Wastewater - ​Nutrient Removal with Passive BioHaven Floating Islands

Project Location:  Elayn Hunt Correctional Facility, St. Gabriel, Louisiana, USA
This case study demonstrates the ability of BioHaven Floating Island (floating treatment wetland / FTW) technology to clean water by substantially reducing nutrient levels.  At a wastewater facility in Louisiana, BioHavens more than doubled removal rates for chemical oxygen demand (COD), ammonia and phosphate. The primary objective was to determine whether the islands could remove unwanted nutrients that were periodically creating noncompliance with the facility’s discharge permit.  The goal is to have the facility continually achieve and maintain compliance.

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Overview
Martin Ecosystems of Baton Rouge, Louisiana, an FII licensee, installed BioHaven floating islands into the Elayn Hunt Correctional Facility oxidation pond in March 2011.  
Location:    St. Gabriel, Louisiana USA
Parameters Studied:    COD, ammonia, phosphate
Environment:    Wastewater pond
BioHaven Size:    Area of 1560 ft2 (145 m2), thickness of 8 inches (20 cm)
Water Source:    Elayn Hunt Correctional oxidation pond
Installation Date:    March 2011
Flow Rate:    208 gpm (47 m3/hr)
Water Body Depth:    3 ft (1 m)
Water Body Area:    5.1 acre (20,600 m2)
% Coverage:    0.7% of pond covered by BioHavens

The BioHavens installed at Elayn Hunt are passive islands without aeration and were planted with three types of vegetation.  Most of the removal efficiency attributed to islands has been found to be due to biofilm attached to both the plant roots and the island matrix itself.

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

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After BioHaven installation, the average percentage removal has been 73%, 38% and 29% for COD, ammonia and phosphate, respectively.  This is substantially better than without the FTWs (52%, 23% and 9%, respectively).  Table 2 shows contaminant removal rates before and after BioHaven installation, along with the net removal rates that can be attributed to the islands.

The BioHaven removal rates are more than double the previous rates for all three parameters and are substantially higher than those measured in other case studies.  Based on these rates, FTWs can be sized to remove a given contaminant load (concentration and flow).

Conclusions
BioHavens have a demonstrated capability to remove excess nutrients such as COD, ammonia and phosphate, along with total suspended solids and other parameters (data not shown).  The total cost of this project was much less than other treatment alternatives, demonstrating that FTWs can help public facilities and private industry achieve and maintain compliance in a cost-effective manner.  BioHaven technology can enhance existing waterways with the concentrated wetland effect, facilitating compliance with increasingly stringent wastewater nutrient, BOD/COD and TSS criteria.

The Louisiana Department of Environmental Quality provided funding for this project, which is owned and operated by the Louisiana Department of Corrections.