David Gleason

mddnr.chesapeakebay.net

David Gleason

Applying Byproduct Materials to Stormwater Treatment

David Gleason, Rufus Chaney,

Allen P. Davis


Problem: Controlling high lead levels

USDA APHIS Bldg. 580

Picture from: Kim, 2010

Site study conducted by Hunho Kim

•Average Pb in roof runoff: 7.6 mg/L

EPA Pb limit for drinking water: 0.015 mg/L

Picture from: Kim, 2010

Corroded walls of the building

•An estimated 72.5 kg Pb leached to the environment

over the building’s lifetime.


A new stormwater ttmt for high Pb and Cu

• (Kim, 2010) utilize agricultural and industrial byproducts:

Steel Slag

Hubcutter Heavies

Compost: grass/food waste

and manure base

from Kim, 2010

from Kim, 2010

• Side-by-side column studies were

conducted to compare media mixtures

http://www.civil.umd.edu/~apdavis/bio-denit-mwwrc.htm


Bench-Scale Experimentation

Media Mix: 25% compost / 5% slag / 70% sand

Desired performance factors:

•Hydraulic conductivity

•High removals across a wide

range of metal loadings

•High total sorption capacity


Current research objectives

1. Evaluate the effectiveness of this media mixture as a

stormwater control measure under field conditions

• Can the Biomat serve as a treatment for metal-contaminated

hotspots

• As a pre-treatment to commonplace BMP s

2. Characterize the long-term stability of pollutants once

captured within the mat

• Will landfill disposal be a feasible option after accumulating high

amounts of lead

• Assess total sorption capacity of the media

3. Optimize treatment


Site 1: Roof runoff collection area


Roof runoff sampling

Lead and copper, shown as red dots here, corrode

throughout the year.

Stormwater

Influent

sampler

Effluent

sampler

During storms, autosamplers take

and store samples in 1-L bottles to

be analyzed in the UMD lab.


Storms Measured to Date

28 different storm events sampled to date

•20 in back (roof RO)

•18 in front (parking lot RO)

Mats were laid in late

August, 2011.


Roof runoff: mean concentrations

Pollutant

Inflow

Concentration

(mg/L)

Outflow

Concentration

(mg/L)

Regulatory

limit

(mg/L)

Total lead 3.1 0.046 0.015

Total copper 0.84 0.015 0.013*

0.009**

Total zinc 0.11 Below D.L.

(0.050)

0.120

*Acute freshwater aquatic toxicity limit

**Chronic freshwater aquatic toxicity limit


Roof runoff mass removals


Inter-storm variability: roof RO site

How often are regulatory limits exceeeded How variable are inflow/outflow concentrations

Ex.: the arrows show that an influent

copper concentration above 1000 ug/L

is expected in 50% of storms.

The dashed lines above represent the

drinking water standard for lead (red) and

Maryland’s chronic aquatic toxicity

standard for copper (blue)


Intra-storm variation in metals concentrations:

roof RO site

Data from December 22, 2011

Lead & copper concentrations decrease significantly during the first few hours of a storm before leveling out.


Phosphorous leaching (from compost)

Mean sampled effluent phosphorous concentration (across all storms): 1.12 mg/L


Phosphorous leaching

• Compost as a treatment media has pros and cons:

• Pb known to form stable solids with P

• Excess P known to spur eutrophication, fish kills

• Potential solutions

• Water treatment residual addition (in progress)

• Selective placement of mats (e.g., as planters)

Algae blooming in a puddle just downstream of the swale.


Characterizing Roof Runoff Inflow and

Outflow

Influent Sample

• high in Pb, Cu

• low in Zn

• low in P

• low in TSS

• pH~6

Effluent Sample

(colored by humics from compost)

• Pb, Cu near regulatory limits

• low in Zn

• increased P

• low in TSS

• pH: 7.5-8


Site 2: Parking lot runoff collection

area


Pollutant flows at the APHIS parking lot

Pb and Cu corrosion

Nutrient inputs from lawn cuttings and dry deposition

Zn, Cu, grit (TSS), and oil & grease

Stormwater

To creek


Field Monitoring: Storm Samples

The drainage area to the swale is much larger

relative to the wooden box in back.

Swale site

Roof site

BIOMAT TREATMENT

UNTREATED

SAMPLES

TREATED

SAMPLES


Mean inflow concentrations to date:

parking lot runoff

Pollutant

Conc. (mg/L)

Total lead 0.011

Total copper 0.007

Total zinc 0.09

Total phosphorous 0.17

Total suspended solids 59.7

•Parking lot RO has dramatically lower metals concentrations

•below regulatory limits on average.

• Sediment and phosphorous levels are higher.


Parking lot runoff mass removals


Inter-storm Variation at the Swale site


Mass removals comparison by site


Why does ttmt efficiency differ

• Compost media:

• Beyond a certain concentration, further reductions with this

media may not be possible.

• Compost at the swale was sieved to >2 mm

• Reduced specific surface area reduces sorption potential

The original swale ttmt mat being

overtopped during a storm event


Why are metals removals so

different at the two sites

• Metals at the inflow points of each site vary:

• different pH values

• different metal sources (roof vs. cars)

• pollutant concentrations

• lead and copper concentrations at the swale are less than 1%

of those observed in the roof RO

• Treatment time:

• larger drainage area & higher hydraulic conductivity

shorter treatment time at the swale


Scaling & Potential Applications

• As a niche treatment to reduce the annual mass loading of

lead and copper from all comparable buildings:


Preliminary Conclusions

• High Pb & Cu removals can be effected in severely

contaminated areas.

• Metals concentrations cannot be reduced in all situations.

• There appears to be an equilibrium pollutant level

associated with this treatment.

• Some phosphorous addition is expected from this ttmt.


Continued work

• Assess the stability of captured metals

• sequential extractions, including TCLP

• Optimizing ttmt of metals, phosphorous

• Addition of water treatment residual to field scale ttmt

• (second mat: 50% sand, 50% water treatment residual)

• Batch experiments with water treatment residual

• Speciation of field samples

• total and dissolved, anionic vs. neutral/cationic

• Modeling equilibrium contaminant concentrations


Authors:

David Gleason

• Rufus Chaney, PhD

• Allen P. Davis, PhD, P.E.

Acknowledgements:

• Wayne Claus (assistance on-site)

• Funding agency:

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