Effect of the clay mineral zeolite on ammonia inhibition of anaerobic thermophilic reactors treating cattle manure

Addition of zeolite counteracted to some extent the inhibitory effect of ammonia during thermophilic anaerobic digestion of cattle manure. In continuously-fed reactor experiments, addition of zeolite delayed the onset of the inhibition and aided process recovery after initial inhibition. The effect was observed mainly when the ammonia concentration was increased gradually, indicating that the major effect of zeolite was not through a direct antagonistic effect towards ammonia but through an increased process resistance to toxic compounds. In batch experiments zeolite had a similar stimulatory effect leading to a decreased lag phase and increased methane production rate in ammonia inhibited reactors.