The effects of two Fulvic acids( F1 and F2) on the nitrification and denitrification processes were investigated in this study.The results showed that F1 could promote the removal of ammonia nitrogen,while F2 had no obvious effect on ammonia removal and the removal efficiencies of ammonia nitrogen with F1 and F2 were 97% and 86% respectively.The use of carbon source with F1 was also higher than that with F2.The content of the intracellular polymer polyhydroxyalkanoate( PHA) was also affected by Fulvic acid,...