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ISSN 2029-7092 online
ISBN 978-609-457-690-4 CD
ISBN 978-609-457-640-9
 Water Engineering

Pekka Stén , John Dahlbacka , Tom Lillhonga , Steven Ulbricht , Sonja Heikkilä , Juha Nieminen

Transient responses of a laboratory-scale activated sludge plant to momentary high sludge loads

Conference Information: 9th International Conference on Environmental Engineering, MAY 22-24, 2014 Vilnius, LITHUANIA
Source: ICEE-2014 - International Conference on Environmental Engineering
Book Series: International Conference on Environmental Engineering (ICEE) Selected papers
ISSN: ISSN 2029-7092 online
ISBN: 978-609-457-640-9 / 978-609-457-690-4 CD
Year: 2014
Publisher: Vilnius Gediminas Technical University Press Technika

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The performance of a laboratory-scale activated sludge plant (capacity approx. 1 dm3 h–1) during various conditions was studied and modeled. The apparatus consists of a primary clarifier, an anoxic selector, an aeration basin and a secondary clarifier. The fully automatized apparatus utilizes the preanoxic configuration, in which nitrate produced in the aerobic zone is recycled back to the anoxic selector which is situated between the primary clarifier and the aeration basin. Under steady-state conditions, using synthetic waste water as the influent, the COD reduction is over 95%, and the nitrogen reduction over 85%. Several spiking experiments at various operational conditions were carried out. In these experiments, in addition to the continuous influent flow, a known volume of concentrated synthetic wastewater was added directly to the aeration basin. The response of the plant was monitored by measuring the COD, as well as the NH4 + and NO3 – concentrations of the effluent. Vibrational spectroscopic methods were also employed. The effluent was monitored with NIR and the N2O emission with FTIR. After introducing the spike, COD of the effluent increases from a value of approx. 30 mg dm–3 (COD of the influent is approx. 300 mg dm–3 ) to 200 mg dm–3 in 2–3 hours and comes down close to the initial value in an additional 5 hours. The behavior of NH4 + concentration in the effluent resembles that of COD, however with a delay of a few hours. The pH in the aeration basin is kept almost constant by PLC-controlled addition of limewater. After introducing the spike, the consumption of limewater goes down during 2–3 hours recovering to the initial values in 12 hours. A model based on mass transport and Monod kinetics was also used to interpret the results and to gain additional information about the process.

Keywords:wastewater treatment; activated sludge plant; laboratory-scale; NIR spectrometry; N2O emission.

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