Biohavens – the only truly bio-mimicking floating wetland – Case Study #17 – Wastewater treatment

8 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.

17. BioHaven® Floating Treatment Wetlands Remove Nutrients and Help Wastewater Facility Achieve Compliance

Scientific Summary

BioHaven® Floating Treatment Wetland (BFTW) Technology is designed around the same principles as a wetland. They are man-made floating islands that provide an optimal habitat for microbial and plant species. See Figure 1. Similar to a wetland, the plants and microbes improve water quality; however BFTWs enhance microbial growth by expanding available underwater surface area; i.e. microbial habitat.

Screen Shot 2015-10-24 at 07.52.15

In fact, an eight-inch thick island covering one square foot of water surface contains 124 cubic feet of surface area. This phenomenon is created through patented island design. The result is a new and strategic means to achieve a concentrated wetland effect. Along with the nutrient removal processes, BFTWs also provide ancillary benefits for water treatment when launched into a water body. They immediately increase retention time as the flow of water is “redirected” through or around the BFTWs. The physical embodiment of the BFTWs also physically traps solids in the water body.

Screen Shot 2015-10-24 at 07.52.23

Screen Shot 2015-10-24 at 07.48.16

Facility Background

The Elayn Hunt Correctional Facility has struggled meeting discharge compliance. Parameters of concern have been elevated levels of Biological Oxygen Demand (BOD), Total Suspended Solids (TSS), and Fecal Coliform. Secondarily, sludge accumulation in the pond has limited the ability for the pond to provide effective treatment. Remediation of this problem would have required extensive dredging of the pond and would have placed a high financial burden on the Department of Corrections at a time when budgets were decreasing.

The Primary goal for this project was to find out if the BFTWs could help the facility achieve and maintain compliance by removing unwanted nutrients. The BFTWs were installed strategically in front of the in flow pipe to have the greatest amount of inflow water passing through the Island matrix and to slow the water as it entered the pond ultimately increasing retention time. This installation location allowed for the greatest amount of treatment opportunity. The three plant species included: Common Rush (Juncus effusus), Pickerelweed (Pontederia cordata), and Arrowhead/Lanceleaf (Sagittaria lancifolia).

Results

At the start of this project enhancing facility compliance was a primary goal. The data suggests that the Islands have met this objective. The average of non compliance events exceeded 5 and sometimes 10 per year in the 5 years before the installation of BioHaven® Floating Treatment Wetlands. Since the installation of BFTWs in March of 2011, there have been only 6 noncompliance events through May 2014, all due to faulty facility equipment.

Screen Shot 2015-10-24 at 07.48.43

Table 1 shows concentrations of the three parameters of concern before and after the BFTW installation. “Before” data were taken in January and March 2011, while “after” data are the averages of monthly data from April 2011 through December 2012. It is assumed that the higher nutrient concentrations seen post-BFTW were also seen periodically before BFTW installation.

Screen Shot 2015-10-24 at 07.49.00

After BFTW installation, the average percentage removal has been 74%, 35%, and 29% for COD, Ammonia, and Phosphate, respectively. This is significantly better than without the FTWs. The BFTW removal rates are substantial and are even higher than those measured in other case studies. Considering these rates, BFTWs can be sized to remove a given contaminant load (concentration and flow).

Conclusions

The total cost of this project was $38,017.61. This included the BioHaven® Floating Treatment Wetlands, installation, plants, and monitoring for one year. Dredging the pond would have had a much higher ticket price estimated at over $1,000,000.00. BioHaven® Floating Treatment Wetlands were installed for 3.8% of that cost; demonstrating their ability to help communities as well as, public & private industry achieve and maintain consistent compliance in a very cost effective manner.

In December of 2012, the BFTWs were completely removed from the wastewater pond. All prior vegetation was removed. The BFTWs were re-planted with Vetiver Grass and re-installed in January 2013. This was done in anticipation of a new study with LSU AgCenter. The chart below shows the Average BOD and TSS removal rates from January 2013 to May 2014. The reduction of BOD and TSS has been an average of 67% for both over the 17 month period.

Screen Shot 2015-10-24 at 07.49.54

In June 2013, Louisiana State University AgCenter began monitoring this project for water treatment and nutrient removal. They will continue to do so for two (2) years.

Screen Shot 2015-10-24 at 07.50.18

 

Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <s> <strike> <strong>