Efficiency of Operation a Hybrid Constructed Wetland Located in the Polesie National Park (Poland) During the Start-Up Period

Abstract

This study assessed the operational efficiency of a hybrid constructed wetland (CW) in its first year of use. The test facility was put into operation in September 2022 and has since been utilized to treat 0.4 m 3 /d of wastewater discharged from a forester’s lodge located in the Polesie National Park in Poland. The treatment plant consists of a two-chamber primary settling tank integrated with a pumping station, and a system of two beds – a vertical flow (VF) reed bed and a horizontal flow (HF) willow bed. During the research period (October 2022 to December 2023), 14 test runs were performed during which 56 sewage samples were collected for physico-chemical and microbiological assays. The results of these tests were used to determine the pollutant removal efficiency of the CW. The composition of treated wastewater was compared against the current Polish requirements for this type of facilities. The study also included measurements of influent and effluent volumes and the amount of rainwater entering the treatment plant. It was shown that precipitation in each month of the study accounted for between 6–34% of influent volume. The volume of wastewater discharged from the treatment plant during the study period was 11% lower than the volume of incoming wastewater combined with rainwater. It was found that the CW removed an average of over 90% of total suspended solids, BOD 5 , COD, Escherichia coli bacteria and fecal enterococci from wastewater. Slightly lower removal efficiencies were achieved in the case of total nitrogen and total phosphorus (60–74%). Already during the start-up period, the composition of treated wastewater discharged from the CW met the requirements set out in the current Polish legal regulations. The present study shows that hybrid VF-HF constructed wetlands can be recommended for use in protected areas for wastewater treatment and protec - tion of water against eutrophication.