| Summary: | 碩士 === 國立交通大學 === 環境工程系所 === 96 === Heavy metals are present in wastewaters released from battery, paint and chemical manufacturing industries. Also, considerable portion of heavy metal containing wastewater is discharged from mining industry i.e. acid mine drainage. Heavy metal disposal problems require urgent solution to avoid serious environmental contamination. The activity of sulfate reducing bacteria (SRB) offers interesting potentials for metal removal and recovery. In the present work, utilization of PVA as a gel matrix for immobilization of SRB was investigated. This study was also focused on the optimization of bio-precipitation process using a statistical method to provide information concerning the effect of amount of SRB immobilized on PVA and copper concentration in biotic experiments. A central composite (CCD) was used to develop a model for the responses. Response surface methodology (RSM) was used to optimize the amount of SRB immobilized (19-235 mg VSS/L), and copper concentrations (10-100 mg/L).
The objective of this research consists of two parts. In the first part, the amount of SRB immobilized on PVA and the copper concentration are considered study their effect on SRB during bioprecipitation experiments as designed by CCD. In the second part, the four responses such as biological copper removal (R1), chemical precipitation and adsorption (R2), specific sulfate reduction (R3) and reaction rate constant (R4) are considered to optimize the amount of SRB immobilized on PVA and copper concentration using RSM.
The bioprecipitation experimental results showed that the sulfate removal was more than 99% and residual copper concentration was less than 1 mg/L in a11 experimental runs within 7 days. The results demonstrated that the copper removal was by bioprecipitation and adsorption on PVA beads. The blank PVA adsorption experiments indicated that the blank PVA and SRB immobilized PVA have copper adsorption capacities of 0.355 and 0.363 mg-Cu2+/g PVA beads, respectively. According to the results of RSM, R1 and R2 responses were not significant but R3 and R4 responses were significant. Result of R4 showed better convergence in the contour plot. The optimal quantity of SRB immobilized on PVA and copper concentration were observed these as 136 mg VSS/L (equivalent to 1.12 mg protein) and 57.9 mg/L, respectively. At there conditions the highest sulfate reaction rate constant (k) as per first-order kinetic was observed as 0.0423 h-1 in 30±2oC.
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