Special Issue "Advances and Challenges in Improving Water Quality with Phosphorus Removal Structures: Scaling Up to the Field"

A special issue of Water (ISSN 2073-4441). This special issue belongs to the section "Aquatic Systems—Quality and Contamination".

Deadline for manuscript submissions: closed (31 December 2020).

Special Issue Editor

Dr. Chad J. Penn
E-Mail Website
Guest Editor
USDA ARS, Natl Soil Eros Res Lab, W Lafayette, IN 47907 USA
Interests: soil chemistry, soil testing, phosphorus recommendations, phosphorus removal structures, nutrient management, thermodynamics of sorption, calorimetry

Special Issue Information

Dear Colleagues,

While reduction of particulate forms of phosphorus (P) from point and non-point sources can be achieved with minimal cost and technology, removing dissolved P remains a challenge. Countless studies spanning over two decades have identified many P sorption materials (PSMs), including several by-products, that are effective at removing dissolved P from solution. Several materials have shown promise in the laboratory, yet scaling up to flowing conditions in the field remains a challenge when considering feasibility and economics. The aim of this Special Issue is to present recent advances and challenges in removing dissolved P at the field-scale with P removal structures. Field studies are preferred, but laboratory experiments are welcome if they specifically address challenges related to field implementation of P removal structures. Experiments solely focused on characterizing PSMs and P sorption isotherms, however, will not be considered for inclusion in this Special Issue. Regarding flow-through experiments conducted at any scale, changes in P loads rather than P concentrations alone must be presented. Studies must also provide information regarding the economics of P removal structure implementation at the field-scale; assessments that only evaluate PSM cost at the field- scale will not be considered. Current challenges in scaling up to field-scale P removal structures include (but are not limited to): 1) achieving a high flow rate while maintaining sufficient P removal; 2) efficiently removing dissolved P from sources with relatively low dissolved P concentrations (i.e. < 0.2 mg/L); 3) re-generating PSMs in-situ; 4) constructing structures on sites with little to no hydraulic head; 5) clogging of media; 6) lack of trained professionals in design and construction of P removal structures; and 7) maintaining low costs in construction and maintenance.

Dr. Chad J. Penn
Guest Editor

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Keywords

  • phosphorus removal structures
  • nutrient losses
  • water quality
  • phosphorus removal
  • phosphorus treatment

Published Papers (9 papers)

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Editorial

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Editorial
The Past, Present, and Future of Phosphorus Removal Structures
Water 2021, 13(6), 797; https://doi.org/10.3390/w13060797 - 15 Mar 2021
Viewed by 479
Abstract
The purpose of this special issue is to explore current challenges and develop a better understanding of the processes that control dissolved phosphorus (P) removal among P removal structures [...] Full article

