TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Method: The biomass is subjected to secondary famine conditions on average for a period of time that is less than 6 days. The method is carried out in a sequencing batch reactor (SBR) (B1) and includes biologically treating the wastewater in the SBR and subjecting the biomass to the primary feast-famine process in the SBR, where after the biomass is subjected to primary famine conditions in one cycle of the primary feast-famine process, deviating from the primary feast-famine process and subjecting the biomass in the SBR to the secondary famine conditions. The method is carried out in an SBR and a side-stream reactor, and comprises conducting the primary feast-famine process in the SBR and transferring at least a portion of the biomass from the SBR to the side-stream reactor and subjecting the biomass in the side-stream reactor to the secondary famine conditions. The portion of the biomass is transferred back and forth between the SBR and the side-stream reactor and where the primary feast-famine process is carried out in the SBR and the biomass is subjected to the secondary famine conditions in the side-stream reactor. The biomass is contained within mixed liquor in the SBR and the method includes subjecting the biomass to repeated feast and famine conditions in the SBR and instigating secondary famine treatment of the biomass while the biomass in the SBR is being subjected to primary famine conditions by transferring at least a portion of the biomass from the SBR to the side-stream reactor and subjecting the biomass in the side-stream reactor to secondary famine conditions. The primary feast-famine cycle includes a primary feast period and a primary famine period, and the method includes maintaining the period of time that the biomass is subjected to secondary famine conditions in the side-stream reactor to a time period greater than the average primary famine period but less than 6 days. The method comprises performing a continuous flow mainstream process, where the primary feast-famine process is carried out in a mainstream and the secondary famine process is carried out in a side-stream. The mainstream includes a primary feast reactor and a primary famine reactor, and the method includes subjecting the biomass to primary feast conditions in the primary feast reactor and subjecting the biomass to primary famine conditions in the primary famine reactor, where the side-stream includes a secondary famine reactor and the method includes subjecting the biomass to secondary famine conditions in the secondary famine reactor and further includes transferring biomass back and forth between the primary famine reactor and the secondary famine reactor. The method includes carrying out the primary feast-famine process in a mainstream, settling at least a portion of the biomass after the biomass is subjected to at least one primary feast-famine cycle, and transferring at least a portion of the settled biomass to a secondary famine reactor and subjecting biomass in the secondary famine reactor to the secondary famine conditions before returning biomass back to conditions of primary feast-famine conditions. The secondary famine reactor is located in a side-stream, and communicates with a biomass return line that is operatively connected between a solids-liquid separator and the mainstream. The method comprises: directing at least a portion of the settled biomass from a solids-liquid separator to the mainstream using return biomass line; transferring biomass back and forth between the return biomass line and the secondary famine reactor; subjecting the biomass in the secondary famine reactor to the secondary famine conditions; subjecting the biomass to the primary feast-famine process by directing the biomass into and through feast and famine reactors in a mainstream and settling at least a portion of the biomass and returning the settled biomass to the feast and famine reactors in the mainstream where the biomass is subjected to alternating feast and famine conditions; subjecting at least a portion of the returning biomass to the secondary famine conditions after which the biomass is returned to the mainstream and directed into and through the feast and famine reactors; directing the biomass into a primary feast reactor in a mainstream and subjecting the biomass to primary feast conditions in the primary feast reactor; after the biomass is subjected to primary feast conditions, directing the biomass to a downstream primary famine reactor in the mainstream and subjecting the biomass to primary famine conditions in the primary famine reactor; after the biomass is subjected to primary famine conditions, directing the biomass to a solids-liquid separator and separating the biomass from treated wastewater; recycling the separated biomass to the mainstream and repeatedly directing the separated biomass through the primary feast and famine reactors; continuing to recycle separated biomass to the primary feast and famine reactors for a selected time period; periodically or continuously directing the at least a portion of the separated biomass to a secondary