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Fiona Napier Urban Water Technology Centre

AN ASSESSMENT OF THE EFFECTIVENESS OF VEGETATION HARVESTING AS A MEANS OF REMOVING NUTRIENTS AND METALS FROM PONDS. Fiona Napier Urban Water Technology Centre Dr Michael Barrett Center for Research in Water Resources Prof Chris Jefferies Urban Water Technology Centre. Why the study?.

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Fiona Napier Urban Water Technology Centre

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  1. AN ASSESSMENT OF THE EFFECTIVENESS OF VEGETATION HARVESTING AS A MEANS OF REMOVING NUTRIENTS AND METALS FROM PONDS Fiona NapierUrban Water Technology Centre Dr Michael Barrett Center for Research in Water Resources Prof Chris Jefferies Urban Water Technology Centre

  2. Why the study? AQUATIC PLANTS HARVESTING INCREASEDMAINTENANCECOSTS

  3. Why the study? AQUATIC PLANTS HARVESTING INCREASEDMAINTENANCECOSTS POLLUTANT REMOVAL BENEFIT?

  4. Key questions to answer • What mass of each selected constituent is removed from the system when vegetation is harvested?

  5. Key questions to answer • What mass of each selected constituent is removed from the system when vegetation is harvested? • How does this figure compare with mass of each constituent being removed by all processes within the system?

  6. Methodology • Desk study

  7. Methodology • Desk study • Chemical mass balance for nutrients and metals in a pond treating urban/highway runoff, using data gathered from a number of published studies.

  8. Data requirements • In-situ pond with established vegetation and receiving urban/highway runoff

  9. Data requirements • In-situ pond with established vegetation and receiving urban/highway runoff • Levels of selected constituents entering and leaving pond

  10. Data requirements • In-situ pond with established vegetation and receiving urban/highway runoff • Levels of selected constituents entering and leaving pond • Known weight of harvested vegetation

  11. Data requirements • In-situ pond with established vegetation and receiving urban/highway runoff • Levels of selected constituents entering and leaving pond • Known weight of harvested vegetation • Chemical composition of removed plant material

  12. La Costa pond • Retention pond on Interstate 5, California

  13. La Costa pond • Retention pond on Interstate 5, California • Recieves flow from 1.7ha catchment (48% impermeable cover), including northbound lanes of highway

  14. La Costa pond • Retention pond on Interstate 5, California • Recieves flow from 1.7ha catchment (48% impermeable cover), including northbound lanes of highway • 3 year water quality monitoring program

  15. La Costa pond • Retention pond on Interstate 5, California • Recieves flow from 1.7ha catchment (48% impermeable cover), including northbound lanes of highway • 3 year water quality monitoring program • Established vegetation, including Typha

  16. La Costa pond • Retention pond on Interstate 5, California • Recieves flow from 1.7ha catchment (48% impermeable cover), including northbound lanes of highway • 3 year water quality monitoring program • Established vegetation, including Typha • Annual programme of Typha harvesting

  17. La Costa Pond Pre-harvest Post-harvest

  18. La Costa pond Data available for pond • Flow data • Input/output concentrations for N, P, Cu, Pb, Zn • Known weight of harvested vegetation

  19. La Costa pond Data available for pond • Flow data • Input/output concentrations for N, P, Cu, Pb, Zn • Known weight of harvested vegetation Data unavailable for pond • Chemical composition of plant material

  20. Additional data sources Criteria for inclusion in study:- • Plant studied must be Typha

  21. Additional data sources Criteria for inclusion in study:- • Plant studied must be Typha • Must be grown in environment containing levels of nutrients and metals similar to La Costa

  22. Additional data sources Criteria for inclusion in study:- • Plant studied must be Typha • Must be grown in environment containing levels of nutrients and metals similar to La Costa • Must be harvested at same point in growing season

  23. Results

  24. Cost effective ? Plant harvesting >70% total maintenance manhours = $14 000 (£7700)

  25. Why include vegetation in ponds? • Aesthetics/amenity • Safety • Habitat • Vector/algae control • Pollutant removal

  26. Reducing costs? Garver, E. G., Dubbe, D.R.. and Pratt, D.C. Seasonal patterns in accumulation and partitioning of biomass and macronutrients in Typha spp Aquatic Botany 32 pp115-127. 1988

  27. Reducing costs? • Study carried out over 2 growing seasons • Identified July of second growing season as time for removing maximum amount of nutrients in minimum amount of biomass

  28. Improving pollutant removal? Fritioff, A. and Greger, M. Aquatic and terrestrial plant species with potential to remove heavy metals from stormwater. International Journal of Phytoremediation 5(3) pp 211-224 (2003)

  29. Improving pollutant removal? • Typha metal accumulation: sediments»roots/rhizome»leaves/shoots • Study showed that some submersed and free-floating aquatic plants have higher metal accumulation capacity in their shoots than emergent species

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