119
Constructed wetland and
Canna Indica
monitoring.
The physicochemical parameters:
pH, BOD, COD, TSS and TN, were monitored according to APHA standard methods. The
number of plants was determined at the beginning and at the end of every HRT, as well as
studying their adaptation and growth during the time of operation of the wetland.
Results
Figure 1 shows the evolution of the efficiencies of BOD and COD removal in the wetland.
During the first week, the wetland was operated at OLR=0.27 kgm
-3
d
-1
, however, it was
observed that plants suffered an important stress, manifested a variegation due to the lack in
chlorophyll, so the OLR was reduced by 50% of its initial value. The next three weeks, the
wetland operated at 0.13 kgm
-3
d
-1
and subsequently the OLR feed was increasing until it
was achieved a steady state, that is COD and BOD removal were constant. Best removal
efficiency was obtained for an OLR=0.45 kg COD m
-3
d
-1
at a HRT of 3 days with 72.9% of
COD, 88.3% of BOD, 72.9% of TSS and 55% of TN removal. Constant removal of COD
and BOD was observed until an OLR= 0.88 kg COD m
-3
d
-1
, however when OLR= 1.32 kg
COD m
-3
d
-1
, a decrease in organic matter removal was obtained with 57.9% of COD,
71.1% of BOD, removal. This OLR can be considered as the maximal that the system can
tolerate, which corresponds to a COD concentration of 4,000 g l
-1
and a HRT of 3 days.
Figure 1. Evolution of the removal efficiency of BOD and COD.
In Figure 2 is observed the results of the population growth of wetland plants. The initial
number of plants was 8, with an average size of 31.5 cm, in the course of time, the number
of
Canna Indica
increased up to 40 plants in a period of 131 days of wetland operation. It is
important to note that the number of plants increased mainly in the wetland later part
(output), however, in the input, there were a major stress in plants, associated with high
concentrations of organic matter in raw water supply that affected their development and
growth. In the first 50 days of operation with OLR relatively low, the plants were adapted
to the substrate of wastewater, presenting a decrease in stress. From OLR of 0.27 kgm
-3
d
-1
,
the stress of the plants dissapeared, the plants grow up in number and in height. Currently a
study of assimilation of macro and micronutrients in plants is being doing.
