3.3. Effect of COD reduction on cumulative gas production
The chemical oxygen demand (COD) of the slurry was considerably reduced by the anaerobic digestion process. The reduction of the COD implies the reduction of the pollutant load from any substrate during the treatment process. The COD reduction and cumulative gas production for R2 is shown in Fig. 5. For reactors R1, R2, R3 and R4, the COD reduction was 46.1, 50.76, 48.23 and 45.12%, respectively. The maximum COD reduction was achieved in the R2 reactor in which the maximum amount of gas was produced. The COD reduction was comparable with the reference value given by Rahman and Muyeed [3].