Processes Reactions Redox potentials(Eh in Mv) Aerobic O2+4e-+4H+ 2H2O 600~400 Anaerobic     Denitrification 2NO3-+10e-+12H+ N2 +6H2O 500~200 Manganese IV reduction MnO2+2e-+4H+ Mn2++2H2O 400 ~ 200 Iron III reduction Fe(OH)3+3e-+H+  Fe2++3H2O 300~ 100 Sulphate reduction SO4- -+8e-+10H+   H2S+4H2O 0~150 Fermentation 2CH2O CO2+CH4 150~220