Enhanced anammox consortium activity for nitrogen removal: impacts of static magnetic field.

Anaerobic ammonium oxidation (anammox) process has been becoming a promising technology for the removal of nitrogenous contaminants from wastewater. In short-term batch tests, we observed the anaerobic ammonium oxidizing activity of anammox consortium increased as the magnetic field varied in the range of 16.8-95.0mT. A maximum 50% increase was obtained at the value of 75.0mT. In order to study long-term effect of magnetic field on anammox consortium, an anammox reactor with magnetic field of 60.0mT was operated in laboratory-scale. The results demonstrated that a significant 30% increase in maximum nitrogen removal rate and an approximate 1/4 saving in cultivation time were achieved by using the magnetic system. Microbiological composition analysis showed that bacterial diversity in the reactor decreased under magnetic-exposed condition. Nevertheless, some strains belonging to Planctomycetales were highly enriched. These findings indicated that the magnetic field was useful and reliable for fast start-up of anammox process since it was proved as a simple and convenient approach to enhance anaerobic ammonium oxidizing activity.