Technological Reliability and Efficiency of Wastewater Treatment in Two Hybrid Constructed Wetlands in the Roztocze National Park (Poland)

The paper presents the results of a 3-year study on the technological reliability and the efficiency of typical domestic wastewater treatment in two hybrid constructed wetland systems (CWs) located in the area of the Roztocze National Park (Poland). The studied objects consist of an initial settling tank and a system of two beds of the vertical flow (VF) and horizontal flow (HF) (VF&ndash
HF) type with reed and willow. The wastewater flow rate in the constructed wetlands systems (CWs) was 0.4 and 1.0 m3/d, respectively. During the study period (2017&ndash
2019) 20 series of analyses were performed and 60 wastewater samples were collected. Based on the obtained results the effects of pollutant removal and the technological reliability were determined, which were specified with the Weibull method. The average efficiency of biochemical oxygen demand (BOD5) and chemical oxygen demand (COD) removal was 96&ndash
99%. Slightly lower effects were obtained in the case of total phosphorus (TP) removal (90&ndash
94%), as well as for total suspended solids (TSS) (80&ndash
87%) and total nitrogen (TN) (73&ndash
86%) removal. The analysed CWs were characterised by 100% technological reliability for BOD5 and COD, as well as a good reliability for TSS and TP (87&ndash
100%) but slightly lower for TN removal (35&ndash
89%). Hybrid CWs of VF&ndash
HF type should be recommended to use in protected areas for wastewater treatment and water resources quality protection.