Selenium Reduction in Constructed Wetland … Presentations/July...Selenium Reduction in Constructed Wetland Treatment Systems: Naturally Attenuating Problematic Pollutants Katie A.

Selenium Reduction in Constructed Wetland Treatment

Systems: Naturally Attenuating Problematic

Pollutants

Katie A. Bland, P.E. Burns & McDonnell

Senior Environmental Engineer

Overview

• What are Constructed Wetlands? • Why the Power Industry? • Westar Energy Pilot Project • Pilot Project Results • Full Scale Design/Construction • Path Forward

• Constructed Wetland Treatment System – “An artificial wetland created or restored…..for

anthropogenic discharge such as wastewater, stormwater runoff, or sewage treatment. Natural wetlands act as a biofilter, removing sediments and pollutants such as heavy metals from the water, and constructed wetlands can be designed to emulate these features.”

Constructed Wetland Treatment System

• Three General Systems – Free Water Cell – Vertical Flow Wetland – Vegetated Submerged Bed Wetland


• Free Water Surface Wetland


• Vertical Flow Bed Wetland


• Vegetated Submerged Bed Wetland


• Stormwater • Mine drainage • Domestic sewage • Landfill leachate • Fairly new to the power industry

CWTS in the Power Industry

A promising technology…

CWTS in the Power Industry

• Polishing FGD Wastewater

• Landfill leachate/CCR Contact Water

• Polishing Biological • Coal Pile Runoff • Stormwater

Westar Jeffrey Energy Center


• Polishing FGD Wastewater – FGD Scrubber upgrade complete in 2008 – Low chlorides – Dewatering/solids removal already in place – Land available – Multiple options considered

• Multiple options considered, with some being complex mechanical systems with high capital costs

• Wide range in cost between CWTS and ZLD


Constructed Wetland Project Jeffrey Energy Center

Plant Reuse

Makeup Lake

Pilot Wetland

Water / Material Balance

Constructed Wetland Project Jeffrey Energy Center

Pilot Wetland Construction Complete

Free Water Surface Cell

Vegetated Submerged Bed

Vertical Flow Bed Wetland Cell

Ecological Risks

Selenium and Mercury Ecological Exposure

Laboratory Column Studies

Pilot Constructed Wetland Results

CONSTITUENT MASS LOAD REDUCTION

AVERAGE INFLUENT

(ug/L)

AVERAGE EFFLUENT

(ug/L)

Mercury 83% 1.2 <0.2

Selenium 92% 114 12*

Boron 42% 3,459 2,120

Fluoride 93% 11,209 1,551

*Selenium: 31% non-detect ( < 5 ug/L )

Some Lessons Learned…

• Topsoil – Selenium • Economically viable • It works!

Full Scale Design/Construction

• Considerations for the full scale design – Further mitigate ecological risk – Flexibility of operation – Extensive Modeling

• Plant Water Balance • CORMIX

– Beneficial Reuse • Cooling tower feed

– Test Pad


• Design Incorporated Ecological Risk Assessment

• Very Long HRT in CWTS - 30+ Days • Synthetics & Upflow • Constructability Challenges

Isolate Mercury and

Selenium


Treatment Soil

Single Sided Geocomposite and Gravel Drains

Compacted Clay Liner (1x10-7 cm/sec)

Tier 1 Soil

Gravel/Sand Drainage Layer

Geotextile

60 MIL HDPE




• Earthwork completed in December of 2013 • Mechanical installation complete in May

2014 • Startup of system is ongoing



Wetlands = Opportunity

• CWTS effectively treats metals including Selenium and other constituents…

Potassium (K)

Aluminum (Al)

Fluoride (F)

Nitrogen (N)

Barium (Ba)

Boron (B)

Chromium (Cr)

Iron (Fe)

Molybdenum (Mo)

Selenium (Se)

Mercury (Hg)

Wetlands = Opportunity

• CWTS provide a green treatment solution that is appealing to the public and local stakeholders

• Edison Electric Award Winner 2014 • Economically appealing • Effective for metals reduction

Questions?

Katie A. Bland, P.E. [email protected]

(816) 823-7042

mailto:[email protected]

Selenium Reduction in Constructed Wetland … Presentations/July...Selenium Reduction in Constructed Wetland Treatment Systems: Naturally Attenuating Problematic Pollutants Katie A.

Documents