Electric ARC Furnace Steel Slag: A Low Cost Industrial Adsorbent for Stormwater Treatment

Pp. 455-484 (30)

Author(s): Nnaemeka C. Okochi, Dena W. McMartin Environmental Systems Engineering, Faculty of Engineering and Applied Science, University of Regina, Regina, Saskatchewan, Canada S4S 0A2, Canada

Affiliation:

Abstract

This chapter discusses the use of Electric Arc Furnace (EAF) slag as a safe, effective and inexpensive end-of-pipe add-on solution for improving the treatment of urban stormwater runoff. Stormwater comprises a complex mixture of constituents, which at elevated concentrations can be very harmful to receiving surface waters. Its treatment therefore requires an optimal mix of technologies or treatment train that achieves acceptable end-point water quality prior to its discharge into an aquatic environment. Existing popular stormwater treatment measures such as grassed swales, detention ponds and constructed wetlands, while effective in removing certain components such as suspended solids, have not fared very well in dealing with dissolved nutrients and heavy metals. In the right concentrations, these become pollutants and find their way to water bodies downstream where they have been known to create a host of health and economic challenges for the communities that rely on these water supplies for their upkeep and well-being. Dissolved phosphorus is of particular interest as it has been known to cause an over-enrichment of nutrients in freshwater habitats around the world, and the subsequent degradation of those water systems. Thus the need for safe, effective and affordable add-on solutions to address this stormwater treatment gap is an important research focus. Industrial by-products, such as EAF slag from the steel recycling industry, provide an interesting option for this treatment challenge in the communities where they are produced. They are largely inexpensive, locally available and present in very large quantities. Their use also lessens the environmental costs of waste disposal for the manufacturing company, and creates additional revenue. This chapter looks at dissolved phosphorus and different studies that conclude the general effectiveness of these industrial materials to remove dissolved phosphorus from solution. Particular interest is paid to EAF slag due to its vast availability in the region under discussion (North America). However, these findings may be extended to other locations around the world where EAF slag, or materials of similar composition and characteristics, are available in significant quantities. The discussions on EAF slag presented in this chapter conclude that it is a low-cost adsorbent with vast potential to effectively sequester dissolved phosphorus from stormwater. This means that EAF slag can act as a viable end-of-pipe add-on technology to existing stormwater treatment systems for improved effluent quality.

Keywords:

Electric arc furnace (EAF) slag, stormwater, pollutants, suspended solids, polycyclic aromatic hydrocarbons (PAHs), organic pollutants, Phosphate removal, adsorption, natural materials, Light weight aggregates (LWA), Industrial by-products.