Up-flow anaerobic sludge bed reactor is an anaerobic biological method for treating sewage, also called up-flow anaerobic sludge bed, the English abbreviation UASB (Up-flow Anaerobic Sludge Bed/Blanket). It was invented in 1977 by Professor Lettinga from the Netherlands.
The sewage passes through the UASB from the bottom up. There is a high-concentration, high-activity sludge bed at the bottom of the reactor, where most of the organic pollutants in the sewage are degraded into methane and carbon dioxide through anaerobic fermentation.
Due to the stirring of water flow and air bubbles, there is a sludge suspension layer above the sludge bed.
The upper part of the reactor is equipped with a three-phase separator to separate digested gas, digestive liquid and sludge particles. The digested gas is led out from the top of the reactor; the sludge particles automatically slide down and settle to the sludge bed at the bottom of the reactor; the digested liquid is discharged from the clarification zone.
UASB has a large load capacity and is suitable for the treatment of high-concentration organic wastewater. A well-running UASB has a high removal rate of organic pollutants, does not require stirring, and can adapt to large load shocks, temperature and pH changes.