SA’s Drinking Water Reservoirs are full of shit. Literally

30 September 2016

(Guest post by Graham Sell – republished with permission – emphasis added)

It was only when I started looking into the controversial award of a Water Use Licence (WUL) to Metsimaholo Municipality (enabling them to pump treated and partially-treated effluent from their Refengkgotso sewerage works into the Vaal Dam at Deneysville) that I realised how deeply in the pooh we are across the whole country – both literally as well as metaphorically.

Before getting back to the specifics of the Refengkgotso pipeline, take a look at the compliance table below to see how your province fares in the Green Drop stakes. The Department of Water Affairs and Sanitation (DWS) Green Drop awards program sets standards for processing raw sewage into an acceptable state for reintroduction into the environment.  As a cornerstone of the program, municipalities are required to regularly test the effluent from their waste water treatment plants to ensure that it complies with prescribed microbiological, chemical, and physical standards.

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So little water, so much poor management of it

17 November 2015

South Africa needs an infrastructure revolution and a change in values if it is to avoid being left high and dry, writes Mmusi Maimane

THEY say countries should never waste a crisis. We need to see South Africa’s drought and water shortages as such an opportunity.

Our water system has reached a point where it could limit economic growth and development, which will therefore affect our social wellbeing and stability. This applies to both the quantity and quality of water available to us. Right now, we need to urgently and strategically manage our transition from a demand-driven to a supply-constrained economy.

With respect to quantity, we are experiencing a rapid increase in demand coupled with a steady decrease in supply. Population growth, immigration and changing consumption habits are pushing up demand. Supply is falling due to crumbling, poorly managed infrastructure aggravated by a shortage of engineers; an El Niño event; and a climate change trend making South Africa a hotter, drier country. This constitutes a looming crisis, despite Water and Sanitation Minister Nomvula Mokonyane’s protestations to the contrary.

To make matters worse, the quality of water is also declining. Our municipal waste-water system, which treats and recycles used water, is under extreme pressure, with as many as 90% of waste-water treatment works dysfunctional. Urban and industrial effluent runs into our rivers, while acid mine drainage and the large amounts of hazardous waste that we are unable to deal with are further contributors to this problem.

It is generally agreed that at least a third but possibly up to two-thirds of our national stored water resources (in dams and watercourses) is eutrophic, meaning that it has dangerously elevated levels of nutrients that cause blue-green algae to flourish. This, in turn, produces chemicals toxic to our health. So pollution and waterborne diseases are also risking our supply.

The political and social risks of this deteriorating situation should be clear. Economic growth — and thus job creation — will be increasingly limited, leading to social instability. This will be exacerbated by rising food prices due to our increasing inability to withstand periodic droughts; our re-allocation of water from agriculture in an attempt to prevent job losses in more labour-absorbing sectors of our economy; and the general desiccation of our land due to overuse and poor farming practices.

Water insecurity will also drive energy insecurity, since energy production relies on water. Of course, water can be “imported” by means of food and energy imports that used water in their production cycle, but that option is becoming less likely because of our balance-of-payments deficit, a situation aggravated by our government’s penchant for presidential jets and the like.

As ever, the poor (particularly women and children, to whom it generally falls to collect water for cooking and washing) will suffer disproportionately — and are least able to adapt, move, or buy their way out of the problem. They are also afflicted by the least competent municipalities.

This is the bad news.

The good news is that a lot can be done to reverse this dismal state of affairs, avert the looming disaster and put South Africa back on the road to water security. Says water expert Professor Anthony Turton: “The transition can be managed, but it will require a carefully formulated strategy, driven by a policy that is based on the best available science, held together by sound political leadership embedded in robust institutions.”

Our challenge is to significantly boost water supplies, massively improve efficiency of use and increase our resilience to drought — all while ending the injustices of water provision in the past and ensuring the integrity of our ecology.

