Nano-bubble flotation technology with coagulation process for the cost-effective treatment of chemical mechanical polishing wastewater

The feasibility of nano-bubble flotation technology (NBFT) with coagulation/flocculation process for the enhanced treatment of chemical mechanical polishing (CMP) wastewater was investigated through laboratory and pilot-scale experiments. As a precursor, the effective combination of activator/collector was identified using a laboratory-scale flotation reactor. The results showed that polyaluminum chloride (PAC)/sodium oleate (NaOl) was the best combination of activator/collector, respectively and its application in the NBFT with coagulation process increased the wastewater clarification efficiency by 40% as compared with traditional coagulation/flocculation process. More than 95% turbidity, total solids and total silica removal efficiencies were observed in the pilot-scale flotation experiments. From the results, it was found that NBFT with coagulation process could be performed effectively at an optimum PAC concentration of 50–60 mg/L (as Al), NaOl concentration of 5–10 mg/L with a recycle ratio of 10–20% and 1 h hydraulic retention time HRT. The cost and performance assessment reflected that CMP wastewater could be treated efficiently at a minimum cost using the present approach.