Graduation thesis discusses faecal wastewater drainage and treatment in villages Jezero, Lukovek and Dolenja Dobrava in municipality Trebnje. In case of a high population density the most suitable is the construction of a public sewerage system with a common small treatment plant (further STP). Outside of agglomeration area, individual STPs or private common systems are used. At the beginning of the graduation thesis the legislation regarding the STPs is presented. Further on, a sewerage system with the corresponding objects is described. Wastewater can be treated in STP in various ways with the usage of procedures described in the thesis. STPs based on mechanic and biological treatment and STPs with fixed-film or attached growth systems and activated sludge are also described. At the end of the thesis a cost comparison of three possible solutions is presented; one common STP, each village with its own STP or individual STPs. As it is shown, the individual systems are the cheapest, except in the agglomeration areas where sewerage systems with STPs are mandatory.