WASTE WATER TREATING APPARATUS

PROBLEM TO BE SOLVED: To provide a waste water treating apparatus capable of efficiently removing the phosphorus contained in inflow water and surely preventing the leakage of the phosphorus into secondarily treated water even if the phosphorus load is high. SOLUTION: The rear stage of an anaerobic vessel 16 of waste water treatment equipment adopting a biological dephosphorization method is provided with a solid-liquid separating means 21 for executing the solid-liquid separation of the activated sludge C withdrawn from the inside of the anaerobic vessel and a dephosphorizing means 22 for removing the ammonia and phosphorus in the separated water in the form of ammonium magnesium phosphate hexahydrate by adding a magnesium compound E to the separated water D of the solid-liquid separating means 21.