There is massive waste and inefficiency in our water systems. Wastage is due to poorly maintained infrastructure, with definitely at least a third but quite possibly up to two-thirds of all reticulated water being lost to failing infrastructure and theft. This means there is massive scope to boost our supply, but we need to channel resources — our best engineering talent and funds — to reverse the infrastructure decline.

This waste is compounded by the inefficient use of water by various sectors. We need to identify the sectors with the most potential for improvement. Here, the agricultural sector offers the greatest gains, because it uses 63% of our water for irrigation. Land management on farms has a major impact on water availability and quality. Soil erosion, for example, changes the flow of our rivers and reduces the storage capacity of our dams, resulting in the need for expensive water filtration and treatment systems. Poorly applied fertiliser and pesticides run off into rivers, polluting our water and killing aquatic life. Clearing alien vegetation is also a cost-effective, job-creating way to increase water supply on farms, because invasive plants use more than twice the water of indigenous vegetation.

Essentially, we need not only an infrastructure revolution, but also one of values. We need to recognise that our economy — and, ultimately, our wellbeing — are reliant on our national ecology, and start to treat our natural environment with the respect and care it deserves. Properly cared for and managed, our wetlands, rivers and organic-rich soil purify our water and provide resilience in times of drought. We need to restore, respect and protect our ecosystems. This requires strong leadership, which we’re not seeing right now.

Similarly, there is vast scope within our manufacturing processes and energy production for water saving, not only through efficiency gains, but through fundamentally changing the way we produce, consume and live. Once again, this begins with good governance.

As in so many other areas of state management, we know what needs to be done, but are falling short on implementation. As Mokonyane said in an interview with Chris Barron last weekend: “If you ask me, we need more bodies with the knowledge and capability, we need better management and better planning. Having the right people in the right place with the ability to do the job.” I couldn’t have said it better myself. All I would add is: “And with the government clearly having failed to rise to this challenge, it is time for a change of leadership, before we are left high and dry.”

•Maimane is the DA leader

(This article first appeared in the Sunday Times, 15 November 2015, page 18.  Republished with permission of the DA and the Sunday Times).


DA has quality of SA’s water resources on its radar

15 November 2015

Aquatic plants are very important stabilizers of waterbodies (Photo: Bill Harding)

Water quality is fundamentally important to South Africa’s future (Photo: Bill Harding)

As someone who has beaten the water quality drum for many years (search this blog for ‘water crisis’ articles) it is always pleasing when politicians recognize the pivotal role that water quality holds for South Africa.  This topic is currently receiving increased attention due to the very severe drought conditions currently being experienced.

The Democratic Alliance has been somewhat quiet on water quality issues since the days when Gareth Morgan held the portfolio.  Today, however, the Sunday Times (November 15, 2015, pg 18, see following post) carried an opinion piece by no less a DA member than its leader, Mr Mmusi Maimane, entitled “So little water, so much poor management of it“.  To my knowledge, addressing such a topic is a first for any leader of a political party in this country!

The article reads, inter alia, that “[to] make matters worse, the quality of water is also declining. Our municipal waste-water system…is under extreme pressure, with as many [sic] as 90% of waste-water treatment works dysfunctional“.  Furthermore, “…possibly up to two-thirds of our national stored water resources in dams and watercourses is eutrophic“.  Here Mr Maimane is referring to the legacy of inaction on the level of wastewater treatment required to prevent South African reservoirs from becoming eutrophic, a legacy that persists from the previous regime of government (see review article here for details).

Mr Maimane correctly notes that, the dire circumstances notwithstanding, there is still hope for mitigation.  What remains is for the ANC government to stop denying that there is a crisis, stop focussing solely on water quantity and to move demonstrably towards the application of more appropriate science and technology for the management of South African surface waters.

(Bill Harding is a South African aquatic scientist with a long history of experience in eutrophication and toxic algae.  He is a Certified Lake Manager – a USA certification and is the only person so registered in South Africa).

