1. Hydraulic Conductivity Experiment Results
Figure 4. Results of Hydraulic Conductivity experiments. The two White Sand trials
resulted in hydraulic conductivities of 153.181 in/hr and 178.831 in/hr, averaging
166.006 in/hour. Conversely, the hydraulic conductivity of the two ZVI trials were
59.023 in/hr and 56.011 in/hr, respectively, resulting in an average of 57.517 in/hr.
A major cause for decreased water quality in Delaware is
nutrient loading of natural waters. This comes in part from
fertilizer and animal manures from the farms of Delaware,
but also from urban sources such as road runoff and
atmospheric deposition. This pollution is only expected to
increase with the rising population, which is alarming due to
the negative environmental implication of nutrient loading,
including eutrophication, which could destroy habitats
causing a loss in economic productivity. To combat this, the
Delaware Department of Transportation is required to
comply with Total Maximum Daily Load regulations. These
regulations set the bar for how much of any pollutant,
including nutrients, can be in surface water and still
maintain water quality standards. While necessary, adhering
to these standards will be quite costly, so any new
technology might be helpful in reducing the financial burden
on taxpayers.
According to recent experiments, biochar has the ability
to absorb a significant amount of ammonium and increase
water retention in the unsaturated zone, which in turn will
increase nitrogen uptake in plants and conversion of
ammonium to nitrogen gas. This means that biochar has the
potential to improve water quality when added to a
bioinfiltration facility. Further research is needed to
understand, modify and improve the performance of
biochar, particularly in engineered bioretention systems that
are often used to treat stormwater runoff from roadways.
Field Experiments
 A 36-hour field experiment was performed on June 29th
and 30th, 2015.
 Water was pumped in through shower heads to simulate
a natural rain event.
 Water samples were taken from multiple locations during
the experiment, and were filtered before being analyzed
for different chemicals by graduate students.
Hydraulic Conductivity Experiments
 The hydraulic conductivity of White Sand and ZVI
samples were measured to determine how stormwater
runoff moved through each type of soil.
 Samples were packed in a column and saturated using
de-aired distilled water to eliminate air exposure. Water
was pumped in slowly to ensure full saturation was met.
 Hydraulic conductivity (K) was determined using the
formula:
K = [(V*L)/(A*H*t)]
where V = volume collected, L = length of the column,
A = cross sectional area of the column, H = head distance,
t = time elapsed
Acknowledgements
This research was made possible by the Delaware Water Resource Center, Dr. Paul
Imhoff, Wenling Tian, and Jin Jing.
In 2014, a pilot-scale test facility was constructed in UD’s north campus to
evaluate biochar-amended stormwater infiltration media. This facility contains side-
by-side treatment cells: one cell is filled with biochar-amended media, while the
second contains a standard bioinfiltraton mixture without biochar. A schematic of
the system is shown below.
Figure 1. Elevation view for pilot-scale test system. Only the new treatment system
is shown. An identical design using conventional treatment media is adjacent to
this system.
The system is fully instrumented for automatic collection of water samples and
monitoring of water content and water pressure in the bioinfiltration media. This
system was designed and constructed by a graduate student. The objective of the
field experiment performed was to demonstrate and quantify any improvement in
removal of nitrogen compounds due to the addition of biochar to the soil.
Figure 2. A graph depicting results obtained from a previous field experiment. This
data shows that water treated in the modified cell contained less Nitrate than that
treated in the control cell. The modified cell tripled the cumulative Nitrate removal.
Figure 3. An image of the setup used for measuring the hydraulic conductivities of
White Sand and ZVI. The 20 cm column being tested in this picture contains ZVI.
Integrating Biochar Amendments in Green Stormwater Management
Systems for Enhanced Nitrogen Treatment of Stormwater Runoff
By Ryan Hall, with assistance from Dr. Paul Imhoff, Wenling Tian, Jin Jing, and the Delaware
Water Research Center
Hydraulic Conductivity Experiments
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NO3-N(ppm)
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Field Experiment SetupAbstract
Methodology