asaturation zone in rain gardens amended with … · iwould)like)to)thank)the)donors)to)the)uwt)...
TRANSCRIPT
THE USE OF A SATURATION ZONE IN RAIN GARDENS AMENDED WITH BIOSOLIDS
TO REDUCE NITROGEN FROM STORMWATER
Sharon Hunter Summer Research Intern
University of Washington-‐Tacoma, Center for Urban Waters
Senior, Environmental Science-‐Biology Track University of Washington-‐Tacoma
• Nitrogen is an essen,al element for life
• Problem: o Excess nitrogen leaches into waterways
o Eutrophica,on o Nitrate concentra,ons 0.2 mg/L can trigger eutrophica,on in surface waters (NOAA 2012)
hEp://westseaEleblog.com/2010/06/new-‐stencils-‐for-‐alki-‐storm-‐drains-‐thanks-‐to-‐matson-‐naviga,on
IntroducKon
• Algal blooms o Fresh water: phosphorus limited
o Marine waters: nitrogen limited
• Global problem
• Local problem o Hood Canal: Sensi,ve to nitrogen (Newton 2012)
hEp://serc.carleton.edu/images/microbelife/topics/red_,de_genera.v3.jpg
EutrophicaKon
• Point Sources
• Natural
• Non-‐point
• Increased impervious surfaces decrease stormwater infiltra,on
Nitrogen Sources
hEp://www.ecy.wa.gov/puget_sound/dissolved02_problem.html
• Organic maEer in soil breaks down to ammonia
hEp://topsoil-‐screener.com/2012/04/nitrogen/
Nitrogen in soil
• Organic maEer in soil breaks down to ammonia
• Nitrifica,on
Nitrogen in soil
hEp://topsoil-‐screener.com/2012/04/nitrogen/
• Organic maEer in soil breaks down to ammonia
• Nitrifica,on
• Denitrifica,on
Nitrogen in soil
hEp://topsoil-‐screener.com/2012/04/nitrogen/
hEp://genome.jgi-‐psf.org/parde/parde.home.html
DenitrificaKon
• Favorable condi,ons for denitrifying bacteria: o Organic carbon o Absence of oxygen
• Intercept stormwater • Increase infiltra,on • Reduces storm water
volume • Removes solids
o May remove dissolved par,cles
hEp://www.fosc.org/AmElmParkUpdateNov2007.htm
Rain Gardens (BioretenKon System)
Soil amendments to improve rain garden efficiency
Rain Garden Soil Research at UW-‐T Urban Waters
• 2011 results for
nitrogen: o Nitrogen higher in effluent than influent
o Decomposing organics in compost and biosolids served as nitrogen source
hEp://www.tacoma.washington.edu/messages/news/2011/3/story1.html
• 2012 Goals o Develop a solu,on to reduce influent nitrogen and *phosphorus from stormwater in a rain garden soil mixture
o Find a produc,ve use for biosolids
hEp://inhabitat.com/tacomas-‐center-‐for-‐urban-‐waters-‐can-‐actually-‐think-‐for-‐itself/
Rain Garden Soil Research at UW-‐T Urban Waters
*The focus of this presenta,on is nitrogen. Please refer to Brian Hite’s research for the phosphorus results.
