When the ratio of DECA was decreased and replaced by increased amounts of AS the highest cumulative methane production of 947 L/m3 was observed in assay B (Fig. 3), although the COD was same in all assays except for the control (Table 6, assay E). The initial dissolved COD for assays AeD was approximately similar, however the COD removal depended upon the ratio of AS (Tables 1 and 6).