Inoculation of Bacillus cereus enhance phytoremediation efficiency of Pistia stratiotes and Eichhornia crassipes in removing heavy metal Pb

Abstract

This study investigates the effects of inoculation rhizhosperic microbes namely Bacillus cereus-NMeHI-Cr2 towards the roots of two locally aquatic macrophytes in removing heavy metals Pb from simulated wastewater. Water lettuce (Pistia stratiotes) and water hyacinth (Eichhornia crassipes) were selected in this study due to their absorption capability and acts as biological filters by accumulating heavy metals in their tissue's bodies. The inoculation of B. cereus-NMeHI-Cr2 onto the roots of P. stratiotes and E. crassipes was conducted in non-continuous horizontal flow (NCHF) reactor with addition of 1.5mg/L of Pb comprising of T2: treatment with inoculation of B. cereus-NMeHI-Cr2, T4: Non inoculation of B. cereus-NMeHI-Cr2 and T6: no plant growth in NCHF reactor (control). After 15 days of cultivation, the treatment integrated with inoculation of B. cereus-NMeHI-Cr2 resulted 83.7% removal efficiency of Pb followed by T4 (70.4%) and T6 (2%) respectively. Furthermore, 63.8 ug/g of Pb was observed in T2 treatment with similar distribution pattern as roots > leaves > stalks in E. crassipes and roots> leaves in P. stratiotes. The physical changes of both plants were also monitored to show any toxicity symptoms experienced as a result of heavy metal Pb. This study validates that the removal of Pb was done via rhizofiltration mechanism as the value of enrichment factor was found below than 1000. The identified plants species with inoculation of Bacillus cereus-NMeHI-Cr2 provides a simple and cost-effective method for application of metal polluted water.