The methanogenic biogranules’ activity reduces by 50% for each gram of biomass that comes into contact with 1.6 mg Cd, 1.0 mg Cr, 0.9 mg Cu, 2.3 mg Ni, 40 mg Pb or 1.6 mg Zn. Based on the specific metal loadings, the relative toxicity-resistances are conventional >> methanogenic > acidogenic biogranules to all the tested metals.