Roots of Aquatic Plants, Macrophytes, Halophytes (Chapter 5)

Summary of Generally Recognized Major Roles of Aquatic Plants in Constructed Wetlands (Refer to Chapter 5: p.345)

Floating Plant Tissue (Above-Water Parts of the Plant)
1. Prevention of light penetration into the water so as to reduce phytoplankton, or algal, growth.2
2. Influence on microclimate for winter insulation.
3. Reduced wind velocity for reducing resuspension of settled solids.
4. Aesthetics and appearance of the treatment system.
5. Nutrient storage in plant tissue for eventual recycle or reuse in agriculture.

Submerged Plant Tissue
1. Nutrient uptake.
2. Pollutant and contaminant filtering.
3. Reduced current and flow velocity for maximizing sedimentation rate while reducing resuspension of settled solids.
4. Provision of surface area for biofilm and microbial and microorganism attachment.
5. Supply of biogenic (photosynthetic) oxygen for increasing aerobic biodegradation and biotransformation of wastes.

Roots and Rhizomes in the Sediment
1. Stabilization of sediment surface, leading to less erosion.
2. Prevention of medium clogging (medium can be sand, soil, gravel, rocks, or a mixture of these) in vertical-flow treatment systems.
3. Supply of oxygen to increase biodegradation and nitrification.
4. Plant exudates of biochemical toxins for pathogen destruction.
5. Nutrient uptake.

The extensive root system of Ipomea aquatica (common name: swamp morning-glory, an invasive weed and a pest species in southeastern United States). Note the thousands of tiny strands of root hair on which denitrifying bacteria and other microorganisms can attach and remove nitrate in the wastewater. (Photograph by Jo-Shing Yang)