4000 mg/l of N-NH4+ and 12 mg/l of Cr+3 caused a 50% reduction in acet
iclastic methanogenic activity of an anaerobic sludge. Methanosarcina-
like and Methanothrix-like cells were differently affected by the toxi
cants. The inhibition caused by Cr+3 was reverted by its removal, by a
ddition of iron and by increasing the biomass.