Biohavens – the only truly bio-mimicking floating wetland – Case Study #14 – mitigation of eutrophication

5 November 2015

The BioHaven range of floating wetlands, also known as floating islands, provides a wide range of wetland aesthetic, habitat and treatment options designed from nature.  DH Environmental Consulting (Pty) Ltd (South Africa) has been partnered with Floating Island International, the designers of the BioHaven range, since 2008.  Over the next while our blog will document some Biohaven case studies.

 14. Floating Treatment Wetlands to Mitigate Lake Eutrophication: Enhanced Circulation and Nutrient Uptake Expand Fish Habitat

Project Location: Research Lake near Shepherd, MT, USA

Simple, cost‐effective water treatment strategies show the ability to transform agricultural effluent into world‐class fish habitat. This case study discusses an ongoing experiment to monitor the efficacy of a floating treatment wetland (FTW) that incorporates air diffuser technology to lift and circulate water through floating stream beds within the FTW. This combination of FTW and efficient water circulation/aeration is trade‐named LeviathanTM, a model of BioHaven floating island, and represents a novel approach to address nutrient loading.


Determining whether biofilm‐based microbes can set the stage for high fish productivity along with nutrient removal was a primary objective of this test.

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Wetland areas have been reduced worldwide while human‐caused nutrient loading has expanded with growing human populations. Mass‐production agriculture as practiced in many developed nations has contributed to numerous cases of hyper‐eutrophication in bodies of water that were previously low in nutrient concentrations. In fresh water, partly as a result of normal seasonal stratification, nutrient loading can deplete oxygen levels within the livable temperature zone for cold‐water fish species.

Floating Island International (FII) is a private research and development‐focused business. Over the last 11 years, FII has developed the BioHaven FTW technology, which mimics the ability of natural peat‐based wetlands to purify water. The Leviathan maximizes surface area and circulation, which are key components of wetland effectiveness. The islands are also designed to provide optimal perennial plant habitat. The Montana Board of Research and Commercialization, along with FII, funded the work described in this case study.

System Background:

Dissolved oxygen and temperature measurements taken on FII’s 6.5‐acre lake outside of Shepherd, Montana in 2008/2009 indicated that stratified water near the surface was too warm to sustain a trout fishery. While temperatures below the stratified warm water layer were sufficiently cool for trout, that zone contained low dissolved oxygen (DO) levels. During late summer at this south‐central Montana lake, no strata of water could consistently provide the cool‐water, high‐DO environment demanded by fish such as rainbow, brown and, especially, Yellowstone cutthroat trout.

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Groundwater containing variable nutrient concentrations enters the lake at an average rate of 80 gallons per minute (gpm). Surface water also flows into the lake at variable nutrient concentrations and flow rates. Evaporative loss and outflow are balanced to maintain the lake level at full pool, which ranges between 29 and 30 feet of depth.

As the lake was filled, a series of BioHaven floating islands covering 5200 square feet of lake area and providing over one million square feet of saturated surface area was installed. Several islands were positioned next to the inflow to maximize exposure to the highest nutrient concentrations. These islands, in combination with the Leviathan system, were designed to maximize biofilm production and move nutrients into and through the food web as organisms attached to underwater surfaces (“periphyton”).

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A 1250‐square‐foot Leviathan system, incorporating floating stream beds and grid‐ powered water circulation, was installed in the lake in April 2009. This system circulates up to 2000 gpm through the stream channels within the island. The Leviathan was constructed of post‐consumer polymer ”matrix,” averaging 25 inches in thickness, with each cubic foot of matrix providing 375 square feet of surface area. The Leviathan pump enabled personnel to pull water from any depth and move it through the stream channels, exposing it to the concentrated surface area (containing a microbial biofilm) and atmospheric oxygen.

