biostudies-literatureUnknown10(1)Santillan EMinistry of Education - SingaporeNational Research Foundation SingaporeSustained disturbances are relevant for environmental biotechnology as they can lead to alternative stable states in a system that may not be reversible. Here, we tested the effect of a sustained organic loading alteration (food-to-biomass ratio, F:M, and carbon-to-nitrogen ratio, C:N) on activated sludge bioreactors, focusing on the stability of nitrification and nitrifiers. Two sets of replicate 5-L sequencing batch reactors were operated at different, low and high, F:M (0.19-0.36 mg COD/mg TSS/d) and C:N (3.5-6.3 mg COD/mg TKN) conditions for a period of 74 days, following 53 days of sludge acclimation. Recovery and resilience were tested during the last 14 days by operating all reactors at low F:M and C:N (henceforth termed F:M-C:N). Stable nitrite accumulation (77%) was achieved throuScientific reports21388https://www.ebi.ac.uk/biostudies/studies/S-EPMC7721871biostudies-literatureSustained organic loading disturbance favors nitrite accumulation in bioreactors with variable resistance, recovery and resilience of nitrification and nitrifiers.PMC7721871Wuertz SSantillan EConstancias FPhua WXfalseSustained organic loading disturbance favors nitrite accumulation in bioreactors with variable resistance, recovery and resilience of nitrification and nitrifiers.Sustained disturbances are relevant for environmental biotechnology as they can lead to alternative stable states in a system that may not be reversible. Here, we tested the effect of a sustained organic loading alteration (food-to-biomass ratio, F:M, and carbon-to-nitrogen ratio, C:N) on activated sludge bioreactors, focusing on the stability of nitrification and nitrifiers. Two sets of replicate 5-L sequencing batch reactors were operated at different, low and high, F:M (0.19-0.36 mg COD/mg TSS/d) and C:N (3.5-6.3 mg COD/mg TKN) conditions for a period of 74 days, following 53 days of sludge acclimation. Recovery and resilience were tested during the last 14 days by operating all reactors at low F:M and C:N (henceforth termed F:M-C:N). Stable nitrite accumulation (77%) was achieved throu2020-01-01T00:00:00Z2020 Dec2025-04-07T00:00:47.388Z2025-04-04T19:12:41.012ZS-EPMC77218713328877510.1038/s41598-020-78314-1