Phosphorus Removal by Steel Slag Filters: Modeling Dissolution and Precipitation Kinetics to Predict Longevity

Abstract

This article presents an original numerical model suitable for longevity prediction of alkaline steel slag filters used for phosphorus removal. The model includes kinetic rates for slag dissolution, hydroxyapatite and monetite precipitation and for the transformation of monetite into hydroxyapatite. The model includes equations for slag exhaustion. Short-term batch tests using slag and continuous pH monitoring were conducted. The model parameters were calibrated on these batch tests and experimental results were correctly reproduced. The model was then transposed to long-term continuous flow simulations using the software PHREEQC. Column simulations were run to test the effect of influent P concentration, influent inorganic C concentration and void hydraulic retention time on filter longevity and P retention capacity. High influent concentration of P and inorganic C, and low hydraulic retention time of voids reduced the filter longevity. The model provided realistic P breakthrough at the column outlet. Results were comparable to previous column experiments with the same slag regarding longevity and P retention capacity. A filter design methodology based on a simple batch test and numerical simulations is proposed.

Modelling constructed wetlands: Scopes and aims – a comparative review

“…It included three steps: (i) dissolution of slag as Calcium oxide (CaO), (ii) phosphorus precipitation and crystal growth in alkaline conditions, (iii) evolution of slag filter properties (slag dissolution rate, porosity and hydraulic conductivity) related to slag exhaustion and to the presence of crystals (Claveau-Mallet et al, 2012). The conceptual model was mathematically expressed in a 1D geochemical model including equilibrium and rates (Claveau-Mallet et al, 2014). The software PHREEQC was used for numerical simulations.…”

“…In order to reach a high number of users, the P-hydroslag the model is reasonably complex as it involves simplifications which are: (i) the wide variability of slag composition resulting in different reactivity is simplified by a CaO dissolution reaction with a rate decreasing over time, (ii) precipitation rates are simplified to basis expressions with good experimental fitting, and (iii) the initial model considered only hydroxyapatite, but its accuracy was greatly improved when monetite and its transformation to hydroxyapatite were added (Claveau-Mallet et al, 2014).…”

Geochemical Characterization of Iron and Steel Slag and Its Potential to Remove Phosphate and Neutralize Acid

“…Previous studies have documented the effectiveness of ferrous slag as a sorbent to remove nutrients and trace elements from solution to control unwanted anthropogenic emissions, as summarized by Piatak et al [1]. Numerous studies have documented the effectiveness of using steelmaking slag to remove phosphorus (P) from wastewaters and agricultural runoff [3][4][5][6][7][8][9][10][11][12][13][14][15]. Ferrous slag has also been shown to be an effective acid-neutralizing agent with applications in the treatment of acid-mine drainage from coal and base-metal operations [16][17][18][19][20][21][22].…”

Enhanced phosphorus removal from wastewater by growing deep-sea bacterium combined with basic oxygen furnace slag

“…As one kind of mass industrial solid waste, open dumping of steel slag not only occupies land but causes potential pollution by dust as well as the alkalinity to air, soil and groundwater (Asuman Korkusuz et al, 2007). Attentions has been attracted to the use of steel slags as potential adsorbents in regulating the phosphorus cycle through uptake from and slowly release to the water as well as alternatives to the basal medium for construction of artificial wetland, tidal flats and seagrass beds recently (Claveau-Mallet et al, 2014;Hayashi et al, 2011;Hussain et al, 2015;Tsukasaki et al, 2015;Yamamoto and Liu, 2013). Among variety slags generated from different steelmaking processes, slag from the basic oxygen furnace (BOFS) presents the highest phosphorus adsorption capacity (Barca et al, 2012;Oguz, 2004).…”

“…HCl) addition. Furthermore, the clogging of slag filters related to the declined pore size and the more compact precipitate structure blocks off the phosphorus removal sustainably (Claveau-Mallet et al, 2014). Therefore, it will benefit more to both ecosystem and waste disposal to develop more eco-friendly phosphorus removal system of BOFS for large-scale water treatment.…”