Source reduction for urban stormwater

729 views

Published on

Presentation discusses "source reduction" for stormwater management.

Published in: Technology
0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total views
729
On SlideShare
0
From Embeds
0
Number of Embeds
8
Actions
Shares
0
Downloads
7
Comments
0
Likes
0
Embeds 0
No embeds

No notes for slide

Source reduction for urban stormwater

  1. 1. Biogeochemical Perspectives on Stormwater Management Larry Baker Water Resources Center and WaterThink, LLC
  2. 2. Goals • Examine problems with best management practices (BMPs) • Examine biogeochemical processes – Process limitations – Sustainability • Applications: – Soluble P – Nitrate removal – Road salt • Human dimension
  3. 3. Limitations of end-of-pipe storm water treatment 1. Low and variable treatment performance 2. High cost:  $1000/Ton SS (Weiss et al. 2007)  $500/kg P 3. Some constituents are not readily treated in BMPs (chloride, soluble P, fecal coliforms) 4. Poor cold weather performance 5. Low sustainabilty (pollutant accumulation, clogging, etc.) 6. Unfair cost allocation – polluted pays
  4. 4. Typical removal efficiencies for structural BMPs Source: Weiss et al., 2007 Type Phosphorus Sediment Ave. % CV, % Ave. % CV, Removal removal % Dry extended 53 ±28 25 ±15 ponds Wet basins 65 ±32 53 ±23 Bioretention 85 ±23 72 ±11 Sand filters 85 ±14 46 ±31 Wetlands 68 ±25 42 ±26
  5. 5. Gas loss: CO2 (decomposition) N2 (denitrification) VOCs Plant uptake N, P, metals Recycled Pollution production Algae growth Water Remaining Sediment pollutants- Soluble P, Sedimentation coliforms, salt, Plant debris suspended solids Adsorption Sediment accumulation P recycling Toxics? Processes in a stormwater pond or wetland
  6. 6. Gas loss: CO2, N2, VOCs Pollution production Clogging Filtration Metal accumulation Soil Adsorption Saturation of Precipitation adsorption sites Nitrate Aquifer Chloride Processes in infiltration BMPs
  7. 7. Level 1: Sources to watershed Level 2: Sources from landscapes to streets Level 3: Source from streets to storm sewer End-pipe-BMPs Detention basins Wet ponds Infiltrations basins Wetlands Pollutant mass balances: Streets are not a source of pollution System boundaries but a conduit for pollution
  8. 8. Level 1 analysis: Effect of lawn P fertilizer restriction Before MN P fertilizer ban After MN P fertilizer ban Source Input rate total, % total, % kg/yr kg/yr Fertilizer 7.5 kg/ha-yr 1,920 73 1,000 0 Dogs 1.2 kg/dog-yr 1,770 23 1,770 86 Irrigation 0.3 mg P/L; 0.2 m/yr 169 2 169 8 Deposition 0.25 kg/ha-yr 125 2 125 6 Total - 3,984 100 3,064 100 23% reduction Conditions: 5 km2 residential neighborhood, 0.5 ha lot size, 20% impervious area on lot; 80% pervious area fertilized; 1 dog/house; irrigation. Updated from Baker and Brezonik, 2007 using MN Ag 2006.
  9. 9. Level 2 analysis: Inputs from boulevard trees to streets Example: maple trees DBH measurement (based on UFORE model) Maples (all species) 50 Leaf fall, kg P per tree 40 y = 0.0009x2.2188 30 R2 = 0.9959 20 10 0 0 50 100 150 Diameter at breast height, cm
  10. 10. 2.5 Particulate P Level 2 analysis 2.0 Soluble P P, mg/L (cont’d): 1.5 Lawn runoff to 1.0 street 0.5 0.0 Source: Barten (1994) M HN HF VHN VHF 3000 For comparison: 2500 Suspended solids SS, mg/L Raw sewage 2000 P = 5 mg/L 1500 SS = 200 mg/L 1000 500 Eutrophic lake: 0 P = 0.05 mg/L M HN HF VHN VHF
  11. 11. Soil P level vs. dissolved P in runoff from turf (left) and bare soil (right) Soldat et al., 2008 Water, Air, Soil Poll.
  12. 12. Level 2 (lawns to street) total P input Assumptions: Atm. Dep. Dogs Trees - Medium fertility lawns 10% - 1 tree per 20 m 0% 20% - 30 m lot width - 0.6 dogs/household Lawn 70% Percentage of total P entering street (total = 8 kg P/km street) Baker et al., Chapter 7, in Assessment of Stormwater BMPs Manual (WRC web page)
  13. 13. Exported clippings Fertilizer P Runoff soluble P Growing turf Mowed grass Runoff particulate P Lawn P cycle Soil inorganic P Soil organic P Leaching Integrating biophysical and social aspects of lawns to reduce soluble P in runoff Baker, Wilson, Fulton, and Horgan, Cities and the Environment, 2008.
  14. 14. Nowak disproportionality concept applied to lawns Nowak et al., 2006 Society and Natural Resources 3 or more fertilizer applications,+ mulching Site management Steep slope, low High infiltration soil nutrient export Site design
