Proceedings available at: http://www.extension.org/67603 Agricultural filter strips are commonly used to treat runoff from agricultural farmstead areas. Many filter strips have been assessed in terms of surface water quality impacts but have failed to determine the fate of pollutants once they have infiltrated the soil subsurface. Two side-by-side filter strips plots were installed to assess the performance of and determine the fate of contaminants in a filter strip system. One of the two plots also contained a pretreatment system to facilitate nitrogen removal in an attempt to reduce nitrate leaching. Both plots were lined with an impermeable membrane to collect subsurface leachate as well as surface runoff. A mass balance could then be determined for these filter strip systems to assess the fate of nutrients and the ability of a low cost pretreatment system to reduce nitrate leaching.

1. Treatment of Silage Runoff with
Vegetated Filter-strips
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
 Filter-strip is a long narrow buffer strip and are used
in agriculture as a BMP
 Used to treat agricultural wastewater
 Slow the rate of runoff
 Organic matter and other pollutants settled out
 Commonly used for feedlot and silage runoff

4. Introduction
 Benefits
 Silage runoff treatment study
 Prescriptive loading
 Seasonal operation and treatment
 Pre-treatment design analysis
 Optimized treatment
 Protection of watersheds
 Reduction in storage volume and hauling
 Pre-Treatment Design
 Increase soil treatment depth
 Provide alternating aerobic and anaerobic soil conditions
to complete the nitrogen cycle

5. Methods
 Experimental Design
 Two filter-strips used for silage runoff application
 Pre-treatment design with alternating aerobic anaerobic
conditions
 Conventional design as a control
 Reduced scale filter-strips 12’ by 4’
 Applied with runoff at a 1:1 filter-strip to bunker pad ratio
 25 year – 24 hour and 2 year - 24 hour design storms
 3 runs of each design storm for both filter-strips
 Application accomplished in October, November, and
early December

6. Filter Treatment Design
 Top View Aerobic
Section
Gravel
Anaerobi Tank
c Section
Retentio
n Tank
Novel Control
Design Filter-strip
Filter-strip
Effluent
Collection

7. Methods – Filter-strip Construction

8. Methods – Filter-strip Construction

9. Methods – Filter-strip Construction

10. Methods – Filter-strip Construction

11. Results - 25 year – 24 hour Concentrations
BOD5 COD SRP TP
Pre-Treatment Design
Influent 27810 19796 176 239
Surface 16080 29280 153 222
Subsurface 9420 13588 8 33
Control
Influent 14100 20290 153 218
Surface NA NA NA NA
Subsurface 6233 9503 8 31
Table 1 Influent, Surface, and Subsurface Nutrient Concentrations for 25 year – 24 hour Design

12. Results - 2 year -24 hour Concentrations
BOD5 COD SRP TP
Pre-Treatment Design
Influent 19890 57360 309 449
Surface 14790 54000 288 397
Subsurface 9075 19350 2 49
Control
Influent 13890 40680 222 363
Surface 12060 36040 191 269
Subsurface 8625 12445 8 56
Table 1 Influent, Surface, and Subsurface Nutrient Concentrations for 2 year – 24 hour Design S

13. Results – Concentrations
 Influent
 Influent to both pre-treatment and control filter-strips had
a low pH (around 4) and were high in organic matter
 Strength of runoff was greater in the influent applied to the
2-yr, 24-hr storm events
 Effluent
 Subsurface effluent from both filter-strips had an almost
neutral pH (around 6.5) and had lowered organic matter
concentrations

14. Results – Concentration Reduction 25 year – 24 hour
Figure 1 Average Reduction of Nutrient Concentrations Grouped by Storm and Filter-Strip
for 25 year – 24 hour design storm

15. Results – Concentration Reduction 25 year – 24 hour
 TP and SRP had the highest subsurface reduction in
concentration for both filter-strips with 95% reduction
for SRP and 85% reduction for TP
 NH3 was the next highest reduction for both filter-
strips at 70%
 Pre-treatment had a BOD5 reduction around 60%
and the control had a reduction about half or 30%

16. Results – Loading Reduction 25 year – 24 hour
Figure 2 Average Reduction of Nutrient Loading Grouped by Storm and Filter-Strip for 25
year – 24 hour design storm

17. Results – Loading Reduction 25 year – 24 hour
 80% and higher loading reduction for SRP and TP
 Increase in NO3 concentrations for the pre-treatment
design
 60% and higher load reduction for all nutrients
except NO3

18. Results Concentration Reduction 2 year – 24 hour
Figure 3 Average Reduction of Nutrient Concentrations Grouped by Storm and Filter-Strip for 2
year – 24 hour

19. Results Concentration Reduction 2 year – 24 hour
 TP and SRP had the highest subsurface reduction in
concentration for both filter-strips with 96-97%
reduction for SRP and 84-87% reduction for TP
 Pre-treatment and Control had a NH3 reduction in
concentration around 26%
 Pre-treatment had higher BOD5 reduction in
concentration at around 54%

20. Results - Loading Reduction 2 year – 24 hour
Figure 4 Average Reduction of Nutrient Loading Grouped by Storm and Filter-Strip for 2 year – 24
hour

21. Results - Loading Reduction 2 year – 24 hour
 Pre-treatment filter-strip had lower infiltration and
higher surface runoff resulting in lower overall load
reduction
 Load reduction for both designs applied with the 2
year – 24 hour design storm were less than 25 year -
24 hour
 2 year – 24 hour applications had more surface runoff
than 25 year – 24 hour surface applications
 Lower temperatures for 2 year – 24 hour applications
resulted in higher surface runoff

22. Conclusions
 80% and higher reduction in concentration of SRP and total P
for both filter-strips applied with silage runoff
 35-65% reduction in concentration of total solids, BOD5 and
COD for both filter-strips
 60% and greater load reduction for 25 year -24 hour design
storm
 Novel Design
 Higher BOD5 reduction
 Increase of Nitrate within effluent
 Application of leachate near freezing can result in lower
infiltration

23. Future Work
 Design storm loading to both filter-strip designs in
spring and summer
 Expanding hydraulic detention times for aerobic and
anaerobic sections within pretreatment
 Incorporation of a polishing step for increased
denitirification in pre-treatment filter-strip design
 Modeling soil moisture and load reduction for filter-
strip applications

24. Acknowledgements
 Dr. Rebecca Larson
 Advisor
 Zach Zopp
 Lab and Field Tech
 Shayne Havlovitz
 Undergraduate Research Assistant
 Dr. John Panuska, Dr.
 Committee Member
 Dr. KG Karthikeyan
 Committee Member

25. Questions?