3.2. Sludge activity
The SMA test results (Fig. 4) of sludge taken from the
pond sediment layer exhibited a negligible level of
methane production during the first 13 h and increased
afterwards. This revealed that approximately 13 h was
required for conversion of organic matter from starch
factory wastewater to produce a sufficient amount of
organic acid (substrate for methane producing bacteria)
that is required for substantial methanogenic activity.
However instantaneous methane production was observed
in the case of sludge taken from pond bulk liquid
layer because of the presence of residual organic acids in
the liquid. The SMA test result obtained from this study
is given in Table 4 along with the other values reported in
literature (Valcke and Verstraete, 1983; James et al.,
1990; Ince et al., 1995). As can be seen from Table 4, the