| dc.description | This research evaluated the oxygen transfer efficiency in beds to be used as aerated constructed wetlands. The research methods included oxygen transfer efficiency evaluations in several
bed configurations using diffused aeration systems. Experiments were conducted at two locations
with different environmental conditions: a) Talca (Chile), 120 m above sea level (m.a.s.l.), 0.99 Atm
and b) Cajicá (Colombia), 2550 m.a.s.l., 0.76 Atm. A column with only clean water and three bed
configurations representing aerated constructed wetlands were evaluated. These configurations
included: (a) coarse gravel, (b) coarse gravel with an empty core in the middle (inner container), and
(c) fine gravel. Three airflow rates were evaluated: (a) low, 0.7 L/min; (b) medium, 2.5 L/min; and
(c) high, 3.6 L/min. The overall oxygen mass transfer coefficient, standard oxygen transfer rate, and
standard oxygen transfer efficiency were the variables calculated from the oxygen transfer evaluation
tests. The research results indicated that in diffused aeration systems, oxygen transfer efficiency was
negatively influenced by environmental conditions, particularly altitude, which limits the driving
force for oxygen transfer into water. Furthermore, the results showed that the size of the gravel used
in the bed is related to the oxygen transfer efficiency: the larger the gravel size, the higher the oxygen
transfer, regardless of the altitude. Finally, research regarding oxygen transfer in aerated constructed
wetlands has signaled the need for a standard procedure for aeration testing, and this work suggests
a new methodology. | |
