Effects of nitrite and ammonium on methane-dependent denitrification

For effective application of methane-dependent denitrification (MDD) in the treatment of wastewater containing NO₂ ^– or NH₄ ⁺, the effect of these inorganic nitrogen compounds on MDD activity needs to be clarified. The MDD activity of sludge acclimatized with CH₄ and O₂ was determined with mineral media of different nitrogen-compound compositions in the presence of 0.21 atm CH₄ and 0.20 atm O₂. Incubations with media containing only NO₂ ^– or two of the three inorganic nitrogen compounds (NO₃ ^–+NO₂ ^–, NO₂ ^–+NH₄ ⁺ or NH₄ ⁺+NO₃ ^–) resulted in MDD activity equal to or higher than that with media containing only NO₃ ^–. However, there was no MDD activity in media containing NO₂ ^– at 10 °C, probably because of serious inhibition of NO₂ ^– on methane oxidation. MDD occurred in media containing only NH₄ ⁺, although the total nitrogen removal efficiency was very low. These results show that NO₂ ^– and NH₄ ⁺, in the presence of NO_x ^–, do not inhibit but rather promote MDD. Consequently, NH₄ ⁺ does not need to be completely oxidized to NO₃ ^– in the nitrification reactor before MDD. However, under psychrophilic conditions, NO₂ ^– seriously inhibited MDD. Therefore, the nitrification reactor must not discharge effluent containing NO₂ ^– under psychrophilic conditions.

Authors and Affiliations

1. Laboratory of Waste Recycling, National Institute of Livestock and Grassland Science, Tsukuba Norindanchi, P.O. Box 5, Ibaraki 305–0901, Japan, , , , ,

   M. Waki,  Y. Tanaka,  T. Osada &  K. Suzuki

Electronic Publication

Reprints and permissions