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Diploma and Master Theses (authored and supervised):

H. Schaar:
"Selective production of nitrite by partial nitrification";
Supervisor: J. Keller, E. Lai, O. Nowak; Institut für Wassergüte, Ressourcenmanagement und Abfallwirtschaft, 2002; final examination: 09-2002.



English abstract:
Nitrogen, in particular ammonium, is one of the major pollutants in wastewater apart from organic compounds (COD). Its release into receiving waters can result in severe disruption of the natural equilibrium in aquatic ecosystems.
On account of this detrimental effect ammonium has on the aquatic environment one must look for ways to increase nitrogen removal.

One approach to more efficient nitrogen removal - the separate treatment of reject water (centrate) deriving from the anaerobic digestion of activated sludge- is discussed in this thesis. Anaerobic ammonium oxidation (ANAMMOX) is a novel process to treat highly nitrogenous wastewater. The optimum molar NO2-/NH4+ ratio for the process is 1.3. As ammonium is the main form of nitrogen in centrate a preceding partial nitrification step to nitrite (nitritation) is necessary. Further oxidation to nitrate should be avoided. Compared to the conventional way of nitrogen removal, the combination of nitrification and denitrification, oxygen savings of up to 40% can be achieved.

The objective of this thesis was to determine whether the selective production of nitrite by partial nitrification could be reliably achieved with centrate from a municipal wastewater treatment plant (Luggage Point Wastewater Treatment Plant in Brisbane, Australia). Five laboratory-scale reactors were operated to test the suitability of the sequencing batch reactor (SBR) and the continuous stirred tank reactor (CSTR) configurations in this role. Furthermore, the effect of bicarbonate supplementation on the degree of nitritation in an SBR was investigated. Since the centrate did not contain enough alkalinity to achieve the optimum molar ratio the amount of ammonium oxidized to nitrite averaged 50% instead of the necessary 57%. The optimum ratio could be easily achieved with the addition of bicarbonate.

The synergetic effect of free ammonia and free nitrous acid inhibition, high temperature and low dissolved oxygen level was most likely the reason for the maintenance of a stable nitrite pathway throughout the experiments in all five laboratory-scale reactors.
The SBR technology in particular proved to be highly suitable for the partial nitrification step to nitrite. In comparison to the CSTR is was far less sensitive to disruptions.

Created from the Publication Database of the Vienna University of Technology.