Anaerobic Reactor

Wastewater is introduced into the bottom of the UASB reactor as uniformly as possible, and the sewage flows upward through the sludge bed containing granular sludge or flocculent sludge. The anaerobic reaction occurs during the contact between wastewater and sludge granules. The biogas (mainly methane and carbon dioxide) produced under anaerobic conditions causes internal circulation, which is beneficial to the formation and maintenance of granular sludge. Some of the gas formed in the sludge layer attaches to the sludge granules, and both attached and unattached gas rise toward the top of the reactor. The sludge rising to the surface impinges on the bottom of the three-phase separator gas emitter, causing the sludge flocs with attached bubbles to degas. After the bubbles are released, the sludge granules will settle to the surface of the sludge bed, and both attached and unattached gas are collected in the gas collection chamber of the three-phase separator at the top of the reactor. The baffle placed just below the gap of the unit acts as a gas emitter and prevents biogas bubbles from entering the settling zone, which would otherwise cause turbulence in the settling zone and hinder granule settling. The liquid containing some residual solids and sludge granules passes through the separator gaps into the settling zone. Since the flow area of the settling zone of the separator's inclined walls increases near the water surface, the upward flow velocity decreases near the discharge point. Due to the reduced flow velocity, the sludge flocs can flocculate and settle in the settling zone. The sludge flocs accumulated on the three-phase separator will to some extent exceed the friction force holding them on the inclined walls, and they will slide back into the reaction zone, where this portion of sludge will again react with the influent organic matter.