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