Surface characteristics of sorptive-filtration storm water media. II: Higher specific gravity (rho(s)> 1.0) oxide-coated fixed media

Most current control strategies for storm water treatment utilize fixed or filter-bed media with specific gravity (rho (s)) greater than 1.0. In contr ast to Part I, Part II focuses on such higher density (rho (s) > 1.0) manga nese-oxide-coated media that can be used in combined unit operations and pr ocesses for in-situ treatment of storm water. Methods were developed to coa t manganese oxides onto sand and cementitious media for storm water treatme nt. With respect to manganese, coatings of ramsdellite produced a point of zero charge (PZC) of 5.2, while mixtures of birnessite and cryptomelane pro duced a PZC of 2.6 Manganese oxide increased the specific surface area (SSA ) of sand and cementitious media. Manganese-oxide-coated sand (MOCS) produc ed a larger SSA (2.48-m(2)/g), as compared with birnessite-coated media (BC M) (1.51 m(2)/g), while the two have a similar surface charge (PZC = 6.4). Manganese-oxide-coated cementitious media (MOCM) produced a significantly l arger SSA (19.49 m(2)/g), as compared with coated sand, and SEM analyses in dicated the surface contained manganese oxide and calcite of thickness 10-3 0 mum. Based on the results, coated cementitious media provided surface cha racteristics that can significantly enhance filtration and adsorption of he avy metal in storm water, in comparison to sand.