Client Profile - Quarry Island Cove Demonstration Project , Oklahoma, USA

Thursday, December 18, 2008

The Poteau Valley Improvement Authority (PVIA) provides water to most of rural LeFlore County in eastern Oklahoma. The source of that water is Wister Lake, a reservoir constructed by the US Corps of Engineers in 1949. Over the last several decades the lake has become highly eutrophic* due to large inputs of phosphorus and sediment from its watershed. Besides the negative effects on lake ecology, this increases the costs of treating the water for drinking and other uses.

In the summer of 2008, PVIA received a matching grant from the U. S. A. EPA through the Oklahoma Secretary of the Environment's office to assist in the development of the Quarry Island Cove Demonstration Project. Named for the cove on in which PVIA's water intake is located, the project has two components: aeration and floating wetlands. Twenty-five fine bubble aerators were placed on the bottom of the lake covering approximately 4.5 acres adjacent to the water system intake. Rising air bubbles cause the water to circulate and circulation increases the dissolved oxygen content of the water. This reduces phosphorus release from lake sediments, oxidizes metals in the lake rather than in the treatment plant, provides an oxygen refuge for fish and other aquatic life, and decreases the growth of cyanobacteria (bluegreen algae) that can cause taste and odor problems.

To complement the circulation and increased oxygen, 16 floating wetland rafts were constructed. Each raft is approximately 4' x 10' and built of HDPE pipe for flotation and a coir mattress that serves as the supporting matrix for the plants. Five of the rafts were planted with Vetiver from Agriflora's nursery, and the rest were planted with a suite of native wetland species collected locally. PVIA is monitoring the growth and survival of the plants to determine which species will perform best. One test for the Vetiver will be how well it survives the Oklahoma winter. So far, Vetiver is showing the best growth, both of plant tops and, more importantly, of roots. Cattails are second to Vetiver, but late season harvesting by beaver has been destructive to cattails but not Vetiver.

Wetland plants growing on the rafts will remove nutrients from the water. In addition, the underwater root surface area will be colonized by bacteria and algae that will also remove nutrients. These microbial and algal biofilms will be fed upon by zooplankton, and the zooplankton by fish, thereby creating an alternative food web and nutrient cycle which should further reduce nutrient concentrations in the water.

Based on the successful construction and growth of the first set of floating wetlands this past summer, PVIA staff are constructing 32 additional rafts this winter for installation next spring. This will triple the number of installed wetlands. Half of the new rafts will be planted with Vetiver. Monitoring of dissolved oxygen levels, plant growth, and nutrient concentrations will be conducted throughout the 2009 growing season.

The design and implementation of this visionary application is in the capable hands of Steve Patterson, a consultant practicing restoration ecology through his firm Bio X Design. Steve's excellent Ecosystem Design blog is excellent reading on novel ecological ideas

Notes on photos: The photos were taken in September after about 3 months growth. The blobs on the rafts in the roots photo are freshwater bryozoa, a filter feeding colonial animal. Vetiver Photo credits: Steve Patterson, Bio x Design.

Another excellent picture and additional information can be found on this article from the Tulsa World newspaper from August 2008. We will continue to follow this project and report on its future progress.


* eutrophic - result of the process by which a body of water becomes enriched in dissolved nutrients (as phosphates) that stimulate the growth of aquatic plant life usually resulting in the depletion of dissolved oxygen (Merriam-Webster)


cjuliard said...

Congratulations to PVIA, Steve Patterson, Bio X Design, Agriflora and the team working on phytoremediation through the use of vetiver and other plants on floats, allowing a biological system to work on a biolgical problem.
The Interntional Vetiver Network is keenly interested in your work and results. We note the pictures and text date from Dec.'08. Is there an update of measurements, pictures of the vetiver weather two winters or other observations? Keep up the excellent work.
Kind regards,
Criss Juliard,The Vetiver Network, (International), North Africa, Mediterranean and Middle East

The Vetiver Network (International) said...

Alberto , you must be pleased with the results thus far. I guess the water was not cold enough o kill the plants off this winter. hope you can get some updated data.


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