Constructed Wetlands as a Water Treatment System: Arcata, California
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Transcript of Constructed Wetlands as a Water Treatment System: Arcata, California
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 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.