Nitrogen, phosphorous, and organic carbon removal in simulated wetland treatment systems

Effects of vegetation, wastewater drawdown, hydraulic retention time (HRT), and media depth on removal of nitrogen, phosphorous, and organic carbon in microcosms were investigated. Synthetic wastewater was added daily to 28 m icrocosms, and effluent was sampled every 12 days for 132 days. Effluent wa s analyzed for ammonium (NH4+-N), nitrate (NO3--N), orthophosphate (PO4(3-) -P), and total organic carbon (TOC). Average percent removal of NH4+-N was significantly greater in microcosms containing plants (67%) than in those w ithout plants (29%). Percent removal Of PO43--P was also significantly grea ter in microcosms with plants (42%) than in microcosms without plants (20%) , but no significant difference was found for TOC removal between microcosm s with plants (67%) and those without plants (74%). Average removal was sig nificantly lower in microcosms with wastewater drawdown than in those witho ut wastewater fluctuation for both NH4+-N (51% versus 83%) and PO4 (3-)-p ( 14% versus 71%). Percent NH4+-N removal was significantly greater in microc osms with a 6-day retention time (80%) than in those with a 2-day retention (53%), and PO4 (3-)-P removal was also significantly greater with a 6-day retention time (55%) than a 2-day retention (29%). No differences were seen in TOC removal due to any of the treatments but HRT, where removal was gre ater microcosms with a 2-day HRT (76%) than in those with a 6-day HRT (60%) . Media depth did not have a significant effect on nutrient removal. Result s of this study demonstrate that required design parameters are different d epending on the nutrient being removed in systems simulated by these microc osms.