| Summary: | 碩士 === 高苑科技大學 === 化工與生化工程研究所 === 101 === In this study, real electroplating wastewater were samples from an electroplating factory located in Gangshan section, Kaohsiung. There are two streams of wastewater in this factory. One is passivation wastewater (chromium wastewater), the other is general wastewater (pre-treatment washing water and electroplating rinse wastewater). The investigation of water quality included pH, DOC, COD, conductivity, turbidity, SS, TS, heavy metals, where the item of heavy of metals contain copper, iron, chromium, nickel and zinc. The water quality of 15 days’ monitor was found the COD and SS of passivation wastewater and general wastewater of COD are 88-530 mg/L, 320- 1598mg/L and 189-2168mg/L, 131-1812 mg/L, respectively. The concentration of Cu and Cr for general wastewater is very low. However, the concentration of Zn, Fe, and Ni is high. On the other hand, the concentration of Cu and Fe for passivation wastewater is very low and the concentration of Zn, Ni, and Cr is high. Moreover, the correlation between COD and DOC, SS and turbidity for both streams wastewater are good agreement.
The processes of precipitation, coagulation, activated carbon adsorption, UV/H2O2 oxidation, and membrane separation were conducted in this study. The removal of SS is more than 95% after 30 minutes of precipitation for both streams of wastewater. Moreover, coagulation can remove heavy metals obviously. The removals are 98%, 99%, 54% for Zn, iron, and nickel of general wastewater, 97%, 84%, 33% for Zn, Cr, and Ni of passivation wastewater, respectively. However, the organic of the two streams of wastewater could not be removed efficiently by coagulation.
The DOC residual of passivation wastewater is 81 mg/L after adsorption of activated carbon combined with UV/H2O2. This water quality could not comply with the water criteria for process in this factory. However, the removal of DOC of general wastewater can reach to 60%-90% after adsorption of active carbon. The residual of DOC can be further mineralized to 3 mg/L by UV/H2O2.
Furthermore, membrane was conducted to separation of conductivity. The conductivity of permeate of UF, NF, and RO are 14100μm/cm, 2780μm/cm, and 780μm/cm, respectively. The water quality of permeate of UF can be reused for pre-treatment rinse water. The water quality of permeate of NF not only can be reused for pre-treatment rinse water but also can be reused for washing water after plating. Importantly, the water quality of permeate of RO can be directly reused in the electroplating plant for pre-treatment washing water, washing water after plating , and passivation washing water. Thus, the passivation wastewater and general wastewater should be treated separately in the electroplating factory. The passivation wastewater is not suitable for reuse. However, the general wastewater can be efficiently reused in the factory by precipitation, coagulation, activated carbon adsorption, UV/H2O2 oxidation, and membrane separation.
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