• Hypothesis 1:
Saturated zone in rain gardens leads to lower concentra,ons of nitrates in the effluent
• Hypothesis 2: The use of a biosolids amendment in rain gardens will increase ammonia in the effluent
Hypotheses
hEp://depts.washington.edu/uwbg/docs/stormwater/11-‐Photos_RainGardens_Cisterns.pdf
• Solids from municipal wastewater
treatment plants
• High in nutrients o Used in hor,culture, landscaping, forestry, gardening
• Currently not approved for rain gardens
hEp://www.cityocacoma.org/Page.aspx?hid=1474
Biosolids
100% Class A Biosolids: carbon source nutrient source
Sawdust: moisture reten,on carbon source
Sand: prevents pooling high infiltra,on rate
WTR (water treatment residual): aluminum and iron based capture phosphates
Soil Amendments
Methods: Soil Columns
• Stra,fied vs. Mixed
• Unsaturated vs. Saturated
� Stra,fied soil columns � Mixed soil columns
Sand 50.2%
o WTR mixed throughout soil (same mass of WTR in both columns)
Ponding
Soil CombinaKons
o WTR/sand boEom 6 inch layer
6 in
12 in
6 in Ponding
• Unsaturated
Unsaturated vs. Saturated
18 in Unsaturated Soil
Ponding 6 in
Saturated Layer 6 in
12 in
Unsaturated Soil
Ponding 6 in
• Saturated
Methods • Packing • Loading
o Synthe,c storm water (influent) o 0.3 mg/L phosphorus o 1.0 mg/L nitrogen
o 8 liters, 2 ,mes/week o 9 “rain events”
Methods • Sampling: Effluent
o Collec,on o First liter flush o Composite: liters 2-‐8
o Filtra,on o 0.45 micron filter
• Analysis o WESTCO Nutrient Analyzer (automated spectrophotometer) at UW-‐T
NO
3/N
O2
– N
Con
cent
ratio
n (m
g/L)
5
10
15
20
25
30
35
40
45
50
55
Rain Events7 81 2 3 4 5 6 7 81 2 3 4 5 69 9
Rain Events
NO
3/N
O2
– N
Con
cent
ratio
n (m
g/L)
5
10
15
20
25
30
35
40
45
50
55
Rain Events Rain Events7 81 2 3 4 5 6 7 81 2 3 4 5 69 9
Influent NO3–N Concentra,on 1.0 mg/L
Error bars +/- 1SD
Nitrates/Nitrites as Nitrogen: StraKfied
1st Liter Flush
Unsaturated Saturated
NO
3/N
O2
– N
Con
cent
ratio
n (m
g/L)
5
10
15
20
25
30
35
40
45
50
55
Rain Events7 81 2 3 4 5 6 7 81 2 3 4 5 69 9
Rain Events7 81 2 3 4 5 6 7 81 2 3 4 5 69 9
NO
3/N
O2
– N
Con
cent
ratio
n (m
g/L)
5
10
15
20
25
30
35
40
45
50
55
Rain Events Rain Events
Error bars +/- 1SD
Nitrates/Nitrites as Nitrogen: StraKfied
Unsaturated Saturated
Liters 2-‐8
Influent NO3–N Concentra,on 1.0 mg/L
1st Liter Flush
Nitrates/Nitrites as Nitrogen
• Stra,fied o First liter flush higher concentra,ons than liters 2-‐8 o Lower nitrite/nitrate concentra,ons in saturated columns than unsaturated columns
NO
3/N
O2
– N
Con
cent
ratio
n (m
g/L)
5
10
15
20
25
30
35
40
45
50
55
Rain Events7 81 2 3 4 5 6 7 81 2 3 4 5 69 9
Rain Events
NO
3/N
O2
– N
Con
cent
ratio
n (m
g/L)
5
10
15
20
25
30
35
40
45
50
55
Rain Events7 81 2 3 4 5 6 7 81 2 3 4 5 69 9
Rain Events7 81 2 3 4 5 6 7 81 2 3 4 5 69 9
NO
3/N
O2
– N
Con
cent
ratio
n (m
g/L)
5
10
15
20
25
30
35
40
45
50
55
Rain Events Rain Events
Error bars +/- 1SD
Nitrates/Nitrites as Nitrogen: Mixed
Unsaturated Saturated
Liters 2-‐8
Influent NO3–N Concentra,on 1.0 mg/L
1st Liter Flush
Nitrates/Nitrites as Nitrogen
• Mixed o First liter flush higher concentra,ons than liters 2-‐8 o Lower nitrite/nitrate concentra,ons in saturated columns than unsaturated columns
7 81 2 3 4 5 6 7 81 2 3 4 5 69 9Rain Events Rain Events
NO
3/N
O2
– N
Con
cent
ratio
n (m
g/L)
1
2
Nitrates/Nitrites as Nitrogen: Saturated
Stra,fied
Liters 2-‐8
Influent NO3–N Concentra,on 1.0 mg/L
1st Liter Flush
* * = below detection limit
3.6 2.5 3.9
7 81 2 3 4 5 6 7 81 2 3 4 5 69 9Rain Events Rain Events
NO
3/N
O2
– N
Con
cent
ratio
n (m
g/L)
1
2
Mixed
* *
Error bars +/- 1SD
• Saturated columns o Lower concentra,ons from mixed than stra,fied for most rain events
o Concentra,ons from mixed effluent on all rain events were lower than influent
