53
harvested from the wetlands and processed. Harvested corn and sesame fruits were stored in a
cardboard box and transferred to the laboratory. The samples of fruit from each treatment cell
were rinsed in dechorionated tap water and the surface and flesh analyzed for coliform bacteria.
Constructed wetlands performance monitoring.
Water quality monitoring was carried out
between October and December of 2013. For the duration of the study, four influent and effluent
water samples were collected from each HSSF CW and preserved in an insulated cooler and
temperatures were maintained at near 5 ºC. Subsequently, and within 24 hours, the samples were
analyzed for organic matter (COD, BOD
5
), ammonium-, nitrate-, nitrite-nitrogen and ortho-
phosphate using methods as described in APHA-AWWAWPCF (2005). Water temperature,
dissolved oxygen (DO), pH and conductivity measurements were obtained by monitoring water
samples from vertical perforated PVC tubes. Measurements of temperature, conductivity, pH and
dissolved oxygen measurements were recorded with WTW 315i Set probes. Paired comparisons
of inlet and outlet concentrations for each HSSF CW were evaluated for COD, BOD
5
, ammonia,
nitrate, nitrite, orthophosphate and total and fecal coliforms. Parameters including temperature,
pH, redox potential and DO were measured
in situ
using hand held sondes (WTW Multi 3420)
Results and discussion
The average values of several physicochemical parameters are in Table 1 both FSSH plants.
There were not were significant differences in water quality parameters between the two systems
planted with
Z. mays
and
S. indicus
and both system showed low redox potential and oxygen
dissolved as is frequently in horizontal sub surface flow constructed wetlands. Plant productivity
also was low and similar among the two species due to low coverage.
Table 1. Averages (SD in brackets) of the water quality parameters in the influent of the HSSF.
Calculations based on 18 to 20 measurements depending on the parameter
Parameter
Zea mays
Sesamum indicus
Temperature,
o
C
25.12 (1.6)
25.1 (1.7)
Oxygen Dissolve, m/L
0.2 (0.22)
0.33 (0.32)
E
H
, mV
-216.8 (126.4)
-209.4 (169.2)
pH,
7.2 (0.32)
7.1 (0.17)
Electric conductivity, uS/cm
Total biomass, dry Kg/m
2
481.3 (121.3)
0.037
(130.2)
0.034
Figure 1 provides information about COD removal in both systems. COD removal averaged 62%
in each system; however the total removal efficiency in the system reached 92%. These results
indicating that organic matter removal can occur with different species plants.
