A careful appraisal of piggery wastewaters should be made mainly because of their high content of organic constituents together with the nitrogen and stringent effluent limitations involved. Specific emphasis should be given to the COD of the wastewater as it contains, aside from a biodegradable portion, a residual fraction which persists throughout the treatment process. Experimental evaluations indicated that the effluent of a laboratory-scale SBR contained significant amounts of non-biodegradable COD. Since SBR was primarily operated to achieve nitrification-denitrification, a method previously developed for the assessment of the influent soluble inert COD, S(I) was modified in a way to reflect the possible impact of the nitrification and denitrification processes. The paper also summarizes the performance of SBR with respect to its nitrogen removal potential from piggery wastewaters.