A Laboratory Study of the Treatability of Synthetic Stormwater Under Varying Conditions Using Electric Arc Furnace Steel Slag

Abstract

Abstract:The investigation of electric arc furnace (EAF) steel slag as a viable add-on technology to existing stormwater systems for the removal of dissolved phosphorus (P) was extended to explore the effects of varying environmental and treatment system conditions. Parameters such as stormwater composition, P concentration, metal concentration, pH, temperature, slag mass and slag particle size were varied. Observations relating to the method of P removal via EAF slag were also carefully considered to explain removal mechanisms involved. Results demonstrated that, although physisorption contributed to P reduction, it was not the key P removal mechanism. Instead, precipitation was observed to be a key removal pathway as evidenced by the correlation between the loss of iron (Fe) from slag and the amount of P removed from solution. The reduced removal of P by slag in a copper-dominant stormwater solution was attributed to the formation of a stable complex formed by the interaction of copper with the slag via the ion-exchange surface model. The stability of this complex inhibits the loss of Fe from the EAF slag and, consequently, P removal by means of precipitation. In terms of the effect of changing environmental and treatment system conditions on the P removal process, stormwater composition, P concentration, metal concentration, pH, temperature, slag mass and slag particle size were found to significantly influence the effectiveness of EAF slag in removing P from a given stormwater system. It was also established that a number of combinations of these factors influence P uptake differently. OPEN ACCESSWater 2012, 4 322

Phosphorus removal by electric arc furnace steel slag adsorption

“…Hence, smaller size of slag has a larger surface area resulting higher adsorption on phosphorus and its removal percentage. These results agreed with the finding in other study [9]. Since the diffusion path decreased as the size of slag decreased, eventually it increased the effectiveness of the penetration of adsorbate as well as then depth of penetration in adsorbent particle resulting higher rate of adsorption.…”

“…Besides that, the results demonstrated the amount of P adsorbed at pH 3.0 was the greatest which indicated the adsorption of P by EAFS is effective under acidic environment. Although these findings are likely support with several studies but in terms of the optimum value of pH, the value is not similar where their studies indicated pH 5 -5.5 consisted of highest P-removal efficiency [8,9]. Due to the variation of chemical composition in the EAFS hence the optimum pH for highest P-removal efficiency is subjected to the chemical composition.…”

“…Various researches indicated that Phosphorus removal efficiency was highly depended on initial P concentration, pH, size of adsorbent, dosage of adsorbent, agitation mode and temperature. In addition, different combinations of these variables will affect P removal efficiency in their own ways [8][9][10]. However, only several parameters will be selected to be investigated while others remained as controlled variables in this paper.…”

The Impact of Temperature on the Removal of Inorganic Contaminants Typical of Urban Stormwater

“…In the case of the remaining materials, precipitation of Zn and Cu was less significant, because pH was within 5.26 to 7.55 for activated carbon, 5.07 to 7.52 for halloysite, 5.08 to 6.56 for zeolite, and 5.05 to 6.95 for diatomite. Removal of heavy metals on zeolite is generally via ion exchange [36], but also takes place through electrostatic adsorption to negatively charged sites on the zeolite surface [31]. Moreover, heavy metals are removed on halloysite and diatomite via ion exchange and surface complexation respectively on permanently charged sites and variably charged sites [40,60].…”

“…In the last decade, aside from infiltration systems (filter strips, soakaways, infiltration trenches, infiltration basins) and significantly influence the daily, monthly and annual variability of the removal efficiency of transported contaminants. Most reports are focused on the analysis of the intensity of contaminant removal at ambient temperatures [30][31][32][33] or on assessing the impact of temperature increases above room temperature on the intensification of the process [34][35][36][37]; fewer studies indicate how temperature decrease, even to 0 °C, influences the ability of reactive materials to remove contaminants [38,39].…”