Three-Dimensional Phosphorus Sorption by Drinking Water Treatment Residuals

1. Three-Dimensional Phosphorus Sorption by Drinking Water Treatment ResidualsKonstantinos C. Makris

2. Rationale • Need long-term solutions to reduce excess soluble P in soils and waters. • Drinking water treatment residuals (WTRs) seem a potential long-term solution. • Why use WTRs: • Cost-effective • Rich in P-loving metals (Fe, Al) • Non-hazardous residuals • High P sorption capacities

3. Synopsis • Macroscopic characterization of WTRs • Microscopic characterization of WTRs • Long-term stability of sorbed P • Spectroscopic analyses • Long-term effects of WTR application to two MI soils • Heat Incubations • Conclusions

4. Macroscopic Characterization

6. P sorption isotherms (23C) after 80d. pH was not adjusted, no shaking.

7. 2nd order reaction rate kinetics P sorption kinetics and a initial pulse input of 10,000 mg P kg-1.

8. P desorption with 5mM oxalate solution in the dark of the P-treated WTRs (initial P load = 10 g P kg-1)

10. Long-term Stability of Sorbed P • Three approaches to “compress” and simulate long-term effects. • Study the physical nature of the adsorbent; micropores may severely restrict sorbed P mobility. • Utilize heat incubations at elevated temperatures (46, 70C) to hasten reactions that could occur in decades in the field. • Monitor longevity of a WTR effect on soil P (5.5 years after WTR application) at two sites (Holland, MI).

11. Physical nature of the WTRs • H0 (1): Micropores in WTRs may be responsible for slow P sorption kinetics, and even slower desorption. • H0 (2): WTRs could ultimately immobilize P.

12. Objectives • To determine mechanisms and pathways of P sorption by WTRs. • To interpret the mechanisms in terms of long-term stability of sorbed P.

14. 1.2 1.0 0.8 SSA ratio 0.6 2 / CO 2 r = 0.84 2 N 0.4 0.2 0.0 0 5 10 15 20 25 TC content (%)

16. Hypotheses With P No P Al-WTR, Bradenton, FL.

17. Mean P adsorption monolayer capacity goethites = 0.24 mg PO4 m-2. gibbsites = 0.095 mg PO4 m-2. (Torrent et al., 1990). (van Riemsdijk and Lyklema, 1980) Total P Uptake Fe-WTR = 7.88 mg PO4 m-2Al-WTR = 1.23 mg PO4 m-2 More than what the monolayer capacity can explain!!!

18. no P, 80d with P, 80d ~20μm ~20μm Particle’s cross section Image P dot map Fe dot map

19. 0.020 LSD α=0.05 = 0.0034 n=15 80d 0.016 Significant interaction, 95% confidence level. P/(P+Fe) 0.012 1d 0.007 0.003 no P with P Fe-WTR, Tampa at the interior of the particles.

20. 0.039 LSD α=0.05 = 0.004 n=10 0.030 NO significant interaction, 95% confidence level. P/(P+Fe) 0.021 80d 0.012 1d 0.003 interior edge Fe-WTR, Tampa of the P-treated particles.

21. Micropore CO2-SSA based on the Dubinin Radushkevich method (DR) of WTRs treated with and without P for 80d.

22. 8A

23. 8A

24. Long-term Stability (2nd approach)Incubations at elevated temperatures (46, 70C). Synthetic Al and Fe hydroxides with and w/o P Soils amended with WTRs: i) Holland, MI. ii) Okeechobee, FL WTRs: with and w/o P System complexity

25. Hypotheses • H0 (1): Elevated temperatures will induce structural changes of particles towards more crystalline structures. • H0 (2): Transformation of the WTRs towards more crystalline phases (aging), would decrease P extractability.

26. crystalline formation detected with XRD (pseudoboehmite) 200mM oxalate extractable P and Al in the Al gels with time at 70C.

32. Monitoring of P extractability in the field 5.5 years after WTR application.

35. Site 1 PSI = ox-P / (ox-Fe + ox-Al)

36. Site 2

37. Conclusions • Multiple lines of evidence that P sorption is three-dimensional (intraparticle diffusion in micropores of WTRs): • minimum P desorption / maximum P sorption • 2nd order kinetics • Changes in SSA / microporosity • microprobe • Micropore-bound P is stable and immobilized.

38. Conclusions • Heat incubations for two years showed no changes in materials crystallinity. Elevated temperatures simply increased the rate of P diffusion towards the interior of the particles • Five and a half years following WTR application to two sites in MI, we observed no release of P with time in the WTR-amended plots.

39. Intraparticle P diffusion in micropores Long-term WTR application field experiment Heat incubations of the WTRs Sorbed P by WTRs may be stable and immobilized in the long-term.

40. Practical Significance • WTRs may be land-applied to agricultural fields, ponds, or to animal wastes to reduce soluble P levels. • Sorbed P may be stable in the long-term unless acidic conditions occur (pH<4). • WTRs land application may be a best management practice to reduce potential P losses in sandy soils.

41. Acknowledgements • This work was funded by a U.S. E.P.A. grant. • Work conducted in Univ. Florida campus:

42. Acknowledgements MY COMMITTIEE PROFESSORS

43. Acknowledgements • Drs. Moudgil, Sartain, Reddy, Ma. • Soil Chemistry Lab-Scott Brinton • Soil Mineralogy Lab-Keith Hollien • PERC Labs- Gill Brubaker • Turf Science Lab- Ed Hopwood

44. Acknowledgements • I would also like to thank: • Greg Means • Bill Pothier • Thomas Luongo • Bill Reve • The Newell-Penthouse residents • L. Walker • N. Kabengi • J. Leader • T. Hanselman

45. SEE YOU ALL IN GREECE THIS AUGUST!