Nitrogen transformation in horizontal and vertical flow constructed wetlands applied for dairy cattle wastewater treatment in southern Brazil

The aim of this study was to evaluate the nitrogen transformations in horizontal and vertical flow constructed wetlands (HFCW and VFCW), working in parallel and applied for dairy cattle wastewater treatment. Both HFCW (26.50 m2 of surface area) and VFCW (14.30 m2 of surface area) were filled up with sand (d10 of 0.3 mm and uniformity coefficient of 2.50) as bed media and planted with Typha domingensis Pers. HFCW and VFCW worked with an influent flow rate of 3.98 m3 week−1 and 4.50 m3 week−1, respectively. Applying an average loading rate of 151.4 gCOD m−2 week−1, 10.3 gTKN m−2 week−1 and 8.2 gNH4+-N m−2 week−1 in HFCW, it was possible to achieve 59% of TN and 58% of NH4+-N removals. In VFCW an average loading rate of 317.2 gCOD m−2 week−1, 21.6 gTKN m−2 week1 and 13.7 gNH4+-N m−2 week−1 were applied and was obtained 23% of TN and 80% NH4+-N removals, where 73% of ammonia removal was due to nitrification process. The macrophytes removed 5.1% and 0.88% of influent N loading rate in HFCW and VFCW, respectively.