Removal Systems. Chad Penn, Josh ... for many years. â Conventional ... High soil P concentrations contribute to long-term, slow P leak ... production waste (red .... except for metal painting and installation ... treatment plant 50-200 dollars/lb P.
Passive Phosphorus Removal Systems Chad Penn, Josh Payne, Jeff Vitale: Oklahoma State University Josh McGrath: University of Maryland Delia Haak: Illinois River Watershed Partnership
P FILTER BACKGROUND AND BENEFITS
Target: Dissolved P • Soils built up with “legacy” P will continue to release dissolved P for many years – Conventional best management practices do little for DP
• Objective: construct P removal structures to trap dissolved P in runoff and tile drainage
Need for P filters
Mehlich-3 Phosphorus (mg kg-1)
• High soil P concentrations contribute to long-term, slow P leak • This is referred to as a “legacy” P issue
Coale, F.J. and R. Kratochvil 2011: Unpublished data
Justification of cost for construction Current BMPs only slightly effective for DP losses
DP: sustained transport for several years
$$ DP: 100% biologically available
P Removal Structure Theory High P water
PSM layer
Clean water is released
Drainage layer
3 Necessary Components • Effective PSM in sufficient quantity • P-rich water must flow through PSM • Ability to retain and replace PSM
Example by-product PSM’s Acid mine drainage treatment residuals
Bauxite mining and production waste (red mud)
Drinking water treatment residuals
Fly ash
Foundry Sand
Steel slag waste
Waste recycled gypsum
Selection Process for PSMs Material Availability
Cost & Transportation
Sodium Soluble salts Potential contaminants
Particle size distribution and bulk density
Sorption characteristics
Hydraulic conductivity
Physical Properties
Total, acid soluble, and water soluble heavy metals
Cartridge Filter? Portable, easy to install Does not work! Limited amount of PSM
Confined Bed • Good for large filter • Ideal for drainage swales that require high peak flow and non restricted drainage – Achieved through shallow PSM with large surface area
Confined Bed Example Structure has handled flow rates over 100 gpm
3 tons >6.35 mm EAF slag, treated 150 acres, 25% overall dissolved P removal after 8 months
Overflow weir
Confined Bed Example • Structure re-loaded with >0.5 mm slag • 33% overall removal after 18 months • Still handles high flow rate
Overflow weir
Tile Drain • Similar to bed, but without confinement • Allows large amount of material to be used • Use flow control to build head • Low cost • Probably best option for ditches
Box Filter • Easily switch out material • Modular design – integrates with flow control – Agri-Drain
• Small ditches or pond overflow • Drawback: Small amount of material
Storm Drain Filter
Performance and Lifetime
– Site conditions – PSM – Design
30 P removed (g kg-1)
• It depends:
25 20
15 10
10
5
Retention time (min)
0 0.5
1
5
10
P concentration (mg L-1)
0.5 15
DESIGN GUIDANCE
General Design Approach Input
Output
Site hydrology P removal & lifetime PSM characterization 1. Peak flow rate 1. Target P removal (%) 1. P sorption 2. Annual flow volume 2. Target lifetime 2. Safety 3. Dissolved P level 3. Physical properties 4. Max footprint
+
Design parameters 1. Area 2. Mass of PSM 3. Depth of PSM
Model
+
Model Verification • Ability to predict design curve is key – Accuracy of inputs
• Golf course structure • UMD structures on Eastern Shore • Pilot scale structure • Laboratory flow-through experiments conducted on new materials
Pilot Scale Filter
Example Pond Filter Data Cumulative P removed (mg kg-1)
70 60 50
40 30
Measured
20
Predicted
10 0 0
50
100 150 P added (mg kg-1)
200
P removed (mg kg-1)
Example Golf Course Structure
P added (mg kg-1)
EXAMPLE DESIGN
Design: Poultry farm in OK Green Creek
proposed structure location
flow direction poultry houses
Design: Poultry farm in OK
Site Conditions • Drainage area: 9 acres – Slope: 6%
• Typical dissolved P: 1 to 2 mg L-1 – Annual dissolved P load: 49 lbs (22 kg) • Assumed 2 mg P L-1
• Goal: remove 45% of annual P load
Sizing the Structure: design curve for potential PSMs Measured directly via flow-through sorption tests or predicted based on chemical and physical properties Unique to each PSM, inflow concentration, and retention time
Structure design: impact of PSM characteristics
• Need to handle peak flow rate • Need to handle P load
Structure design: impact of PSM characteristics
• Need to handle peak flow rate • Need to handle P load
Potential design options to meet given P removal and 16 cfs flow Mass (Mg)
Cumulative year 1 removal (%)
Lifetime (yrs)
Hydraulic conductivity (cm s-1)
Area (m2)
PSM depth (cm)
WTR*
7
37
21
0.01
286
2.3
AMDR†
4
50
7
0.009
225
2.2
Fly ash‡
3 (plus 95% sand)
50
3.6
0.03 (mixed with 95% sand)
406
13
>6.35 cm slag§
171
21
1.4
1.0
190
50
Treated > 6.35 cm slag**
36
45
3.5
1.0
40
50
PSM
Completed Structure
Completed Structure
Completed Structure
Design: Tile drained field in IN • 40 acre tiled drained field to bio-reactor – Peak flow rate: 80 gpm – Typical P concentration: 0.2 to 0.5 mg L-1 – Annual P load: 0.5 kg (from 1 mil L yr-1) – Hydraulic head: 17.89 cm (over 90 ft length)
• Target removal: 3 year lifespan, 25 or 50% • Maximum area: 400 sq ft • Material: Sieved Slag
Additional Support • Design software currently being created – Provide interactive design guidance based on user inputs – Will be made available to NRCS
• NRCS Standard will be completed after software is completed • Commercialization may be key to dissemination
Comparison to other BMPs • In the short term there is no BMP that can appreciably reduce soluble P losses where flow cannot be reduced – P “mining” with hay crops or corn to reduce soil P levels • Sharpley et al. (2009): only 4.6 mg/kg decrease per year in Mehlich-3 P with continuous corn • Not very fast
Comparison to other BMPs • Treatment wetlands – Require excessive retention time (days), thus requires many acres of space if high flow rates are to be treated • inefficient
Slag transportation, sieving, coating: $853 Earth work for pad & berms: $846 Paint, seed, & erosion mat: $613 TOTAL: ~ $5000 Includes profit from private companies except for metal painting and installation • Annual renewal estimated at $1213
Economics • Economics will vary greatly between locations • Westville structure could have been constructed for less money by using other materials • Consider that it costs a waste water treatment plant 50-200 dollars/lb P removed – Easier to remove P at a high P concentration, point source
