Abstract: Taking food waste anaerobic fermentation broth as a carbon source had been a favorable way to improve the denitrification effect of sewage treatment plants. Therefore， it was worth studying to improve the small molecular organic acids in the fermentation products that were easily utilized by denitrifying bacteria. Combined with the restriction factors of anaerobic fermentation， the effects of pH on the composition and denitrification performance of volatile organic acids and organic acids such as lactic acid in food waste fermentation broth were studied. The results showed that pH adjustment was conducive to the hydrolysis and acidification process， there was no significant difference of organic acids concentration at different pH. And when the pH was adjusted to five， though the soluble carbon sources in the fermentation products was low， but the concentration of lactic acid and organic acid was highest in the soluble fermentation products， reached 67.77% and 93.04%， respectively. The denitrification performance of using fermentation broth with different pH as carbon sources was tested. The result showed that pH adjustment was also beneficial to improve its denitrification performance， the higher of lactic acid content in the fermentation broth， the stronger the denitrification capacity of the fermentation broth was， the faster the denitrification rate was， and it was less likely to lead to the accumulation of [NO-2]-N accumulation. In summary， when the pH was adjusted to 5， the concentration of the soluble carbon source would be limited by hydrolysis， but its composition was more suitable as a carbon source for denitrification.

Key words: food waste, pH , VFAs, lactate, denitrification