The aim of the study was the scientific and practical aspects of the operation of a household wastewater treatment plant which consisted of two constructed wetland beds, with vertical and horizontal wastewater flow. The study was conducted over a 12-month period from March 2022 to February 2023. During the study period, wastewater quality monitoring parameters were measured in mechanically and biologically treated wastewater. The following indicators were analyzed: BOD5, COD, TSS, TN, N-NH4+ and TP. In addition, the following parameters were examined: the amount of inflowing wastewater, precipitation, atmospheric air temperature and temperature of both constructed wetland beds at a depth of 0.6 m below the surface. The mean reduction rate after all the treatment process was at the following levels: BOD5 - 96 %, COD - 92 %, TSS - 90 %, N-NH4+ - 90 %, TN - 62 %, TP - 58 %. Nomograms that allow predicting concentrations of the tested parameters in treated effluent on the basis of mechanically treated wastewater quality and rainwater loading of both constructed wetland beds were developed. As a practical aspect, it was shown that there is no need to run the so-called “winter flow”, i.e. when the atmospheric air temperature is below 0 °C. Furthermore, it was suggested to simulate the recirculation of treated wastewater, as an addition to mechanically treated wastewater, which would result in an increase in the efficiency of pollutants disposal in the biological part of the facility.