ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Effect of influent nitrogen concentration on feasibility of short-cut nitrification during wastewater treatment in activated sludge systems

Pavel Svehla, Josef Radechovsky, Helena Hrncirova, Lukas Pacek, and Jan Bartacek

Department of Agro-Environmental Chemistry and Plant Nutrition, Czech University of Life Sciences in Prague, Kamycka 129, Prague 6 165 21, Czech Republic

E-mail: hrncirovah@af.czu.cz

Abstract: The inhibitory effect of free ammonia and free nitrous acid on nitrite-oxidising bacteria (NOB) was studied in a laboratory-scale sequencing batch reactor with a suspended microbial culture. The reactor was operated at 15°C, with a dissolved oxygen concentration in excess of 5 mg L⁻¹ and a nitrogen-loading rate of 0.2 kg m⁻³ d⁻¹. Diluted reject water with varying total ammonia nitrogen (TAN) concentrations was used as influent. N-NO⁻₂ represented more than 90 % of all of the oxidised nitrogen, with influent TAN concentrations of 600 mg L⁻¹, 300 mg L⁻¹ and 150 mg L⁻¹, respectively. With a TAN concentration of 75 mg L⁻¹, a gradual increase in N-NO⁻₃ concentration was detected, indicating the threshold value enabling short-cut nitrification (SN) to be between 150 mg L⁻¹ and 75 mg L⁻¹ under the pertaining conditions. Next, the influent concentration of TAN was gradually increased from 75 mg L⁻¹ to 1000 mg L⁻¹ but the nitrite accumulation was not restored. This indicates that once NOB are established in the suspended microbial culture, even high TAN concentrations are not sufficient for NOB inhibition.

Keywords: activated sludge system – free ammonia – free nitrous acid – input nitrogen concentration – short-cut nitrification – nitrite-oxidising bacteria

Full paper is available at www.springerlink.com.

DOI: 10.1515/chempap-2015-0095

Chemical Papers 69 (7) 921–929 (2015)