The special strains used are suitably selected to convert most of the organic substrate into CO2 and water, while a smaller fraction is incorporated into new biomass, compared to ordinary heterotrophic bacteria that dominate conventional activated sludge systems. Product micronutrients stimulate biological activity inside the activated sludge flocs where oxygen penetration is limited, so as anoxic/anaerobic conditions locally prevail, resulting in degradation of organic constituents with reduced biomass yield production, if compared to purely aerobic conditions. Also, due to the rich hydrolytic potential of the special strains used, a greater part of the hardly biodegradable solids contained in the influent – which would have been removed without being converted with the primary or secondary surplus sludge stream – by applying the bioaugmentation technology can be partially or totally hydrolyzed, making it accessible to biological degradation so as only a part is eventually converted to biosolids, while the most of it is biologically degraded. Finally, because of the metabolism of the added strains (facultative anaerobic), they are capable to grow under oxygen limitation conditions (anaerobic and anoxic), so as the prolongation of the non-aerated zones in the main biological reactor is feasible, resulting in significant energy savings.