Treatment of wastewater from raw rubber processing industry using water lettuce macrophyte pond and the reuse of its effluent as biofertilizer

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 experiment is 21.3 ± 6.7 g. The chemical composition of the resulting water lettuce biomass shows it could be utilized as forage for feeding animals.