Fitting a new scum removal system with a new screw conveying system, Collection/ discharge System, Replacement of all Pipes, Accessories and Supporting structures, Replacement of Stationary Pipe Bridge Scum drainage system, Supporting the structure in the middle of the rotating bridge and The outer ground of the clarifier, with new foundation works at clarifier edge, Connection of the new Pressure pipe to the scum drainage pipe system. Installations of a by-pass chamber allowing part of the scum flow to be diverted in the return sludge collection chambers