Research

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Article
Performance of a Ditch-Style Phosphorus Removal Structure for Treating Agricultural Drainage Water with Aluminum-Treated Steel Slag
Water 2020, 12(8), 2149; https://doi.org/10.3390/w12082149 - 30 Jul 2020
Cited by 6 | Viewed by 918
Abstract
Several structural, treatment, and management approaches exist to minimize phosphorus (P) transport from agricultural landscapes (e.g., cover cropping and conservation tillage). However, many of these practices are designed to minimize particulate P transport and are not as effective in controlling dissolved P (DP) [...] Read more.
Several structural, treatment, and management approaches exist to minimize phosphorus (P) transport from agricultural landscapes (e.g., cover cropping and conservation tillage). However, many of these practices are designed to minimize particulate P transport and are not as effective in controlling dissolved P (DP) losses. Phosphorus removal structures employ a P sorption material (PSM) to trap DP from flowing water. These structures have been successful in treating surface runoff by utilizing aluminum (Al)-treated steel slag, but subsurface tile drainage has never been tested with this material. The goal of this study was to evaluate the performance and economics of a ditch-style P removal structure using Al-treated steel slag for treating agricultural subsurface drainage discharge. The structure treated subsurface drainage water from a 4.5 ha agricultural field with elevated soil test P levels. Overall, the structure removed approximately 27% and 50% of all DP and total P (TP) entering the structure, respectively (i.e., 2.4 and 9.4 kg DP and TP removal). After an initial period of strong DP removal, the discrete DP removal became highly variable. Flow-through analysis of slag samples showed that the slag used to construct the structure was coarser and less sorptive compared to the slag samples collected prior to construction that were used to design and size the structure. Results of this study highlight the importance of correctly designing the P removal structures using representative PSMs. Full article
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Article
Development of a Regeneration Technique for Aluminum-Rich and Iron-Rich Phosphorus Sorption Materials
Water 2020, 12(6), 1784; https://doi.org/10.3390/w12061784 - 23 Jun 2020
Cited by 3 | Viewed by 595
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 [...] Read more.
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. Full article
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Article
Utilization of Steel Slag in Blind Inlets for Dissolved Phosphorus Removal
Water 2020, 12(6), 1593; https://doi.org/10.3390/w12061593 - 03 Jun 2020
Cited by 5 | Viewed by 889
Abstract
Blind inlets are implemented to promote obstruction-free surface drainage of field depressions as an alternative to tile risers for the removal of sediment and particulate phosphorus (P) through an aggregate bed. However, conventional limestone used in blind inlets does not remove dissolved P, [...] Read more.
Blind inlets are implemented to promote obstruction-free surface drainage of field depressions as an alternative to tile risers for the removal of sediment and particulate phosphorus (P) through an aggregate bed. However, conventional limestone used in blind inlets does not remove dissolved P, which is a stronger eutrophication agent than particulate P. Steel slag has been suggested as an alternative to limestone in blind inlets for removing dissolved P. The objectives of this study were to construct a blind inlet with steel slag and evaluate its ability to remove dissolved P, nitrogen (N), and herbicides. A blind inlet was constructed with steel slag in late 2015; data from only 2018 are reported due to inflow sampling issues. The blind inlet removed at least 45% of the dissolved P load and was still effective after three years. The dissolved P removal efficiency was greater with higher inflow P concentrations. More than 70% of glyphosate and its metabolite, and dicamba were removed. Total N was removed in the form of organic N and ammonium, although N cycling processes within the blind inlet appeared to produce nitrate. Higher dissolved atrazine and organic carbon loads were measured in outflow than inflow, likely due to the deposition of sediment-bound particulate forms not measured in inflow, which then solubilized with time. At a cost similar to local aggregate, steel slag in blind inlets represents a simple update for improving dissolved P removal. Full article
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Article
Chemical Clogging and Evolution of Head Losses in Steel Slag Filters Used for Phosphorus Removal
Water 2020, 12(6), 1517; https://doi.org/10.3390/w12061517 - 26 May 2020
Cited by 1 | Viewed by 610
Abstract
The objective of this study was to propose a conceptual model of clogging in alkaline granular filters. Two slag columns were operated for 600 days and monitored using piezometers and tracer tested at regular intervals. The type of influent (organic or inorganic) affected [...] Read more.
The objective of this study was to propose a conceptual model of clogging in alkaline granular filters. Two slag columns were operated for 600 days and monitored using piezometers and tracer tested at regular intervals. The type of influent (organic or inorganic) affected the loss of effective porosity in the filters. Well organized and loose crystal structures were observed by scanning electron microscopy in columns with inorganic and organic influents, respectively. It was postulated that the formation of crystals in unorganized structures results in confined voids that are not accessible for water flow, thus accelerating porosity loss. The effect of the combination of chemical clogging and biofilm on the porosity loss is higher than the effect of these two factors separately. The Kozeny-Carman equation for hydraulic conductivity could not efficiently predict the evolution of head losses in the column fed with an inorganic influent. The crystal structure and connectivity in the presence of homogeneous or heterogeneous precipitation are concepts that could improve predictions of hydraulic conductivity. The results of this study highlighted the importance of the inlet zone on the development of pressure head in alkaline granular filters. Future research on clogging should focus on precipitation mechanisms in the inlet zone and on the design of the feeding system. Full article
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Article
Using Steel Slag for Dissolved Phosphorus Removal: Insights from a Designed Flow-Through Laboratory Experimental Structure
Water 2020, 12(5), 1236; https://doi.org/10.3390/w12051236 - 26 Apr 2020
Cited by 5 | Viewed by 893
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 [...] Read more.
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. Full article
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Article
Performance of Field-Scale Phosphorus Removal Structures Utilizing Steel Slag for Treatment of Subsurface Drainage
Water 2020, 12(2), 443; https://doi.org/10.3390/w12020443 - 07 Feb 2020
Cited by 14 | Viewed by 1635
Abstract
Reducing dissolved phosphorus (P) losses from legacy P soils to surface waters is necessary for preventing algal blooms. Phosphorus removal structures containing steel slag have shown success in treating surface runoff for dissolved P, but little is known about treating subsurface (tile) drainage. [...] Read more.
Reducing dissolved phosphorus (P) losses from legacy P soils to surface waters is necessary for preventing algal blooms. Phosphorus removal structures containing steel slag have shown success in treating surface runoff for dissolved P, but little is known about treating subsurface (tile) drainage. A ditch-style and subsurface P removal structure were constructed using steel slag in a bottom-up flow design for treating tile drainage. Nearly 97% of P was delivered during precipitation-induced flow events (as opposed to baseflow) with inflow P concentrations increasing with flow rate. Structures handled flow rates approximately 12 L s−1, and the subsurface and ditch structures removed 19.2 (55%) and 0.9 kg (37%) of the cumulative dissolved P load, respectively. Both structures underperformed relative to laboratory flow-through experiments and exhibited signs of flow inhibition with time. Dissolved P removal decreased dramatically when treated water pH decreased <8.5. Although slag has proven successful for treating surface runoff, we hypothesize that underperformance in this case was due to tile drainage bicarbonate consumption of slag calcium through the precipitation of calcium carbonate, thereby filling pore space, decreasing flow and pH, and preventing calcium phosphate precipitation. We do not recommend non-treated steel slag for removing dissolved P from tile drainage unless slag is replaced every 4–6 months. Full article
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Article
Phosphorus Removal and Carbon Dioxide Capture in a Pilot Conventional Septic System Upgraded with a Sidestream Steel Slag Filter
Water 2020, 12(1), 275; https://doi.org/10.3390/w12010275 - 17 Jan 2020
Cited by 2 | Viewed by 1394
Abstract
The objective of this work was to demonstrate the removal of the phosphorus and carbon dioxide capture potential of a conventional septic system upgraded with a sidestream steel slag filter used in recirculation mode. A pilot scale sidestream experiment was conducted with two [...] Read more.
The objective of this work was to demonstrate the removal of the phosphorus and carbon dioxide capture potential of a conventional septic system upgraded with a sidestream steel slag filter used in recirculation mode. A pilot scale sidestream experiment was conducted with two septic tank and drainfield systems, one with and one without a sidestream slag filter. The experimental system was fed with real domestic wastewater. Recirculation ratios of 25%, 50% and 75% were tested. Limestone soils and non-calcareous soils were used as drainfield media. The tested system achieved a satisfactory compromise between phosphorus removal and pH at the effluent of the septic tank, thus eliminating the need for a neutralization step. The phosphorus removal efficiency observed in the second compartment of the septic tank was 30% in the slag filter upgraded system, compared to −3% in the control system. The slag filter reached a phosphorus retention of 105 mg/kg. The drainfield of non-calcareous soils achieved very high phosphorus removal in both control and upgraded systems. In the drainfield of limestone soil, the slag filtration reduced the groundwater phosphorus contamination load by up to 75%. The removal of chemical oxygen demand of the drainfields was not affected by the pH rise induced by the slag filter. Phosphorus removal in the septic tank with a slag filter was attributed to either sorption on newly precipitated calcium carbonate, or the precipitation of phosphate minerals, or both. Recirculation ratio design criteria were proposed based on simulations. Simulations showed that the steel slag filter partly inhibited the biological production of carbon dioxide in the septic tank. The influent alkalinity strongly influenced the recirculation ratio needed to raise the pH in the septic tank. The recirculation mode allowed clogging mitigation compared to a mainstream configuration, because an important part of chemical precipitation occurred in the septic tank. The control septic tank produced carbon dioxide, whereas the slag filter-upgraded septic tank was a carbon dioxide sink. Full article
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Review

