Effect of electron donors on anammox coupling with nitrate reduction for removing nitrogen from nitrate and ammonium

Anammox coupling with nitrate reduction under various electron donors was studied using sludge acclimatized to have anammox and denitrification activities. Due to a deficiency in electron donors for NO3- reduction, anammox activity in an inorganic medium containing NO3- and NH4+ was lower than that in NO2- and NH4+. Anammox could use NO2- competitively against denitrifiers under a very limited NO2- concentration, and additions of swine wastewater or acetate stimulated anammox activity in an inorganic medium containing NO3- and NH4+ with no inhibition effects. However, a high concentration of swine wastewater caused an exponential increase in denitrification activity. The addition of hydrogen and iron stimulated anammox activity in an inorganic medium containing NO3- and NH4+, but iron showed an inhibitory effect on anammox in a medium containing NO2- and NH4+. Hydrogen was shown to be advantageous since it did not increase denitrification even when its addition was increased.