famine reactor and subjecting the biomass to secondary famine conditions in the secondary famine reactor; and after the separated biomass has been subjected to secondary famine conditions, directing at least a portion of this biomass back to the mainstream and subjecting the biomass to repeated feast and famine conditions in the mainstream. The biomass treated in the secondary famine reactor is treated in the primary feast reactor and then in the primary famine reactor before reaching the secondary famine reactor. The primary feast and famine conditions are carried out in primary feast and famine reactors, where the secondary famine is carried out in a secondary famine reactor, and the primary feast reactor is arranged in a mainstream and the primary famine reactor is arranged in a first side-stream and the secondary famine reactor is arranged in a second side-stream reactor, where the method includes subjecting the biomass to primary feast conditions in the primary feast reactor, after subjecting the biomass to primary feast conditions in the primary feast reactor, directing the biomass to a solids-liquid separator and separating biomass from mixed liquor, directing the separated biomass to the primary famine reactor and subjecting the separated biomass to primary famine conditions, cycling the biomass through the primary feast reactor, solids-liquor separator and the primary famine reactor and back to the primary feast reactor a selected number of cycles, and transferring at least a portion of the biomass from the primary famine reactor to the secondary famine reactor and subjecting the biomass in the secondary famine reactor to secondary famine conditions, and returning at least of portion of the biomass in the secondary famine reactor back to the rest of the biomass that is cycling through primary feast and famine reactor. The solids-liquid separator is operatively interconnected between the primary feast reactor and the primary famine reactor, where the biomass is subjected to primary famine conditions after the biomass is subjected to primary feast conditions in the mainstream and after the biomass is separated from mixed liquor by the solids-liquid separator. The biomass is subjected to secondary famine conditions for a period of time that is greater than or equal to the average primary feast-famine retention time or cycle time. The method comprises: carrying out the primary feast process in a mainstream, settling at least a portion of the biomass after the biomass has been subjected to primary feast conditions and subjecting the biomass to primary famine conditions in a side-stream reactor, and exchanging at least a portion of the biomass back and forth between the side-stream reactor and a secondary side-stream famine reactor so as to expose biomass to conditions of secondary famine also in a side-stream; and carrying out a portion of the primary famine process in a mainstream, settling at least a portion of the biomass after the biomass has been subjected to primary feast conditions and primary famine conditions in the mainstream, carrying out another part of the primary famine process in a side-stream where the biomass is subjected to primary famine conditions in the side-stream, subjecting the biomass to the secondary famine process in a secondary side-stream reactor, and transferring the biomass back and forth between the secondary famine side-stream and the primary famine side-stream reactors. The primary famine is achieved in part before the solid-liquid separator. The biomass is substantially subjected to secondary famine conditions at one time. The portions of the total process biomass are repeatedly subjected to secondary famine conditions at any given time. The method includes repeatedly subjecting portions of the biomass to secondary famine conditions such that statistically all of the biomass is on average conditioned by the effect of extended famine conditions imparted by the secondary famine process. The biomass in the process is subjected to secondary famine conditions on average at least once every four solids retention times (SRTs) for the biomass in the process. The method includes operating the secondary famine reactor under anoxic conditions and denitrifying wastewater in the secondary famine reactor, providing a SRT for the suspended biomass in the process, retaining the biomass in the secondary famine reactor for a period of time less than the SRT, directing the wastewater and biomass from the secondary famine reactor to a solids-liquid separator, separating the biomass from the wastewater, and recycling the separated biomass to the primary feast reactor and/or primary famine reactor. The average flow rate of the separated biomass recycled to the primary feast reactor and/or primary famine reactor is 0.2-2 times the average flow rate of the wastewater stream directed to the primary feast reactor. The wastewater and biomass form a part of mixed liquor, where the flow rate of mixed liquor recycled from the primary famine reactor to the primary feast reactor is one and five times the average flow rate of the wastewater directed into the primary feast reactor.