Nutrient Reduction in Stormwater Pond Discharge Using a Chamber Upflow Filter and Skimmer (CUFS)

Stormwater runoff is a known pollutant source capable of causing surface water degradation, especially in highly populated areas such as Central Florida. Wet detention ponds manage this stormwater, but most of the ponds do not remove enough nutrients, specifically nitrogen and phosphorus, to meet total maximum daily load regulations. This paper presents the use of a chamber upflow filter and skimmer (CUFS) filled with a specific green sorption medium as process modification of stormwater retention ponds, which can increase the removal of nitrogen and phosphorus in the stormwater runoff. Green sorption medium consists of recycled and natural materials that provide a favorable environment for pollutant removal. Water enters the system through the skimmer, which floats on the surface of the detention pond. It travels from the skimmer to the bottom of the chamber where heavier particles settle out before entering the upflow filter. The upflow filter contains 61 cm (24 in.) of green sorption medium providing physicochemical and microbiological processes to remove nitrogen and phosphorus under anoxic/anaerobic conditions. After this treatment, water flows up through the filter and out of the system and eventually travels to Lake Jesup, a eutrophic lake in Central Florida. A total of 28 storm events and seven baseflows were sampled from the site in Seminole County, and ten storm events were sampled from a pilot study of CUFS for statistical analysis and performance evaluation. Significant reductions by the CUFS were confirmed in terms of turbidity, orthophosphorus, total phosphorus, and total suspended solids when the mean values were compared at a 95% confidence level. Reductions also occurred for total nitrogen (TN), but could not be proved by the mean comparison in the field test, whereas the pilot-scale application of the CUFS proved effective for reducing TN at a 95% confidence level. Hydraulic retention time should be increased so as to improve the design for TN removal in future applications.