Water vapor and air transport through ponds with floating aquatic plants.

The purpose of this paper is to estimate the evaporation rate in the purification of wastewater by aquatic plants with aeration. Evaporation of surface water is important in dewatering processes. In particular, this is true in arid climates, where evaporation rates are high. Aeration is known to enhance the wastewater purification process, but it increases concurrently the water evaporation rates. Evaporation and evapotranspiration rates were tested under field and laboratory conditions. Batch experiments were performed to study the levels of evaporation and evapotranspiration in free-water-surface, aquatic-plant systems. The experiments verified that, in these systems, the rate of evaporation increased as a result of aeration in the presence and absence of the aquatic plants. The evaporation rates resulting from aeration were found to be significant in the water balance governing the purification process. A preliminary model for description of the effect of rising air bubbles on the transport of water vapors was formulated. It is shown that aeration may account for a significant part of water losses that include surface evaporation.