title: Thermophilic biological nitrogen removal in industrial wastewater treatment.
abstract: Nitrification is an integral part of biological nitrogen removal processes and usually the limiting step in wastewater treatment systems. Since nitrification is often considered not feasible at temperatures higher than 40 °C, warm industrial effluents (with operating temperatures higher than 40 °C) need to be cooled down prior to biological treatment, which increases the energy and operating costs of the plants for cooling purposes. This study describes the occurrence of thermophilic biological nitrogen removal activity (nitritation, nitratation, and denitrification) at a temperature as high as 50 °C in an activated sludge wastewater treatment plant treating wastewater from an oil refinery. Using a modified two-step nitrification-two-step denitrification mathematical model extended with the incorporation of double Arrhenius equations, the nitrification (nitrititation and nitratation) and denitrification activities were described including the cease in biomass activity at 55 °C. Fluorescence in situ hybridization (FISH) analyses revealed that Nitrosomonas halotolerant and obligatehalophilic and Nitrosomonas oligotropha (known ammonia-oxidizing organisms) and Nitrospira sublineage II (nitrite-oxidizing organism (NOB)) were observed using the FISH probes applied in this study. In particular, this is the first time that Nitrospira sublineage II, a moderatedly thermophilic NOB, is observed in an engineered full-scale (industrial) wastewater treatment system at temperatures as high as 50 °C. These observations suggest that thermophilic biological nitrogen removal can be attained in wastewater treatment systems, which may further contribute to the optimization of the biological nitrogen removal processes in wastewater treatment systems that treat warm wastewater streams.
authors: Environmental Engineering and Water Technology Department, UNESCO-IHE Institute for Water Education, Westvest 7, 2611, Delft, The Netherlands, c.lopezvazquez@unesco-ihe.org.
authors: C M
authors: CM
authors: Lopez-Vazquez
authors: M
authors: M
authors: Kubare
authors: D P
authors: DP
authors: Saroj
authors: C
authors: C
authors: Chikamba
authors: J
authors: J
authors: Schwarz
authors: H
authors: H
authors: Daims
authors: D
authors: D
authors: Brdjanovic
mesh_terms: D001419:Bacteria / Q000378:metabolism*; D058440:Denitrification; D006358:Hot Temperature; D017404:In Situ Hybridization, Fluorescence; D007220:Industrial Waste; D008962:Models, Theoretical; D009584:Nitrogen / Q000378:metabolism*; D062065:Wastewater / Q000737:chemistry* / Q000382:microbiology*; D014873:Water Pollutants / Q000378:metabolism*; D018508:Water Purification / Q000379:methods*
chemical_list: D007220:Industrial Waste; D009584:Nitrogen; D062065:Wastewater; D014873:Water Pollutants