Nutrient Removal in Pilot-Scale Constructed Wetlands Treating Eutrophic River Water: Assessment of Plants, Intermittent Artificial Aeration and Polyhedron Hollow Polypropylene Balls

Seven experimental pilot-scale subsurface vertical-flow constructed wetlands were designed to assess the effect of plants [Typha latifolia L. (cattail)], intermittent artificial aeration and the use of polyhedron hollow polypropylene balls (PHPB) as part of the wetland substrate on nutrient removal from eutrophic Jinhe River water in Tianjin, China. During the entire running period, observations indicated that plants played a negligible role in chemical oxygen demand (COD) removal but significantly enhanced ammonia-nitrogen (NH4-N), nitrate-nitrogen (NO3-N) total nitrogen (TN), soluble reactive phosphorus (SRP) and total phosphorus (TP) removal. The introduction of intermittent artificial aeration and the presence of PHPB could both improve COD, NH4-N, TN, SRP and TP removal. Furthermore, aerated wetlands containing PHPB performed best; the following improvements were noted: 10.38 g COD/m(2) day, 1.34 g NH4-N/m(2) day, 1.04 g TN/m(2) day, 0.07 g SRP/m(2) day and 0.07 g TP/m(2) day removal, if compared to non-aerated wetlands without PHPB being presented.