The project concerns the construction of the internal sewage networks of the agglomerations of Nigrita and Terpni of the Municipality of Visaltia, Serres, the collection through these sewage systems of the agglomeration of Terpni at the required pumping station and the sewage systems of the agglomeration of Nigrita at the limit of the agglomeration and their transfer for treatment to the existing waste water treatment plant, the modernisation and extension of which is foreseen in order to harmonize with the requirements of Directive 91271EEC on urban waste water collection and treatment infrastructures in agglomerations C with a population of 200015000 inhabitants.