Enhanced Biodegradation and Release Pattern of Heavy Metal from Spent Laptop Batteries using Pseudomonas and Bacillus Species in Freshwater

Abstract

Aim: To evaluate Enhanced-Biodegradation and Release Pattern of Heavy Metal from Spent Laptop Batteries using Pseudomonas and Bacillus species in Freshwater
 Study Design: The study employs experimental design, statistical analysis of the data and interpretation.
 Place and Duration of Study: Freshwater was collected from Isiokpo River, Isiokpo town in Ikwerre L.G.A, Rivers state, Nigeria within co-ordinates 50 02’14’’N and 60 54’50’’E, These samples were transported with ice pack to the Microbiology Laboratory of the Rivers State University, for analyses within 6 hours. Spent laptop batteries were obtained from Ogbunabali Laptops Shoping Complex Garrison area of Port Harcourt, Nigeria. Three sets of the brand of battery (HP, Dell and Acer).
 Methodology: A total of twelve (12) experimental set-up with three controls (each of the three laptop batteries in freshwater without augmenting organisms) while the other nine were enhanced with augmenting microbes. In step 1, Stock toxicant solution was prepared by soaking the spent Laptop batteries ( of average weight of 300-400g,  in two (2) liters of sterilized freshwater in a sterile trough with vented top for aeration, of dimension 12 x 7.5 x 6cm separately for each set-up, The soaking (Toxicant preparation) lasted for 3 months (about 92 days). In step 2, Five hundred milliliters (500ml) of each set-up was transferred into sterile Conical flask plugged with cotton wool perforated for aeration; each was inoculated with five milliliter (5 ml) of the test organisms (Pseudomonas and Bacillus species broth, singly and consortium) separately and monitored  for duration 0, 30, 60 and 90 days respectively using the spread plate techniques. The bacterial cultures were incubated at 37°C for 24 hours while fungal cultures were incubated for three (3) days at 35°C. Parameters monitored were Heavy metal (Lithium, Cadmium, Chromium, iron and Lead) concentration, Total Heterotrophic Bacteria, Total Heterotrophic Fungi, Lithium Utilizing Bacteria, Cadmium Utilizing Bacteria, Chromium Utilizing Bacteria, Iron Utilizing Bacteria, Lead Utilizing Bacteria, Lithium Utilizing Fungi, Cadmium Utilizing Fungi, Chromium Utilizing Fungi, Iron Utilizing Fungi, Lead Utilizing Fungi.
 Results: Enhanced biodegradation and release pattern of heavy metal from spent laptop batteries using Pseudomonas and Bacillus species in freshwater was evaluated and the concentration of heavy metals (Lithium, Cadmium, Chromium, iron and Lead) found associated with the spent laptop batteries (HP, Dell and Acer) were increasing simultaneously with time in all set-ups from day 1 to day 90. The control (without augmenting microbes) has the highest concentration of heavy metals from day 1 to 90 followed by set-ups augmented with Bacillus specie followed by set-ups augmented with Pseudomonas specie, least in set-ups augmented with the consortium of the 2 isolates. The changes in concentration of heavy metals during biodegradation of which Cd < Cr <   Li < Fe < Pb respectively, for all spent laptop batteries used in this study. Percentage (%) degradation potential of the consortium of Bacillus species and Pseudomonas species for Li-HP, Li-Dell, and Li-Acer shows a higher percentage (%) release of 22.68%, 37.63% and 24.22% respectively as compared to the individual strains of for Bacillus species and Pseudomonas species. With Pseudomonas species having 10.03%, 18.65%, and 11.24%, followed by Bacillus species having 8.46%, 12.49%, and 7.20% for Li-HP, Li-Dell, and Li-Acer respectively.
 Conclusion: The study identifies the degradability potential of Bacillus and Pseudomonas species to degrade spent laptop battery in freshwater. it shows that the consortium was able to degrade the batteries better than the individual strains. It is recommended that spent laptop batteries discharged into aquatic environment should be enhanced with broth culture of eco-friendly species of Pseudomonas and Bacillus for quick degradation.