After 17 months of operation, water clarity had improved from a low of 14 inches of visibility to as much as 131 inches. The Secchi disk reading is now 228 inches (19 feet) during the winter. Simultaneously, the water temperature gradient was reduced, creating a larger zone of “livable” water for fish. Two age classes of Yellowstone cutthroat trout were introduced 13 and 14 months into the test. Through the summer of 2010, a favorable temperature/dissolved oxygen strata ranging from the water surface down to a depth of at least 12 feet was maintained as potential cutthroat habitat. One‐year‐old and two‐year‐old black crappies were also introduced two months into the test, and naturally‐occurring northern yellow perch were present in the lake when it was filled. All three species have flourished.

The shaded area in the first chart below contains favorable conditions (DO and temperature) for cold‐water fish, with a much larger zone of favorable habitat in 2010 after the Leviathan design was enhanced and additional aeration was installed. The second chart shows the extent of the larger zone of cool, high‐DO water that was available for fish in 2010.

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Fish catch rates and growth rates are now being monitored at the lake. Initial data show that experienced fishermen can catch up to one perch per minute. Visual observations from diving and an underwater viewing station indicate that perch approaching or exceeding the Montana state record of 2 pounds 2 ounces now inhabit the lake.

The research lake is relatively unique in that it supports fish accustomed to cold water (Yellowstone cutthroat trout), temperate water (perch) and warm water (crappies). Montana officials have made two unsuccessful attempts at sustaining cutthroat populations in an adjacent stretch of the Yellowstone River, which is located a half‐mile away from the research lake.

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The new aeration scheme in the lake improves water quality by incorporating dissolved phosphorus and nitrogen into the aquatic food web, in the form of periphyton, while limiting the growth of deleterious algae. Total phosphate concentrations are reduced from 0.040 mg/L to 0.025 mg/L, while total nitrogen concentrations decrease from 0.55 mg/L to 0.01 mg/L.

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Algae tests result in higher [water] bills

26 June 2014

The quality of drinking water supplies is becoming increasingly threatened by pollution (Photo: Bill Harding)

The quality of drinking water supplies is becoming increasingly threatened by pollution (Photo: Bill Harding)

PORT CLINTON — Ottawa County water customers are paying 4.5 percent more for their water this year, partly because of the cost of removing toxins caused by harmful algae. Blue-green algae that grows on Lake Erie in late summer and early fall can produce a toxin, called microcystin, that can cause gastrointestinal illness and skin irritations.  Normal water treatment processes don’t always remove the toxin from the finished drinking water, causing plants like Ottawa County’s to use additional chemicals, methods and testing to make sure the water coming from the tap is safe.

Read more »

USA House of Representatives approves Harmful Algal Blooms Act

12 June 2014

Algal blooms impact on marine and freshwater resources worldwide (Photo: Bill Harding)

Algal blooms impact on marine and freshwater resources worldwide (Photo: Bill Harding)

Good news for research and management of noxious algae in the United States!  This week the US House of Representatives passed Bill S. 1254, which “reauthorizes the Harmful Algal Blooms and Hypoxia Research and Control Act.  Harmful algal blooms (HABs) occur when colonies of algae grow out of control while producing toxic or harmful effects on people, fish, shellfish, marine mammals, and birds. The bill maintains and enhances an interagency program led by the National Oceanic and Atmospheric Administration (NOAA), which will be responsible for promoting a national strategy to help communities understand, predict, control and mitigate freshwater and marine HAB and hypoxia events; enhancing, coordinating, and assessing the activities of existing HABs and hypoxia programs; providing for development of a comprehensive research plan and action strategy, including a regional approach to understanding and responding to HAB events; and requiring an assessment and plan for Great Lakes HABs and hypoxia”. Read more »

Be prepared for seasonal blue-green algal blooms

24 December 2013

Blue-green algal blooms are seasonally-common right now!  (Photo: Bill Harding)

Blue-green algal blooms are seasonally-common right now! (Photo: Bill Harding)

It’s that time of year in South Africa again – temperatures have warmed up and so have nutrient-enriched dams and ponds.  Many have developed algal blooms that could be toxic, so beware!

