Author
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Hubbard, Robert |
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Submitted to: Emerging Environmental Technologies
Publication Type: Book / Chapter Publication Acceptance Date: 6/23/2009 Publication Date: 1/15/2010 Citation: Hubbard, R.K. 2010. Floating Vegetated Mats For Improving Surface Water Quality. Emerging Environmental Technologies. Interpretive Summary: Methods are needed to protect and improve water quality. Technologies for wastewater commonly include using constructed wetlands or land application. A new concept is to use floating vegetated mats to cover part of the surface water body. The mats grow on floating platforms. Roots of the plants reach into the water and take up nutrients. Biomass can be harvested from the mats or in the case of grasses or horticultural plants, the plants can be transplanted. Harvested biomass can be used to make compost for use as a soil amendment, or potentially for use in making biofuel. Both past and ongoing research has shown that floating vegetated mats can be used to grow biomass and remove nutrients from wastewater. Completed experiments on both moderately and severely contaminated swine lagoon wastewater have shown that species can be found to grow in such waters. With the moderately contaminated swine lagoon wastewater we were able to grow and produce cattail and maidencane. With the severely contaminated swine lagoon wastewater we grew two varieties of bermuda grass and a wild millet. Preliminary research using floating mats on aquaculture wastewater showed that iris grew best. The aquaculture wastewater had much lower levels of N and P than the wastewater from the swine lagoons. Future use of floating mat technology will depend on research to match plant species to water quality, determine which species produce the most biomass and remove the most nutrients, development of methods for using the biomass such as composting, using as a bioenergy feedstock, or else directly transplanting material, development of engineering techniques to completely mechanize the process, and economic analyses of all facets of this emerging technology. Technical Abstract: Contamination of surface and ground waters is an environmental concern. Pollution from both point and nonpoint sources can render water unsuitable for use. Surface waters of concern include streams, rivers, ponds, lakes, canals, and wastewater lagoons. Lagooned wastewater from confined animal feeding operations CAFO’s represents an extreme in water quality problems. Wastewater lagoons are used for primary treatment which includes settling of solids and loss of gases by volatilization. Additional methods are often used to treat the wastewater from the lagoons. These methods include passing the wastewater through constructed wetlands, where both plant uptake and biological processes such as denitrification remove or retain nutrients, and application of the wastewater to agricultural or forestry land. A new concept for improving surface water quality including that of wastewater lagoons is to grow vegetation on floating platforms in the water body. Little research has been conducted in this area, although this technology basically is application of hydroponics using floating platforms for the vegetation which utilizes nutrients contained in contaminated waters. Research conducted by USDA-ARS and the University of Georgia at Tifton, GA has focused on determining the feasibility of growing vegetation to produce biomass and remove nutrients from contaminated surface water bodies. This chapter explains the concepts and techniques involved in using floating vegetated mats on contaminated water bodies for nutrient removal, reports results from completed studies, discusses ongoing projects, and identifies research needs for this emerging technology. |
