Passive Phosphorus Removal Systems

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Coale, F.J. and R. Kratochvil 2011: Unpublished data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%

• Curve #: 78 – Peak flow rate, 2yr-24hr storm: 16 cfs – Annual flow volume: 9 acre-ft

• 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

Design: Tile drained field in IN

Design: Tile drained field in IN

Design: Tile drained field in IN

Design Options: sieved slag

Target lifetime @ 25% removal (yr)

Mass (tons)

Depth (in)

Head (in)

Peak flow (gpm)

Total lifetime (yr)

Cumulative removal (%)

Area (sq ft)

1

5.5

6.8

6.8

206

9

10

239

3

16.5

27

10

718

6

33

54

10

1436

Not enough area

Design Options: coated slag Target lifetime @ 50% removal (yr)

Mass (tons)

Depth (in)

Head (in)

Peak flow (gpm)

Total lifetime (yr)

Cumulative removal (%)

Area (sq ft)

1

4.7

6.8

6.8

2181

18

12

148

6

9.5

6.8

6.8

4363

36

12

296

10

15.7

60

12

494

Not enough area

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

– P is not really removed from the system

ECONOMICS

Economics Example: Westville • Metal & custom fabrication: $2677 – ¼” carbon steel

• • • • •

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 Example: Westville Year

$

P removal (lbs.)

1 2 3 4 5 6 7

4989 1213 1213 1213 1213 1213 1213

22 22 22 22 22 22 22

Cumulative P removal cost ($/lb P) 226.77 140.95 112.35 98.05 89.46 83.74 79.66

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

www.p-structure.blogspot.com