Fly-ash, a waste product from coal combustion, has a high phosphorus sorption rate and could be an interesting media to used in bioretention filter to improve stormwater quality. However, fly-ash decreases the hydraulic conductivity. For this reason, fly-ash was transformed in pellets to freedom from this constraint by Dr. Glenn Brown from Oklahoma State University.
The objective of this study was to test the fly-ash pellets designs on phosphorous removal and to design underdrain pipes filled with this medium for bioretention filters.
Fly-ash pellets were created in two sizes 0.08-0.25 and 0.25-0.5 inch. For both pellets sizes, column leaching experiments were conducted at constant flow (6 ml/min) using a synthetic solution of phosphorous at a concentration of 1mg/l.
Data collected were fit with a model for tracer transport using the software Chem Transport. The mobile-immobile mechanism was modeled and the retardation factor was estimated from the model.
Experimental set-up