Anaerobic wastewater treatment technology has become one of the most popular technologies due to its economic and environmental benefits. Therefore, a reliable method to study the specific methanogenic activity (SMA) of anaerobic sludge is presented using SMA test. This test helps to determine suitable organic loading rate (OLR) to the anaerobic process. Meanwhile, SMA act as a benchmark to the anaerobic system performance where a slight change in SMA stipulate the accumulation of inhibitory substances from influent wastewater. One of the possible substances that inhibit the anaerobic digestion process is the presence of excessive light metal ions such as sodium (Na+) from the wastewater. The objective of this research was to investigate the specific methanogenic activity of anaerobic sludge in anaerobic filter and anaerobic digester as well as to compare and analyze anaerobic methanogenic bacteria under the effect of potentially inhibitory compound in both anaerobic digester and anaerobic filter. Two sources of inoculums (one from the anaerobic digester and one from the anaerobic filter) were adapted with sodium with varied range of concentrations which was 0 to 5 g Na + /l, before conducting SMA test by means of pressure differences. For the anaerobic digester, the SMA varied from 0.25 to 0.31 g COD/g VS.day meanwhile for the anaerobic filter, the SMA varied from 0.40 to 0.51 g COD/g VS.day. The result obtained confirmed that sludge from POME have better tolerance towards sodium than influents from petrochemical wastewater.