|
Bioretention Cells (Rain Gardens) |
|
Rain garden used for on-site stormwater
management at a commercial property.
Source: LID Center
(click on thumbnail
for enlarged view)
|
Monitoring of bioretention cells has shown their
ability to remove a wide range of pollutants. A number
of pollutants including metals, total suspended
solids, insoluble phosphorus, and oil and grease are
removed from stormwater by filtering through the
bioretention cells mulch and soil media. Soluble
nutrient removals are achieved through microbial
activity in the soil media and plant uptake. Aerobic
conditions generally prevail in bioretention cells,
encouraging nitrification. Nitrate removals have been
inconsistent, but research is proceeding to evaluate
the use of a continually submerged, anaerobic segment
of the bioretention cell to enhance denitrification.
Bioretention cells have also been effective at
reducing stormwater volumes and peak flow rates by
encouraging detention in the soil media and
infiltration into surrounding soils.
|
Bioretention Cell (Rain
Garden)
Pollutant Removal Effectiveness
|
Parameter |
% Removal / % Decrease |
|
Copper |
92
99 |
|
Lead |
92
99 |
|
Nitrate |
0
80 |
|
Oil
and Grease |
> 98 |
|
Phosphorous |
0
80 |
|
Total Suspended Solids |
> 91 |
|
Zinc |
92
99 |
|
Flow
volume |
80
98 |
|
Peak
flow rate |
44
57 |
Sources:
Davis, A.,
M. Shokouhian, H. Sharma, and C. Minami, Laboratory Study
of Biological Retention for Urban Stormwater Management,
Water Environment Research, Vol. 73, Num. 1, Jan/Feb 2001,
pp. 5-13.
Davis, A.,
M. Shokouhian, H. Sharma, C. Minami, and D. Winogradoff,
Water Quality Improvements through Bioretention: Lead,
Copper, and Zinc Removal, Water Environment Research,
Vol. 75, Num. 1, Jan/Feb 2003, pp. 73-81.
Dietz, M.
and J. Clausen, A Field-Based Evaluation of
Rain Garden Flow and Pollutant Capture.
Hsieh, C.
and A. Davis, Multiple-Event Studies of Bioretention for
Treatment of Urban Stormwater Runoff, Diffuse Pollution
Conference Dublin 2003.
http://www.ucd.ie/dipcon/docs/theme04/theme04_11.PDF
Hunt, B.,
Bioretention Use and Research in
North Carolina
and other
Mid-Atlantic States, The NCSU Water Quality Group Newsletter, May 2003, Num.
109, ISSN 1062-9149, pp. 1-11.
Kim, H.,
E. Seagren, and A. Davis, Engineered Bioretention for
Removal of Nitrate from Stormwater Runoff, Water
Environment Research, Vol. 75, Num. 4, July/August 2003, pp.
355-67.
Sharkey,
L., and W. Hunt, Case Studies on the Performance of
Bioretention Areas in
North Carolina.
Stack, R.,
and A. Davis, Bioretention: Construction and Operation of
Research and Education Facilities.
