In-plant treatment process of fluidized bed crystallizers in the removal of copper-containing wastewater

Fluidized bed reactors (FBRs) have long been utilized in the removal of pollutant ions; however, these technologies in Taiwan were relatively immature. The objective of this work was to study the feasibility of real-plant process of fluidized bed crystallizers in the treatment of copper-containing industrial wastewater. In order to achieve a high efficiency of copper removal, some important factors including dose manner, hydraulic loading, effluent pH control, and recycle ratio were investigated.
In this part of the experiments, the main point was to maintain the crystallization condition in the metastable region, and controlling several factors helped attain this purpose. Results showed that the optimum removal could be reached when the effluent pH was controlled at the level of 9.0, and the treated water had a stable Cu concentration as well. Hydraulic loading also had significant influence on the removal of Cu. When the hydraulic loading was adjusted to 42~46 m/h, the FBR had the relatively best efficiency of Cu removal. Moreover, maintaining the recycle ratio at 10/1 was the most suitable for the FBR system. Under these conditions, the Cu removal could be achieved above 99%.
When the experiments were focused on in-plant treatment, there were some results presented in this work. First, fines producing in the FBR tanks – causing higher precipitation ratio – were also investigated because they were important indicators of poor crystallization. Second, in the continuous treatment process, the efficiency of FBRs was affected gravely by the changeable concentration of inflow wastewater. Finally, filtration units locating after the FBR treatment process was necessary to the removal of fines and to the stability of effluent water.