Removal Efficacy of Nursery Tail-Water Nitrogen and Phosphorus using Ferric aided Zeolite Sieves with or without Bioreactors

Nitrogen (N) and Phosphorus (P) runoff from containerized nurseries contributes to eutrophication in impaired US waterways. Best management practices (BMPs) have been in development for much of the agricultural sector to help combat this problem. Unfortunately, the only approved BMP for the containerized nursery industry is >95% runoff containment of >19 mm rainfall through the use of retention ponds. This study aimed to evaluate the effectiveness of ferric aided zeolite sieves with or without bioreactors as a potential BMP for N and P removal of containerized nursery production tail-water. A continuous flow of nursery tail-water was pumped through nine treatment trains for twelve weeks along with a 4.5 mg·L-1 injection of iron using ferric sulfate. Aqueous nutrient samples were collected weekly and electrochemical properties were measured in situ. The ferric aided zeolite sieve without woodchip bioreactor achieved an average P removal efficiency of 29.8% with no effect on N removal. Woodchip bioreactors preceding zeolite had a net increase of P (-3.3%), but was effective for N removal with an average rate of 14.3%. Higher N removal was expected by the denitrification bioreactors; however, retention times, presumably >24hrs, and high sulfur concentrations led to dissimilatory nitrate reduction to ammonium (DNRA) as opposed to the desired denitrification which results in the product of innocuous dinitrogen gas. Results indicate that ferric aided zeolite+woodchip bioreactor treatment trains may be effective for N and P reduction in nursery tail-water if designed properly to avoid excessive retention times in the denitrification bioreactors.