  15. 15. 25 Target these Low slope 20 Steep slope % runoff 15 Modeled runoff for 1” storm 10 5 0 Sand Fine-sand Clay-fine Clay Soil type • Target vulnerable lawns (biophysical dimension)
  16. 16. 100 % of homeowners 80 “Casual” “Perfectionist” 60 40 20 0 0 1 or 2 3 or 4 >5 # of fertilization times 2. Tailor messages to homeowner types (social dimension)
  17. 17. Adaptive management for road salt 300,000 MNDOT Salt use, tons/yr 250,000 200,000 150,000 100,000 50,000 0 19 -60 19 -64 19 -68 19 -72 19 -76 19 -80 19 -84 19 -88 19 -92 19 -96 20 -00 4 -0 59 67 75 79 87 99 63 71 83 91 95 03 19
  18. 18. 200 Stream chloride, mg/L 150 y = 31.352e0.0437x R2 = 0.85 100 50 0 0 10 20 30 40 % impervious Relationship between % impervious surface and average stream chloride Sander, Novotny, Mohseni, and Stefan, 2008
  19. 19. Adaptive management schematic Road crews add salt for snow/ice event. Salt quantities recorded dialogue Sensor network records specific conductance; temperature Event analyzed by team - Weather - Pavement conditions - Stream chloride Recommendations summarized; transmitted to road crews
  20. 20. Why adaptive management should work • “Salt” easy to measure – conductivity • There are many alternatives - Alternative salts (calcium acetate, etc.) - Alternative methods – pre-wetting; brine • Public works crews are small, dedicated • Communication would be fairly easy • Many learning opportunities • Could save money and improve safety • Nothing else will work – chloride is conservative
  21. 21. Mi Inflow ss is s Precipitation 16.86 ipp 2.42 Evaporation i+ 1.37 Withdrawal Mi nn 0.18 es ot a Ri Wastewater 0.41 Outflow ve rs 17.99 Runoff 0.82 Groundwater pumping 0.46 Recharge 0.46 (assumed) Will stormwater management alter the Twin Cites hydrologic balance?
  22. 22. Summary • Structural BMPs are necessary but not sufficient to meet water quality goals • We need to move toward a multiple barrier strategy LID design  source reduction  structural BMPs • Understanding biogeochemical processes – and limitations – tends to move point of control upstream • Urban biogeochemistry involves human choice and the biophysical system • Stormwater management is part of broader urban water management – hydrologic balance, etc.
  23. 23. References • Baker, L.A. 1998. Design considerations and applications for wetland treatment of high-nitrate waters. Water Science Technology 38: 389-395. • Baker, L. 2007a. Instant runoff [on source reduction for stormwater]. Star and Tribune, Minneapolis. • Baker, L. A. 2007b. Urban stormwater: getting to the source. Storm water 8:8. • Baker, L. A., R. Holzalksi, and J. Gulliver. 2008a. Source reduction.in J. a. J. A. Gulliver, editor. Minnesota stormwater assessment manual. Minnesota Water Resources Center, St. Paul. • Baker, L. A., P. Westerhoff, and S. M. 2006. An adaptive management strategy using multiple barriers to control tastes and odors. Journal of the American Water Works Association 98:113-126. • Baker, L. A., B. Wilson, and D. D. Fulton. 2008b. Disproportionality as a framework to target nutrient reduction from urban landscapes (invited paper). Cities and the Environment. 1:Artilce 7. • Baker, L. A., B. Wilson, J. Gulliver, O. Moshir, A. J. Erickson, and R. M. Hozalski. 2008c. Process assessment framework.in J. Gulliver, and J. Anderson, editor. Assessment of Stormwater Best Management Practices. Minnesota Water Resources Center St. Paul. • Ingersoll, T. and L. A. Baker. 1998. Nitrate removal in wetland microcosms. Water Research . 32:766-684. • Nowak, P., S. Bowen, and P. Cabot. 2006. Disproportionality as a framework for linking social and biophysical systems. Society and Natural Resources 19:153-173. • Soldat, D. J., A. M. Petrovic, and Q. M. Ketterings. 2008. Effect of soil phosphorus levels on phosphorus runoff concentrations from turfgrass. Water, Air, Soil Poll. online. • Weiss, P. T., J. S. Gulliver, and A. J. Erickson. 2007. Cost and pollutant removal of storm-water treatment practices. J. Water Resources Planning and Management 133:218-229. Most of my articles can be downloaded from my WRC web site: http://wrc.umn.edu/aboutwrc/staff/baker/index.html (click on “vita”) Non-technical articles can also be downloaded from WaterThink.com

×