The invention discloses a double-mode
nitrogen-
phosphorus treating
system for
sewage and a method and belongs to the field of
sewage treatment. The method is characterized in that
sewage passes through a reaction tank and a secondary
settling tank in sequence to realize enhanced
denitrification and dephosphorization; when the overflowing
sludge operation mode is adopted, the total-
phosphorus removing ratio is more than 90% or the
effluent TP is less than 1mg / L, deltaBOD / deltaTN is less than 4, the maximum flow flux of all areas in the
system is not more than 2.2Q, and the
phosphorus containingratio of returned
sludge is more than 4%. The double-mode
nitrogen-phosphorus treating
system disclosed by the invention has the advantages that high-efficiency
denitrification and dephosphorizationis achieved, the operation is energy-saving and low-carbon, the load is high, the occupied area is small, the denitrifying dephosphorization is realized, the TN removing ratio is not limited by the
return ratio, the control is simple and the operation and the management are convenient and the like. The double-mode
nitrogen-phosphorus treating system consists of the reaction tank, the secondary
settling tank and a connecting pipeline; the reaction tank comprises a pre-hypoxic area, an anaerobic area, a middle
settling area, an aerobic nitrating area, a denitrifying area, an aerobic decarbonizing area and a water discharging area in sequence from the water feeding end to the water discharging end; connecting pipelines include a main water feeding
pipe, a
branch water feeding
pipe, a water discharging
pipe, a
sludge overflowing pipe, a sludge returning pipe, a remaining-sludge discharging pipe and the like; the technological process is simple.