During the Annual meetings (2010) of the Ameriacan Society of Agronomy, Soil Science Society of America and the Crop Science Society of America, a special session was organized entitled: Emerging technologies to remove phosphorus from surface and ground waters.
Click here for the background of the session, and for links to Audio files and to Recorded presentations. Below you can find for each presentation: title, authors, a link to the recorded presentation and the abstract.

Emerging technologies to remove nonpoint phosphorus sources from surface water and groundwater - Introduction
Anthony Buda, USDA-ARS-PSWMRU; Gerwin Koopmans, Alterra; Wim Chardon, Alterra; Ray B. Bryant, USDA-ARS-Pasture System and Watershed Management Research Unit

Water treatment residuals for immobilizing phosphorus in surface and ground waters.
Herschel Elliott, Pennsylvania State University; George O'Connor, Department of Soil and Water Science.
Water treatment residuals (WTRs) are environmentally benign byproducts from purification of water supplies for potable or industrial uses. Because Al and Fe salts are commonly used to remove turbidity and color from source waters, WTRs contain reactive hydrous Al and Fe oxides with P-fixing properties. Methods employing WTRs to reduce P loss from agricultural land include: (1) incorporation into soils with excessive soil test P, (2) Co-blending with nutrient sources, and (3) buffers or barriers to intercept P in surface or ground water flows. Effective application rates and methods remain an area of intense research. Large-scale implementation of WTRs for controlling off-site P losses to sensitive water bodies is hindered by state regulations, inability of P indices to credit their use, and insufficient supplies of locally available WTRs.

Factors and processes that influence chemical interactions between phosphorus and iron oxides.
Liping Weng, Wageningen University; Willem Van Riemsdijk, Wageningen University; Tjisse Hiemstra, Wageningen University; Gerwin Koopmans, Alterra
To obtain optimal efficiency in treating runoff waters using mineral adsorbents requires a good understanding of the factors and processes that influence the P and mineral interaction. This presentation reviews the mechanisms of P sorption by a variety of materials that have potential for use in P treatment applications. Factors such as pH, ionic strength, ion composition and presence of natural organic matter play a crucial role in the effectiveness of P adsorption by minerals. The interplay between these factors shows a complicated pattern and can sometimes lead to controversial results, As a consequence, it makes selection of optimal conditions for P removal not straightforward. With the help of mechanistic modeling, the net macroscopic effect of single and combined factors can be understood and can be predicted. Recent progress of mechanistic modeling of P adsorption to mineral adsorbents will be reviewed and examples in modeling P adsorption under the influence of solution chemistry will be presented.

Innovative technologies for phosphorus reduction from non point pollution sources.
Aleksandra Drizo, University of Vermont; Eamon Twohig, University of Vermont; Hugo Picard, PhosphoReduc Environmental Solutions
PhosphoReduc™ Filter systems for P removal from both point and nonpoint pollution (NPP) sources have been developed as a result of over 10 years of research and testing on over 70 different adsorbing materials in numerous laboratory, and pilot and demonstration projects. PhosphoReduc™ Filter systems for P removal from NPP sources was developed in 2006, as a simple, passive system consisting of one or more filter units placed in drainage pathways either in agricultural or urban landscapes. Since 2006, the performance of the systems has been tested on several locations in the USA and Canada. The results showed evidence on the efficacy of PhosphoReduc™ filter systems in reducing P from both high and low effluent concentrations and a variety of pollutant loadings. In addition, the systems have minimal land area and no energy requirements, minimal operation and maintenance costs and simple installation and as such are cost efficient and beneficial to the environment.

Mitigation options to remove non-point source phosphorus from runoff in New Zealand and Australia.
Richard McDowell, AgResearch Ltd; David Nash, Primary Industries Research Victoria (PIRVic)
The loss of phosphorus (P) from land to water is detrimental to surface water quality in many parts of New Zealand and Australia. Farming, especially pasture-based dairying, can be a source of that P. Strategies to mitigate the P loss from farms vary in their effectiveness and costs due to differences in farm management systems, topography, stream density and climate. In the absence of significant financial assistance, a range of fully-costed strategies are required to ensure that the best mix of mitigation measures can be found for each farm. We present a summary of the efficacy and cost of a range of mitigation options available now, or under development, to lessen P loss from grazed grassland farms and catchments. Mitigations are classified as those that intervene in on-farm management (e.g., optimum soil test P, low solubility P fertilizer, effluent spreading), amendments such as alum, and tile drain filters, and edge of field (in-stream sorbents, buffer strips, constructed wetlands, and dams for water recycling). We considered components of cost-effectiveness such as material, labour and opportunity costs to assess the best options for a “typical” dairy farm in Southland, New Zealand. Although many P mitigation options are available, an analysis of strategies that target on-farm management options such as effluent and fertilizer management were the most cost-effective way of decreasing P losses (cost beneficial to 65 USD $/kg P conserved) although their overall impact is limited. Field amendments that may capture more P than preventing P loss by on-farm management were not as cost-effective (25-500 USD $/kg P conserved), but better than edge-of-field strategies, such as wetlands (250->500 USD $/kg P conserved). However, it is important to note that these latter measures often have other benefits, such as N removal and/or modification of peak flows.

