Constructed Wetlands as aWater Treatment System:

Arcata, California

Ricky EbersohlSSC 570-601

Fall 2008

Background2,5

Wetlands serve to reduce and remove toxins from the environment

Wetlands provide a buffer for flood control and draughtAbsorb and hold excess

water during rainy seasonsSlowly release water

during drier timesWetlands provide a

unique habitat fororganisms of all kinds

Source: North Queensland Area Consultative Committee

Background1,2,5,6,7

Aquatic plants that help to remove contaminants Broad-leafed arrowhead (Sagittaria latifolia) Lotus (Nelumbo lutea) Elodea (Elodea canadensis) Pickerelweed

(Pontederia cordata) Wild rice (Zizania aquatica) Mosquito fern (Azolla mexicana) Wild celery

(Vallisneria americana) Big duckweed

(Spirodela polyrhiza) Lesser duckweed (Lemna minor)

Source: http://www.okpond.com/

Background1

Organic nitrogen Aerobic/anaerobic (ammonification) Affects oxygen levels in

the wetlands Removal – mineralization into

inorganic formsAmmonia/ammonium/nitrates

Toxicity to fish Nitrates can decrease the blood’s

ability to transport oxygen Removal – in soils, nitrification (aerobic) and

denitrification (primarily anaerobic) and taken up by plants

Source: http://www.sciencedaily.com/

Background1

PhosphorusPlants

Stored during the growing seasonReleased when the plants die

SoilsStored in sediments

(phosphorus sink)Redox potential – wetland

soils can reduce iron andrelease bound phosphorus

Dependent largely onoxygen concentrations

Source: USGS Water Resources

Overview2,5

PurposeStorm water control and

managementMunicipal wastewater

treatmentAgricultural wastewater

treatmentLandfill leachate managementRunoff control

ComponentsSoil and drainage constructionWaterAquatic plantsMicro-organisms

Source: Colorado State University

Overview2,5

Advantages over conventional wetlandsGenerally independent of groundwater

channelsPurpose-specific design (efficient)Develop and mature quicklySize remains constant

Source: United Nations Environment Programme

How It Works

Source: City of Arcata

How It Works3

Primary treatmentUses multiple steps to remove

larger solid objectsGenerates and then removes

bulky sludgeAerobic and anaerobic digesters are used to

stabilize sludge for removalSludge is dried and removed

Source: City of Arcata

Source: United Nations Environment Programme

How It Works3

Secondary treatmentUses oxidation ponds and

treatment wetlandsOxidation ponds

Utilizes bacteria to break downorganic material

Utilizes algae to provide oxygenTreatments wetlands

Utilizes a marsh setupCattails and other marsh

plants help remove ammonia,nitrogen, and phosphorus

Reduces total and fecal coliform and settles remaining waste residue

Source: City of Arcata

Source: City of Arcata

How It Works3,7

Tertiary treatmentEnhancement marshes

Final stage, in most casesProvides habitatProvides recreational facilitiesLowers nutrient contentReduces BOD (measures organic matter content)Reduces effluent in a final stepResulting water can be directly released into the

environment

Source: City of Arcata

Source: City of Arcata

How It Works3,6

DisinfectionChlorination

Used to destroy pathogensRemoves ammoniaReduces sludge buildup

DechlorinationSulfur dioxide is used to

remove chlorine from thesterilized water

Resulting water is safe forrelease into theenvironment, outside ofthe wetlands

Source: City of Arcata

Source: City of Arcata

Water Quality Results4

Average for total dissolved solidsAverage for chlorine and sulfatesAverage for specific conductanceZero positive for coliformZero positive for

fecal bacteriaZero positive for e.coliNegative for leadNegative for copper

Source: http://www.thebacteriabusters.com/

References1. Australian Natural Resource Management. “Wetland ecosystem

condition: nutrients (phosphorus and nitrogen)”. http://www.nrm.gov.au/publications/factsheets/me-indicators/inland-aquatic/wetland-condition-nutrients.html. Accessed October 26, 2008.

2. Campbell, Craig S. and Michael H. Ogden. Constructed Wetlands in the Sustainable Landscape. John Wiley & Sons, Inc. New York, p.270. 1999.

3. City of Arcata – Arcata Marsh & Wildlife Sanctuary. http://www.cityofarcata.org/index.php?option=com_content&task=view&id=20&Itemid=47. Accessed October 25, 2008.

4. City of Arcata – Drinking Water 2007 Water Quality Report. http://www.cityofarcata.org/images/stories/city_of_arcata_consumer_confidence_report_2007.pdf. Accessed October 26, 2008.

5. DeBusk, William F. “Wastewater Treatment Wetlands: Applications and Treatment Efficiency”. University of Florida, Institute of Food and Agricultural Sciences (UF/IFAS). May 1999.

6. Hawkins, Julie. “Constructed Treatment Wetlands”. USDA-NRCS. USDA-NRCS. April 1, 2008.

7. Kadlec, Knight, Robert H., Robert L. Treatment Wetlands. CRC Press LLC, 1996.