In this paper, the pollutant removal efficiency and the reliability of a vertical and horizontal flow hybrid constructed wetland (CW) planted with common reed, manna grass, and Virginia mallow were analyzed. The wastewater treatment plant, located in south-eastern Poland, treated domestic sewage at an average flow rate of 2.5 m3/d. The tests were carried out during five years of its operation (2014–2018). The following parameters were measured: biochemical oxygen demand (BOD5), chemical oxygen demand (COD), total suspended solids, total nitrogen, and total phosphorus. The results showed that more than 95% of BOD5, COD, and total phosphorus was removed in the tested CW system. The average effectiveness of removal of total suspended solids and total nitrogen exceeded 86%. A reliability analysis performed using the Weibull probability model showed that the removal reliability in the tested CW was very high for BOD5, COD, total suspended solids, and total phosphorus (100%). The probability that the total nitrogen concentration in the treated effluents would reach the limit value (30 mg/L) established for effluents discharged from a treatment plant of less than 2000 PE (population equivalent) to standing waters was 94%. The values of all the pollution indicators in wastewater discharged to the receiver were significantly lower than the limit values required in Poland. The investigated hybrid CW system with common reed, manna grass, and Virginia mallow guaranteed stable low values of BOD5, COD, total suspended solids, and total phosphorus in the treated wastewater, which meant it was highly likely to be positively evaluated in case of an inspection.

The paper presents the results of research on the effects of removing pollution from domestic wastewater in two beds of constructed wetland systems with vertical flow. Bed I was planted with common reed (Phragmites australis Cav. Trin. Ex Steud.), whereas bed II with Glyceria maxima (Glyceria aquatica L.). The surface of each of the beds amounted to 30 m 2 , and the hydraulic load of each of them amounted to 0.033 m 3 •m-2 •d-1. The study showed very good results in the removal of most of the analyzed indicators of contamination, which were similar in both analyzed beds. They were, respectively: 91 and 93%-for total suspended solids, 96 and 98%-for BOD 5 , 96 and 94%-for COD Cr , 88 and 86%-for ammonia nitrogen and 87 and 88%-for total phosphorus. Much smaller effects were reported with regard to total nitrogen removal-55% in bed I with common reed and 54% in bed II with Glyceria maxima. The tested beds also eliminated the number of coliform bacteria and faecal coliform bacteria quite effectively. Average effects of the removal of coliform bacteria in bed I and II were 99.74%, in the case of faecal coliform 98.06% and 97.94% respectively. Values of basic indicators of contamination (total suspended solids, BOD 5 and COD Cr) in the wastewater discharged from the analyzed beds met the requirements of the Regulation of the Minister of the Environment of 2014. The test results obtained in the first year of operation of the analyzed beds show that neither of the applied plants significantly improves the results of contaminant removal.