EFFECTS OF LIMEROCK AND NON- FARMED MUCK SUBSTRATES ON STORMWATER TREATMENT AREA PERFORMANCE

Transcription

1 EFFECTS OF LIMEROCK AND NON- FARMED MUCK SUBSTRATES ON STORMWATER TREATMENT AREA PERFORMANCE Thomas A. DeBusk 1, Kevin Grace 1, Mike Jerauld 1 Dawn Sierer-Finn 1, Manuel Zamorano 2 and Michelle Kharbanda 1 1 DB Environmental, Inc., Rockledge, FL, USA 2 South Florida Water Management District, West Palm Beach, FL, USA April 22, 2015

2 Vegetation communities characteristic of STA flow paths For Everglades STAs, several early studies demonstrated that SAV communities offer the greatest promise for achieving low outflow [TP]

3 STA-3/4 Emergent Emergent Emergent Submerged Submerged Submerged Typical STA configuration- wetland communities developed on previously farmed soils: emergent vegetation (EAV) front end, submerged vegetation (SAV) back end

4 STA-2 There exist two unique flow paths in STA-2: Cell 3, primarily SAV, with most of the footprint situated on prior farm land and Cell 5 Cell 6 Flow-way 4 Cell 4 Flowway 1 Flowway 3 Cell 3 Flow-way 2 Cell 2 Cell 1 Cell 1, primarily EAV, developed on a relic marsh parcel that was not previously farmed (NPF) Cell 7 Flow-way 5 Cell 8

5 Total P Concentrations in the Water Column Along the Flow-Ways of STA-2 Cells 1 and 3 TP (µg/l) July 2001 Sept 2005 n=20 Sept 2005 Jan 2010 n=16 Inflow A C E G I Outflow Cell SRP DOP PP 100 P (µg/l) Cell 1 0 Inflow A B C D E F G H I J Outflow 2/25/14

6 Limerock substrates also are under investigation in a configuration termed Periphyton STAs (PSTA) The PSTA concept generally refers to: Treatment wetland with a lime rock (LR) substrate, achieved either through muck removal or LR cover placed over muck Deployed as a back end STA community The lime rock provides a stable substrate, and therefore minimizes potential sediment P contribution to water column via diffusive flux, bioturbation and/or macrophyte mining Vegetation that develops/persists is adapted to low P conditions, and can support microbial communities that contribute to removal of relatively recalcitrant P forms (e.g., dissolved organic P [DOP])

7 Aerial photo of STA-3/4 PSTA Cell

8 Mean inflow and outflow [TP] for STA-2 Cells 1 & 3, and the STA-3/4 PSTA Cell Inflow Outflow TP (µg/l) STA 2 Cell 3 STA 2 Cell 1 PSTA Average of annual means from May 2007 April 2013, excluding WY 2010 Source: 2013 SFER, 2014 SFER and 2015 SFER

9 Comparison of soils that accrete in PSTA and SAV wetlands PSTA Cell 2B-SAV Cell 3B-SAV

10 TP content of surficial soils in outflow regions of the wetlands TP (mg/kg) STA2 Cell 3 STA 2 Cell 1 PSTA Cell

11 Depth (cm) SRP (µg/l) Outflow region soil porewater soluble reactive phosphorus (SRP) profiles for STA-2 Cells 1 & 3; and for the STA-3/4 PSTA cell STA 2 Cell 3 STA 2 Cell 1 PSTA Cell

12 The EAV SAV PSTA flow path in the STA-3/4 central flow-way Flow direction EAV SAV PSTA km

13 SAV EAV Surface water [TP] along the central STA-3/4 EAV, SAV and PSTA flow path in June 2014 PSTA 0 25 Surface Water TP (µg/l) A B C D Inflow B E G I L Outflow STA 3/4 Central Inflow Cell 2A Outflow Upper SAV Cell PSTA Cell

14 Surface water phosphatase enzyme activity along the central STA-3/4 EAV, SAV and PSTA flow path in June APA PDE Surface Water Enzyme Activity (µm MUF released/hr) STA 3/4 Central Inflow Cell 2A Outflow A B C D Inflow B E G I L Outflow Upper SAV Cell PSTA Cell APA- alkaline phosphatase activity PDE phosphodiesterase activity

15 Production of phosphatase enzymes also may account for the low outflow TP levels achieved by Cell 1 P (µg/l) SRP DOP PP Inflow A B C D E F G H I J Outflow Enzyme Activity (µm MUF released/hr) *MDL PDE APA * * * * * * * * * * * * Inflow A B C D E F G H I J Outflow 2/25/14

16 Wetlands that are lime rock based, and those developed on NPF lands, can provide slightly lower outflow TP concentrations than those constructed on farmed muck soils Neither soil TP content nor porewater [SRP] appear to correlate well with outflow P concentrations for these systems Both lime rock based, and NPF wetlands, exhibit elevated outflow region phosphatase enzyme activity Additional investigations are underway on phosphatase enzyme activity and soil chemical parameters in these flow paths Summary This research was jointly funded by the Everglades Agricultural Area Environmental Protection District and the SFWMD