The presence of a short circuit flow in a denitrifying activated sludge tank was identified and modelled. Tracer tests with pulse addition of lithium salt were used to investigate the hydraulics of the tank. The lithium concentration in the effluent was detected and residence time distribution (RTD) curves were generated. Hydraulic models based on completely stirred tank reactors (CSTRs) in series were generated from the RTD curves and the models were compared. The short circuit problem was successfully described using the Martin model, where the inflow is divided into two strands. Each strand was modelled as a number of CSTRs in series. At a normal flow the results of the model show that the tank has 12.8% dead volume, 85.8% main volume and 1.3% short circuiting volume. The inflow was divided into 91.9% entering the main volume and 8.1% entering the short circuiting volume. The mean velocity of the short circuiting stream was estimated to 0.4m/s. At maximum flow the short circuiting stream was even larger and handled 24.3% of the flow. The short circuiting stream was identified in the upper part of the tank due to the position of the inlet and the outlet. The configuration of a tank including the use of baffles, the geometry of the inlet and mixer configuration should be considered carefully if short circuiting is to be avoided.
Skip Nav Destination
Article navigation
Research Article|
November 01 2005
Short circuiting in a denitrifying activated sludge tank
R. Kjellstrand;
*Chemical Engineering and Environmental Science, Chalmers University of Technology, SE-412 96 Göteborg, Sweden, (E-mail: robert.kjellstrand@hb.se; claes@cre.chalmers.se; mohammad@cre.chalmers.se)
**School of Engineering, University College of Borås, SE-501 90 Borås, Sweden
E-mail: robert.kjellstrand@hb.se
Search for other works by this author on:
A. Mattsson;
A. Mattsson
***Gryaab, Karl IX:s väg, SE-418 34 Göteborg, Sweden, (E-mail: ann.mattsson@gryaab.se)
Search for other works by this author on:
C. Niklasson;
C. Niklasson
*Chemical Engineering and Environmental Science, Chalmers University of Technology, SE-412 96 Göteborg, Sweden, (E-mail: robert.kjellstrand@hb.se; claes@cre.chalmers.se; mohammad@cre.chalmers.se)
Search for other works by this author on:
M.J. Taherzadeh
M.J. Taherzadeh
*Chemical Engineering and Environmental Science, Chalmers University of Technology, SE-412 96 Göteborg, Sweden, (E-mail: robert.kjellstrand@hb.se; claes@cre.chalmers.se; mohammad@cre.chalmers.se)
Search for other works by this author on:
Water Sci Technol (2005) 52 (10-11): 79–87.
Citation
R. Kjellstrand, A. Mattsson, C. Niklasson, M.J. Taherzadeh; Short circuiting in a denitrifying activated sludge tank. Water Sci Technol 1 November 2005; 52 (10-11): 79–87. doi: https://doi.org/10.2166/wst.2005.0681
Download citation file:
Sign in
Don't already have an account? Register
Client Account
You could not be signed in. Please check your email address / username and password and try again.
Could not validate captcha. Please try again.
Impact Factor 2.430
CiteScore 3.4 • Q2
13 days submission to first
decision
1,439,880 downloads in 2021