Proceedings available at: http://www.extension.org/67602 Silage leachate is a high strength waste which contributes to surface and groundwater contamination of various pollutants from runoff, direct leaching through concrete storage structures, and infiltration of runoff. Feed storage is required for the majority of dairy operations in the country (which are expanding in size and fed storage requirements) leading to widespread potential contamination. Limited data on silage leachate quality and treatment has made management and regulation based solely on observation. This project investigated three bunker silage storage sites to assess the water quality characteristics of silage leachate and runoff from various feed sources and surrounding environmental factors. Surface samples were collected from feed storage structures and analyzed for numerous water quality parameters. Using collected hydrologic data, contaminant loading was analyzed for various storm events and assessed for first flush effects and potential to impact handling and treatment designs. Determination of first flush provides essential data for separation of waste streams (high and low strength) to ease management in terms of operation and cost, reduce loading to treatment systems, and reducing the overall environmental impact.

1. Silage Runoff Characteristics
Michael Holly
University of Wisconsin - Madison
Dr. Rebecca Larson, Advisor
April 3rd, 2013

2. Introduction
 Silage
 Fermented forage used as animal feed
 Corn and alfalfa are commonly used forage for dairy
operations
 Silage Leachate
 Liquid by-product from ensiling forage
 High nutrient concentration
 Silage Runoff
 Flow of surface excess water over an area containing
silage

3. Introduction
 Silage Runoff Characteristics
 Nutrient concentrations within silage runoff are variable
 Dependent on the following factors
 Event size
 Seasonality
 Bunker condition
 Silage quantity
 First-flush
 Analyzed in studies of urban runoff
 80% of the total pollutant mass is transported within the first
30% of the total volume (Bertrand-Krajewski el al.,1998)

4. Introduction
 Impacts
 Surfacewater
 Phosphorus and nitrogen loading of watersheds
 Oxygen depletion
 Eutrophication and fish kills
 Low pH erodes structures and harms vegetation
 Groundwater
 Conversion of organic nitrogen to nitrates
 Metal leaching
 Contamination of aquifers

5. Introduction
 Benefits of Silage watersheds
Runoff
Characterization
 Knowledge of
relationship of loading
throughout an event
 Reduction of utilized
manure storage and
hauling
 Improved treatment of
silage runoff
 Standards for
protection of

6. Introduction
Characteristic Raw Silage Residential
Leachate Wastewater
pH 3.5-5.5 6-9
P (mg/L) 300-600 5-20
Organic N (mg/L) 800-3,700 5-40
NH3 (mg/L) 350-700 10-50
BOD5 (mg/L) 12,000-90,000 100-400
Table 1 Typical Silage Leachate and Residential Wastewater Characteristics (McDonald et. al.,
1991 and Burks, et al., 1994)

7. Introduction
 Horizontal Bunkers
 Common type of silage
storage for large dairies
 Filled immediately after
harvest
 Forage is compacted and
sealed
 High potential for silage
runoff

8. Methods
 Three Sites Sampled in WI over Spring, Summer
and Fall
 Arlington Agricultural Research Station (AARS)
 US Dairy Forage Research Center (DFRC)
 Private Producer
 ISCO Automated Samplers Used for Sampling
 2 Samples per bottle, 14 bottles total
 Flow activated samples
 Samples refrigerated within sampler
 Analysis
 Completed at UW-Madison
 Alkalinity, NH3, BOD5, COD, NO2, NO2 + NO3, SRP, pH,
total P and total solids

9. Methods - AARS
 530 head dairy
 1.3 acre concrete
silage bunker
 0.3 acres pad
 1 acre bunker
 Separate surface
and subsurface
collection system
 Surface samples
collected

10. Methods - AARS

11. Methods - DFRC
 350 Head Dairy
 0.6 acre asphalt
bunker
 0.2 acres
bunker pad
 0.4 acres
bunker
 No subsurface
collection
 Surface
samples
collected for
analysis

12. Methods – DFRC

13. Methods - Private Producer
 3,500 head dairy
 1.7 acre bunker
 0.5 acres bunker pad
 1.2 acres bunker
 Surface and
subsurface were
routed to the same
culvert
 Surface and
subsurface was
sampled

14. Methods – Data Analysis
 Average Storm Nutrient
Concentrations (mg/L)
 Normalized Cumulative
Pollution Load Curves
 Dimensionless plot of the
distribution of pollutant
load with volume
(Tabei et. al., 2004)

15. AARS – Storm Characteristics
Max Average Max Average
Duration, intensity, Intensity, Flow, Flow,
No. Date Depth, in h in/h in/h cfs cfs
1 11/2/2011 0.98 14.3 0.36 0.0698 0.639 0.046
2* 11/5/2011 1.5 24.2 0.72 0.0190 n/a n/a
3 4/26/2012 0.52 86.5 0.04 0.0056 0.857 0.085
4 5/30/2012 0.19 7.3 0.12 0.0267 0.699 0.236
5 7/18/2012 1.7 17.7 0.36 0.0972 2.544 0.253
6* 7/24/2012 0.64 7.7 0.92 0.0821 n/a n/a
7* 7/24/2012 0.56 46.9 1.16 0.0119 n/a n/a
8 8/2/2012 0.05 47.6 0.04 0.0010 1.818 0.016
9 8/7/2012 0.18 103.7 0.04 0.0001 3.774 0.230
Table 2 AARS Storm Characteristics

