Methanogens utilize ammonia as a source of nitrogen, and ammonium-rich substrates can be successfully treated in UASB reactors. Simultaneous presence of high sulfide concentrations
in a UASB may support denitrification; at high sulfide levels ammonium may even act as electron donor for N2 production. These aspects notwithstanding, accumulation of ammonium ions can alter the intra cellular pH and the activities of methane-synthesizing enzymes may be inhibited by free ammonia [