increased from 5kg/m~3/d to a constant 10kg/m~3/d and other operation conditions were the same as the steady state. After 5 days'perturbation experiment. Effluent COD increased from 100 mg/L to 9516.1 mg/L but the effluent pH decreased from 6.56 to 3.34. So the amount of the sodium bicarbonate was increased in order to keep the pH in the ASBR was 6.0. The accumulations rate of the COD and VFA in the ASBR were 1912.4 mg/L/d and 694.41 mgCOD/L/d respectively. The accumulations rate of the acetate, propionate, butyrate, isobutyric, isovaleric and valeric were 173.38, 459.1, 14.4, 0.64, 0.37 and 42.92mgCOD/L/d respectively. The acetogen, propionatogen, butytatogen, isobutyricgen, isovalericgenand valericgen were inhabited at the 13th cycle, 13th cycle, 19th cycle, 7th cycle, 7th cycle and 25th cycle respectively. The amount of the methane gas of the organic gas produced was decreased from 68.5% to 29%. A11 these indicat ASBR has the ability of enduring perturbation.