Using FGD gypsum to remove soluble phosphorus from agricultural drainage waters.
Ray B. Bryant, USDA-ARS-Pasture System and Watershed Management Research Unit; Anthony Buda, USDA-ARS-PSWMRU; Peter Kleinman, USDA-ARS; Clinton Church, USDA-ARS; Joshua McGrath, University of Maryland; Karen Grubb, University of Maryland; Salil Bose, Constellation Energy
After several decades of applying chicken litter to meet crop demands for nitrogen, high levels of legacy phosphorus (P) in soils of the Delmarva Peninsula are a major source of soluble P entering drainage ditches that empty to the Chesapeake Bay. In April, 2007, Flue Gas Desulfurization (FGD) gypsum was used to construct a ditch filter to precipitate soluble P as calcium phosphate. Filtration through a bed of FGD gypsum removed 35 to 90 % of the P from ditch flow that passed through the filter. Although chemically effective, large flow events topped the weir, and P rich waters flowed to the Manokin River. Simultaneously, research on groundwater hydrology in Coastal Plain soils of the Delmarva showed that overland flow accounts for <10 % of P export to ditches. Lateral groundwater flow, during storm events when water tables are high, is the major pathway for soluble P delivery to ditches. In August, 2009, gypsum “curtains,” consisting of FGD gypsum-filled trenches parallel to the ditch, were installed and monitored by piezometers. Lateral flow rates were not diminished by the gypsum curtains, and soluble P was reduced by 50 to 95% as groundwater passed through the high calcium environment of the buried gypsum. Environmental concerns due to higher levels of mercury (Hg) and arsenic (As) in FGD gypsum than in naturally occurring mined gypsum were determined to be unfounded. Filtered water had no detectable Hg. Arsenate, which is present in elevated levels in poultry litter- amended soils, behaves similarly to phosphate. Data show lower levels of soluble As after filtration through both the ditch filter and the curtain. The potential for applying “spent” gypsum at typical amendment rates was assessed. There may be potential to use the calcium phosphate rich gypsum as fertilizer if it is applied before crops need the nutrient.

Use of reactive materials to bind phosphorus.
Gerwin Koopmans, Alterra; Willem Chardon, Alterra; Jan Groenenberg, Alterra
Phosphorus (P) losses from agricultural soils have caused surface water quality impairment in The Netherlands. The generic Dutch fertilizer and manure policy, which strives towards equilibrium fertilization in 2015, will not be sufficient to reach the surface water quality standards of the European Water Framework Directive in 2015, due to the large amounts of P accumulated in Dutch soils. Accordingly, additional measures have to be considered to further reduce P enrichment of surface waters. At present, innovative remediation practices are developed using reactive barriers placed along ditches or retention filters at the end of tile drains to remove P from soil waters. Other practices include the use of amendments blended with land-applied P sources (e.g., manure) to reduce P solubility or P-rich topsoil to decrease P release by the soil solid phase. For these practices, many different reactive materials have been proposed, which can be categorized as natural materials, industrial byproducts, and man-made products. Before field application, the phosphorus binding capacity (PBC) of these materials, which is strongly related to their chemical composition (i.e., Fe, Al, and Ca), should be known as a criterion for material selection and in order to be able to estimate the amount of material needed to control P solubility at the desired level. In addition to the PBC, the reactive materials should have a good hydraulic conductivity to minimize the risk of system clogging. Also, their concentration of inorganic contaminants has to be evaluated, because especially industrial byproducts may contain elevated levels of heavy metals. We will present results of a laboratory study during which physical and chemical properties of two reactive materials (iron sludge and iron-coated sand) and their PBC's (batch and column experiments) were measured. These materials are produced as byproducts during the purification of deep groundwater for drinking water.

