Given the growing demand for drinking water globally, the actual problem is of protecting surface and underground water bodies when discharge, i.e. returning to nature used contaminated water in the form of wastewater. Nevertheless, today there are numerous wastewater treatment procedures that allow the preservation of water resources, directed in the first place at protecting drinking water, as well as other water bodies. The topic issue of this paper is creating a conceptual solution of WWTP Supetarska Draga. The data needed for the calculation are taken from the "Feasibility Study of Public Sewage System in the Area of Agglomeration Rab, Supetarska Draga and Lopar". The initial part of the paper analysed all the data to be collected to determine the capacity of the WWTP and the required degree of wastewater treatment. Based on defined inputs dana (hydraulic and biological load), the technological calculation of the WWTP facility was carried out. Then the procedure is described, i.e. the way wastewater is treated by passing through WWTP objects. In the final part of the work, an approximative bill of quantities was created on the basis of which the indicative price necessary for the construction and commissioning of the WWTP was obtained, and drafts of the corresponding facilities were also drawn up.