| Summary: | Can iron enhanced sand filtration capture total phosphorus and soluble phosphorus (phosphate) from agricultural tile drainage? A monitoring study measured the total phosphorus and phosphate capture performance of an iron enhanced sand filter (IESF) installed to treat agricultural tile drainage in Wright County, MT, USA. Overall, for natural rainfall-induced tile drainage events monitored between June and November 2015 and again in 2016, the IESF captured 66% ± 7% (α = 0.05, n = 21) of the influent total phosphorus mass and 64% ± 8% (α = 0.05, n = 31) of the influent phosphate mass. Removal of total phosphorus and phosphate was approximately uniform for large and small rainfall-induced tile drainage events and varied from 42% to 95% for total phosphorus and 9% to 87% for phosphate. The IESF treated 290 m of treated depth since installation, and results indicate that performance is similar or better than constructed wetlands or other IESFs, though not as good as laboratory experiments of IESFs. Routine and non-routine maintenance was performed throughout the project to ensure adequate phosphorus capture and flow rate through the IESF.
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