Long-term nitrite-oxidizing bacteria suppression in a continuous activated sludge system exposed to frequent changes in pH and oxygen set-points. (15th September 2022)

• Record Type: Journal Article
• Authors: Antileo, Christian; Jaramillo, Francisco; Candia, Oscar; Osorio, Aahilyn; Muñoz, Carlos; Farías, Jorge; Proal-Nájera, José B.; Zhang, Qiqi; Geissen, Sven-Uwe
• Is Part Of: Journal of environmental management. Volume 318(2022)
• Publication Date: 2022-09-15
• Subjects: Long-term partial nitrification -- Intermittent kinetic inhibition -- Continuous activated sludge reactor -- Supervisory control; Environmental policy -- Periodicals; Environmental management -- Periodicals; Environment -- Periodicals; Ecology -- Periodicals; 363.705
• DOI: 10.1016/j.jenvman.2022.115545
• Languages: English
• ISSNs: 0301-4797

Abstract

Abstract: Research has proven the adaptation of nitrite-oxidizing bacteria to unfavorable environmental conditions, and this work presents a novel concept to prevent nitrite oxidation during partial nitrification in wastewater. The approach is based on the real-time updating of mathematical models of the process to search for optimal set-points of pH and oxygen concentration in a continuous activated sludge reactor with a high sludge age (20.3 days). A heuristic optimization technique by 13 optimum set-points simultaneously maximized the degree of ammonia oxidation ( α ) and nitrite accumulation ( β ), achieving an ( α + β ) = 190% per day. The activated sludge reactor was conducted for 780 days under three control schemes: open-loop control, fuzzy model supervisory control and phenomenological supervisory control. The phenomenological supervisory control system achieved the best results, simultaneously reaching 95% ammonium oxidation and 90% nitrite accumulation. The Haldane kinetics were analyzed using steady-state concentrations of all nitrogen species, concluding that the simultaneous maximization of α + β led to selecting set-points at the extreme values of the following ranges: pH = 7.5–8.5 and DO = 0.8–1.0 mg O2 /L, which enabled the inhibition of one nitrifier species. At the same time, the other one was relieved from inhibition. The 16sRNA assays indicated that the nitrite-oxidizing bacteria presence (genera Nitrobacter and Nitrospira ) shifted from 32% to less than 8% after 280 days of continuous operation with optimal pH and oxygen set-points. Graphical abstract: Image 1