Abstract: A method for operating a wastewater treatment plant for treating effluent, in particular for recovering phosphorus from the effluent to be treated and for respecting a phosphorus discharge limit in the effluent. The method includes the steps of carrying out an enhanced biological phosphorus removal process on at least a part of the effluent to be treated in a water line of the plant, deriving a sludge from the effluent that is being treated in the water line of the plant, subjecting the derived sludge to a step of acidification giving an acidified sludge, and carrying out a step of a first recovery of a phosphorus product in a liquid phase of the acidified sludge or directly in the acidified sludge giving a re-usable product and a phosphorus depleted acidified sludge.