Biohavens – the only truly bio-mimicking floating wetland – Case Study #20 – nutrient removal

14 November 2015

Nutrient Removal from Reclaimed Water with Floating Treatment Wetlands

Project Location: Pasco County, Florida USA

An independent study conducted by CH2M Hill demonstrates the ability of BioHaven® floating treatment wetland (FTW) technology to further reduce nutrient levels in reclaimed municipal wastewater, which would assist in meeting total maximum daily load (TMDL) limits. In addition to removing total nitrogen (TN) and total phosphorus (TP), FTWs provided the ancillary benefits of:

  •   Increasing wildlife habitat;
  •   Reducing local nuisance insect populations; and
  •   Increasing pond aesthetics.


CH2M Hill supervised installation of 20 FTWs in a test pond containing approximately five million gallons of reclaimed water from the Pasco County Master Reuse System (PCMRS). Each FTW measured 8 ft x 10 ft and accommodated 154 plants. The primary objective of this study was to quantify nitrogen removal by the FTWs, in the hopes of demonstrating the benefits of FTWs in TMDL-limited watersheds. Total nitrogen is the parameter currently limiting reclaimed water use within the PCRMS. FTWs were envisioned as a more efficient alternate to treatment wetlands where land area may be constrained.

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The PCMRS is a regional reclaimed water transmission and distribution system providing wastewater effluent disposal for Pasco County and the City of New Port Richey. With 15 golf courses and approximately 12,000 residential users connected, the PCMRS reclaims approximately 20 million gallons per day (mgd) of advanced secondary treated effluent from seven local WWTFs.

Water Quality Effects

FTWs had a positive effect on TN, TP and pH as shown below:

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Removal of TN and TP was substantially higher during the FTW performance period than during the control period. Nutrients were still removed during the control period, probably due to some bacterial activity and solids settling in the test pond. However, bacterial and plant nutrient removal processes were substantially enhanced during the performance period. Net nutrient removal rates attributable to the FTWs can be calculated by subtracting the control removal from the performance removal. Those rates, based on the amount of FTW present in ft3, were 1.7 lb/yr/ft3 for TN and 0.54 lb/yr/ft3 for TP.

Most of the total nitrogen was present as nitrate. It was found that water temperature, which averaged 23oC during the performance period, did not affect nitrate removal over the temperature range examined.

pH increased in the test pond as algal photosynthesis produced a large amount of alkalinity. However, this pH increase was mitigated during the performance period and values (recorded automatically every hour) were much less variable with the FTWs.

No removal of TSS or BOD was seen in the study. TSS increased by over an order of magnitude due to algal growth in both the performance and control periods. The influent BOD was typically less than 5 mg/L.

Removal Mechanisms

It has been noted in previous FTW studies that only 10-20% of the nutrient removal is performed by plants, with the majority of nutrient removal performed by bacteria attached to the FTW matrix and plant roots (biofilm). In the Pasco County study, plant samples were harvested during the performance and control periods to analyze the nitrogen, phosphorus and carbon contained in the plants. It was estimated that only 0.3% of the nitrogen removed was contained in above-ground plant matter during the performance period, and 0.8% during the control period. The remaining nitrogen removal can be attributed to plant roots, bacterial activity and chemical/physical processes. A mass balance estimated that 57% of the TN removed during the performance period was denitrified to nitrogen gas.

