Performance assessment of chemical mechanical planarization wastewater treatment in nano-electronics industries using membrane distillation

Abstract

Wastewater from chemical mechanical planarization (CMP) processes in nano-electronics industries must be treated properly in order to fulfil local and international environmental regulations. This study is focused on a performance assessment of membrane distillation (MD) technology for CMP wastewater treatment. A new prototype of air gap membrane distillation (AGMD) module was utilized, with feed water consisting of CMP wastewater collected from imec, Belgium. The module was tested at different operating conditions (temperatures, flow rates and filtration time) and responses in terms of separation efficiency, permeate water quality, transmembrane flux, specific heat demand and exergy efficiency were determined. High quality permeate was produced in all trials, i.e. conductivity ~2.11 µS/cm, pH ~5.4, TOC ~1.13 ppm, IC ~0.24 ppm, TDS ~1.18 ppm and COD ~ 1.9 ppm; for most of the contaminants the separation efficiency was >99%. These findings clearly show that the resulting MD permeate does not exceed environmental regulations for release to recipient, and the permeate can even be considered for reuse. Moreover, the determined specific heat demand at different operating conditions was varying between 1390 and 2170 kWh/m3 whereas; the achievable exergy efficiency was ~19%.