Prepose the anoxic zone to enhance phosphate and nitrogen removal from wastewater with low C/N ratio

Biological nutrient removal processes tend to give phosphate release the priority in getting volatile fatty acids to assure high phosphate removal efficiency and develop denitrifying phosphate removal. In this study, the effect of giving the priority to denitrification on phosphate removal was studied on pilot and bench scale experiments. Laying the anoxic zone in front of the anaerobic one, nitrogen was removed more quickly and thoroughly, and the phosphate removal efficiency was increased by 10%. Bench scale experiments indicated that, denitrifying phosphate removal has caused nitrite accumulation and inefficient Polyhydroxyalkanoates (PHAs) consumption. More available PHAs and higher ratio of more reduced PHAs (i.e. poly-beta-hydroxyvalerate and poly-beta-hydroxy 2-methyl valerate) have helped to enhance total phosphate removal during Oxic stage.