Phytoremediation Potentials of Azolla filiculoides L. and Lemna minor L. for Heavy Metals from Soft Drink Factory Effluent: The Case of Hawassa Millennium Pepsi Cola Factory, Hawassa, Ethiopia

Abstract

Heavy metal pollution is increasing in the aquatic resources of Hawassa City, Ethiopia, with the expansion of industrial activities. Existing wastewater treatment technologies for the remediation of heavy metals are costly and don’t provide a satisfactory solution. Therefore, the aim of this study was to investigate the phytoremediation potential of Azolla filiculoides and Lemna minor for six heavy metals (Cr, Co, Ni, Zn, Cd, and Pb) when exposed to the soft drink factory effluent. The experiment was conducted for 14 days. The levels of pH, temperature, EC, TSS, TDS, COD, and BOD were examined on 0, 7, and 14 days. Heavy metal concentrations in the effluent and plants were analyzed using inductively coupled plasma mass spectrometry (ICP-MS). The percentage of heavy metal removal and bioconcentration factor (BCF) were calculated using the standard formula. The average concentrations of heavy metals in both macrophyte treatments were in the following order: Zn > Pb > Cr >Ni >Co > Cd. ANOVA revealed significant differences (p< 0.05) between the two macrophytes in the removal of all tested parameters. The maximum removal was revealed for Cr (97.52%) by L. minor compared to A. filiculoides (90.04%). The BCF values for L. minor and A. filiculoides were in the following order: Zn > Co > Ni > Cd > Pb > Cr and Co > Zn > Cd >Ni > Cr > Pb, respectively. In conclusion, both macrophytes were good phytoremediation candidates for the treatment of soft drink factory effluent. Further investigation is needed to enhance the performance of the treatment systems.