A 3-year detailed investigation on the use of water lettuce macrophyte pond for the purification of wastewater
from rubber processing industries and the reuse of the final effluent as biofertilizer is presented.
Baseline wastewater quality information was collected on a monthly basis and analysed for one year
before the introduction of water lettuce to 50% pond surface cover. This was done to reliably determine
the parameters that exceeded limits and need treatment. These parameters are: phosphate, nitrates, pH,
biological oxygen demand, conductivity, turbidity, total dissolved solid and total suspended solid. The
effluents from the macrophyte ponds were then monitored mainly on monthly basis for chemical, physical
and biological parameters. The treatment and analyses of parameters with exceedance were carried
out in the ponds, using the retention periods of 2 weeks, 4 weeks, 8 weeks and 12 weeks for 1st, 2nd
and 3rd inoculations. The result of the study showed a progressive reduction in the level of wastewater
contaminants fed into the macrophyte pond. Significant reductions within permissible limits were
obtained for most of the parameters except TSS and turbidity. Final effluent from the ponds was also
found to boast the height, stem girth, leaf area and biomass yield of maize plant. Maximum plant height
of 117.5 ± 7.6 cm was obtained using treatment 2 at 63 day after planting. The weight of cob produced
from treatment 2 is 46.2 ± 6.1 g while the weight of cob produced by the control experimentis 21.3 ± 6.7 g.
The chemical composition of the resulting water lettuce biomass shows it could be utilized as forage for
feeding animals