The purpose of this study was to improve the removal nutrient removal efficiency at low COD/TN ratio municipal wastewater. The applicability of raw food fermentation supernatant(FFS) as external carbon source in low organic strength municipal wastewater in Korea. A laboratory scale experiments were conducted to compare performance characteristics of AOAS(Anoxic-Oxic-Anoxic-Stripper) at various external carbon sources. Three external carbon sources which were methanol, synthetic food fermenter supernatant and raw food fermenter supernatant(FFS2) derived from the laboratory acid fermenter were added to anoxic zone for the improvement of nutrients removal efficiencies. Food fermenter supernatants were good external carbon source for denitrification similar to methanol.