source reduction for urban stormwater
DESCRIPTION
Presentation discusses "source reduction" for stormwater management.TRANSCRIPT
Biogeochemical Perspectives on Stormwater Management
Larry Baker
Water Resources Center and
WaterThink, LLC
Goals• Examine problems with best management
practices (BMPs)• Examine biogeochemical processes
– Process limitations– Sustainability
• Applications:– Soluble P– Nitrate removal– Road salt
• Human dimension
Limitations of end-of-pipe storm water treatment
1. Low and variable treatment performance 2. High cost:
$1000/Ton SS (Weiss et al. 2007)
$500/kg P3. Some constituents are not readily treated in BMPs
(chloride, soluble P, fecal coliforms)4. Poor cold weather performance5. Low sustainabilty (pollutant accumulation,
clogging, etc.)6. Unfair cost allocation – polluted pays
Type Phosphorus Sediment
Ave. %
Removal
CV, % Ave. % removal
CV, %
Dry extended ponds
53 ±28 25 ±15
Wet basins 65 ±32 53 ±23
Bioretention 85 ±23 72 ±11
Sand filters 85 ±14 46 ±31
Wetlands 68 ±25 42 ±26
Typical removal efficiencies for structural BMPsSource: Weiss et al., 2007
Pollution production
Gas loss: CO2 (decomposition) N2 (denitrification) VOCs
Sedimentation Plant debris Adsorption
Remaining pollutants-Soluble P, coliforms, salt, suspended solids
Sediment
Processes in a stormwater pond or wetland
Water
Plant uptakeN, P, metals
Algae growth
Recycled
Sediment accumulationP recyclingToxics?
Pollution production
Processes in infiltration BMPs
Gas loss: CO2, N2, VOCs
Aquifer
FiltrationAdsorptionPrecipitation
Soil
NitrateChloride
Clogging
Metal accumulationSaturation of adsorption sites
End-pipe-BMPsDetention basinsWet pondsInfiltrations basinsWetlands
Level 2: Sources from landscapes to streets
Level 1: Sources to watershed
Level 3: Source from streets to storm sewer
Pollutant mass balances:System boundaries
Streets are not a source of pollution but a conduit for pollution
Level 1 analysis: Effect of lawn P fertilizer restriction
Conditions: 5 km2 residential neighborhood, 0.5 ha lot size, 20% impervious area on lot; 80% pervious area fertilized; 1 dog/house; irrigation. Updated from Baker and Brezonik, 2007 using MN Ag 2006.
Source Input rate total,kg/yr
%
Fertilizer 7.5 kg/ha-yr 1,920 73
Dogs 1.2 kg/dog-yr 1,770 23
Irrigation 0.3 mg P/L; 0.2 m/yr 169 2
Deposition 0.25 kg/ha-yr 125 2
Total - 3,984 100
total, kg/yr
%
1,000 0
1,770 86
169 8
125 6
3,064 100
Before MN P fertilizer ban After MN P fertilizer ban
23% reduction
Maples (all species)
y = 0.0009x2.2188
R2 = 0.9959
0
10
20
30
40
50
0 50 100 150
Diameter at breast height, cm
Le
af f
all,
kg
P p
er
tre
e
Level 2 analysis: Inputs from boulevard trees to streets
Example: maple trees(based on UFORE model)
DBH measurement
Suspended solids
0
500
1000
1500
2000
2500
3000
M HN HF VHN VHF
SS
, m
g/L
0.0
0.5
1.0
1.5
2.0
2.5
M HN HF VHN VHF
P, m
g/L
Particulate P
Soluble PLevel 2 analysis (cont’d): Lawn runoff to street
Source: Barten (1994)
For comparison: Raw sewage P = 5 mg/L SS = 200 mg/L
Eutrophic lake:P = 0.05 mg/L
Soil P level vs. dissolved P in runoff from
turf (left) and bare soil (right)
Soldat et al., 2008 Water, Air, Soil Poll.
Trees
20%
Lawn
70%
Atm. Dep.
0%
Dogs
10%
Level 2 (lawns to street) total P input
Assumptions:- Medium fertility lawns- 1 tree per 20 m- 30 m lot width- 0.6 dogs/household
Percentage of total P entering street(total = 8 kg P/km street)
Baker et al., Chapter 7, in Assessment of Stormwater BMPs Manual(WRC web page)
Growing turf
Soil inorganic P Soil organic P
Fertilizer P
Runoff soluble P
Runoff particulate P
Exported clippings
Mowed grass
Leaching
Integrating biophysical and social aspects of lawns to reduce soluble P in runoff
Baker, Wilson, Fulton, and Horgan, Cities and the Environment, 2008.
