Oxygen Transport through Selected Aquatic Macrophytes

The extent of O2 transport from aerial plant tissue into the root zone was evaluated for several floating and emergent aquatic macrophytes that have characteristics favorable for wastewater treatment. The highest O2 transport rates from aerial tissue into the root zone were associated with plants having a small root mass. As root mass increased, the rate of O2 transport decreased for aquatic macrophytes evaluated. Pennywort (Hydrocotyle umbellata L.) had the highest O2 transport rate of all aquatic macrophytes with an overall rate of 3.49 g O2 kg−1 dry root mass h−1. Pickerelweed (Pontederia cordata L.) had the highest O2 transport capacity of emergent plants with a rate of 1.54 g O2 kg−1 h−1. Waterhyacinth [Eichhornia crassipes (Mart.) Sollms], an important floating aquatic plant in wastewater treatment, had a transport rate of 1.24 g O2 kg−1 h−1. Nitrification in a waterhyacinth‐based water treatment system due to O2 transport was calculated to vary from 6 to 22 kg ha−1 d−1.