New Evidence for Rejuvenation of Phosphorus Retention Capacity in EAF Steel Slag

Abstract

The purpose of this research was to investigate phosphorus (P) retention capacity and rejuvenation potential of electric arc furnace (EAF) steel slag from Quebec and New Zealand (NZ) iron melter slag (IMS). Columns filled with slag materials were fed with dairy effluent and subjected to two feeding and one resting cycle(s). P retention capacities and rejuvenation potentials were determined after each feeding cycle. Elemental composition and mineralogical analysis were performed on IMS samples. Finally, chemical fractionation analysis was conducted on both NZ IMS and Quebec EAF steel slags. The results revealed that initiating a resting period in EAF steel slag filters prior to reaching their P saturation point increased the overall filter P retention capacity by 49.5 and 42.4% compared to 28% in a filter which had its resting period initiated after reaching P saturation. The rejuvenation property could play a significant role in full-scale applications by prolonging life expectancy and increasing cost efficiency. P retention and rejuvenation by NZ slag materials was negligible relative to EAF steel slag material from Quebec. Chemical fractionation analysis revealed differences between materials, indicating that the highest quantities of P were bound to Ca and Fe in EAF steel slag and to Ca and Al fractions in iron melter slag. This study also demonstrates that slag's performance is dependent on the source of the material and the steel making practices. Therefore, testing of the P adsorptive capability and, if relevant, the rejuvenation potential of individual steel mill slags, should be a prerequisite prior to their use in field applications.

EAF Steel Slag Filters for Phosphorus Removal from Milk Parlor Effluent: The Effects of Solids Loading, Alternate Feeding Regimes and In-Series Design

“…Similarly, Weber et al [19] reported that there was not a significant difference in the DRP loading rates and removal efficiencies between filters fed with wastewater that had been pretreated by a constructed wetland (75%) versus untreated effluent (72%) ( Table 1). However, the filters fed with pretreated effluent (at lower TSS loading rates) had a 2.2 fold longer life-span then filters fed without a constructed wetland pretreatment [18,19].…”

“…Drizo et al [18] recently provided a description of the chemical composition of this material. Based on the previous research conducted at the UVM CWRC [18,19] two different particle sizes of EAF steel slag material were employed: 5-10 mm and 10-20 mm, with the larger size used at the inlets to reduce the incidence of clogging. Slag particles were weighed and added to the filters in layers approximately 0.05 m in height.…”

“…Slag particles were weighed and added to the filters in layers approximately 0.05 m in height. Each layer was leveled and compacted, and the remaining space in the filter height was recorded [18,19,25]. The average weight of the 5-10 mm EAF slag aggregates in each of the four filters was 340.6 kg, while the average weight of the 10-20 mm slag material aggregates was 74.13 kg, representing 82% and 18% of total filter weight, respectively.…”

“…Steel slags, a co-product of steel production, have demonstrated the greatest capacity to remove P from a variety of wastewaters [16,17]. Over the past 15 years there has been significant scientific evidence showing the efficiency of electric arc furnace (EAF), blast furnace (BF) and iron melter (IM) steel slags in P removal from a variety of wastewaters [16][17][18][19][20]. However, despite this evidence, apart from New Zealand [18,20,21], there are currently very few full-scale steel slag filters in operation for the removal of P from wastewater [22].…”

“…The first field testing of EAF steel slag filters (EAF SSF) as an innovative method for P reduction from mixed barnyard and milk parlor waste effluent was conducted at the University of Vermont (UVM) Constructed Wetlands Research Center (CWRC), [18,19]. The results from these investigations demonstrated that EAF SSF reduced the dissolved reactive phosphorus (DRP) by 75% and 72%, respectively, when treating dairy waste effluent with and without constructed wetland pretreatment [19].…”