Nitrates/Nitrites as Nitrogen
7 81 2 3 4 5 6 7 81 2 3 4 5 69 9
NO
3/N
O2
– N
Con
cent
ratio
n (m
g/L)
10
20
30
40
50
60
70
80
Rain Events Rain Events
Error bars +/- 1SD
Ammonia as Nitrogen: StraKfied
Unsaturated Saturated
Liters 2-‐8
1st Liter Flush
118.3
Ammonia as Nitrogen: StraKfied
• Stra,fied columns o Ammonia most likely originated in biosolids as organic nitrogen
o Unsaturated and saturated columns showed similar behavior, but without a discernible paEern
7 81 2 3 4 5 6 7 81 2 3 4 5 69 9
NO
3/N
O2
– N
Con
cent
ratio
n (m
g/L)
10
20
30
40
50
60
70
80
260
280
300
320
Rain Events Rain Events
Error bars +/- 1SD
Ammonia as Nitrogen: Mixed
Unsaturated
Liters 2-‐8
1st Liter Flush
422.8
7 81 2 3 4 5 6 7 81 2 3 4 5 69 9
NO
3/N
O2
– N
Con
cent
ratio
n (m
g/L)
10
20
30
40
50
60
70
80
260
280
300
320
Rain Events Rain EventsSaturated
Ammonia as Nitrogen
• Mixed columns o First rain event resulted in highest concentra,ons rela,ve to other 8 rain events
o Unsaturated and saturated columns showed similar behavior, but without a discernible paEern
• As expected, a saturated layer influences nitrate concentra,ons o Satura,on does not seem to influence ammonia concentra,ons
• As expected, high concentra,ons of ammonia were observed in effluent o Consistent with the 2011 study
Discussion
Conclusion: Goal 1
• Develop a solu,on to reduce influent nitrogen from stormwater in a rain garden soil mixture o Hypothesis: Saturated zone in rain gardens leads to lower concentra,ons of
nitrates in the effluent
• Columns with saturated zone released ~ 80% less nitrate/nitrites than columns without satura,on
• WTR mixed throughout the soil column released less nitrite/nitrate than stra,fied column
Conclusion: Goal 2
• Find a produc,ve use for biosolids o Hypothesis: The use of a biosolids amendment in rain gardens will
increase ammonia in the effluent
• Our results imply biosolids were a nitrogen source
• Higher concentra,ons nitrogen in effluent than influent
• WTR mixed throughout the soil column released less nitrite/nitrate than stra,fied column
• Comparable amounts of ammonia were released in the two types of soil combina,ons and in the saturated vs. unsaturated columns
Next Steps
• Add plants to rain garden soil study
• Prewash biosolids at the TAGRO plant
I would like to thank the donors to the UWT Urban Waters Fund, especially Urban Waters Board members and the Port of Tacoma for suppor,ng this summer's internship program Addi,onal thanks to: Alex Gipe Andy James, Ph.D. Brian Hite Connor Bacon Joel Baker, Ph.D. Jus,n Miller-‐Schulze, Ph.D. Kurt Marx UW-‐Tacoma
Acknowledgements
hEp://www.portocacoma.com/Page.aspx?cid=3218
Adelsman H. Ini,al Recommenda,ons for Local Source Reduc,on [Internet]. Department of Ecology [Cited 2012 Sept 09]. Available from: hEp://www.ecy.wa.gov/water/marine/oa/20120620_localsourcereduc,on.pdf
[ISBMP]. Interna,onal Stormwater Best Management Prac,ces (BMP) Database. 2012. Pollutant Category Summary
Sta,s,cal Addendum: TSS, Bacteria, Nutrients, and Metals. Newton, J. Low Dissolved Oxygen in the Hood Canal [Internet]. Hood Canal Dissolved Oxygen Program; 2012 [Cited 2012 Sept
09]. Available from: hEp://www.hoodcanal.washington.edu/aboutHC/scienceprimer.jsp [NOAA]. Na,onal Oceanic and Atmospheric Administra,on. Water Quality [Internet]. Cited 2012 Sept 09.
Available from: hEp://nerrs.noaa.gov/doc/siteprofile/acebasin/html/envicond/watqual/wqintro.htm. RiveE MO, S.R. Buss, P. Morganb, J.W.N. Smith, and C.D. Bemment. Nitrate aEenua,on in groundwater: A review of
biogeochemical controlling processes. Water Research. 2008; 42: 4215-‐32.
References
QuesKons?
hEp://www.mychamplain.net/forum/3rd-‐annual-‐roocop-‐river-‐rain-‐garden-‐contest