Use of sorbent-amended compost filter socks in grassed waterways to reduce nutrient losses in surface runoff.
Martin J. Shipitalo, USDA-ARS; Britt Faucette, Filtrexx International, LLC; James Bonta, USDA-ARS; Lloyd Owens, USDA-ARS
Surface runoff from fields used to grow row crops frequently has high concentrations of sediment, nutrients, and herbicides, particularly in the first few events after tillage and planting. Compost filter socks placed in grassed waterways can further reduce sediment concentration as this runoff is transmitted offsite, but are generally ineffective in removing dissolved agrochemicals. In this study, we routed the runoff from one tilled and one no-till watershed (~1.0 ha) planted to corn into parallel, 30-m long, grassed waterways designed by the NRCS. Three, 46-cm dia., mesh bags (filter socks) filled with composted bark and wood chips were placed 5 m apart across the upper half of one waterway and three socks were similarly placed in the lower portion of the other waterway to determine if they increased removal of sediment and dissolved chemicals. A proprietary sorbent, Nutriloxx, was added to the filter socks to increase nutrient retention. Automated samplers were used to obtain samples above and below the treated segments of the waterways for two crop years. The effectiveness of the grassed waterways and filter socks was highly dependent on the timing and size of the runoff events and tillage treatment. In 2009 there were no sizable runoff events during the growing season. Consequently, sediment loses were minimal and no significant effects on sediment concentration were detected. Similarly, nitrate and ammonium nitrogen losses were inconsequential and not affected by filter sock installation. Averaged for both watersheds, however, the amended filter socks contributed to a significant additional 27% reduction in dissolved phosphorus concentration (range + 59% to -2%) compared to waterways without filter socks. The filter socks significantly increased sulfate concentrations up to 22-fold in the first sampled event, but sulfate concentrations declined rapidly with subsequently runoff events.

Phosphorus removal from agricultural drainage ditches using gypsum filter structures: changes in soil phosphorus forms due to application of phosphorus saturated gypsum.
Karen Grubb, University of Maryland; Joshua McGrath, University of Maryland; Chad Penn, Oklahoma State University; Ray B. Bryant, USDA-ARS-Pasture System and Watershed Management Research Unit
Agricultural drainage ditches can provide a direct connection between agricultural fields and surface waters. Certain drainage ditches have been shown to deliver high loads of phosphorus (P) to sensitive water bodies. One potential way to reduce nutrient loads in agricultural drainage ditches is to install filter structures containing P sorbing materials (PSMs) such as gypsum to remove P directly from ditch flow. One of the projected advantages of such a system would be the potential application of PSMs to agricultural fields to provide nutrients for crop production. The purpose of this study was to evaluate in the laboratory the feasibility of such a strategy. Gypsum was saturated at two levels on the mass basis of P, and applied to two soil types, a silt loam and a sandy loam. The solution was applied at both a high and low rate. The treated soils were incubated at 25° C and samples were collected at 0, 1, 7, 28, 63, 91, 119, and 183 days after saturation. Changes in chemically defined P forms in the soil will be discussed.

Material characterization for designing phosphorus removal structures: consideration of kinetics.
Dustin Stoner, Oklahoma State University; Chad Penn, Oklahoma State University; Joshua McGrath, University of Maryland
Use of industrial by-products as phosphorus (P) sorbing materials (PSMs) have shown great potential for removing P most importantly dissolved P from wastewaters, drainage water, and surface runoff. Characterization of these materials is a vital first step for the proper design and incorporation of P removal structures to high P terrestrial systems. The purpose of this study was to quantify P sorption rate onto several industrial by-products using a flow-through approach. Materials were characterized for properties that affect P sorption and include Fe, Al, and Ca concentrations and forms, pH, and electrical conductivity. Five solution P concentrations were passed through PSMs at five different retention times. Samples were collected periodically over a five hour period. The results of the above experiment will be used to determine potential environmental risk and effective life span for a particular P removal structure. Phosphorus sorbing materials can play an important role in the future agro-environmental practices and policy’s as P losses from terrestrial environments continue to undergo continued scrutiny with the every growing chance of increased regulation.

