BioHaven Floating Islands

From Landscape SA – February 2023

Biohavens are plantable floating island devices that provide a range of water treatment, habitat creation and aesthetic benefits for stormwater detention ponds, wetlands and water features. The units mimic the behavior of natural floating islands and by virtue of their construction, provide a totally natural appearance as opposed to the float-borne platforms commonly used for these applications.

The appropriate interception and treatment of urban runoff, variously containing sediments, nutrients, pollutants, or toxicants, is essential for the protection of streams, rivers and wetlands. In the urban sector, stormwater retention ponds provide frontline support within a somewhat limited arsenal of management tools. Recently a new technology, BioHaven® Floating Islands, has revolutionized the manner in which retention ponds may be effectively integrated into stormwater management planning for new developments. Additionally, they offer a wide range of options for the rehabilitation or enhancement of artificial water features.

The functional value of stormwater retention ponds is limited by a number of factors: they are typically prone to large fluctuations in water levels, rendering the creation of vegetated shorelines or in-pond submerged vegetation difficult. They often have steep banks with very little shoreline to work with. Vegetated ponds work poorly in a stochastic system – i.e. plugs of stormwater flow at irregular intervals. This, in turn, limits the options for maintaining a constantly submerged and circulating environment, in which the essential biological engine, the ‘biofilm’ or layer of bacteria adhering to the submerged surfaces of aquatic plants, is continually active. The largest component of the water treatment services provided by these systems occurs in the biofilm layer. Variable water levels, with constant exposure, desiccation and loss of the biofilm layer, results in the ‘biological engine’ of the pond not always being ‘switched on’ and ready to process new batches of stormwater. Retention ponds are further constrained by the limited space available in which to construct them, plus many other limiting factors.

BioHaven Floating Islands are the outcome of a process of bio-mimicking or bio-mimetics, a process whereby natural processes of form and function are integrated with artificial systems.

Floating Island International has, based on the attributes of natural floating islands, created a product that closely mimics nature. Natural floating islands are by no means new to science: they have been described over a period of 300 years (e.g.Van Duzer, 2004). What is new is the manner in which the BioHaven technology has so successfully mimicked nature.

The islands, or concentrated floating wetlands, are formed from a recycled, nonwoven and nontoxic polyester fiber matrix, bound with a UV resistant latex binder – creating a structure akin to a woven pot-scourer – approximately 0.2m in depth and with a tensile strength in excess of 3000 kg. The result is a massive surface area per square meter of island, with one square meter of island providing 220m2 meters of total surface area on which the biofilm can form. In a conventional, reeded surface flow wetland, this I m2 would equate to I 45 m2 of reedbed, operated continuously at an average depth of 0.3 m! The saving for land area is immediately apparent, as are the cost savings in terms of construction, establishment and operation.

With respect to water treatment, sustained functioning of the BioHaven biofilm is always ‘switched on’ and is independent of water depth in the pond. Thus, the BioHaven-equipped pond is not constrained by biological lag time – i.e. until the biofilm is regenerated after a period of low water levels and exposed plant and inert surfaces typical of a conventional pond or small reedbed. System start-up and establishment is also much shorter; with BioHaven islands becoming fully vegetated and established within as little as 60 days.

Although the BioHaven island can be utilized solely as a biofilm support system, the islands can also be planted with aquatic or terrestrial vegetation in accordance with the client’s requirements. Given that the treatment function is now independent of vegetation on the shorelines, problems of unsightly, exposed shorelines are now completely resolved and other means of constructing the pond sides and edges can be considered. Retention ponds, or sectors thereof, can now be made deeper; thus, enhancing the hydrodynamic stability and reducing the risk of sediment washout. Pond cleaning and maintenance aspects are rendered significantly easier.

Over 3100 launches of BioHaven islands have been made worldwide since the release of the product in 2005.The water treatment capabilities have been subjected to peer-reviewed scientific scrutiny by two organizations, the New Zealand Institute of Water and Atmospheric Research (NIWA, Headley and Tanner; 2006 ; Tanner and Headley, 2008) and the Montana Board of Research and Commercialization Technology (Stewart, 2007). The published results of these investigations have shown that significantly higher levels of nutrient assimilation and toxicant (e.g. trace metals) sequestration are possible using BioHavens, as opposed to conventional wetland processes. Efficacy has also been demonstrated in a Yale University study on the mitigation of estrogen impacts on fish. While local performance data is still to be assembled, reports from other countries indicate removal rates in ranges of grams per square meter of island per day for certain elements. These levels are simply not achievable in small ponds or reedbed systems. From the results accumulated to date, it has been possible to develop models to indicate the area of Biohaven islands required for a particular application.

Small fishpond Island adds beauty to the waterway

Floating islands are not only suited for stormwater ponds – but they also provide a range of opportunities for just about any type of waterway, natural or wastewater and industrial effluent ponds, farm ponds and mining effluent dams and treatment systems. The potential for use in cleansing mine drainage is considered to be enormous. They provide almost unlimited opportunities for habitat creation or restoration, as well as considerable aesthetic benefits as the islands can be planted with a wide range of vegetation types. Additionally, they are being applied as bridging structures, walkways, jetties, floating vegetable gardens – with options for links to reuse of grey water and numerous other applications including bank stabilization. Given that such small areas of wetland are required relative to the body of water being managed, use of BioHaven modules has proved beneficial in examples such as zoo ponds. While the island modules are manufactured in a range of standard shapes, they can be configured to specific needs or joined together in various combinations. Buoyancy can be adjusted to support heavy weights such as walkways, docks and gazebos. Further, BioHaven units will be of enormous use to golf course developments, in ponds where it is traditionally very difficult to establish vegetation and provide habitat and water quality polishing.

The availability of BioHavens has, using a single technology, solved almost all of the problems commonly encountered with the effective use of stormwater retention ponds and small reedbeds. This is a significant step forward in advancing the capacity of ecological engineering to support the balance between development and protection of water resources.

References

Headley TR and Tanner CC (2006) Application of Floating Wetlands for Enhanced Stormwater Treatment A Review. NIWA Client Report prepared for the Auckland Regional Council. Report HAM2006- I24.

Stewart, F (2007) Biomimetic Floating Islands that Maximize Plant and Microbial Synergistic Relationships to Revitalize Degraded Fisheries, Wildlife Habitats and Human Water Resources. Final Report to the Montana Board of Research and Commercialization Technology

Tanner CC and Headley TR (2008) Floating treatment wetlands – an innovative solution to enhance removal of fine particulates, copper and zinc. Journal of the New Zealand Water Works Association July 2008:26-30.
Van Duzer C (2004) Floating lslands: A Global Bibliography. Cantor Press, Los Altos Hills, California. 400 pages plus illustrations.
Floating Island International is represented in South Africa by DH Environmental Consulting (www.dhec.co.za) which has already commenced with presentations detailing the opportunities possible with this technology. The modules will initially be imported but local manufacture under license is in the pipeline.

DH Environmental Consulting has 20 years of wetland assessment experience in South Africa and has obtained the sole distributorship for BioHavens. Dr Bill Harding (PhD) is a professional limnologist and aquatic ecologist (PrSciNat), and a certified lake manager, NALMS, USA. Email bill@dhec.co.za