Long term partial nitritation of anaerobically treated black water and the emission of nitrous oxide |
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Authors: | MS de Graaff G Zeeman MCM van Loosdrecht |
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Affiliation: | a Wetsus, Centre of excellence for sustainable water technology, Agora 1, P.O. Box 1113, 8900 CC Leeuwarden, The Netherlands b Wageningen University, Sub-department of Environmental Technology, P.O. Box 8129, 6700 EV Wageningen, The Netherlands c Delft University of Technology, Department of Biotechnology, Julianalaan 67, 2628BC Delft, The Netherlands |
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Abstract: | Black water (toilet water) contains half the load of organic material and the major fraction of the nutrients nitrogen and phosphorus in a household and is 25 times more concentrated, when collected with a vacuum toilet, than the total wastewater stream from a Dutch household. This research focuses on the partial nitritation of anaerobically treated black water to produce an effluent suitable to feed to the anammox process. Successful partial nitritation was achieved at 34 °C and 25 °C and for a long period (almost 400 days in the second period at 25 °C) without strict process control a stable effluent at a ratio of 1.3 NO2-N/NH4-N was produced which is suitable to feed to the anammox process. Nitrite oxidizers were successfully outcompeted due to inhibition by free ammonia and nitrous acid and due to fluctuating conditions in SRT (1.0-17 days) and pH (from 6.3 to 7.7) in the reactor. Microbial analysis of the sludge confirmed the presence of mainly ammonium oxidizers. The emission of nitrous oxide (N2O) is of growing concern and it corresponded to 0.6-2.6% (average 1.9%) of the total nitrogen load. |
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Keywords: | Black water Partial nitritation Nitrous oxide emission Autotrophic nitrogen removal |
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