Lawn P cycle
3 or more fertilizer applications,+ mulching
Steep slope, low infiltration soil
Nowak disproportionality concept applied to lawnsNowak et al., 2006 Society and Natural Resources
High nutrient export
Site design
Site management
0
5
10
15
20
25
Sand Fine-sand Clay-fine Clay
Soil type
% r
un
off
Low slope
Steep slope
Target these
1.Target vulnerable lawns (biophysical dimension)
Modeled runoff for 1” storm
0
20
40
60
80
100
0 1 or 2 3 or 4 > 5
# of fertilization times
% o
f h
om
eow
ner
s
2. Tailor messages to homeowner types(social dimension)
“Casual” “Perfectionist”
Adaptive management for road salt
MNDOT Salt use, tons/yr
0
50,000
100,000
150,000
200,000
250,000
300,000
y = 31.352e0.0437x
R2 = 0.85
0
50
100
150
200
0 10 20 30 40
% impervious
Str
eam
chl
orid
e, m
g/L
Relationship between % impervious surface and average stream chloride Sander, Novotny, Mohseni, and Stefan, 2008
Event analyzed by team - Weather - Pavement conditions - Stream chloride
Road crews add salt for snow/ice event.Salt quantities recorded
Sensor network recordsspecific conductance; temperature
Recommendations summarized; transmitted to road crews
Adaptive management schematic
dialogue
• “Salt” easy to measure – conductivity• There are many alternatives
- Alternative salts (calcium acetate, etc.)- Alternative methods – pre-wetting; brine
• Public works crews are small, dedicated• Communication would be fairly easy• Many learning opportunities• Could save money and improve safety• Nothing else will work – chloride is conservative
Why adaptive management should work
Mississippi + M
innesota Rivers
Inflow16.86
Outflow17.99
Wastewater 0.41
Withdrawal0.18
Groundwater pumping0.46
Recharge0.46 (assumed)
Evaporation1.37
Precipitation2.42
Runoff0.82
Will stormwater management alter the Twin Cites hydrologic balance?
Summary
• Structural BMPs are necessary but not sufficient to meet water quality goals
• We need to move toward a multiple barrier strategy
LID design source reduction structural BMPs
• Understanding biogeochemical processes – and limitations – tends to move point of control upstream
• Urban biogeochemistry involves human choice and the biophysical system
• Stormwater management is part of broader urban water management – hydrologic balance, etc.
References• Baker, L.A. 1998. Design considerations and applications for wetland treatment of high-nitrate
waters. Water Science Technology 38: 389-395.• Baker, L. 2007a. Instant runoff [on source reduction for stormwater]. Star and Tribune,
Minneapolis.• Baker, L. A. 2007b. Urban stormwater: getting to the source. Storm water 8:8.• Baker, L. A., R. Holzalksi, and J. Gulliver. 2008a. Source reduction. in J. a. J. A. Gulliver, editor.
Minnesota stormwater assessment manual. Minnesota Water Resources Center, St. Paul.• Baker, L. A., P. Westerhoff, and S. M. 2006. An adaptive management strategy using multiple
barriers to control tastes and odors. Journal of the American Water Works Association 98:113-126.
• Baker, L. A., B. Wilson, and D. D. Fulton. 2008b. Disproportionality as a framework to target nutrient reduction from urban landscapes (invited paper). Cities and the Environment. 1:Artilce 7.
• Baker, L. A., B. Wilson, J. Gulliver, O. Moshir, A. J. Erickson, and R. M. Hozalski. 2008c. Process assessment framework.in J. Gulliver, and J. Anderson, editor. Assessment of Stormwater Best Management Practices. Minnesota Water Resources Center St. Paul.
• Ingersoll, T. and L. A. Baker. 1998. Nitrate removal in wetland microcosms. Water Research . 32:766-684.
• Nowak, P., S. Bowen, and P. Cabot. 2006. Disproportionality as a framework for linking social and biophysical systems. Society and Natural Resources 19:153-173.
• Soldat, D. J., A. M. Petrovic, and Q. M. Ketterings. 2008. Effect of soil phosphorus levels on phosphorus runoff concentrations from turfgrass. Water, Air, Soil Poll. online.
• Weiss, P. T., J. S. Gulliver, and A. J. Erickson. 2007. Cost and pollutant removal of storm-water treatment practices. J. Water Resources Planning and Management 133:218-229.
Most of my articles can be downloaded from my WRC web site:http://wrc.umn.edu/aboutwrc/staff/baker/index.html (click on “vita”)Non-technical articles can also be downloaded from WaterThink.com