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Lanthanum-modified clay

Lanthanum-modified clay. An innovative new tool for the phosphorus management toolbox. Lanthanum. A “rare earth” element (REE) with a number of medical and industrial uses Preferentially binds with phosphate (PO 4 3- ) ions

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Lanthanum-modified clay

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  1. Lanthanum-modified clay An innovative new tool for the phosphorus management toolbox

  2. Lanthanum A “rare earth” element (REE) with a number of medical and industrial uses Preferentially binds with phosphate (PO43-) ions The reaction product is a naturally-occurring mineral (rhabdophane; LaPO4) that is essentially insoluble in water (Ksp< 10 –27 ) Medicinal use – lanthanum is the active ingredient in an FDA-approved medication (FosrenolTM) used to control serum phosphate levels in patients with advanced kidney disease

  3. Lanthanum (cont.) Widely distributed in soils and sediments throughout the world USGS data indicate that the average concentration in soils and sediments in the continental U.S. is around 30 mg/kg The “rare” in “rare earth” refers to the availability of deposits large enough to be mined economically

  4. Potential Water Quality Application From C.S. Reynolds “Ecology of Phytoplankton” (2006) • As a phosphorus management tool, modified clay minerals based on lanthanum offer: “the P-binding properties of metal oxides and hydroxides but without causing the toxicity problems that direct dosing of (say) iron or aluminum salts might cause to water bodies” • And are: “especially effective, removing phosphorus from solution and firmly immobilizing it in the particulate sedimentary fraction”

  5. R&D Background A lanthanum-modified bentonite clay was developed and tested by Australian government researchers in the Commonwealth Scientific and Industrial Research Organization (CSIRO) in the late 1990s • Douglas, G.B., J.A. Adeney, and M.S. Robb. 1999. A novel technique for reducing bioavailable phosphorus in water and sediments. In: International Association Water Quality Conference on Diffuse Pollution, pp. 517–523. • Robb, M., B. Greenop, Z. Goss, G. Douglas, and J. Adeney. 2003. Application of Phoslock®, an innovative phosphorus binding clay, to two Western Australian waterways: preliminary findings. Hydrobiologia 494: 237–243

  6. Commercialization as “Phoslock™” • Raw materials: • Inactive carrier - bentonite clay • Active ingredient - lanthanum (5 % by weight), exchanged for sodium ions in the clay matrix • Patented by CSIRO; production rights licensed to Phoslock Water Solutions, Ltd. • Binds phosphate ions under a wide range of pH and redoxconditions (including anoxia)

  7. Key PO4 Phoslock Mode of action: adsorbs and chemically binds bioavailable phosphorus (forming rhabdophane) Before application Following application During application Phoslock strips PO4 from the water column and forms a thin (1-2 mm) layer at the sediment surface Phoslock settles through water column

  8. Water quality benefits following treatment 1) As PO4 levels are reduced, P becomes the limiting nutrient and the N:P ratio increases 2) These changes reduce algal biomass (and cyanobacterial dominance, if present) 3) PhoslockTM adsorbs “internally recycled” PO4 as it is released from sediments 4) In shallow water bodies, it also appears able to adsorb “new” P introduced to the water column via inflows

  9. Calculating dose rates • Based on the mass of BAP present in the water column and upper layer (e.g., upper 5-10 cm) of sediments • Requires standard water quality data (TP, SRP, alkalinity, etc.) • Sediment samples also needed, for P fractionation analysis • Basic water and P budget information (inputs, outputs) • 100 kg of PhoslockTM binds approximately 1 kg of BAP • Dose depends on mass of BAP present and post-application P target level

  10. Application Methods

  11. Global Phoslock Applications • >150 applications to date, on several continents • Australia & New Zealand • China & SE Asia • South Africa • Germany, Poland, the Netherlands • UK (Scotland) • Canada (Ontario) • US (California)

  12. Toxicological Issues • Human health • PhoslockTM applications to waterbodies do not pose human health risks • Bentonite has very low toxicity to humans (acute oral toxicity LD50>15 g/kg); approved as a food additive • La used in human medicine (FosrenolTM); FDA approved dose of 750 – 3,000 mg/day • PhoslockTM recently approved by NSF/ANSI for use in potable water treatment • Eco-toxicology • Potential for La toxicity to zooplankton if high PhoslockTMdoses are applied to water with low alkalinity (<20 mg/L) and/or low PO4-P (<5 µg/L) concentrations • Pre-application jar tests are used to ensure that appropriate dose rates are used under such conditions • EC50 for free La ≈ 20 – 150 mg/L • La concentrations in treated lakes typically 0.02 – 0.10 mg/L

  13. Numerous publications, reports, and case studies are available… • http://www.phoslock.com.au/technical.php • http://www.phoslock.eu/?subject=en-publications

  14. Potential uses in Florida? Managing BAP levels in eutrophic waters where P is the primary nutrient causing impairment May be particularly helpful for managing eutrophic lakes and reservoirs that have large internal P loads (e.g., systems where external source reductions alone will not be sufficient or cost-effective) Achieving P reduction goals for TMDLs and NNC Reducing P exports from older stormwater management systems? (Current research by the Lake Simcoe Region Conservation Authority [LSRCA] in Ontario)

  15. Thanks for your time! Contact Information: Gerold Morrison, Ph.D. AMEC Environment & Infrastructure gerold.morrison@amec.com tel. 863-640-2385

  16. Some References Douglas, G.B., J.A. Adeney, and M.S. Robb. 1999. A novel technique for reducing bioavailable phosphorus in water and sediments. In :International Association Water Quality Conference on Diffuse Pollution, pp. 517–523. Egemose, S., K. Reitzel, F. Andersen, and M.R. Flindt. 2010. Chemical lake restoration products: sediment stability and phosphorus dynamics. Environ. Sci. Technol. 44:985–991 Groves, S. 2010. Eco-toxicity assessment of Phoslock®. Phoslock Water Solutions, Limited. NSW, Australia. 32 pp. (http://www.phoslock.com.au/docs2/24.%20Eco-toxicity%20Assessment%20Report-May%202010-Final.pdf) Lürling, M.L., and Y. Tolman. 2010. Effects of lanthanum and lanthanum-modified clay on growth, survival and reproduction of Daphnia magna. Water Research 44:309 – 319 McNabb, T. 2011. A new tool for proactive water quality restoration. Land and Water, May/June 2011, pp. 18 – 23 (http://sepro.com/documents/Phoslock/CaseStudies/Phoslock%20Case%20Study%20-%20ANewTool.pdf) Persy, V.P, G.J. Behets, A.R. Bervoets, M.E. DeBroe, and P.C. D’Haese. 2006. Lanthanum: a safe phosphate binder. Seminars in Dialysis 19:195–199 Reynolds, C.S. 2006. Ecology of Phytoplankton. Cambridge University Press. Cambridge, UK. 535 pp. Robb, M., B. Greenop, Z. Goss, G. Douglas, and J. Adeney. 2003. Application of Phoslock®, an innovative phosphorus binding clay, to two Western Australian waterways: preliminary findings. Hydrobiologia 494: 237–243 Ross, G., Haghseresht, F., Cloete, T.M., 2008. The effect of pH and anoxia on the performance of Phoslock®, a phosphorus binding clay. Harmful Algae 7: 545–550

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