Conflicting information exists about the tolerance of methanogens to ammonia. Hydrogenotrophic methanogens were reported to be more tolerant to free ammonia than aceticlastic methanogens under thermophilic conditions ( Angelidaki and Ahring 1993; Sasaki et al.2011a).Supporting materials prevent ammonia inhibition and acetate accumulation by proliferating aceticlastic methanogens in the inner region,although hydrogentrophic methanogens can grow Evan in suspended fractions at a free ammonia level of 0.29 gN/l ( Sasaki et al.2011a). However, wiegant and Zeeman (1986) observed that hydrogentrophic methanogenc were more sensitive to ammonia than aceticlastic methanogens. Research evidence also shows that syntrophic decomposition by acetate - oxidizing bacteria and hydrogentrophic methanogens dominate in mesophilic conditions under high ammonia levels (Schnurer and Nordberg 2008).