TECHNOLOGY FOCUS - ENVIRONMENT - Preferred Process: The process further comprises: aerobically treating a second portion of the first solids-rich sludge to produce an at least partially aerobically treated sludge; combining at least a portion of the at least partially aerobically treated sludge with the wastewater; thickening the first portion of the first solids-rich sludge prior to anaerobically digesting the first portion of the first solids-rich sludge; aerobically treating the portion of the second solids-rich sludge prior to combining the portion of the second solids-rich sludge with the wastewater; combining a second portion of the first solids-rich sludge with the portion of the second solids-rich sludge; separating a solids-lean fluid from the first solids-rich sludge prior to anaerobically digesting the first portion of the first solids-rich sludge; combining at least a portion of the solids-lean fluid with the second portion of the first solids-rich sludge, and the portion of the second solids-rich sludge; aerobically treating the combination of the at least a portion of the solids-lean fluid, the second portion of the first solids-rich sludge, and the portion of the second solids-rich sludge to form an at least partially aerobically treated combination; combining the at least partially aerobically treated combination with the wastewater; anoxically treating the wastewater and the at least partially aerobically treated combination to produce an anoxically treated wastewater, and promoting aggregation comprising introducing methanogenic bacteria from the anaerobically digested sludge into the first mixed liquor. In the process: thickening the first portion of the first solids-rich sludge comprises producing a solids-rich sludge having a first concentration of methanogenic bacteria; and anaerobically digesting the first portion of the first solids-rich sludge comprises producing an anaerobically digested sludge having a second concentration of methanogenic bacteria, the first concentration is a significant fraction of the second concentration. In the process, precipitating one of the phosphorus containing compound and the nitrogen containing compound from the second solids-lean portion comprises: adjusting a pH of the second solids-lean portion; contacting the solids-lean portion with an alkali earth metal salt; or precipitating struvite from the second solids-lean portion. The method further comprises: reducing a hydraulic retention time of one of the at least one biological reactor and the anaerobic digester; producing a biological floe in the at least one biological reactor having an aerobic outer layer and one of an anoxic and an anaerobic core; increasing a rate of production of methane in the anaerobic digester; and directing methanogenic bacteria from the outlet of the anaerobic digester, through an aerobic treatment operation, and to the inlet of the anaerobic reactor. In the method, producing the biological floe in the at least one biological reactor comprises: increasing the organic loading of the at least one biological reactor; or reducing an amount of oxygen supplied to the at least one biological reactor. Preferred Components: The first concentration is at least 10% (preferably 50%) of the second concentration.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The alkali earth metal salt comprises magnesium, preferably magnesium chloride.    TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: The system further comprises: a third separator fluidly connected downstream of the first sludge outlet and upstream of the digester inlet, and having a third solids-lean fluid outlet and a thickened sludge outlet; an aerobic treatment unit having an aerobic inlet in fluid communication with the first sludge outlet, a second digester outlet of the anaerobic digester, and with the third solids-lean fluid outlet, and having an aerobic outlet in fluid communication with the treatment unit inlet. In the system, the first treatment unit, the first separator, and the third separator are configured to produce a thickened sludge having a first concentration of a methanogenic bacteria and the anaerobic digester is configured to produce a digested anaerobic sludge having a second concentration of the methanogenic bacteria, the first concentration is a substantial fraction of the second concentration. In the system, the third separator contains a first consortium of bacteria with a concentration of methanogenic microorganisms that is a substantial fraction of a concentration of methanogenic microorganisms in a second consortium of bacteria contained in the anaerobic digester, where the substantial fraction is at least 10%, preferably 50%. EXAMPLE - No suitable example given.