Process and installation for removing nitrates from residual waters in cities

The invention relates to an anoxic­-anaerobic­-aerobic biological process for removing nitrates and phosphorus from residual waters, which uses pre­fermented primary mud hydrolysate as supplementary carbon source. According to the invention, the process consists in treating the residual water in an area of
denitrification at a retention time of 7 h in the presence of pre­fermented mechanical mud, the reaction mixture flows gravitationally in an anaerobic reaction area where there is performed the dephosphorisation at a retention time of 2 h, where from it reaches the aerobic phase where there are performed the biodegradation and nitrification at a retention time of 7 h, at a mud concentration of 3 gds/l, afterwards the mixture is subjected to decantation there resulting removing efficiency of 86% for nitrates and 75% for total phosphorus.