Chemical amendment of dairy cattle slurry for control of phosphorus in runoff from grasslands.
Raymond B. Brennan, National University of Ireland, Galway; Mark Healy, National University of Ireland, Galway; Owen Fenton, Teagasc
It is estimated that agriculture accounts for 38% of all pollution in Ireland’s waterways. The EU Water Framework Directive (WFD; 2000/60/EC) recommends research and development of new pollution mitigation measures to achieve the 2015 target of surface and groundwaters of ‘good status’. In intensive dairy farming systems, phosphorus (P) inputs can exceed P outputs. Over time, soil test P (STP) levels build up after repeated manure applications, and this can increase the risk of P loss to a waterbody. There is also the risk of incidental losses when landspreading slurry. Amendments could potentially mitigate P losses in strategic areas, while allowing farmers to dispose of slurry cheaply, and utilise nitrogen (N) and other nutrients in the slurry. The aim of this study was to identify amendments with the potential to reduce P and suspended sediment (SS) loss from agricultural grassland in Ireland arising from the land application of dairy cattle slurry. First, an ‘agitator test’ was used to identify the optimal rates of amendment addition to slurry to reduce soluble P, and to estimate associated costs. Amendments examined included alum, poly aluminium chloride, ferric chloride, lime, flyash, flue gas desulphurisation by-product, and alum-based water treatment residuals. Intact grassland soil specimens were saturated for 24 hr. After saturation was complete, 500 ml of deionised water was added to the beaker. The agitator paddle was then lowered to the mid-depth of the beaker in the overlying water and rotated at 20 rpm for 24 hr. This rotational speed corresponded with a tangential velocity of 0.034 m/s at the perimeter of the paddle. The most effective amendments (alum, poly aluminium chloride, ferric chloride, lime) were identified based percentage reduction in dissolved reactive P (DRP) and on cost effectiveness. Next, flumes 200-cm-long by 22.5-cm-wide by 5-cm-deep with side walls 2.5 cm higher than the soil surface, containing intact soil from a dairy farm treated with dairy slurry and amended slurry were subjected to simulated rainfall with an intensity of 11.5 mm hr-1. All experiments were conduced in triplicate. All runoff samples were tested for SS, DRP, total dissolved phosphorus (TDP) and total phosphorus (TP). Results showed that alum had the best potential to be a cost-effective amendment at low application rates (1.11 Al: TP). Compared to a slurry-only treatment (the study control), alum was best at reducing DRP in surface runoff. It reduced mean flow-weighted concentration (MFWC) of DRP by an average of 83% over 3 successive rainfall events, compared to 69% for lime, 86% for poly-aluminium chloride, and 67% for ferric chloride. Alum reduced the MFWC of TP loss by an average of 93% and particulate P (PP) by over 95%, compared to the study control. Future work will examine these treatments at field-scale, and will examine the effect of amendments on metal availability, and on gaseous emissions form slurry.

Reducing phosphorus runoff from biosolids with water treatment residuals.
Philip Moore Jr., USDA-ARS; Jason de Koff, USDA-ARS; Peter Kleinman, USDA-ARS; Rod Williams, University of Arkansas; Randy Young, Arkansas Natural Resources Commission
A large portion of the biosolids (sewage sludge) produced in the U.S. are incinerated or placed in landfills because of potential water quality problems, such as phosphorus (P) runoff. The objective of this study was to evaluate the effects of chemical amendments, including water treatment residuals (WTRs), on P runoff from biosolids. Rainfall simulations were conducted in 2006 on small plots fertilized with biosolids that had been treated with alum, ferric chloride or an alum-based WTR. The WTR was added a rate of 20% by weight. In 2007 rainfall simulations were conducted using WTR/biosolid blends of 15 and 30% by weight, which were allowed to incubate for three weeks prior to application. During year 1, soluble P loads in runoff with the 20% WTR treatment were not significantly different from alum or ferric chloride and resulted in a 48% reduction in soluble P runoff. Soluble P runoff loads in year 2 were reduced by 78% and 85%, respectively, with the 15 and 30% mixtures of WTRs. Greater reductions in P runoff found in the second year indicate that longer storage times may allow for greater P adsorption, most likely caused by P diffusion into micropores. Mixing biosolids with WTRs will allow for greater land application of biosolids and WTRs, which will greatly reduce the costs associated with landfilling and incineration of these two resources, while protecting the environment.

Treatment of golf course runoff using a phosphorus removal structure.
Chad Penn, Oklahoma State University; Joshua McGrath, University of Maryland; Greg Bell, Oklahoma State University; Dennis Martin, Oklahoma State University
Runoff dissolved phosphorus (P) losses are more difficult to control compared to particulate losses, especially because the former cannot be prevented via erosion control. A P removal structure designed to filter dissolved P from passing runoff was constructed using blast furnace steel slag as the sorption material. This structure was located in a drainage ditch that receives runoff from a golf course and several suburban neighborhoods. Background dissolved P concentrations were around 1 ppm. Water samples are collected before and after entering the structure with automatic samplers and all samples were analyzed for various parameters, including dissolved P. The overall design and effectiveness of the structure will be presented.