Biological Point of Use Water Treatment
Dr. Joerg Winter
(DAS Environmental Expert GmbH)
There has been an increasing interest in point of use (PoU) water systems in the semiconductor industry. The motivation to consider PoU water systems are (i) limiting the need for adjusting fab infrastructure – e.g. for treatment of PoU gas abatement wastewater, expansion of production, introduction of new manufacturing materials – and (ii) mitigate issues that can occur during transportation of water through pipes, such as precipitation and biofilm growth. In a fab in Asia, a semiconductor manufacturer has been faced with the challenge of very stringent wastewater effluent requirements for VOCs without existing infrastructure for corresponding treatment. When considering a cost-effective PoU wet scrubber system for the treatment of waste gas which contains mainly ammonia, fluoride, and isopropanol (IPA), a PoU water system became part of the solution. The PoU water system was to remove the IPA from the wet scrubber wastewater prior to discharge into the existing fluoride treatment. Though uncommon in the semiconductor sub-fabs, a biological PoU water treatment system was developed and set-up in the sub-fab for this particular application. Besides introducing the topic of PoU water treatment systems in the semiconductor industry and the motivations for developing and installing the biological PoU water treatment system, the presentation addresses the aspects of safety requirements and performance of the biological PoU water system. For the latter, data from the field is presented that provides information about the extent of IPA removal and process stability, including test data from ramp-up procedures that allow bringing the biological system from idle mode to be ready for production conditions within a few days.