Using Floating Vegetated Mats To Treat Aquaculture Wastewater

Agricultural Research Service scientists in Tifton, Georgia, are testing the feasibility of using floating vegetation to remove nutrients from aquaculture wastewater. The long-term goal is to develop a system to treat wastewater, return it to ponds for reuse, and use the nutrients to produce biomass, or plant material.

The current study is being conducted jointly by ARS and the University of Georgia’s Aquaculture Unit in Tifton. It builds on previous research showing that vegetation can be grown on floating mats in swine-wastewater lagoons.

Wastewater from the fish-production ponds is pumped into 340-gallon aquaculture tanks. Each tank has a 10-foot-square floating mat on which the vegetation grows. The researchers are currently testing 12 different plant species: St. Augustinegrass, Tifton 85 bermudagrass, common bermudagrass, canna lilies, iris, bamboo, bulrush, cattail, bordergrass, napiergrass, reeds, and maidencane.  So far, the iris is the best performer.

In the second part of the study, beginning in spring 2009, researchers will determine the effects of the vegetation on water quality and the amount of nutrients removed when plant biomass is harvested.

The plant material will be harvested on an as-needed basis and the plant tissue analyzed for nitrogen, phosphorus, and potassium. Harvested plant material has several potential uses. It can be transplanted, used as feedstock for energy production, or composted and used as a soil amendment.

 This research is part of Soil Resource Management (#202), and Manure and Byproduct Utilization (#206), two ARS national programs described on the World Wide Web at www.nps.ars.usda.gov.

Extracted from an article by Sharon Durham, Agricultural Research Service Information Staff from the January 2009 issue of Agricultural Research magazine.