Filtering mediums for treating stormwater runoff: Lessons from ditch drained agriculture

Transcription

1 Filtering mediums for treating stormwater runoff: Lessons from ditch drained agriculture R.B. Bryant USDA Agricultural Research Service University Park, PA Workshop: Re-plumbing the Chesapeake Watershed, October 9, 2010

2 A safe operating space for humanity Johan Rockström, et al Nature 461,

3 Denitrification A microbially facilitated process of nitrate reduction (performed by a large group of heterotrophic facultative anaerobic bacteria) that may ultimately produce molecular nitrogen (N 2 ). Microbes consume carbon and scavenge nitrate NO 3 2 NO 2 NO N 2 O N 2 Greenhouse gas

4 Denitrification Wall Wood Chips Biochar Photos courtesy of Zach Easton Virginia Tech

5 3:30 Dr. Laura Christianson (Conservation Fund Freshwater Institute) Wood chip bioreactors: A cutting edge strategy for water quality

6 Phosphorus sorption reactions P reacts with Ca, Fe, Al, and OM PO 4 + Ca CaHPO 4 precipitation Surface reactions: exchange, ligand with iron, aluminum, organic matter

7 P sorbing industrial byproducts FGD gypsum synthetic gypsum (calcium) Acid mine drainage treatment residuals (Fe & Al oxides) Fly ash Bauxite mining and production waste (red mud) Drinking water treatment residuals (alum) Steel slag waste

8 Flue Gas Desulfurization Gypsum Low contaminants Widely available Silt size Handles easily High solubility releases Ca Precipitation reaction is relatively slow

9 Coal Combustion Fly Ash Contains heavy metals Widely available Sand to gravel size Handles easily Insoluble Fe and Al Sorption reaction is relatively rapid

10 Drinking Water Treatment Residuals Low contaminants Widely available Ground to gravel size Raw material must be dried and ground Aluminum sulfate (alum) Rapid sorption reaction

11 Acid Mine Treatment Residuals Contains heavy metals Available in PA Silt to gravel size Handles easily Fe and Al oxides Rapid sorption reaction

12 Bauxite (Aluminum ore) Mining Waste Contains heavy metals Jamaica mines Silt to gravel size Handles easily Carbonate, Fe oxides, clays Rapid sorption reaction

13 Steel Slag Waste Contains heavy metals Widely available Gravel size Handles easily Fe and Al oxides and Ca Rapid sorption reaction and Ca precipitation

14 Soil test P levels are high on the Eastern Shore of Maryland Restricted to fields where the Maryland P Index was run (FIV > 150 only) Garrett Allegany (no data) Washington Frederick Carroll Baltimore Harford Cecil Mean Maryland P Fertility Index Value Montgomery Howard (no data) Prince George s Charles Anne Arundel St. Mary s Calvert Kent Queen Anne s Talbot Dorchester Caroline Wicomico UMES Worcester Somerset Average P FIV = 374

15 No change in soil test P after one decade of continuous corn : Zero P additions High soil P has water quality consequences 3 Allegheny Plateau Ridge & Valley Piedmont Coastal Plain Mehlich-3 soil P (mg/kg) Lime 2 1 Dissolved P in runoff (mg/l) UMES 0 Maryland, USA (Kleinman et al., 2010)

16 P Loss (kg/ha) Total P loads from drainage ditches Annual loads vary with precipitation UMES Experiment Station Former Poultry Farm 467 mg/kg 382 mg/kg 466 mg/kg Ditch filter protects 40 acres mg/kg mg/kg 421 mg/kg 2 1

17 FGD gypsum filter 1 st generation 120 tons of FGD gypsum (5 truck loads) 30 m

18 P Removal by filtration

19 P removal efficiency is greatest at low flow rates 100 P removal efficiency (%) mean P removal efficiency = 75% Flow rate through filter (L day -1 m -2 )

20 Arsenate behaves like phosphate As concentrations in filtrate < ditch drainage water Solution Label P IN P OUT As IN As OUT Instrument mg/l detection limit mg/l UMES UMES UMES UMES max

21 P removal by gypsum filter for April 13, 2007 Storm event: 0.64 inches of rain in 13 hrs. P Entering Ditch kg P entering filter kg P bypassing filter 0.00 kg P removed by filter kg P not removed by filter kg P entering Manokin R kg

22 P removal by gypsum filter for April 18, 2007 Storm event: 3.31 inches of rain in 30 hrs. P entering ditch 8.22 kg P entering filter 0.66 kg P bypassing filter 7.56 kg P removed by filter 0.51 kg P not removed by filter 0.15 kg P entering Manokin R kg

23 Dissolved P (KG) Dissolved P loads in 17 storm events P that bypassed filter (total = 21 kg) P removed by filter (total = 2.5 kg)

24 Flow rate (L/s) Maximum flow rate through gypsum over time tillage siltation?

25 Depth below land surface (cm) P transport processes in Coastal Plain soils 0 50 Mehlich-3 P P concentration Drainage ditch 300 mg kg mg kg -1 5 mg L -1 2 mg L -1 10% 90 % mg kg mg L

26 Depth below land surface (cm) FGD gypsum curtain 2 nd generation 0 Mehlich-3 P P conc. Gypsum curtain Drainage ditch 300 mg kg -1 berm 5 mg L mg L mg kg -1 5 mg kg -1 2 mg L mg L mg L mg L

27 FGD gypsum curtain 2 nd generation Width 30cm Depth 1.5m 8 curtain segments: 20 m berm

28 FGD gypsum curtain 2 nd generation Applying the practice at a larger scale

29 Detention pond inlet Clean out Drainage control structure Perforated inlet pipe To filter

30 Filter vault simultaneous testing of multiple systems Inlet (from pond) Filter System 2 Filter System 1

31 Filter vault (top view) Head pressure control Back pressure control Backwash routing Influent (from pond) Partic. filter Bio. reductant Chem. sorbant Treated effluent Backwash routing Partic. filter Chem. reduct. Chem. sorbant Treated effluent Backwash routing

32 Questions?