The Effect of Heavy Metal Lead (Pb) on the Growth of Ammonia-Degrading Bacteria and Physical Changes of Eichhornia crassipes in Groundwater Phytoremediation

Abstract

Water hyacinth (Eichhornia crassipes) has been extensively used for heavy metal phytoremediation and stimulating microorganism growth in the effort to break down organic pollutants by the exudate secreted by the plant. This study aims to figure out the growth of the ammonia-degrading bacteria population and figure out the physical changes occurring in water hyacinth during the Pb phytoremediation process. The phytoremediation method was performed under the batch system with the treatments: P1 with water hyacinth for groundwater with 2 ppm of Pb; P2 with water hyacinth for groundwater with 4 ppm Pb; and P0 with no water hyacinth and Pb addition. Observations include the growth of ammonia-degrading bacteria, ammonia concentration, Pb analysis, observation of physical changes, and measurement of biomass of the water hyacinth. Results show that the nitrifying bacteria population growth rate was higher in the 2 ppm Pb treatment than in the 4 ppm Pb treatment. The implication was that there occurred a higher ammonia concentration decrease in P1 by 0.43 mg/L from the initial concentration of 1.21 mg/L. As for the water hyacinth's physical changes, a lower growth rate happened to the 4 ppm Pb treatment, resulted in lower biomass of 75.46 g in the said treatment than in the 2 ppm Pb (79.00 g). The use of water hyacinth in phytoremediation also prompted the bacterial growth to break down organic waste, but high concentrations of heavy metals will influence the growth of the aquatic plant, water hyacinth.