Device and method for strengthening anaerobic fermentation of excess sludge and backflow of fermentation liquor to strengthen nitrogen and phosphorus removal of sewage

The invention discloses a method and a device for strengthening anaerobic fermentation of excess sludge and backflow of fermentation liquor to strengthen nitrogen and phosphorus removal of sewage. The method comprises the following steps: a pretreatment stage: adding an alkali solution and a complexing agent into the excess sludge obtained in a sewage treatment stage, and pre-stirring and mixing; an anaerobic fermentation stage; a nitrogen/phosphorus separation and recovery stage; and a fermentation liquid recycling stage. The device comprises a pretreatment system, an anaerobic fermentation system, a nitrogen/phosphorus separation and recovery system and a fermentation liquor backflow system. The method has the advantages that the acid production effect of the anaerobic sludge is improved, and the main component in the produced VFA is acetic acid which is easily utilized by water treatment microorganisms, so that the release of nitrogen and phosphorus in sludge cells is enhanced; recycling of a carbon source