Ancillary Benefits

Four main benefits have been historically attributed to FTWs:

  1. Water purification,
  2. Habitat improvement,
  3. Erosion protection and
  4. Enhanced landscapes.

Benefits identified in the Pasco County study were:

  •   Wildlife habitat. Wildlife was observed on several occasions utilizing the FTW habitat. Birds included black-necked stilts, clapper rails, boat-tailed grackles and ducks (which built nests). Turtles were also observed resting on the FTWs.
  •   Nuisance insect species control. The FTW habitat also benefits smaller organisms such as aquatic and terrestrial insects. These invertebrates find refuge and food sources within the dense submerged roots and emergent vegetation. Insects that are dependent on water bodies for habitat, such as dragonflies and damselflies, can help reduce the local populations of nuisance species through natural predation. During the performance period, WWTF staff noted no large hatches of midges, which can be a nuisance to people and even be vectors for the spread of diseases such as West Nile virus, and – contrary to previous years – there were no complaints by neighboring residents.
  •   Aesthetics. Adding FTWs to the WWTF pond increased the overall aesthetics. The variety of grasses, rushes and flower plants on the FTWs provided natural aesthetics to a pond otherwise devoid of vegetation.


  •   Floating treatment wetlands (FTWs) installed in a test pond removed substantial concentrations of total nitrogen and total phosphorus from reclaimed water. Nutrient removal with FTWs was significantly greater than when the FTWs were removed from the system.
  •   Plant uptake provided only a small percentage of the total nitrogen removal.
  •   FTWs provide productive habitant for invertebrates and wildlife. A diverseselection of vegetation and species was sustained on the islands.

{This is the last of 2o case studies published in this series}

Biohavens – the only truly bio-mimicking floating wetland – Case Study #18 – eutrophication

12 November 2015

BioHaven® FTWs Remove Nutrient Loads from Eutrophied Lake

Project Location: Yingri Lake, Jinan, China

At an urban lake in China, large reductions in chemical oxygen demand (COD), biochemical oxygen demand (BOD), total nitrogen and total phosphorus were measured within three months after BioHaven® floating treatment wetland (FTW) installation, which met the project objectives. The primary goal of reducing algae blooms was also achieved.


The purpose of this floating island application was to prevent summer algae blooms by reducing the nutrient load in an urban lake. Reductions in nutrient levels were anticipated to increase the overall health of the lake by decreasing algae growth, increasing dissolved oxygen levels and decreasing odors. The location is Yingri Lake at Quancheng Park in Jinan, a city of seven million people in North China near the east coast.

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Yingri Lake had typically experienced a severe algae bloom every spring; however, no algae bloom was seen in 2010 after the FTW installation in April.


  •   Large reductions in COD, BOD, total nitrogen and total phosphorus were measured within three months after FTW installation, which met the project objectives.
  •   The islands are aesthetically pleasing.
  •   It is unclear why dissolved oxygen concentrations decreased; however, the primary related goal of reducing algae blooms appears to have been achieved.

The looming water crisis, and its causes

11 November 2015

(Author: Anthony Turton)

Sitting on the Horns of a Dilemma: Water as a Strategic Resource in South Africa

South Africa is a water-constrained country with a vital need to conserve, manage, and expand its limited water resources as efficiently as possible. Since 1994, however, strategic planning has deteriorated, along with operational efficiency. Under the supposed imperatives of ‘transformation’, skilled engineering and other professional staff have been driven out of water boards (responsible for bulk water supply) and municipalities (charged with local reticulation and often also with waste management).

Municipalities are now discharging around 4 billion litres of untreated or partially treated sewage into the country’s rivers and dams every day. The Government refuses to admit the extent to which water quality has deteriorated, and a public health crisis now looms. Various reforms are feasible, but the ruling party shows little willingness to allow practical reality to prevail over its transformation ideology.

That water constraint

South Africa’s rainfall is half the global average, making it a water-scarce country. The first proposal for the construction of large dams was made in the 1870s.

In 1886 Thomas Bain, a civil engineer in the public roads department in the Cape, followed up with a book on ‘water finding’ and‘dam-making’, which urged state intervention in the construction of hydraulic (water-driven) infrastructure as an essential foundation for economic growth and social cohesion.

