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I-70 Greenfield Rest Area Constructed Wetland

I-70 Greenfield Rest Area Constructed Wetland. Faculty/Staff: R. S. Govindaraju, J. E. Alleman, and T. J. Cooper Students: T. P. Chan and N. R. Shah . School of Civil Engineering Purdue University March 29, 2005. https://engineering.purdue.edu/ResearchGroups/Wetland. Project Involvement.

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I-70 Greenfield Rest Area Constructed Wetland

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  1. I-70 Greenfield Rest AreaConstructed Wetland Faculty/Staff:R. S. Govindaraju, J. E. Alleman, and T. J. Cooper Students:T. P. Chan and N. R. Shah School of Civil Engineering Purdue University March 29, 2005 https://engineering.purdue.edu/ResearchGroups/Wetland

  2. Project Involvement INDOT: Financial support & technical guidance JTRP & Purdue: Research sponsorship ‘Hydraulic’ project: to track and evaluate flow rates and fate ‘Environmental’ project: to track wastewater treatment efficacy J.F. New: Sub-contracted design engineering for wetlands Indiana Department of Health: Wetland discharge permitting RQAW: Design engineering Heritage: Project construction

  3. Wastewater Treatment Clean Water Waste ?

  4. o o o Basic Lagoon Clean Water Waste • Very simple!

  5. Basic Lagoon

  6. o Clean Water Waste o o Basic Lagoon O2 O2 O2 O2 O2 O2 O2 • Very simple! • However, mixing depends on wind! • Therefore, sometimes poorly mixed • Poor mixing means poor aeration • Oxygen supply will then be poor • Lagoon may stink!!

  7. o Clean Water Waste o o Aerated Lagoon O2 O2 • Improved aeration • Better oxygen supply • Better biological kinetics • Smaller lagoon

  8. Aerated Lagoon Floating Mechanical Aerator

  9. o Clean Water Waste o o Aerated Lagoon ? O2 O2 • Improved aeration • Better oxygen supply • Better biological kinetics • Smaller lagoon • However, not very attractive… • and windborne disease issues

  10. Constructed Wetland (CW) Clean Water Waste

  11. Subsurface-Flow CW

  12. Typical Wetland Plants

  13. Characteristics Clean Water Waste • Constructed Wetland • Wetland plants tolerate routine submergence • High plant density • High plant root mass • High rate plant root release of oxygen • High bacterial growth on plant root surfaces • High biochemical degradation of waste

  14. How Does it Work? Enhanced?Biometabolism Clean Water Waste

  15. O2 Media Media Media O2 O2 O2 Plant Root O2 O2 Media Media O2 O2 Plant Root O2 O2 O2 O2 Plant Root O2 O2 Media O2 Media Media O2 O2 Media O2

  16. Media Media Media Plant Root • Constructed Wetland • Plants release oxygen via photosynthetic activity • High microbial activity on, and adjacent, to plant roots • However, oxygen may still be a critical limiting factor Media Media Plant Root Plant Root Media Media Media Media

  17. Extensive bacterial Colonization of root tip surface area!

  18. How to Increase DO? • Direct aeration • Rapid changes in water level • Expose thin water films and biofilms on the wetland substrate and plant roots to air • Large surface area  rapid and substantial oxygenation of the rhizosphere. • Greenfield rest area • Fill-and-Draw concept

  19. Fill-and-Draw CW 'Draw' O2 Concept developed by J.F. New!! Our facility is one of first in the US to use this strategy!! Clean Water Waste

  20. Fill-and-Draw CW 'Fill' Clean Water Waste

  21. Fill-and-Draw CW 'Draw' O2 Clean Water Waste

  22. Challenges at Rest Areas • Remote location • Rural locale • Away from existing sewer and POTW • High wastewater strength • Low-flush toilets • High variability in wastewater flow • Large increase in traffic volume during rush hours and holidays • Limited personnel

  23. Project Location

  24. Project Overview • Unique challenges • Long (3+ miles) sewer line to the city POTW • Low flush toilets; flow restrictive faucets • High strength wastes (BOD, Ammonia) • Odor problem at city lift station • Surcharges by the city • Pretreatment using constructed subsurface wetlands • Biofield (and city sewer) for effluent disposal

  25. Why Wetlands? • Conventional technologies • Pros: proven technologies • Cons: high capital and maintenance costs • Subsurface constructed wetlands • Pros: • Low maintenance • Aesthetic / positive public perception • Cons: • Large footprint • Lack of supporting data

  26. Greenfield Wetland System

  27. Design Parameters • Design flow rate: 10,000 gpd • Wastewater characteristics: • BOD5 ~ 450 mg/L • NH3-N ~ 150 mg/L • TSS ~ 180 mg/L

  28. Septic Tanks

  29. Wetland Cells 1 & 2

  30. Wetland Cells 1 & 2 Vegetated subsurface flow wetland Vertical filter

  31. @ Outlet of Cells 1 & 2

  32. Wetland Cell 3

  33. Biofield

  34. Automatic Sampler

  35. Flow Meters

  36. First Year in Operation • Wetland cells planted on August 12, 2003 • October 2003 – June 2004 • Startup period • Overflow mode • North side only • Mid June 2004 – present • Draw-and-fill mode (time-based) • Full Operation beginning in October

  37. Daily Rainfall and Flow Totals Tailing response to rainfall - Daily Cycle - Weekly Cycle - Seasonal Cycle

  38. Flow Data • Variability in flow • Daily Cycle • Weekly Cycle • Monthly Cycle • Extreme events: • High traffic volume during holidays • Rainfall • > 2-fold increase in daily flow • Effects of ET and rainfall • 1 mm ET / rainfall 300 gal decrease / increase in flow volume

  39. D Outflow from Cells 1 & 2 No overflow Overflow at filling cell Draw-and-fill mode: 12-hour cycle during Saturday – Monday 24-hours cycle during Tuesday – Friday

  40. Hydraulic Retention Time

  41. Dynamic Modeling • Complex flow scheme • Changing water levels • Recirculation • Overflows • Simplifying assumptions • Treat wetland cells as giant buckets • Instantaneous overflow • Estimate HRT • Basis for design of similar systems

  42. Hydraulic Retention Time *The value in parenthesis is the estimated HRT as if in the over-flow mode.

  43. Wetland Performance • - Definite pattern of increased performance… • Obvious correlation with increased plant and root density • However, lagging ammonia removal problem!! • Strong suggestion that oxygen is limited! TSS % Removal BOD NH3 Days of Operation

  44. Wetland Performance

  45. Wetland Performance • Ponding • Lack of air-filled layer between water table and peat moss layer • Limited root growth • Invasive plant species • Overflows during the fill cycle • Short-circuiting

  46. Continuing/Future Activities • Continuing data collection and analysis • “Tweaking” the system for optimum treatment effectiveness • Additional of a surge tank • Development of hydraulic and treatment process model • Modifying existing wetland design guidelines, tailored to rest area application

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