Removal and Recovery of Phosphorus Using Modified Geotextiles

Marketing Paragraph: Statement of Purpose: This poster presentation will outline the research conducted determining the possibility of removing and recovering phosphorus from stormwater runoff through the implementation of modified geotextile in green infrastructure and low impact development stormwater control measures (SCMs). Phosphorus is an essential nutrient in agriculture, however, when found in excess in natural waterways it can negatively impact aquatic environments through eutrophication or harmful algal blooms. This project investigated implementation of a geotextile impregnated with iron in three different SCMs: infiltration trenches, green roofs, and biofiltration cells. A flow dosed with excess phosphorus was introduced to lab scale systems of each SCM and outflow concentrations were measured to determine the removal capacity of the implemented geotextile. Erosion and sedimentation control materials such as wheat straw, pine wood chips, coconut coir, GeoHay, and aspen excelsior were also dosed with iron to determine if a more sustainable alternative to plastic geotextiles could be implemented. The results from this study will provide insight into implementing modified geotextile as a simple method of improving nutrient removal in stormwater SCMs and offer a potential alternative source of phosphorus.

Full Abstract: Complete Proposal for Your Session: Nutrients, such as nitrogen and phosphorus are commonly found in stormwater runoff originating from both urban and rural areas. In excess, phosphorus can negatively impact aquatic environments through eutrophication, which leads to harmful algal blooms. Current stormwater control measures (SCMs) target the increased quantity of stormwater runoff from the growth of impervious areas by detaining/retaining runoff or promoting infiltration. However, these practices’ ability to remove pollutants such as nutrients from runoff can vary and do not always prevent excess nitrogen and phosphorus from entering natural waterways. Geotextiles are commonly used within SCMs to provide separation and reduce the transport of suspended sediment. The objective of this research project is to evaluate enhanced geotextiles that are designed to capture phosphorus and allow for its recovery for reuse. Iron, which is known to be effective at adsorbing phosphorus, was dosed into nonwoven geotextiles. Three SCMs were chosen for evaluation: infiltration trenches, green roofs, and biofiltration cells. A lab scale infiltration trench designed following guidelines from the Georgia Department of Transportation Drainage Manual, as well as green roof modules, were constructed to test with and without the modified geotextile. Simulated runoff was introduced containing 0.4 mg/L of phosphorus, the average concentration found in runoff according to the National Stormwater Quality Database (NSQD). This simulated runoff was used to determine the removal capacity of the geotextile based on the concentration of phosphorus remaining in the outflow. Flow was also introduced without phosphorus to determine the baseline removal or leaching of nutrients from each SCM. Following testing the modified geotextile was removed from each practice and treated to determine the possible recovery of phosphorus that was adsorbed onto the material. For the biofiltration tests various media were evaluated in columns in combination with geotextile to determine an effective combination for infiltration and nutrient removal. The media tested includes iron filings, glass beads, washed sand, topsoil, wood chips, and biochar. Since geotextiles primarily consist of plastics, other possible materials including wheat straw, pine wood chips, coconut coir, recycled carpet, and aspen excelsior are planned to be tested for their ability to be dosed with iron for possible sustainable and environmentally friendly alternatives. The results from testing for this project, planned to take place in December and January, will offer insight into potential simple modifications to typical SCMs that could help improve water quality in natural waterways and provide a possible new source of phosphorus, a heavily utilized resource in agriculture.