|WANG, LINHUA - South China Botanical Garden|
|Huang, Chi Hua|
|YAN, JUNHUA - South China Botanical Garden|
Submitted to: Water
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/20/2020
Publication Date: 4/26/2020
Citation: Wang, L., Penn, C.J., Huang, C., Livingston, S.J., Yan, J. 2020. Using steel slag for dissolved phosphorus removal: Insights from a designed flow-through laboratory experimental structure. Water. 12(5). Article 1236. https://doi.org/10.3390/w12051236.
Interpretive Summary: Tile drainage is a common and efficient way of moving excessive water from agricultural lands. Nevertheless, the drained water also carries dissolved nutrients that have caused ecological damages. Steel slags, from steel processing plants, have been shown to have potential to remove dissolved phosphorus. In this research, we specifically designed a 4-segment flow through system that can be used to quantify the effects of different slag mass and retention time in one experimental run. We found the phosphorous retention efficiency was greater with more slag mass and longer retention time. Since more slag mass can also reduce the flow velocity, hence slowing down water drainage from the field. The trade off between more efficient phosphorus removal, i.e., using more slags, and how fast water needs to be drained from the field needs to be considered during the design of a phosphorus removal system.
Technical Abstract: Steel slag, a byproduct of the steel making process, has been adopted as a material to reduce non-point phosphorus (P) losses from agricultural land. Although substantial studies have been conducted on characterizing P removed by steel slag, few data are available on the removal of P under different conditions of P input, slag mass, and retention time (RT). The objective of this study was to investigate P removal efficiency as impacted by slag mass and RT at different physical locations through a horizontal steel slag column. Downstream slag segments were more efficient at removing P than upstream segments because they were exposed to more favorable conditions for calcium phosphate precipitation, specifically higher Ca2+ concentrations and pH. These results showed that P is removed in a moving front as Ca2+ and slag pH buffer capacity are consumed. In agreement with the calcium phosphate precipitation mechanism shown in previous studies, an increase in RT increased P removal, resulting in an estimated removal capacity of 61 mg kg-1 at a RT of 30 min. Results emphasized the importance of designing field scale structures with sufficient RT to accommodate the formation of calcium phosphate.