Patent ID: 8409440

Claim:
A method for the biological purification of wastewater employing a reactor comprising a first compartment ( 2 ) and a second compartment ( 4 ) which communicate with each other in the lower part, the wastewater to be treated arriving in the first compartment, the second compartment containing aerobic granular sludge and being at atmospheric pressure, and an injection of oxygen-containing gas being provided in the lower part of the second compartment, wherein: the granular sludge forms a bed ( 5 ) in the second compartment ( 4 ); the reactor is made to operate in sequential batch mode according to a cycle comprising two phases, namely: an anaerobic first phase during which: the first compartment ( 2 ) is filled under vacuum with wastewater to be treated, then the pressure in the first compartment is suddenly brought back to atmospheric pressure in order to rapidly discharge a volume of wastewater to be treated into the second compartment ( 4 ) in which no injection of oxygen-containing gas takes place and the above two operations are repeated several times in order to introduce and distribute a sufficient volume of effluent in pulsed sequential mode in the second compartment ( 4 ), the biological reactions being carried out in an anaerobic medium with the pulsed expanded sludge bed ( 5 ) under the effect of the hydraulic stress of the feed; an aerobic second phase during which: the feed of wastewater to be treated is stopped, the shutter of a sludge-concentrating zone ( 10 ) being placed in the closed position, an injection of oxygen-containing gas takes place in the second compartment ( 4 ), the biological reactions being carried out in an aerobic medium with sludge stirred under the effect of the gas injection, the gas injection is stopped and the granular sludge left to rapidly settle and the treated wastewater is extracted from the second compartment, the shutter of the sludge-concentrating zone being placed again in the open position; after which another cycle starts.