Droplets contains lots of useful information about blue-green algae and their toxins.  In the USA, the Centre for Disease Control has produced a very useful facts sheet that provides all the essential background.  South Africa does not have any resources focussed on algal blooms (!) or where to get help should one develop problems after being in contact with toxic algae.  DH Environmental Consulting can be approached for guidance and we have ability for rapid on-site toxin testing and algal identification.  Algal blooms pose a threat  to humans, pets and livestock.  They should not be underestimated.

We will shortly be releasing an App that will enable users to send us details of algal blooms they come across so that we can build a geographic database of bloom occurrence.  In the meantime you are welcome to email us information and photographs of what you saw, to

Merry Xmas!

Breakthrough Discovery Links Blue-Green Algae With Motor Neuron Disease

17 October 2013

(This press release was made by University of Technology, Sydney and is repeated here verbatim as part of Droplet’s information program on the possible links between BMAA and motor neuron disease – search Droplets for ‘BMAA’ for more information).

In summary:

  • For the first time UTS and US research has found a link between toxins produced by blue-green algae and motor neurone disease
  • Over 90 per cent of motor neuron diseases have had no known cause or cure

A recently identified link between a toxic amino acid found in blue-green algae and several motor neuron diseases could help researchers devise a therapy for the fatal conditions. Read more »

Blue-green algal blooms close Lake Erie beaches

17 July 2013

All beaches in the Chatham-Kent area of Lake Erie (Canada) have been closed as a result of dense cyanobacterial blooms. There is a stunning photo of a bloom off this shoreline at this link.

The Chatham-Kent Public Health Unit is advising the public to avoid exposure to the blue green algae.

  • Do not swim or wade in any water when a noticeable green surface scum or green discolouration of the water is present

  • Do not use the water for drinking, bathing or showering

  • Do not allow children, pets or livestock to drink or swim in the water.

  • Do not boil the water or treat it with a disinfectant, as this will release more toxins into the water

  • Eating fish caught in water where cyanobacterial blooms occur is not recommended. Read more »

A Little P can cause Big Problems

1 March 2013

Herewith a few CyanoAlerts to start off March!

A newcomer to Droplets CyanoAlert is Ella Lake – which is in Northern Ontario, rural Canada, one of dozens of lakes just south of the Trans Canada Highway.  Ella has a reported blue-green algal bloom – despite having very low levels of phosphorus (see graphic below) – illustrating the important fact that a little nutrient enrichment can cause a big problem.  Such low levels of Phosphorus is the stuff of dreams for us here in South Africa! Read more »

Research shows the way to fix Iowa’s eutrophication problem

7 January 2013

The US state of Iowa featured a lot in these posts during 2012.  Many Iowan lakes are enriched with nutrients, a lot of which comes from agriculture – not just suspected of coming from agriculture, actually shown to be.  So, how to deal with a big portion of the problem is clear – throw effort at the polluted agric runoff and get it down to acceptable levels.  OK, it may not be that simple as a press report today suggests:

First, unlike the approach used for cities, the strategy continues to rely on all-voluntary farm conservation programs, which have fallen short of protecting our waters in the past. Even though research clearly shows significantly increasing farmer participation in conservation programs is critical for success of the plan, the document does not set timetables or goals to ensure that this will happen. Read more »

Algal blooms hotting up down south

18 December 2012

And you thought that Spielberg character made up aliens that look like me? (Empusa guttula, female. Photo: Bill Harding)

Things are hotting up down here in the Southern Hemisphere and through the heat haze from my veranda I am kept awake by the regular fall of over-ripe plums from a tree that has become a veritable wildlife sanctuary for all sorts of birds, bees, beetles and the handsome guy in the picture above, well he was just passing through!

The increasing seasonal heat is closely associated with the increased number of algal bloom reports. Read more »

DHEC surveys links between toxic algae and motor neuron disease

29 May 2011

In a first for South Africa, Dr Bill Harding from DH Environmental Consulting (DHEC) will conduct a research survey to test for links between cyanobacteria (blue-green algae) and neurodegenerative diseases (Motor Neuron Disease, MND; Parkinsons Dementia Complex, PDC;  and Alzheimers). Read more »