Effect of nutrient and inoculation on metal removal from simulated wastewater by Pistia stratiotes and Eichhornia crassipes

• Main Author: Nur Zaida Zahari
• Format: Thesis
• Language: English; English
• Published: 2014
• Subjects: TD419-428 Water pollution
• Online Access: https://eprints.ums.edu.my/id/eprint/42828/1/24%20PAGES.pdf; https://eprints.ums.edu.my/id/eprint/42828/2/FULLTEXT.pdf; https://eprints.ums.edu.my/id/eprint/42828/

Heavy metals are recalcitrant in the environment and are considered as one of the major environmental problem. This has led to intensive research on their removal from wastewater by various technologies such as phytoremediation. The main aim of this study is to evaluate the potential of two locally available floating aquatic macrophytes, P. stratiotes (water lettuce) and E. crassipes (water hyacinth) in removing heavy metals Pb, Zn, Ni, Cd and Cr in single and mixed conditions at 0.2 mg/L, 0.5 mg/L and 1.0 mg/L from simulated wastewater using CVIF reactor for 15-day period. The concentration of metals in wastewater and plants were determined by ICP-OES. The heavy metals removal percentages of single and mixed were varied for different metals and initial concentration exposed. The removal of Pb in single exposure was found to be faster as compared to other metals at all concentration levels. This was further proven by the removal percentage of 98.8% at initial concentration of 1.0 mg/L after 7 days cultivation. The results also showed that E. crassipes was more tolerant towards Pb either in single or mixed as compared to P. stratiotes whereby the uptake amount was higher by 2 times. The uptake and distribution of single metals Pb, Zn, Ni, Cd and Cr were higher in roots by almost 5-fold as compared in leaves and by 15-fold in stalks respectively, whereas in mixed metals by almost 3.5-fold as compared in leaves and by 7.8-fold in stalks of E. crassipes. The plants cultivated in 0-fold nutrition level showed the highest Pb removal percentage. The percentage removal of Pb at 1.5 mg/L is shown in descending order as 0-fold (99.6%) > 1-fold (94.7%) > 2-fold (85.4%) nutrient levels. In comparison, the removal percentages of Pb at 2.0 mg/L is higher at 0-fold nutrient (83.5%) followed by 1-fold nutrient (58.9%) and 2-fold nutrient (37.8%). The distribution pattern of single Pb at 1.5 mg/L and 2.0 mg/L with addition 0,1 and 2-fold nutrient levels showed that Pb are highly uptake in roots by 2-fold as compared to leaves and stalks in both plants. The inoculation of Pb-tolerant B. cereus 1-NMeHI-Cr2 (T1) onto the roots of P. stratiotes and E. crassipes CVIF reactor had displayed a higher removal percentage with 99.6% followed by T2 with (99.4%). The attachments of Pb-tolerant B. cereus 1-NMeHI-Cr2 to roots of both plants have shown by SEM images. In addition, the inoculation of B. cereus 1-NMeHI-Cr2 (T1) using CVIF reactor had displayed an increase by 0.2 % in the removal of Pb as compared to T2 (without inoculation). The efficiency of removal by CVIF reactor indicates the circulation of wastewater provides adequate aeration to the roots system of both plants thus enhance the microbial activity in the roots system. The results also shown that both plants have a similar distribution pattern of Pb in plant tissues at all treatments as roots > leaves > stalks (E. crassipes). However, both plants recorded a different uptake value (uptake capacity) whereby roots was higher by 3-fold as compared to leaves and stalks (E. crassipes). The physical changes such as roots become fragile or decay and yellowing and wilting of leaves for both plants were monitored throughout the experiments. Studies with regard to aquatic plants combination to be used in engineered wetland treatment ponds should be seriously undertaken for developing more efficient, natural and economic approach in removing heavy metals from contaminated water. The ability of P. stratiotes and E. crassipes to remove heavy metals especially Pb had indicates their potential in treatment of metal polluted water. This supports the idea that the interaction between aquatic plants and beneficial rhizospheric microbes can enhance the role of plants to remove heavy metal pollutants and are considered to be an important component in phytoremediation technology.