Total nitrogen removal in an aerobic/anoxic membrane biofilm reactor system

The hydrogen-based membrane biofilm reactor (MBfR) is effective for reducing nitrate-N to N₂ gas, but most wastewaters contain ammonium-N. Here, we document that an aerobic/anoxic MBfR system achieves nearly total N removal (<2 mgN/L) when the influent N is ammonium. The aerobic/anoxic MBfR couples two MBfR modules. The aerobic MBfR is supplied O₂ and brings about nitrification of ammonium to nitrate or nitrite. The anoxic MBfR is supplied H₂ and brings about denitrification to N₂ gas. Total N removal is most strongly influenced by the O₂ pressure in the aerobic module: too low O₂ caused poor nitrification, while too high O₂ inhibited denitrification in the anoxic module. Hydrogen pressure does not strongly affect total-N removal, and the best total-N removal occurs when the H₂ and O₂ pressures are similar.