CK Ventures Ltd.
Title of Session: Treatment Technologies
Title of Paper: Wetlands
for wastewater treatment
Author: Curt Kerns, M.Sc., R.P.Bio., C.F.S.
Affiliation: CK Ventures Ltd.
Date of Session: November 8, 1999
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Presentation: Wetlands for Wastewater Treatment
Definitions:
Wetlands: Those lands which at least seasonally water is at or
above soil level.
Wastewater: Those waters to which substances have been added.
Watershed:
Those
areas which respect gravity, not political subdivisions.
Introduction:
· Wetlands have a myriad of functions:
remove and detoxifying substances carried by and dissolved in water
nutrient sinks
sequester heavy metals
slow water release from storm events
recharge aquifers
vital wildlife habitat
express human and economic values
· North America formerly had vast areas of wetlands, associated with virtually all major and many minor river systems. Over their extensive range beavers made wetland ponds to further filter and treat runoff. Draining and diking by agriculturists caused wetlands being turned into croplands and essentially mined for their nutrients. As development proceeded in North America, now lacking the functions of wetlands, ocean discharge of wastewaters was deemed to be the solution.
Discussion:
· Ocean discharge of wastewaters is not the solution. On-land, plant-based tertiary treatment essentially mimicking how nature functions, is. Bioaccumluation of human-made toxicants are resulting in wastes returning to land to haunt us. One of the ways returning wastes are in evidence is in wildlife. Adult sockeye salmon returning to pristine wilderness areas of Alaska have been demonstrated to be the source of industrial compounds discharged and blown from lands. Their carcasses have been found to be the source of contaminants now found in grayling. Sockeye feed lowest on the food web of all species of Pacific salmon. The “good news” is that most of the world’s other oceans are far more polluted than the Subarctic Pacific.
Website: http://www.uaf.edu/seagrant/NewsMedia/98ASJ/06.04.98_Salmon.html.
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As British Columbia salmon commingle on the same feeding grounds as do Alaska salmon, we can expect the same contamination to be occurring. Orcas off our coast are in a rapid decline. An estimated one-half of all the newborn and young whales in the area of Southern Vancouver Island have died within the last six years, cutting the native Orca population to 82 from 95.1 Killer whales from further north who feed largely on marine mammals show even higher levels of pollutants. Indications are that B.C. Orcas are some of the most chemically contaminated marine mammals in the world.2. PCBs (poly-chlorinated-biphenols) and other substances originating from land both as aerosols and in wastewater are implicated. Levels of PCBs detected in B.C. Orcas are in excess of those found in beluga whales in the St. Lawrence River1.
· Wastewater management cannot be done in isolation, but rather requires a watershed approach:
Website: http://www2.co.clermont.oh.us/clermont/xl.htm
Land area estimated to effectively treat and manage wastewater comprises about 1 - 3% of the average watershed.
· Increases in global temperatures are projected to warm and consequently dry the east side of Vancouver Island and the Lower Mainland inordinately. Summer flows of salmonid streams will further decrease. Wastewater treated and detoxified could be the source of water for stream flow augmentation.
· Aquatic and terrestrial plants can be used to detoxify, remove nutrients, heavy metals, and all but eliminate pathogens from wastewater streams from major cities, industrial processes, communities, commercial developments, acid mine drainage, landfill leachate, agricultural runoff, all the way down to single family dwellings.
Performance of Arcata, Calif. Constructed Wetland (spec.htm)
· Forest lands can effectively receive considerable quantities of wastewater while maintaining very effectively treatment. Over 25 meters/yr. have been applied to what was a dry oak forest. Intensive investigations revealed excellent water treatment efficiencies.
3,000 gpm of beet processing wastewater (beetsea.jpg)
Forest receiving 1,000 in per year of wastewater (seabrook.jpg)
· Overland flow, that is spreading wastewater through grasses in broad, shallow swales or fields, has been demonstrated for over 30 years to also be a very effective tertiary treatment procedure.
The criteria are well established.
Single family dwellings can benefit from Constructed Wetlands. In the U.S. over 500 homes with primary treatment alone followed by what essentially amounts to an aquatic plant-filled ditch with very high quality water coming out the other end demonstrate well the feasibility. Unfortunately it not that simple. To insure public health concerns are met further treatment followed by disinfection is required. In areas that would otherwise require a mound system as the ground will not perk, secondary treatment followed by UV disinfection and then a Constructed Wetland is recommended. The latter will not only perform better, protect public health, and
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ground- and receiving waters, but also cost less. To meet Ministry of Health regulations any overflow should be directed to a gravel-filled trench, preferably as narrow and deep as the equipment will allow.
Single Family Dwelling, primary treatment, lineal Constructed Wetland (cwsfdp.gif)
Single Family Dwelling, secondary, UV, Constructed Wetland
British Columbia already has a number of Constructed Wetlands that have demonstrated excellent treatment capabilities. Constructed Wetlands work well in areas that form ice cover in the winter.
Constructed Wetland in Prince George (weland1-4.bmp)
Conclusions:
North America has lost most of its original wetlands, consequently the functions of wetlands to filter, precipitate, and detoxify wastes from water. “Big Pipe” solutions are not solutions at all, merely deferring the problem resulting in pollution of the world’s oceans. We in British Columbia are seeing it in the contamination of our salmon as well as the rapid loss of Orcas. As low levels of contamination bioaccumulate, toxicity increases further up the food chain. Humans are at the top of the food chain. Planning must be done on a watershed basis. Areas that can be readily sewered have been. Decentralization using primary or secondary treatment followed some sort of by land-based, vegetative treatment is the way to proceed. Land-based treatment methodologies such as Constructed Wetlands, forest application, low and high rate overland flow, and drip irrigation all have their uses. Ancillary benefit can often result or can be designed in: stormwater runoff desynchronization, winter retention for summer releases to augment stream flows, aquifer recharge, wildlife habitat, and human passive recreation and education.
1Lunman, K. (1999). B.C. killer whales threatened by PCBs’, Canadian marine researchers conclude. The Globe & Mail, Oct. 13, p. 2.
2Tafler, S. (1999). The killer whales off B.C.’s coast are dying. The Globe & Mail, Oct. 15, p. 15.