Performance of pilot-scale vertical flow constructed wetlands treating simulated municipal wastewater: effect of various design parameters

Ten pilot-scale, cylindrical, vertical flow constructed wetland units, of diameter 0.82 m and height 1.5 m, were designed, constructed, and operated treating a simulated municipal wastewater in parallel experiments. The operation scheme was 2 days feeding and 6 days resting. The 10 wetland units had various porous media materials (i.e., carbonate material, material from river bed, zeolite, and bauxite), two vegetation types (i.e., common reeds and cattails), and three total thicknesses of the porous media (i.e., 50, 80, and 90 cm). Water quality samples were collected at the inlet and the outlet of each unit, and were analyzed in the laboratory for BOD5, COD, TKN, ammonia nitrogen, nitrate, nitrite, TP, and ortho-phosphate. This article presents the results obtained after operation of these systems for one full year. Organic matter removal proved to be very good in all 10 units, since it reached on the average 71.1% and 66.9% for BOD5 and COD, respectively. Nitrogen removal was also satisfactory (47.1% for TKN and 42.2% for NH4 +--N). TP and ortho-phosphate retention rates reached about 36.9% and 37.9%, respectively.