UASB Reactor

UASB is an upflow anaerobic sludge bed. UASB consists of three parts: sludge reaction zone, (gas, liquid, solid) three-phase separator (including sedimentation zone) and gas chamber. This process has the dual characteristics of anaerobic filtration and anaerobic activated sludge method. Wastewater passes through the anaerobic sludge bed reactor from bottom to top. There is a high-concentration and high-activity sludge layer at the bottom of the reactor, where most of the organic matter is converted into CH4 and CO2. Due to the agitation of gaseous products and the adhesion of bubbles to sludge, a sludge suspension layer is formed above the sludge layer. A three-phase separator is provided on the upper part of the reactor to complete the separation of gas, liquid and solid phases. The separated digestion gas is discharged from the upper part, the separated sludge automatically slides into the sludge layer, and the effluent flows out from the clarification zone.

Pool design shapes are round, square, and rectangular. The height of the sludge bed is generally 3-8m, and it is mostly built with reinforced concrete.

Process characteristics

1. The sludge concentration in UASB is high, with an average sludge concentration of 20-40gVSS/L;

2. The organic load is high and the hydraulic retention time is short. When medium-temperature fermentation is used, the volumetric load is generally about 5~10kgCOD/m3.d;

3. There is no mixing and stirring equipment. The upward movement of the biogas generated during the fermentation process makes the sludge on the upper part of the sludge bed suspended, and the sludge layer on the lower part is also stirred to a certain extent:

4. The sludge bed is not filled with carriers, which saves construction costs and avoids clogging problems caused by fillers:

5. UASB is equipped with a three-phase separator, and usually no sedimentation tank is set. The sludge separated by the sedimentation area returns to the sludge bed reaction area, and sludge return equipment is usually not required.

The anaerobic method is suitable for medium and high concentration organic wastewater. Some organic matter is difficult to degrade for aerobic biological treatment, but it is degradable for anaerobic biological treatment, such as solid organic matter. Colorant anthracenequinone and some ammonia nitrogen dyes, etc.