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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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Abstract
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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