A WASTE MINIMIZATION STUDY OF A CHELATED COPPER COMPLEX IN WASTE-WATER - TREATABILITY AND PROCESS ANALYSIS

This study demonstrated an integrated waste minimization approach for the printed circuit board manufacturing shop of Lawrence Berkeley Labo ratory (LBL). It included process waste assessment, process optimizati on and treatability analysis of the treatment system, and source reduc tion assessment. The results of a process waste assessment indicated t hat over 99.5% of the waste stream was rinsewater and less than 0.5% w as characterized as hazardous waste. This finding led to a thorough so urce reduction assessment. From the process and treatability analysis, it was found that an organic chelating ligand in the wastewater was c ausing a copper precipitation problem. The results of a series of benc h and process experiments indicated that optimization of pH, chemical dosage, and addition of ferrous sulfate were needed to destabilize the complexed copper. The destabilization mechanism of Cu-EDTA with ferro us sulfate at pH 6-9 was discussed. Different separation/recycling tec hnologies were also evaluated through the source reduction assessment. A closed-loop process was simulated and designed. Through the source reduction and treatment process optimization efforts, at least 90% red uction of total acid wastes and wastewater and more than 99% metal rem oval were achieved. A material life cycle analysis was also performed. The results indicated that a total quality control strategy is crucia l to minimize wastes and reduce product rejection rate.