When South Africa became a republic in 1961, one of the State’s first major projects was the creation of a scheme to transfer water from one river basin to another. This was achieved via the Orange-Fish-Sundays scheme, which transfers water from the Gariep Dam in the Free State to arid areas in the Eastern Cape. This initiative was specifically designed not only to address the water challenge in parts of the Karoo but also to restore investor confidence after the Sharpeville shootings in 1960.

In 1970 came the report of the Commission of Enquiry into Water Matters. This report warned that South Africa’s economic development would always be water-constrained unless a coherent plan was implemented by the State to overcome this obstacle. In response, the Government imposed a tax on the bulk sale of water (the first of its kind in the world) to fund a new body called the Water Research Commission. This commission was given the task, in partnership with the Council for Scientific and Industrial Research (CSIR), of developing the science and engineering technology needed to address the country’s endemic water scarcity and so promote economic growth and prosperity.

Working from this foundation, South Africa became a global leader in the management of water. This allowed the country to develop the most diversified economy in the world compared with other nations with similar climatic regimes. One of its great achievements in the 1970s was the CSIR’s development of the first sewage recycling technology.

This cutting- edge innovation was put into operation in Windhoek (in what was then South West Africa and is now Namibia) in response to the absolute water scarcity in the city. This development was also part of a wider strategic initiative to harness water from a multiplicity of sources. South Africa thus became globally recognised for its ability to achieve economic growth and development despite its fundamental water constraint, which was largely overcome through high levels of technical ingenuity.

The National Water Act of 1998

After the transition to democracy in 1994, the new Government adopted the National Water Act of 1998 as one of its first ‘transformation’ interventions. This removed riparian and other common-law rights to water and made the State the public trustee of the nation’s water resources. It also gives the State the power to decide on ‘the equitable allocation of water in the public interest’, in order to address past racial and gender discrimination.

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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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Biohavens – the only truly bio-mimicking floating wetland – Case Study #12 – wastewater treatment

3 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.

 12. BioHaven® Floating Treatment Wetlands Improving Waste Water Treatment!

Project Location: Harrisonburg, Louisiana


The Village of Harrisonburg has struggled to meet Louisiana discharge permit regulations for several years due to the ineffective design of their waste water oxidation pond. The design of the system limits their ability to treat their waste water by confining treatment to two-thirds of an acre when their pond is actually 5 acres in size. The entire pond is not being used efficiently and effectively. The discharge parameters of concern have been Total Suspended Solids ( TSS), Ammonia, and Carbonaceous Biochemical Oxygen Demand (CBOD). Due to limited budgets, the Village of Harrisonburg has been unable to correct the system problems.

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Project Cost

Martin Ecosystems assisted the Village of Harrisonburg in applying for and securing $50,000 of Strategic Economic Development Program (SEDAP) funding through the Delta Regional Authority for this project.

System Design

Martin Ecosystems strategically installed BioHaven Floating Treatment Wetlands in front of the influent pipe and against the existing curtains in order to have maximum water flow through the BFTWs. This increases retention time and provides maximum treatment.


In May, Martin Ecosystems discovered that nutria were climbing onto the Islands and eating the recently planted Vetiver grass. It appears that the damage is minimal as not all BFTWs have been effected.

Martin Ecosystems has plans to install fencing around the perimeter of the islands in order to keep nutria, turtles, and other wildlife off of the islands until the vegetation has had enough time to establish itself.


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In May, Martin Ecosystems discovered that nutria were climbing onto the Islands and eating the recently planted Vetiver grass. It appears that the damage is minimal as not all BFTWs have been effected.

Martin Ecosystems has plans to install fencing around the perimeter of the islands in order to keep nutria, turtles, and other wildlife off of the islands until the vegetation has had enough time to establish itself.

April discharge reports have shown reductions of 30%-50% in all three parameters of concern with two achieving compliance. This is only one month, but is very encouraging.

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Biohavens – the only truly bio-mimicking floating wetland – Case Study #11- Bass benefit

2 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.

