Method and installation for controlled microbiome shift for biomass densification in a biological treatment of a raw influent

An installation for controlled biomass densification in a biological treatment of a raw influent, said installation comprising:

• a biological tank containing free suspended biomass having a first inlet, a second inlet and a first outlet, the biological tank being configured to be fed at the first inlet with at least a part of the raw influent and return activated sludge (RAS) to produce a mixture of treated water and activated sludge (AS) recovered at the first outlet;
• a separation unit, having a first inlet, a first outlet and second outlet, the separation unit being configured to be fed at the first inlet with the activated sludge (AS) and to produce an effluent recovered at the first outlet and a return activated sludge (RAS) recovered at the second outlet;
• an extracting device configured to extract at least part of the return activated sludge (RAS) and/or part of the activated sludge (AS) as a first source of a waste activated sludge (WAS);
• an external gravity-based selector having a first inlet, a first outlet and a second outlet, the external gravity-based selector being configured to be fed at the first inlet by at least part of the return activated sludge (RAS) and/or part of the activated sludge (AS) and to generate an overflow intended to be extracted at the first outlet as a second source of the waste activated sludge (WAS) and an underflow comprising a first part of dense biomass aggregates recovered at the second outlet;
• a dense biomass aggregate production and/or sustaining unit having a first inlet, optionally a second inlet, a optionally third inlet, and a first outlet, the dense biomass aggregate production and/or sustaining unit tank being configured to be fed at the first inlet with at least a part of the raw influent and optionally at the second inlet with the underflow and to form a second part of dense biomass aggregates, such as aerobic granular sludge (AGS) or biofilm, recovered at the first outlet;
• the biological tank being further configured to be fed at the second inlet with the produced second part of dense biomass aggregates of the production and/or sustaining unit and optionally with at least part of the first part of dense biomass aggregates of the undertow, thereby obtaining a densified biomass;
• a controller of the amount of the raw influent fed to the dense biomass aggregate production and/or sustaining unit and/or a controller of the amount of the waste activated sludge (WAS) extracted from the first source of the waste activated sludge (WAS) and/or from the second source of the waste activated sludge (WAS).