Slide1: 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?: Why the study? AQUATIC PLANTS HARVESTING INCREASED MAINTENANCE COSTS


Why the study?: Why the study? AQUATIC PLANTS HARVESTING INCREASED MAINTENANCE COSTS POLLUTANT REMOVAL BENEFIT?


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


Key questions to answer: 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?


Methodology: Methodology Desk study


Methodology: 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.


Data requirements : Data requirements In-situ pond with established vegetation and receiving urban/highway runoff


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


Data requirements : 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


Data requirements : 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


La Costa pond: La Costa pond Retention pond on Interstate 5, California


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


La Costa pond: 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


La Costa pond: 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


La Costa pond: 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


La Costa Pond: La Costa Pond Pre-harvest Post-harvest


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


La Costa pond: 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


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


Additional data sources: 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


Additional data sources: 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


Results: Results


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


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


Reducing costs?: 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


Reducing costs?: 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


Improving pollutant removal?: 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)


Improving pollutant removal?: 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