Effects on the underlying water column by ecologically engineered floating vegetation mats

Abstract

Engineered floating vegetation mats are emerging applications of ecological engineering that have promising water quality improvement and habitat creation applications. However, relatively little research has been published regarding their construction or effects on the underlying water column. The objectives of this study were to determine appropriate design characteristics and the effect of ecologically engineered floating vegetation mats (EFVM) on the underlying water column. Four EFVM designs were constructed of drainpipe, burlap, mulch, utility netting, and reused polyethylene bottles, and then planted with Typha spp. and Juncus effusus. The water column beneath EFVM in two test ponds was compared to that in an open water control pond. Dissolved oxygen concentrations and pH were lower, diurnal temperature range was dampened, and sulfate/nitrate reduction was greater under the EFVM with respect to the control. Alkalinity was also greater under EFVM. Results reinforced previous findings indicating that Typha spp. is a suitable species for EFVM creation. However, a more robust planting matrix is necessary to encourage faster growth and protect against wind and wave action damage. Although plant propagation was limited, results suggest that EFVM may be applied to encourage reducing, thermally insulated conditions for passive treatment of acid mine drainage a wide range of other pollutants. Specifically, they may be employed to improve short and longterm performance of vertical flow bioreactors for acid mine drainage treatment by lowering dissolved oxygen concentrations in the water column and providing a continual source of organic carbon to the underlying substrate. Copyright © (2010) by the American Society of Mining & Reclamation.