Nitrous oxide emissions from deammonification process under different operation conditions.

Sammanfattning: Wastewater treatment plays significant role in the environmental protection. The process has direct impact on quality of air and water. All treated sewage reaches fresh water reservoirs as well as gasses escaping from the process are emitted to the atmosphere. Main aim of the thesis is to determine N2O emissions from partial nitritation/Anammox (deammonification process) in one-stage system applied in MBBR technology. Whole project was operated successfully on two pilot-scale reactors parallel, fed by the same reject water. Both reactors were filled to capacity of 200 L each, where 40% of the working volume was fulfilled by Kaldnes carriers suspended in liquid by mechanical stirrer. First reactor (R1) presented strategy of intermittent aeration with ratio (R=1/3) and stable DO concentration at amount of 1.5 mg O2/L, whereas second one (R2) operated in constant aeration with variable values of dissolved oxygen which differ in range of 1.0-2.5 mg O2/L. Every week analyses of ammonium and nitrogen forms were carried out in influent and effluent by Hach-Lange cuvettes. Results of measurements showed high NH4+-N removal efficiency of approximately 95% for R1 reactor and 86% for R2. During the process, the continuous measurement of nitrous oxide in gaseous and liquid phase was performed by Teledyne data logger and Unisense microsensor. Measurements during 4 months resulted in assessment of nitrous oxide emission tendency dependent on aeration system. The result from reactor R1 showed that 1.0-2.4% of N-load was emitted as N2O to the atmosphere, and 0.05-0.28% was released as dissolved N2O in outgoing water. Regarding reactor R2 tendency of nitrous oxide production is similar. Estimated emission of N2O in gaseous phase in reactor R2 is 1.4-2.0% of nitrogen load and 0.02-0.39% in liquid phase. All gathered results are shown in the appendix of the paper.