The use of constructed wetlands to reclaim wastewaters for receiving water quality improvement and to provide sources of water for salmonid restoration and recovery efforts
Integrating Approaches For Habitat And Salmon Management: The use of Constructed Wetlands to reclaim wastewaters for receiving water quality improvement and to provide an often-steady source of water for salmonid restoration and recovery efforts.
Author: Curt Kerns, M.Sc., R.P.Bio., C.F.S.
Affiliation: CK Ventures Ltd.
Date of Session: April 10, 2000


Wetlands: Those lands which at least seasonally water is at or above soil level.

Wastewaters: Those waters to which substances have been added

Watersheds: Those areas in which water respects gravity, not political subdivisions.

Waste Treatment: The returning of the constituent components of waste compounds to carbon dioxide, water, and minerals.


North America once 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 to be turned into croplands and essentially mined for their nutrients. As town grew into cities, wetlands are routinely filled for space. Many a highway has been built through marshes as its cheaper.

Since Europeans landed, over half of the wetlands of North America have been lost. California has lost 99% of its former wetlands. As development proceeded in North America, now lacking the functions of wetlands, riverine and ocean discharge of wastewaters was deemed to be the solution. The effect upon coastal waters has been devastating. Ecological changes are occurring at an increasing rate. Coastal waters do not process excessive nutrients well unless they are in an elemental form such as occurs with upwelling. Urea has been found to differentially favor dinoflagellates over that of diatoms. The sheer quantity of nutrients coming from land has become a problem. When nitrogen to phosphorus to silica ratios become skewed, species and taxa of phytoplankton utilized by economically beneficial species of fish and shellfish flourish. Immense disruptions occur. It grows worse with the addition of the wastes from each animal, from each human, from each suburban lawn, or fertilized cropland is added. And it’s the world over, not just North America.

The Problem:

The essential problem with wetlands has been that the benefits are diffuse and the property owners have hitherto only been able to extract value by destruction of wetland functions. Ocean and riverine discharge of untreated or even partially treated wastewaters are causing ecological disruptions of an unprecedented scale. Discharge into coastal waters of the 25 billion plus liters of sewage per day from North America is wreaking havoc with the waters of the continental shelf. Bioaccumulation of human-made toxicants is resulting in wastes returning to land to haunt us. One of the ways returning wastes are in evidence is in wildlife. Adult sockeye salmon Oncorhynchus nerka 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 so should be expected to be the least contaminated. The “good news” is that most of the world’s other oceans are far more polluted than the sub Arctic Pacific. As British Columbia salmon commingle on the same feeding grounds as do Alaska salmon, we can expect the same contamination to be occurring here.






Killer whales from further north who feed largely on marine mammals show even higher levels of pollutants. Indications are that B.C. orca are some of the most chemically contaminated marine mammals in the worldTafler, S. (1999). The killer whales off B.C.’s coast are dying. The Globe & Mail, Oct. 15, p. 15. PCBs (poly-chlorinated-biphenyls) and other substances originating from land both as aerosols and in wastewaters are implicated. Levels of PCBs detected in B.C. orca are in excess of those found in beluga whales in the St. Lawrence RiverLunman, K. (1999). B.C. killer whales threatened by PCBs’, Canadian marine researchers conclude. The Globe & Mail, Oct. 13, p. 2.. Hormone interfering substances found in pesticides, herbicides, plasticizers, and detergents also originating from land are also implicated.

A hundred years ago harmful algae blooms, or red tides, were typically found only in northern waters such as off the coast of New England and the Maritimes on the East Coast and in B.C. and Alaska waters. By fifty years ago, they occurred off most major cities. Now they surround North America. In 1998, over 400 sea lions died from the ill effects of a harmful algae bloom in Monterey Bay, California.

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.

The Solution:

The solution to pollution is NOT dilution; it is land-based treatment utilizing plants. On-land, plant-based tertiary treatment of all wastewaters, essentially mimicking how nature functions, is the solution. Now, with the widespread use of constructed wetlands beginning, direct economic value can be derived from wetland functions. Ratepayers who would see their taxes go up to build new or expand existing wastewater treatment facilities can save millions of dollars by paying for the leasing of wetlands for wastewater treatment.

We must restore wetland functions to wastewater treatment. Communities across the world are using Constructed Wetlands for domestic wastewater treatment. Naturally occurring wetlands for water and wastewater treatment have long been used to treat wastewater. London, England has used wetlands to treat its wastewater for over a century. Now cities such as Sacramento, California, and Phoenix, Arizona have built pilot-scale wetlands and are in the process of scaling up their operations to full-scale treatment.

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

Constructed Wetlands (CW) are probably the most flexible water treatment and retention mechanism yet discovered. Aquatic and terrestrial plants are useful for treating municipal effluents from major cities, industrial wastewater, agricultural runoff, storm water runoff, animal wastes, acid mine drainage, landfill leachate, domestic wastewater from subdivisions, office complexes, shopping centers, and individual businesses and homes. Plants can be used to detoxify, remove nutrients, heavy metals, and all but eliminate pathogens from wastewater streams of most all types. Constructed Wetlands are a relatively new (to North America) water pollution control technology. Constructed Wetlands are the treatment of waste compounds from contaminated water using aquatic plants, microorganisms, and physiochemical processes that occur in shallow ponds.

Questions and Answers about Constructed Wetlands

In the Pacific Northwest, Arcata, California has used a Constructed Wetland to excellent advantage since 1986.



Diagram & Performance of Arcata, Calif. Constructed Wetland

Constructed Wetlands for single-family dwellings are the wave of the future. They offer unparalleled treatment effectiveness, achieving true tertiary treatment, reliability that is way beyond that which we are accustomed to, plus can actually cost less than other treatment methodologies that are not nearly as effective. In the U.S. over 500 homes with primary treatment alone followed by what essentially amounts to an aquatic plant-filled lineal 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, high rate aeration secondary treatment followed by UV disinfection and then a Constructed Wetland is the future. Wetlands can provide superior performance, better protect public health, ground- and receiving waters, and can also cost less. To meet B.C. Ministry of Health regulations any overflow should be directed to a gravel-filled trench, depending upon specific site constraints, preferably as narrow and deep as the equipment will allow.








Forestlands 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 gallons per minute of beet processing wastes
Photo by Bob Bastion, USEPA, Office of Wastewater Management, Washington, D.C.


26.7 meters (1,000 inches) per year aerial spraying in Seabrook, NJ of food processing wastewaters
Photo by Bob Bastion, USEPA, Office of Wastewater Management, Washington, D.C.

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 here.

Agriculture is an important source of point and non-point nutrients.


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.

Northern Pothole Lakes


Constructed Wetland in Prince George





Land area estimated to effectively treat and manage wastewater comprises only about 1 - 3% of the average watershed. Here is what the widening of drainage ditches did for the peak flows for one community.

Thesis Evaluation of A Small In-Stream Constructed Wetland in North Carolina's Coastal Plain


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 Cascadia are seeing it in the contamination of our salmon as well as the rapid loss of orca. 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 for water and wastewater. Areas that can be readily attached to "the big pipe" have been. Decentralization on a watershed basis 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 restoration, and human recreation and education