 11. Floating Island Provides Bass Spawning Habitat

Project Location: Elephant Butte, New Mexico USA

The New Mexico Bass Fishing Association’s mission is to enhance bass fishing habitat and opportunities within the state. A subgroup of the association, Kids of the Southwest, undertook a project in 2009 to increase the bass population at Elephant Butte, NM. These youth partnered with the New Mexico Game and Fish Department, marina owners and other local interested parties after discovering a Floating Island International licensee, Floating Islands West, which has developed floating botanical gardens to increase fish and other wildlife habitat, along with providing water quality improvements.

Floating Islands West designed a portable spawning bed for fish that includes a cover and protection for the fry. After Kids of the Southwest arranged for the island purchase, they assembled the island, gathered and transplanted the necessary plants, filled the spawning beds with gravel, and used paddle boats to deploy the island.

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Kids of the Southwest is a Junior Bassmaster Club based in Las Cruces, NM, and is affiliated with Cedar Cove Bass Anglers in Elephant Butte, NM. The group strives to develop life skills in young people while educating them to exercise leadership and support for responsible recreational fishing, and stewardship of aquatic resources.

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Biohavens – the only truly bio-mimicking floating wetland – Case Study #10 – Phosphorus to fish

1 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.

10. From Phosphorus to Fish: Beneficial Use of Excess nutrients

Project Location: Shepherd, Montana

Fishing can be the primary method for transitioning excess nonpoint source nutrients from water, according to recent studies performed by Floating Island International (FII). This case study summarizes results of FII’s patented floating treatment wetland (FTW) technology and associated lake stewardship to remove nutrients from Fish Fry Lake, a 6.5‐acre lake at FII’s research center, along with producing outstanding fishing opportunities. Nearly all of the phosphorus and nitrogen entering the lake from agricultural runoff is now mitigated through a moderately aggressive fish‐harvesting program. The next goal is to address nutrients accumulated at the lake bottom in organic accretion.

The primary factors transforming Fish Fry Lake from a eutrophic pond to a productive fishery have been:

  • Higher dissolved oxygen (DO) concentrations due to aeration and mixing;
  • Lower overall water temperatures and a greatly expanded livable zone for fish due to aeration and mixing;
  • Introduction of substrate to support periphyton, which provides a food source for fish; and
  • Better penetration of sunlight into the water column from reduced turbidity, which enhances growth of diatom‐based periphyton

The last two factors are directly due to introduction of floating islands, while the first two are derived from features installed with the latest embodiment of floating islands.


As recently as July 2008, Fish Fry Lake was a small pond with low DO concentrations, high summer water temperatures, colorful algae blooms and a small population of wild northern yellow perch. Today it supports crappie, a burgeoning population of perch and possibly the easternmost population of Yellowstone cutthroat trout. This dramatic change was made possible by:

  • Deepening the pond to 28 feet and extending its reach to 6.5 acres;
  • Strategically locating several aerators throughout the lake;
  • Adding and growing 5,200 square feet of FTWs; and
  • Introducing crappie and cutthroat.

The FTWs are a mix of BioHavens® (passive islands) and one LeviathanTM (Figure 1). The Leviathan is a new embodiment of FTW with aeration and forced circulation via an airlift directional diffuser. All islands in Fish Fry Lake, which are constructed of recycled post‐consumer plastic matrix, have been planted with native vegetation.

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Over 4,400 of FII’s floating islands have been launched around the planet over the past decade, with the largest (51,000 square feet) recently installed in New Zealand’s Lake Rotorua. Seven other island projects exceeding 20,000 square feet have been launched in New Zealand, Singapore and the U.S. Over $3 million has been invested in research through FII, the Center for Biofilm Engineering at Montana State University and the National Institute of Water and Atmospheric Research in New Zealand. In combination with these pre‐eminent research centers, FII has compiled a unique database between floating islands and fisheries enhancement.

