Optimization of the Nitrogen Removal at Käppala Wastewater Treatment Plant

Author: Sundin, Anna Maria

Source: Water Practice, Volume 1, Number 5, November 2007 , pp. 1-13(13)

Publisher: Water Environment Federation

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Kappala association operates Kappala WWTP, a wastewater treatment plant designed for 220 000 m3/day. The plant comprises of mechanical, biological, chemical treatment and a final filtration step. During 2002-2003 the discharge limit of total nitrogen of 10 mg/l in the effluent was nearly exceeded, and measures were taken to improve the nitrogen removal. An uneven internal loading of supernatant from the dewatering was found to be the main cause of the inefficient nitrogen removal. A control strategy using online redox measurements in the end of the anoxic zone to control the nitrate recirculation has been evaluated, looking at the nitrogen removal efficiency and the energy consumption. The results of the project led to an increase of the degree of N-removal from 75 to 81%, corresponding to 8.7 mg/l as a yearly average in the effluent tot-N. During 2005 the energy consumption at Käppala WWTP was 27.8 GWh, corresponding to 24% of the operating cost of the plant. The results of an energy survey of the plant are also presented.
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