Project Title

Simultaneous Removal of Nitrogen and Phosphorus from Stormwater by Zero-Valent Iron and Biochar in Bioretention Cells

Collaborating Universities

University of Delaware
Newark, DE 19716

University of Virginia
351 McCormick Dr.
P.O. Box 400742
Charlottesville, VA 22904-4742

Principal Investigator(s)

Pei Chiu (UD), Email:
Paul Imhoff (UD) Email:
Teresa Culver (UVa) Email:

Funding Source(s) and Amounts Provided (by each agency or organization)

US DOT: $149,999
UD: $152,614
UVa: $109,733

Total Project Costs

$149,999 Federal/ $154,754 Match

Start Date


Completion Date



The transportation sector is frequently identified as a significant, if not primary, source of nutrients (nitrogen and phosphorus) to receiving waters.  To achieve increasingly stringent regulatory requirements with existing technologies requires purchase of more real estate for stormwater treatment at considerable expense.  To ameliorate this problem, we will evaluate two waste products, biochar and zero-valent iron (ZVI), as amendments to soil media in bioretention systems.  Previous laboratory studies have shown that each amendment alone is capable of removing or transforming nitrogen or phosphorus compounds.  We postulate that treatment efficiency can be enhanced considerably by combining biochar and ZVI, which would result in smaller land requirement to achieve a prescribed level of treatment.  Laboratory experiments will be conducted at the University of Delaware to quantify the ability of biochar and ZVI to remove nitrate and phosphorus.  A field study will be conducted by the University of Virginia in conjunction with the City of Charlottesville, VA, where biochar and ZVI will be used as amendments in a bioinfiltration facility.  Soils and stormwater characteristics selected for the laboratory study will match those for the field site.  Data from the biochar/ZVI treatment system will be compared with a field study using biochar alone supported by the National Fish and Wildlife Federation in Delaware, and a pilot-scale system employing biochar separate from ZVI, supported by the Delaware Department of Transportation.  Results will be shared with managers in transportation agencies, e.g., Delaware Department of Transportation and Maryland Transit Administration, whom the PIs have established relationships with through ongoing projects.


Successful completion of this proposed study will lay the foundation for use of a sustainable, effective methodology for nutrient management in the field.  This technology emphasizes material reuse in that theamendments (biochar and ZVI) are both obtained from waste materials.  Commercial distributors of these amendments already exist, and this work would establish a new market sector (stormwater management) for these sustainable materials.  The PIs have already established working relationships with multiple stormwater managers (DelDOT, Maryland Transit Administration, UVa Facilities, City of Charlottesville, and County of Albemarle).All of these government partners have a record of early adoption of innovative sustainable stormwater approaches to reduce nutrient levels in order to comply with the Chesapeake Bay TMDL.  In addition, the PIs have also been collaborating with the private engineering and environmental consulting industry, including A. Morton Thomas & Associates, Inc. (AMT), reGENESIS Consulting Services, LLC, Andrew T. Der & Associates, LLC, and Biohabitiats, Inc.  The team was recently awarded a grant by the National Fish and Wildlife Foundation to apply biochar to reduce roadway runoff and nitrogen leaching in Delaware.  In particular, Mr. Charles H. Hegberg, President of reGENESIS, is a collaborator on this project who brings 30 plus years of experience in environmental, engineering consulting, and construction to the study.  Mr. Hegberg has been a strong promoter of green materials and sustainable technology and will be instrumental in the transfer of this technology to transportation agencies and other stakeholders.  The PIs and Mr. Hegberg are planning on submitting proposals to the NSF SBIR/STTR programs to accelerate broad deployment of this new, potentially disruptive technology in the emerging market of stormwater management.
Results of this study are relevant to many regions struggling with nutrient management.  The results are of special importance to the transportation sector, which is often held responsible for a large portion of nutrient loads.  Fori nstance, in one North Carolina TMDL study (Lake Jordan Watershed), a region comprised of six cities, including Durham and Greensboro, and parts of nine counties, the NCDOT was determined to be the largest single responsible party with respect to both the nitrogen and the phosphorus loads, and thus NCDOT was responsible for removing the largest portion of excess nutrient loads.  To implement the proposed technology requires relatively minor alterations in established stormwater management approaches, so rapid adoption, if demonstrated effective, is anticipated.  All of the PIs are successful researchers (all received the NSF CAREER award) with an extraordinary record of national and international dissemination of their work.  Their previous work has been cited more than 4,000 times.  Results of this study will be disseminated within academic publications and presented at regional and national conferences, such the ASCE Environmental and Water Resources Institute World Water Congress in May 2016.  Furthermore, dissemination to practitioners via traditional training programs, such as those sponsored by state transportation centers, and webinars will be pursued.


This project will establish a demonstration site for enhanced nutrient removal in a bioretention system using biochar and ZVI.  Field results will be compared to the results of the laboratory experiments at UD.  Furthermore, the results will be compared to other field studies by the PIS of system with either amendment or with biochar or ZVI only.  The State of Delaware (DelDOT) is supporting construction of pilot-scale bioinfiltration cells (control + biochar/ZVI amended) on the UD campus to assess the removal of nitrogen from stormwater.  The data from the DelDOT project will be compared with results from this project, where both biochar and ZVI are co-located in the saturated zone, which we postulate further enhances nutrient removal.
Understanding the longevity of any treatment system and being able to predict its performance over seasons and in different geographical locations is critical information for policy makers. ONly with such information is it possible to assess the cost-effectiveness of new technologies, such as the biochar/ZVI treatment system proposed here.

Web Links to Reports and to the Project website