Water Supply Vol 2 No 1 pp 37–46 © IWA Publishing 2002
Nitrification in rapid sand filter: phosphate limitation at low temperatures
L.T.J. van der Aa*, L.J. Kors**, A.P.M. Wind***, J.A.M.H. Hofman**** and L.C. Rietveld*****
*Amsterdam Water Supply, P.O. Box 8169, 1005 AD Amsterdam, The Netherlands. Delft University of Technology, P.O. Box 5048, 2600 GA Delft, The Netherlands
**Amsterdam Water Supply, P.O. Box 8169, 1005 AD Amsterdam, The Netherlands
***Amsterdam Water Supply, P.O. Box 8169, 1005 AD Amsterdam, The Netherlands
****Amsterdam Water Supply, P.O. Box 8169, 1005 AD Amsterdam, The Netherlands
*****Delft University of Technology, P.O. Box 5048, 2600 GA Delft, The Netherlands
ABSTRACT
In winter 1995-1996 the RSF of AWS River-Lake Waterworks suffered from ammonium breakthrough. Research indicated that the nitrification was limited by stagnated growth of the nitrifying bacteria due to low phosphate concentrations at low temperatures (0-3°C). Phosphoric acid was dosed prior to the RSF (dose 35-50  g PO43- -P.l-1) to stimulate bacteria growth. Two weeks after starting the addition, ammonium removal in the RSF had recovered.
AWS is conducting research on alternatives for production capacity extension. Several alternatives involve the construction of an additional RSF prior to the reservoir. Pilot experiments on RSF prior to the reservoir show that complete nitrification in these additional RSF is possible. The phosphate concentration should amount at least 10 g PO43- -P.l-1.
A model has been developed to predict nitrification in RSF. The model confirms the results from both the River-Lake Waterworks' RSF as from the pilot RSF. The model is used for process control and scenario studies.
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