Open-Water Unit Process Wetlands

Prof. Kara NelsonCivil and Environmental EngineeringUniversity of California, Berkeley

AEES Workshop, UC BerkeleyOctober 6, 2015

Reinventing our Nation’s Urban Water Infrastructure, www.renuwit.org

Outline

• What are unit process wetlands?

• How do open water cells work?

• Applications

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Unit Process Wetlands

Jasper, Justin T., Mi T. Nguyen, Zackary L. Jones, Niveen S. Ismail, David L. Sedlak, Jonathan O. Sharp, Richard G. Luthy, Alex J. Horne, and Kara L. Nelson. “Unit Process Wetlands for Removal of Trace Organic Contaminants and Pathogens from Municipal Wastewater Effluents.” Environmental Engineering Science 30, no. 8.

• Improve treatment capability of constructed wetlands (water quality)• Make constructed wetlands more attractive to engineers

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Shallow, open water, unit process wetland

Pilot-scale facility in Discovery Bay, CA; designed by Prof. Alex Horne4

Design Features

• 15-20 cm depth

• 1-2 d HRT

• Bottom is lined to prevent growth of macrophytes

• Dominated by biomatlayer on bottom

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Comparison to other natural treatment systems

• Compared to a typical constructed wetland, the open-water wetland has:– Shallower depths– Requires lining to prevent growth

of macrophytes

• Compared to a high-rate algal pond, the open-water wetland has:– Biomat instead of planktonic

algae (shallower depth)– Greater light penetration– Similar high DO, pH

Schematic from Lightbody et al. (2009)

Turner Rd. Winery, CA (Photo credit: Alex Horne)

Delhi, CA 6

Co-Benefits

• Improve water quality – Nutrients

– Trace Organics

– Pathogens

• Habitat

• Aesthetics

• Recreation

• Flood control

• Applications– Secondary (nitrified)

wastewater effluent

– Constructed wetland or pond effluent

– Effluent-dominated rivers that serve as potable water supplies

– Restoration using recycled water

– Stormwater

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Unit Process Wetland

Research Site

Pilot-scale wetlands in Discovery Bay, CA8

Target contaminants and Treatment mechanisms

• Nitrate

– Denitrification

• Trace Organics

– Direct and indirect photolysis

– Biotransformation

– Sorption

• Pathogens

– Sunlight disinfection

PublicationsJasper, J. T., and D. L. Sedlak. (2013). "Phototransformation of Wastewater-Derived Trace Organic Contaminants in Open-Water Unit Process Treatment Wetlands." Environmental Science & Technology. 47: 10781-10790.

Jasper, J. T., Z. L. Jones, J. O. Sharp, and D. L. Sedlak. (2014). "Biotransformation of Trace Organic Contaminants in Open-Water Unit Process Treatment Wetlands." Environmental Science & Technology48:5136-5144.

Jasper, J. T., Z. L. Jones, J. O. Sharp, and D. L. Sedlak. (2014). "Nitrate Removal in Shallow, Open-Water Treatment Wetlands." Environmental Science & Technology 48:11512-11520.

Nguyen, M. T., J. T. Jasper, A. B. Boehm, and K. L. Nelson. (2015). "Sunlight inactivation of fecal indicator bacteria in open-water unit process treatment wetlands: Modeling endogenous and exogenous inactivation rates." Water Research 83:282-292.

Silverman, A.I., Nguyen, M.T., Schilling, I.E., Wenk, J., and Nelson, K.L. (2015) “Sunlight inactivation of viruses in open water unit process treatment wetlands: Modeling endogenous and exogenous mechanisms.” Environmental Science and Technology. 49(5):2757–2766

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Composition of biomat

Jasper, Justin T., Zackary L. Jones, Jonathan O. Sharp, and David L. Sedlak. (2014) “Biotransformation of Trace Organic Contaminants in Open-Water Unit Process Treatment Wetlands.” Environmental Science & Technology 48, no. 9.

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Nitrate Removal Processes

Jasper, Justin T., Zackary L. Jones, Jonathan O. Sharp, and David L. Sedlak. “Nitrate Removal in Shallow, Open-Water Treatment Wetlands.” Environmental Science & Technology 48, no. 19 (2014): 11512–20.

kmol/y

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Trace Organic Contaminant Removal Processes

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Removal by direct and indirect photolysis Removal by sorption and biodegradation

Jasper, Justin T., Zackary L. Jones, Jonathan O. Sharp, and David L. Sedlak. (2014) “Biotransformation of Trace Organic Contaminants in Open-Water Unit Process Treatment Wetlands.” Environmental Science & Technology 48, no. 9.

Jasper, J. T., & Sedlak, D. L. (2013). Phototransformationof Wastewater-Derived Trace Organic Contaminants in Open-Water Unit Process Treatment Wetlands. Environmental Science and Technology

Biomat, light

Biomat, dark

No biomat

Sunlight Inactivation Processes

PPRI = Photo-Produced Reactive Intermediates

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Disinfection model for open water wetland

Silverman, A., Nguyen, M., Schilling, I., Wenk, J., Nelson, K. (2015) “Sunlight inactivation of viruses in open water unit process treatment wetlands: Modeling endogenous and exogenous mechanisms.” Environmental Science and Technology

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Wetland surface area (ha) per MGD of water

Dec Mar Jun Sep Dec0

10

20

30

40

A13-l

og (h

a M

GD

-1)

Prado wetlands

Easterly wetlands

E. coli

MS2

Non-pigmented enterococci

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Orange County Water District DemonstrationSanta Ana River:- Effluent dominated in dry season- Used for groundwater recharge (defacto indirect potable reuse)

Prado wetlands designed to provide nitrate removal

Orange County Water District (OCWD)

16Groundwater Recharge Basins

Prado WetlandsAverage flow ~ 6.5 m3/s (64 MGD)

Surface area ~ 350 acres

Prado open-water wetland demonstration cells

• Performance metrics

– Better treatment than vegetated cells (nitrate, trace organics, pathogen indicators)

– Ability to provide O&M (good observational skills needed)

– No decrease in habitat value

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Surface area ~ 6 acres

What Next?

• Design manual

• Outreach materials

• Better understand co-benefits (ecosystem restoration, flood control)

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UC Berkeley students from Ecological Engineering course (CE113) at Discovery Bay