Shortcut biological nitrogen removal in hybrid biofilm/suspended growth reactors |
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| Institution: | 1. Eawag, Swiss Federal Institute for Aquatic Science and Technology, Department of Surface Waters-Research and Management, 6047 Kastanienbaum, Switzerland;2. Key Laboratory of Coastal Environment and Resources of Zhejiang Province, School of Engineering, Westlake University, Hangzhou, China;3. Eawag, Swiss Federal Institute for Aquatic Science and Technology, Department of Process Engineering, 8600 Duebendorf, Switzerland;4. Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Air Pollution & Environmental Technology, 8600 Duebendorf, Switzerland;5. Department of Environmental Sciences, University of Basel, Basel, Switzerland |
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| Abstract: | A shortcut biological nitrogen removal (SBNR) process converts ammonium directly through nitrite to nitrogen gas, thus requiring less aeration and carbon. We evaluated a hybrid SBNR (HSBNR) reactor containing an anoxic tank followed by an aerobic tank and a settling tank. The aerobic tank was filled with polyvinyl alcohol sponge media (20%, v/v) to attach and retain ammonium oxidizers. Two configurations of the HSBNR reactor were tested for treating a wastewater with high strength ammonium and organic electron donor. The HSNBR reactors accumulated nitrite stably for 1.5 years and maintained a high free ammonia (FA) concentration (20–25 mg/L) and a low dissolved oxygen (DO) concentration (<1 mg/L) in the aerobic tank. Apparently, the biofilm carriers increased the solids retention time (SRT) for ammonium oxidizers, while high FA and low DO selected against nitrite oxidizers and promoted direct denitrification of nitrite in the aerobic tank. The significant amount of chemical oxygen demand (COD) was removed by shortcut denitrification of nitrite in the anoxic tank. |
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