By biomimicking nature, floating islands provide the “concentrated wetland effect” that transitions nutrients up the food chain. Instead of nutrients short‐circuiting into monocultures of algae, floating islands provide substrate‐‐the enhanced surface area that transitions nutrients from periphyton (the microbial and algae community attached to underwater surfaces) to fish (Figure 2).

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Fish Fry Lake now supports a very productive perch fishery. From June through October 2011, 1,928 perch were harvested from the lake. Experienced fishermen averaged one perch every two minutes, with a typical harvest of 26 lbs/wk. On October 13, 2011, several fishermen caught 166 perch weighing a total of 35 lbs. On March 10, 2012 (shortly after ice‐out), five people caught 161 fish in two hours. Two hundred fish were tagged and introduced to the lake in 2011. Six of these tagged fish were among the 161 fish caught, suggesting that about 5,400 harvestable fish now inhabit the 6.5‐ acre lake. Figure 3 shows a typical perch harvest in 2011.

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In the 2011 study, perch were measured and classified by age, through otolith and scale aging. Perch in Fish Fry Lake were significantly larger than perch in the 95th percentile measured in a study by Jackson and Quist:

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Fish in Fish Fry Lake consume periphyton and organisms generated by nutrients flowing into the lake, from surface water and groundwater, and are not directly fed. In contrast, aquaculture ponds feed fish to maximize productivity. The fish yield measured at Fish Fry Lake was 26 lbs/wk or 4 lbs/acre/wk. Tilapia yield in fertilized freshwater ponds in Indonesia (Hansen et al., 1991) was measured at about 5 kg/ha/day, or 31 lbs/acre/wk. Therefore, fish yield at Fish Fry Lake is 10‐20% of yield in the fertilized ponds. Yield is consistent with the inflow of nutrients, since Fish Fry Lake has about 10% of the nitrogen inflow (0.01 g N/m2/day) as the fertilized ponds in the study.

Phosphorus inflow to Fish Fry Lake is estimated at 0.28 lbs/wk, based on an average concentration of 0.041 mg/L at an estimated flow of 80 gallons per minute. The average phosphorus concentration in perch is 1.0%, based on measurements by FII and other researchers. This means that the average fish harvest of 26 lbs/wk removed 0.26 lbs/wk of phosphorus. Thus, the amount of phosphorus removed via fishing was 0.26/0.28 or 93% over the study period. In a follow‐up study, FII is now tracking whether the total annual phosphorus load can be harvested during 2012.

An experienced fisherman at Fish Fry Lake can catch perch at a rate of one fish every two minutes. For the average fish weighing 0.25 lb, 3.7 hr/wk of fishing time is required to keep up with the incoming phosphorus, and to maintain a healthy waterway (Figure 4). This would require a fish harvest of 110 lbs/mo.

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Water Quality Improvements

During the first 12 months after the lake was filled, water clarity averaged 14 inches via Secchi disk. Introduced substrate, the filter‐like polymer matrix comprising the islands as well as plant roots that grow through the islands and their biofilm‐based periphyton, reduced turbidity significantly. In December 2011, three‐and‐a‐half years after the pond was filled, water clarity exceeded 19 feet. A summary of the water quality improvements is shown in Table 2.

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Similar waterways in the region are typically much more turbid due in part to clay colloids associated with the region’s geomorphology. Another contributing factor to regional waterway turbidity has been phytoplankton blooms associated with nonpoint source nutrient loading of nitrogen and phosphorus.

Biofilm present on the island matrix mechanically removes suspended solids, including colloidals and algae that bond to it. Competition for nutrients provided by biofilm‐ based microbes also reduces the turbidity level associated with algae blooms. Sunlight can then energize additional oxygen and food‐generating diatom‐based periphyton, even at depth.

In addition to the positive effect of sunlight, laminar aeration has also contributed to higher DO levels at depth. In summary, the combination of sunlight and dissolved oxygen at depth has resulted in the natural transition of excess nutrients into fish via periphyton.