Wei Zhang - Fly-Ash-Amended Sand as Filter Media in Bioretention Cells to Improve Phosphorus Removal

Version 1

      Publication Details (including relevant citation   information): Zhang, Wei, Brown, Glenn O, Storm, Daniel   E, Zhang, Hailin, Water Environment Research,   2008, 80 (6), pp 507-516

      Abstract: This study identified material with   high phosphorus sorption suitable for bioretention filter media.   Materials examined were fly ash, two expanded shales, peat moss,   limestone, and two common Oklahoma soils—Teller loam and   Dougherty sand. The peat moss was a phosphorus source, while the   two soils, limestone, and one expanded shale had only modest   sorption capacity. One expanded shale and the fly ash had   significant phosphorus sorption. Fly ash is unsuitable for use in   a pure form, as a result of its low permeability, but phosphorus   sorption on the sand was increased significantly with the   incorporation of small amounts of fly ash. Column leaching   experiments found that the sand with 2.5 and 5% fly ash and the   better expanded shale had linear, non-equilibrium transport   retardation factors of 272, 1618, and 185, with first-order rate   coefficients of 0.153, 0.0752, and 0.113 hour −1,   respectively. Desorption experiments showed that the phosphorus   sorption on the sand/fly ash mixture is largely nonreversible.   Transport simulation assuming a 1-m-deep sand/fly ash treatment   layer, with 5% of the watershed area, showed that the sand/fly   ash filter media could effectively treat 1 mg/L influent for 12   years in a paved watershed and 34 years in a grassed watershed   before exceeding Oklahoma's scenic rivers' phosphorus criterion   of 0.037 mg/L. Significant phosphorus removal would continue for   over 100 years.

      Address (URL): http://dx.doi.org/10.2175/106143008X266823