The movement and fate of phosphorous inputs from residential stormwater runoff were investigated in a 1.0 hectare hardwood wetland near Sanford, Florida. This wetland receives stormwater runoff from a large residential community through a small shallow canal and provides treatment prior to discharge to Hidden Lake. Field investigations were begun in 1984 and were divided into the following tasks: (1) assessment of the quantity of nutrients and heavy metals entering the wetland by way of stormwater runoff, (2) measurement of the attenuation (3) monitoring of the concentrations of nutrients and heavy metals in groundwaters, (4) accumulation of nutrients and heavy metals in the sediments of the wetland, (5) examination of the typical chemical associations binding nutrients and heavy metals to the sediments using sequential extraction procedures, and (6) investigation of the importance of redox potential and pH on metal-sediment stability with regard to the release of phosphorous from wetland sediments.
After entering the wetland treatment system, stormwater inputs were observed to exhibit general reductions in pH, specific conductivity, dissolved oxygen, ORP and alkalinity with increasing flow distance.
Concentrations of both dissolved orthophosphorus and total phosphorus increased during flow through the wetland system and were found to be closely correlated to decreases in pH and ORP. A stagnant control area, removed from runoff influence was found to exhibit elevated concentrations of phosphorus when compared to the flowpath area. Water quality characteristics in groundwaters beneath the flowpath were very similar to surface water characteristics, with dissolved oxygen and ORP levels decreasing with depth, whereas phosphorous concentrations increased. Groundwaters in the stagnant control are exhibited significantly elevated concentrations of phosphorous, TOC, color, and iron when compared to groundwaters in other locations.
Patterns of accumulation and deposition of sediment bound phosphorous along the wetland flowpath were investigated and found to increase substantially from the inlet canal to a distance of 50 m after which they declined slightly throughout the remainder of the wetland flowpath. Also apparent was the attenuation of sediment phosphorous concentrations with increasing sediment depth, with the majority of the phosphorous being retained in the top 10 cm.
The removal potential for dissolved orthophosphorus in wetland systems was found to be the greatest in flowthrough systems with sediment contact basted on kinetic rate experiments performed at the study site. The majority of the dissolved orthophosphorus removal, 75 percent was found to occur within the first 24 hours of contact with the wetland sediments after which only slight decreases in concentration occurred. Stagnant systems as well as systems with less sediment contact were not effective in providing attenuation of dissolved orthophophorus concentrations as well as other water quality parameters.
Harper, Harvey H.
Master of Science (M.S.)
College of Engineering
Length of Campus-only Access
Masters Thesis (Open Access)
Fries, Benjamin M., "Fate of Phosphorus from Residential Stormwater Runoff in a Southern Hardwood Wetland" (1986). Retrospective Theses and Dissertations. 4945.