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Antileo C, Jaramillo F, Candia O, Osorio A, Muñoz C, Farías J, Proal-Nájera JB, Zhang Q, Geissen SU. Long-term nitrite-oxidizing bacteria suppression in a continuous activated sludge system exposed to frequent changes in pH and oxygen set-points. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2022; 318:115545. [PMID: 35752006 DOI: 10.1016/j.jenvman.2022.115545] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Revised: 05/24/2022] [Accepted: 06/14/2022] [Indexed: 06/15/2023]
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.
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Affiliation(s)
- Christian Antileo
- Department of Chemical Engineering, University of La Frontera, Cas. 54-D, Temuco, Chile.
| | - Francisco Jaramillo
- Department of Electrical Engineering, Faculty of Physical and Mathematical Sciences, University of Chile, Av. Tupper 2007, Santiago, Chile.
| | - Oscar Candia
- Facultad de Ingeniería, Universidad Autónoma de Chile, 5 Poniente 1670, Talca, Chile.
| | - Aahilyn Osorio
- Department of Chemical Engineering, University of La Frontera, Cas. 54-D, Temuco, Chile.
| | - Carlos Muñoz
- Department of Electrical Engineering, Faculty of Engineering and Sciences, University of La Frontera, Cas. 54-D, Temuco, Chile.
| | - Jorge Farías
- Department of Chemical Engineering, University of La Frontera, Cas. 54-D, Temuco, Chile.
| | - José B Proal-Nájera
- Instituto Politécnico Nacional, CIIDIR-Unidad Durango, Calle Sigma 119, Fracc. 20 de Noviembre II, Durango, Dgo., C.P. 34220, Mexico.
| | - Qiqi Zhang
- Department of Environmental Technology, Technische Universität Berlin, 10623, Berlin, Germany.
| | - Sven-Uwe Geissen
- Department of Environmental Technology, Technische Universität Berlin, 10623, Berlin, Germany.
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