Environmental Engineering Reference
In-Depth Information
Chapter 9
Floating Vegetated Mats for Improving
Surface Water Quality
Robert K. Hubbard
Abstract
Contamination of surface and ground waters is an environmental con-
cern. 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 opera-
tions (CAFOs) 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 denitrifica-
tion 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 then utilizes nutrients contained in the contaminated waters. Research con-
ducted 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. The research has shown that dif-
ferent plant species can be found to grow on floating platforms in a range of different
water qualities. In the most contaminated water tested thus far, anaerobic swine
lagoon wastewater, it was determined that plants remove nutrients to their maxi-
mum capacity such that total removal of nutrients from the water body is a function
of biomass produced. 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.
