Within the framework of the achievement of the objective of the Strategic Plan of the Ministry of Agriculture, Rural Development and the Environment concerning quality assurance and the protection of water resources and the water environment in the field of liquid waste, the full implementation of the Directive 91/271EEC on the treatment of urban waste water, is a priority. The construction of sewage systems for the management of urban waste water within the framework of the Directive contributes in dealing with sewage problems arising due to the overflow of sewers, which cause pollution and contamination of the subsoil and underground water, due to the infiltration of waste water into the subsoil. In addition, important benefits arise from the operation of the central sewage systems, such as the production of recycled water and sludge which may be used as soil improvers.