16. Results - AARS
0.98 0.52
’ ’
0.05’ 1.7’
Figure 1 Normalized Nutrients vs. Normalized Flow for AARS Grouped by Season

17. Results - AARS
 Maximum average storm nutrient concentrations for
NH3, BOD5 and TP took place during early spring
 Minimum concentrations for COD and TP occurred in
the summer
 Storms three, five and eight illustrated an increase in
concentrations with flow and a moderate delayed
storm curve
 A mild first flush occurred in the fall

18. DFRC – Storm Characteristics
Max Average Max Average
Duration, intesity, Intensity, Flow, Flow,
No. Date Depth, in h in/h in/h cfs cfs
1 10/23/2011 0.19 7.283333 0.32 0.02375 0.628 0.048818
2 11/2/2011 1.04 12.63333 0.48 0.152461 0.766 0.191801
3 11/8/2011 1.14 17.33333 0.52 0.12 0.79 0.146787
4 4/29/2012 0.76 12.25 0.4 0.057281 1.141 0.167488
5 5/30/2012 0.28 6.983333 0.16 0.036894 0.348 0.059283
6 7/18/2012 1.26 3.45 3.68 0.33767 0.684 0.127977
7 7/24/2012 0.56 41.18333 0.84 0.013363 2.663 0.194389
8 8/26/2012 0.38 21.78333 0.08 0.014462 1.536 0.051788
9 9/6/2012 0.03 77.91667 0.04 0.00036 0.923 0.019656
10 10/9/2012 0.19 6.466667 0.08 0.026525 0.036 0.009285
11 10/13/2012 0.33 12.8 0.08 0.026946 0.171 0.019054
12 10/14/2012 0.28 20.21667 0.04 0.0126 0.45 0.034852
13 10/25/2012 0.28 9.266667 NA NA 0.13 0.011481
Table 3 DFRC Storm Characteristics

19. Results - DFRC
0.56 1.26’ 1.14
’ ’
0.52 0.76’ 0.19
’ ’
Figure 4 Normalized Nutrients vs. Normalized Flow for DFRC for Select Storms

20. Results - DFRC
Figure 2 BOD5 and COD (mg/L) vs. Cumulative Flow for DFRC Storms One, Three and Ten

21. DFRC Sample Bottles October Event
Figure 3 Samples Bottles for DFRC Storm Number One

22. Results - DFRC
 Maximum average storm concentrations for
NH3, BOD5, COD, SRP, TKN, TP, and TS took place
immediately after filling the bunker (large amount of feed
on pad)
 Minimum average storm concentrations for
BOD5, COD, and SRP occurred during the summer with
a large storm (high dilution effect)
 In the fall runoff indicated strong decay of nutrient
concentrations with accumulated flow
 In the spring weak first flush
 In summer with large storm events with high peak flows
resulted in a more delayed nutrient loading

23. Private Producer – Storm Characteristics
Max Average Max Average
Duration, intesity, Intensity, Flow, Flow,
No. Date Depth, in h in/h in/h cfs cfs
1 4/29/2012 0.71 10.9 0.36 0.0639 15.412 1.378684
2 5/30/2012 0.53 38.81667 0.36 0.013731 8.433 0.706653
3 7/18/2012 0.82 11.91667 0.92 0.063687 32.945 3.081982
4 7/24/2012 0.75 8.116667 0.92 0.093755 7.472 0.726338
5 7/25/2012 0.49 6.766667 0.72 0.073995 4.864 0.943187
6 8/9/2012 0.44 6.9 0.68 0.065835 9.67 1.459689
7 8/16/2012 0.51 6.616667 0.64 0.079687 7.821 1.513229
8 8/25/2012 0.52 34.7 0.28 0.01508 7.821 0.665683
9 10/13/2012 1.74* 31.21667 NA NA 3.071 0.296152
10 10/17/2012 0.67* 14.95 NA NA 1.681 0.173354
11 10/18/2012 0.78* 145.4333 NA NA 0.894 0.014115
Table 4 Private Producer Storm Characteristics

24. Results – Private Producer
0.51 0.53
’ ’
0.52 0.49’
’
Figure 5. Normalized Nutrients vs. Normalized Flow for Select Private Producer Storms

25. Results – Private Producer
 Lag time in sample collection may have missed peak
concentrations
 Max flow weighted nutrient concentrations for NH3, COD, TKN,
TP, and TS took place during filling
 Minimum flow weighted concentrations for NH3, BOD5, SRP,
TP and TS were in the spring (a large portion of the feed and
all corn silage had been used)
 Some summer runoff events displayed a moderate delayed
storm curve
 Following filling in the fall, data demonstrated a moderate first
flush

26. Conclusions
 Strongest first flush evidence took place in the fall
while strongest delayed storm curves were
documented in the summer
 Highest average storm nutrient concentrations were
in the fall following filling and sometimes in the
spring
 Lowest average storm nutrient concentrations were
in the summer
 Highest concentrations among all sites was for
DFRC’s initial samples in the fall (due to collection
methods)

27. Acknowledgements
 Wisconsin Groundwater Coordinating Council
 Funding
 Dr. Rebecca Larson
 Advisor
 Zach Zopp
 Lab and Field Tech
 Shayne Havlovitz
 Undergraduate Research Assistant
 Dr. John Panuska
 Committee Member
 Dr. KG Karthikeyan
 Committee Member

28. References
 Burks, B.D. and M.M. Minnis (1994). "Onsite
Wastewater Treatment Systems. " Madison, WI:
Hogarth House, Ltd.
 McDonald, P., et al. (1991). The Biochemistry of
Silage, Scholium International: 340.
 Taebi, A. and R. Droste (2004). "First flush pollution
load of urban stormwater runoff." Journal of
Environmental Engineering and Science 3(4): 301-
309.

29. Questions?