Biological Removal of Zinc from Automotive Hazardous Paint Sludge: a comparison between an endogenous Pseudomonas aeruginosa isolate and Acidithiobacillus thiooxidans PTCC۱۶۹۲

Research on the hazardous waste of paint sludge is mostly focused on recovering the sludge and pollution control with methods such as solidification. This research aimed to study the comparison of biological removal of zinc from paint sludge using a native Pseudomonas aeruginosa strain and Acidithiobacillus thiooxidans PTCC ۱۶۹۲. Samples of water-based paint sludge were collected under aseptic conditions. Isolation of endogenous strains was performed in Bushnell-Haas (BH) medium from paint sludge, and A. thiooxidans PTCC ۱۶۹۲ was cultured in the medium ۱۱۹. Optimization of the process parameters for the biological removal of zinc was performed using the design of the experimental (DOE) method for both organisms. The results showed that A. thiooxidans is capable of biological removal of zinc with a higher pulp density and with a more extended bioleaching period. The results of the chemical analysis show the removal of zinc metal by ۵۷.۷۶% compared to P. aeruginosa by ۳۶.۳۹%, and, the removal of other metals such as Cr, Ni, Pb, and Cd were observed in the residual sludge from the process. Energy Disperse X-Ray Analysis (EDX) showed the more favorable effect of this bacterium in reducing heavy metals.