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Review
Field Scale Demonstration of Fly Ash Amended Bioretention Cells for Stormwater Phosphorus Removal: A Review of 12 Years of Work
Water 2021, 13(12), 1632; https://doi.org/10.3390/w13121632 - 10 Jun 2021
Viewed by 468
Abstract
In 2007, ten bioretention cells were constructed in Oklahoma as part of a full-scale technology project to demonstrate stormwater phosphorus reduction. The filter media used was amended with 5%, Class C fly ash by weight to increase phosphorus and heavy metal retention. In [...] Read more.
In 2007, ten bioretention cells were constructed in Oklahoma as part of a full-scale technology project to demonstrate stormwater phosphorus reduction. The filter media used was amended with 5%, Class C fly ash by weight to increase phosphorus and heavy metal retention. In 2014, core samples were collected from four of the cells, and three were instrumented for continuous water monitoring for the following year. This paper will review the design, construction, computer modeling of phosphorus retention, and measured phosphorus removal after seven years of operation. Total phosphorus retained in the sampled cells showed reductions in effluent water concentrations of 68 to 75%, while total effluent mass reductions of 51 to 93% were achieved. Total phosphorus accumulation in the cells measured in cores ranged from 0.33 to 0.60 kg/year, which was somewhat greater than the annual calculated effluent reduction of 0.27 to 0.41 kg/year. While good, phosphorus retention was not as high as computer modeling predicted. Other research on the cells, including hydraulics, heavy metal adsorption, and microbial transport, is summarized. Experimental challenges with phosphorus extraction from samples are also discussed. All experience and results suggest that fly ash amendments are an effective option for phosphorus removal in bioretention cells. Full article
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