124
wastewater was collected and batch applied to each unit at a rate of 42 L/m
2
/day, which
provided a hydraulic retention time of approximately 3 days.
Plant growth and wastewater quality monitoring
Local macrophytes
Cyperus liguralis
and
Echinochloa colonum
were collected near
Barranquilla and acclimated for one month with wastewater before being planted in the
wetlands. The macrophytes´ height was measured with tape measure (3 m). At the end of
the study, samples of plant shoots, rhizomes and roots were collected from an area of 0.66
m
2
. Three influent and effluent grab-samples were taken weekly, during morning hours,
and analyzed for COD, ammonia–N, nitrate–N, orthophosphate and sulfate. Measurements
of oxidation/reduction potential (ORP), dissolved oxygen (DO), electric conductivity and
temperature were obtained using hand held sondes (WTW Multi 3420). Measurements and
analyses of water samples were as described in APHA-AWWA-WEF (1998) or according
to manufacturer’s guidelines. Total and fecal coliform bacteria populations were
enumerated using the membrane filtration method using 0.45 μm pore size membrane
filters (Millipore Corp) and selective agars, EMB (Eosin-Methylen blue). Data analyses
included calculations of treatment means and standard deviations as a function of time and
macrophytes.
Results and discussion
Table 1 provides parameter values as a function of treatment. The average values of several
physicochemical parameters showed similar characteristic for both systems, the redox
potential and electric conductivity were slightly higher in
E. colonum
.
Table 1. Averages (SD in brackets) of the water quality parameters in the effluent of the
HSSF. Calculations based on 25 to 28 measurements depending on the parameter
Parameter
Cyperus ligularis
Echinochloa colonum
Temperature,
o
C
27.7 (±2.1)
26. 1 (±1.7)
Oxygen Dissolve, mg/L
1.8 (±0.9)
1.9 (±0.9)
E
H
, mV
247.6 (±70.8)
268.3 (±90.6)
pH,
7.0 (±0.1)
7.0 (±0.1)
Electric conductivity, uS/cm
557.8 (± 171.8)
646.6 (±258.1)
Total biomass, dry Kg/m2
-
2.5
Figure 1 shows the removal of COD and ammonium in treatments. The planted systems'
removal rates measured 92% and 83% for
C. ligularis
and
E. colonum
respectively. These
high efficiencies demonstrate that organic matter removal can occur with various
macrophytes. These results are consistent with those reported by Vega
et al
. (2013) respect
C. articulatus
in similar experimental.
