Mathematical modelling of an intermittent anoxic/aerobic MBBR: Estimation of nitrification rates and energy savings. (1st November 2022)

• Record Type: Journal Article
• Authors: Montecchio, D.; Mattei, M.R.; Esposito, G.; Andreottola, G.; Ferrentino, R.
• Is Part Of: Journal of environmental management. Volume 321(2022)
• Publication Date: 2022-11-01
• Subjects: Environmental policy -- Periodicals; Environmental management -- Periodicals; Environment -- Periodicals; Ecology -- Periodicals; 363.705
• DOI: 10.1016/j.jenvman.2022.116026
• Languages: English
• ISSNs: 0301-4797

Abstract

Abstract: This study aimed at modelling the performance of a novel MBBR configuration, named A/O-MBBR, comprised of a pre-anoxic reactor, with an HRT of 4.5 h, coupled with an intermittent anoxic/aerobic MBBR (HRT = 6.8 h). The lab-scale system was fed with municipal wastewater with an average influent Total Ammonia Nitrogen (TAN) and total COD (TCOD) concentrations of 46 mg of TAN-N L −1 and 310 mg TCOD L −1 . During the whole experimental period, TAN removal efficiency was always higher than 96%; denitrification was also very effective, achieving nitrate and nitrite concentrations in the effluent both lower than 5 mg NOx -N L −1 on average. Moreover, TCOD average removal efficiency was equal to 85%. Modelling was performed to investigate the nitrification efficacy enhancement; to this aim, a biofilm model was developed, adopting the equations for mixed-culture biofilms and the Activated Model Sludge n°1 (ASM1) for the biological processes rates. The model allowed to determine the maximum uptake rate for autotrophic growth (μA was 2.5 d −1 ) and the semisaturation constant (KOA was 0.2 mg O2 L −1 ), suggesting that the nitrification process was 3-fold faster than average and very effective at low oxygen concentrations. The model estimated that about 85% of TAN was removed by the biofilm and only the remaining part by suspended biomass in the bulk liquid. Finally, it was assessed that the A/O-MBBR configuration allowed for a 45–60% savings of the energy requirement compared to a Benchmark WWTP layout. Highlights: A coupled anoxic reactor with an intermittent anoxic/aerobic MBBR was studied. Nitrogenous compounds removal was extremely effective even at short HRTs. Calibrated nitrification kinetics were 3-fold higher than average. Model simulations estimated that 85% of TAN removal occurred within the biofilm. A/O-MBBR allowed for an energy reduction of 45–60% compared to conventional treatments.