Development of a Regeneration Technique for Aluminum-Rich and Iron-Rich Phosphorus Sorption Materials

Abstract

The reduction of dissolved phosphorus (P) transport to water systems is of critical importance for water quality. Phosphorus sorption materials (PSMs) are media with high affinity for dissolved P, and therefore serve as the core components of P removal structures. These structures can intercept dissolved P in surface and subsurface flows, before discharge into water bodies. While the P removal ability of PSMs has been extensively studied, lesser is known about the capacity to regenerate and recover P from P-saturated PSMs. This article evaluates a methodology to recover the P removal ability of aluminum- and iron-rich P-saturated PSMs. A series of flow-through experiments were conducted, alternating between P sorption (0.5 and 50 mg L − 1 P) and desorption with potassium hydroxide (KOH; 5 or 20 pore volumes [PV]), varying residence times (0.5 min and 10 min), and number of recirculations (0, 6 and 24). Across two cycles of sorption-desorption, Alcan, Biomax and PhosRedeem showed an average P recovery of 81%, 79%, and 7%, with standard deviation of 10%, 21% and 6%, respectively. The most effective regeneration treatment was characterized by the largest KOH volume (20 PV) and no recirculation, with up to 100% reported P recovery. Although KOH at 5 PV was less effective, the use of recirculation did increase P recovery. The lifetime of Al/Fe-dominated PSMs in P removal structures can be extended through feasible regeneration techniques demonstrated in this study, for both high and low P concentration scenarios.

Techno-Economic Analysis of Phosphorus Removal Structures

“…This is especially relevant when using manufactured PSMs, which are more costly compared to industrial byproducts. A treatment with potassium hydroxide has been tested with P recovery as high as 95% for spent Alcan . The authors argue that while it is tempting to consider the value of the recovered P, the mass of dissolved P being lost to surface waters and sequestered in P removal structures is very small compared to agronomic requirements.…”

“…We tested various media in laboratory column experiments to estimate the P 40% threshold. ,− This is the amount of P sorbed (in kg) when the system degrades to 40% cumulative P removal. Some of the most effective materials include steel metal shavings (herein denoted “metal shavings”), steel slag, promoted alumina (ActiGuard AFS50, an iron-enhanced activated alumina, also known as Alcan), and activated alumina (ActiGuard AA400G).…”

Introduction to P‐TRAP software for designing phosphorus removal structures

“…However, if Actiguard AAFS50 (Axens Solutions), an Fe-coated alumina, is selected and RT goal is changed to 0.5 min with use of corresponding design curve, only 7.9 Mg is required to meet the goals. Although this material is initially expensive (∼US$3.2 kg -1 ), it can be regenerated after P saturation (Scott et al, 2020). Steel shavings, on the other hand, are ∼US$0.22 kg -1 .…”