A Field Study of Biochar Amended Soils: Water Retention and Nutrient Removal from Stormwater Runoff

Transcription

1 A Field Study of Biochar Amended Soils: Water Retention and Nutrient Removal from Stormwater Runoff Funded through the Chesapeake Bay Stewardship Fund by a National Fish and Wildlife Foundation grant Joseph D. Brown, Sr., P.E. University of Delaware, Department of Civil and Environmental Engineering

2 Outline Background Research Hypotheses Experimental Methods Preliminary Results Future Research

3 What is Biochar? Produced from the pyrolysis of wood or waste biomass Important properties High surface area High porosity Significant cation exchange capacity High adsorption capacity Stable carbon structure

4 Biochar s Potential Benefits: Decreased overall stormwater runoff rates & volumes Reduced soil erosion and sedimentation Reduced nutrient & metal loading Improved groundwater recharge Reduced flooding

5 Background Research Biochar Impact on Soil Hydraulic Properties: K sat Increased 4X Water Retention Increased 30% Impact on Nutrient Removal 43% NO 3 Reduction 6.1% increase in NO 3 in control cell without biochar Depth (cm) Ctrl-wet Exp-wet Ctrl-dry Exp-dry Volumetric water content (m 3 /m 3 ) Jing Tian, Jing Jin, Paul T. Imhoff, Pei C. Chiu, Daniel K. Cha, Mingxin Guo, Julia A. Maresca Capillary pressure head (cmh 2 O)

6 Research Hypotheses: Roadside Filter Strips: Biochar increases water retention unsaturated hydraulic conductivity hydraulic residence time of pollutants in soils Roadside Swales: Biochar increases water retention hydraulic residence time

7 Project Site: Rt 896 & Bethel Church Road Middletown, De

8 Experimental Methods Filter Strips Test Equipment: Soil Moisture sensors Water potential & temperature sensors Automated water samplers Ultrasonic flow sensors Rain gauge

9 Experimental Methods Filter Strips

10 Experimental Methods Roadside Filter Strips Control Strip 4% Biochar Strip

11 Experimental Methods Swale Test Equipment: Soil Moisture sensors Rhizon Pore Water Samplers Rain gauge

12 Experimental Methods Swales

13 Experimental Methods Parameters: Soil Data: Volumetric Water Content Soil Water Potential Soil ph and Temperature Electrical Conductivity Soil Compaction Unsaturated Hydraulic Conductivity Nitrogen Compounds in Pore Water Surface Water Data: Stormwater Runoff Rate and Volume Influent and Effluent N Loading (Total N, NH 3, NO 3, NO 2, TOC, etc.) Total Suspended Solids

14 Results Runoff Profile (Typical Rain Event) 1200 Storm Event 27: Area Flow Rates 1000 Sampler 1 Water Flow Rate, (ml/s) Sampler 2 Sampler 3 Roadway Runoff Control Biochar Rainfall, (in/hr) /24/ :36 6/24/ :04 6/24/ :33 6/24/ :02 Date

15 Results Cumulative Runoff (Typical Rain Event)

16 Stormwater Runoff Summary Results for 57 Rain Events Average Peak Stormwater Runoff Rate Reduction: 46.74% (Std Dev: 64.06%) Average Cumulative Stormwater Runoff Volume Reduction: 66.70% (Std Dev: 24.41%)

17 Results Soil Moisture Content NFWF Soil Moisture Content cm Depth: 83% Increase Volumetric Water Content, (m3/m3) cm Depth: 50% Increase cm Front Control cm Front Control 0-15 cm Back Control cm Back Control 0-15 cm Front Biochar cm Front Biochar 0-15 cm Back Biochar cm Back Biochar 0.0 2/10/ :00 4/20/ :00 6/29/ :00 Date 9/7/ :00 11/16/ :00

18 Results Infiltration 450 Saturated Hydraulic Conductivity Tillage: % Increase K sat (cm/day) Biochar: % Increase Undisturbed Control 4% Biochar

19 Results Compaction Compaction Testing Summary Depth, (cm) Cone Stress, (kg/cm 2 ) Existing 11/15/15 Biochar 12/08/15 Control 12/08/15 Biochar 7/31/16 Control 7/31/16 Biochar 11/18/16 Control 11/18/16 Existing 11/18/16 Root Growth Limit

20 Results Grass Growth Control Strip (4/25/2016) 4% Biochar Strip (4/25/2016)

21 Results Dissecting Microscopic Imagery Existing Soil Existing Soil with 4% Biochar

22 Results Soil Temperature 40.0 NFWF Soil Temperature Control Biochar 25.0 Temperature, (oc) /10/ :00 4/20/ :00 6/29/ :00 9/7/ :00 11/16/ :00 Date

23 Future Work Instrument swales Spring 2017 Monitor and test throughout 2017 Conduct water quality experiments Author recommendations for regulatory credit applications for use of biochar Model the hydrodynamics of stormwater flow and infiltration using Richard s equation and results from lab and field experiments

24 Acknowledgements: Advisor: Dr. Paul Imhoff, Dr. Gerald Kauffman Consultants: Charles Hegberg, Larry Trout Funded By: National Fish and Wildlife Foundation thru the Chesapeake Bay Stewardship Fund Fellow Researchers: Sriya Panta, Seyyed Ali Akbar Nakhli, Susan Yi, Tian Wenling, Jing Jin, Fang Tan In Cooperation with: DelDOT