I-70 Greenfield Rest Area Constructed Wetland Wastewater Treatment System Research Project (SPR-2455, SPR-2456, SPR-2487) R. S. Govindaraju, J. E. Alleman, T. J. Cooper, T. P. Chan, V. Jain School of Civil Engineering Purdue University

July 14, Project Location

July 14, Project Overview Surcharges by City Unique challenges  Long (3+ miles) sewer line to City POTW  Low flush toilets; flow restrictive faucets  High strength wastes (BOD, Ammonia) Pretreatment using constructed subsurface wetlands  Biofield (and city sewer) for effluent disposal

July 14, Why Wetlands? Conventional technologies  Pros: proven technologies  Cons: high capital and maintenance costs Subsurface constructed wetlands  Pros: Low maintenance Aesthetic  Cons: Large footprint Lack of supporting data

July 14, Wastewater Charateristics High strength  BOD~450 mg/L  NH3~150 mg/L Flow rate  Design: 10,000 GPD  Peak: >20, 000 GPD

July 14, Treatment System Design FeaturesFunctions/Benefits 2 10,000-gal septic tanks in seriesPrimary treatment 2 parallel subsurface constructed wetlands (cells 1 & 2) ~ alternately drained & filled ~ 56 ft by 56 ft and 3 ft deep gravel beds with a peat moss top layer Enhance oxygen transfer by constant draining and filling; thus promote nitrification and shorten designed hydraulic retention time Recirculation of cells 1 & 2 effluent back to 2nd septic tank Dilute high-strength wastewater; enhance mixing

July 14, Treatment System Design (con’t) FeaturesFunctions/Benefits Polishing plug-flow wetland (cell 3) ~ 20 ft by 40 ft and 2 ft deep gravel beds with a peat moss top layer Provide further treatment; allow comparison between plug-flow and draw-and-fill flow regimes Biofield ~ elevated sand mound seeded with prairie grass ~ bed area: 333 sq ft; basal area: 1652 sq ft Denitrification; disposal of treated effluent via evapotranspiration and infiltration to subsoil.

July 14, Instrumentations Flow meters  Magnetic flow meters for pressurized flow  Flume and weir flow chambers with ultrasonic level sensors for open channel (gravity) flows. Automatic samplers at various points of the system A weather station to measure rainfall, windspeed, and temperature. Monitoring wells installed within the wetland cells and also at the biofield.

July 14, Design Schematic

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July 14, Unfinished Items… Installations of automatic samplers and weather stations SCADA system  Control, data logging and collection system  Remote (web) access and control

July 14, What’s next? Startup  When?  How? Startup procedures (provided by RQAW)  Who? INDOT responsibilities … Purdue responsibilities … Long-term monitoring

July 14, Research Activities Dynamic model of the wetland hydraulics  Alternate draw-and-fill scheme; time-varied inflow; recirculation  Model simulations help formulate optimal management strategy

July 14, Research Activities (con’t) Survey to rest area operators  compare and evaluate the proposed system to existing treatment technologies Tracer tests Evaluation of the effectiveness of the system Development of design guidelines for constructed wetland systems with specific application in rest area facilities.

July 14, On the web