title: A new mathematical model for nitrogen gas production with special emphasis on the role of attached growth media in anammox hybrid reactor.
abstract: The present study emphasised on the development of new mathematical models based on mass balance and stoichiometry of nitrogen removal in anammox hybrid reactor (AHR). The performance of AHR at varying hydraulic retention times (HRTs) and nitrogen loading rates (NLRs) revealed that nitrogen removal efficiency (NRE) increases with increase in HRT and was found optimal (89 %) at HRT of 2 days. Mass balance of nitrogen revealed that major fraction (74.1 %) of input nitrogen is converted into N2 gas followed by 11.2 % utilised in biomass synthesis. Attached growth media (AGM) in AHR contributed to an additional 15.4 % ammonium removal and reduced the sludge washout rate by 29 %. This also enhanced the sludge retention capacity of AHR and thus minimised the formation of nitrate in the treated effluent, which is one of the bottlenecks of anammox process. Process kinetics was also studied using various mathematical models. The mass balance model derived from total nitrogen was found most precise and predicted N2 gas with least error (1.68 ± 4.44 %). Model validation for substrate removal kinetics dictated comparatively higher correlation for Grau second-order model (0.952) than modified Stover-Kincannon model (0.920). The study concluded that owing to features of high biomass retention, less nitrate formation and consistently higher nitrogen removal efficiency, this reactor configuration is techno-economically most efficient and viable. The study opens the door for researchers and scientists for pilot-scale testing of AHR leading to its wide industrial application.
authors.affiliation: Department of Environmental Science and Engineering, Indian School of Mines, Dhanbad, 826004, India. tomarswati4@gmail.com.
authors.forename: Swati
authors.initials: S
authors.lastname: Tomar
authors.affiliation: Department of Environmental Science and Engineering, Indian School of Mines, Dhanbad, 826004, India. skgsunil@gmail.com.
authors.forename: Sunil Kumar
authors.initials: SK
authors.lastname: Gupta
mesh_terms: D000641:Ammonia / Q000378:metabolism*; D000693:Anaerobiosis; D018533:Biomass; D019149:Bioreactors / Q000382:microbiology*; D003470:Culture Media / Q000737:chemistry*; D005740:Gases / Q000378:metabolism*; D008962:Models, Theoretical; D009566:Nitrates / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D010084:Oxidation-Reduction; D012722:Sewage / Q000382:microbiology
chemical_list: D003470:Culture Media; D005740:Gases; D009566:Nitrates; D012722:Sewage; D000641:Ammonia; D009584:Nitrogen
keywords: Anammox hybrid reactor; Attached growth media; Kinetics; Modelling; Nitrogen gas production