Effect of Low-Density Static Magnetic Field on the Oxidation of Ammonium by Nitrosomonas europaea and by Activated 
Sludge in Municipal Wastewater  

Jasmina Filipič1,2, Barbara Kraigher2, Brigita Tepuš1, Vanja Kokol3 and Ines Mandić-Mulec1

1Ptuj Municipal Service Corporation, Puhova ulica 10, SI-2250 Ptuj, Slovenia 
2University of Ljubljana, Biotechnical Faculty, Department of Food Science and Technology, Večna
 pot 111, SI-1000 Ljubljana, Slovenia
3University of Maribor, Faculty of Mechanical Engineering, Institute for Engineering Materials and Design,
 Smetanova ulica 17, SI-2000 Maribor, Slovenia

Article history
Received March 2, 2014
Accepted February 23, 2015

Key words: 
biological wastewater treatment, static magnetic field, sequencing batch reactors, ammonia-oxidising bacteria, nitrification

Ammonium removal is a key step in biological wastewater treatment and novel approaches that improve this process are in great demand. The aim of this study is to test the hypothesis that ammonium removal from wastewater can be stimulated by static magnetic fields. This was achieved by analysis of the effects of static magnetic field (SMF) on the growth and activity of Nitrosomonas europaea, a key ammonia-oxidising bacterium, where increased growth and increased ammonia oxidation rate were detected when bacteria were exposed to SMF at 17 mT. Additionally, the effect of SMF on mixed cultures of ammonia oxidisers in activated sludge, incubated in sequencing batch bioreactors simulating wastewater treatment process, was assessed. SMFs of 30 and 50 mT, but not of 10 mT, increased ammonium oxidation rate in municipal wastewater by up to 77 % and stimulated ammonia oxidiser growth. The results demonstrate the potential for use of static magnetic fields in increasing ammonium removal rates in biological wastewater treatment plants. 


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