Examination of additional treatment methods of silicon-containing wastewater considering economic and environmental aspects

Research output: Types of ThesisMaster thesis


Backgrinding is a crucial step in semiconductor device fabrication. Backgrinding wastewater has distinctive attributes as it only comprises high-purity water and fine particles without any chemicals. Moreover, the wastewater can produce hydrogen as a byproduct through the reaction of water and high-purity silicon particles. Therefore, this study examined additional treatment methods for silicon-containing wastewater, considering the characteristics of the wastewater and the potential risk of hydrogen using a backgrind sludge from Robert Bosch Semiconductor Manufacturing Dresden GmbH (RBDD). 240 t of sludge was disposed of in 2022 after removal of fine particles in wastewater using Ultrafiltration (UF). The disposal cost of backgrind sludge represented the highest amount of waste management cost within the facility. This also contributes to the high waste generation rate of the facility. Hence, two different thickening methods were examined: Chemical Mechanical Treatment (CMT) and physical treatment using a decanter centrifuge. The characteristics of silicon-containing wastewater and the available treatment methods were investigated through literature reviews. The step chains involved in the chemical and mechanical treatment at the Bosch Reutlingen were investigated with the associated principles. The backgrind wastewater at RBDD was characterised by the analysis of quality, particle size distribution, Scanning Electron Microscopy (SEM)/ Focused Ion Beams (FIB), and Energy-dispersive X-ray spectroscopy (EDX). The actual amount of hydrogen was measured in the system to assess the possible risks. Moreover, Capital Expenditure (CapEx) and Operation Expenditure (OpEx) were evaluated to compare the economic viability of the project. CO2 emissions associated with with the additional treatment methods were also assessed. It was concluded that both CMT and a decanter installation are beneficial from economic perspectives. Both methods are expected to decrease the carbon footprints. However, the positive impact is significantly greater with a decanter, due to the recycling of silicon waste. Keywords: Silicon-containing wastewater, Sludge dewatering, Water-splitting, Silicon recovery, Techno-economics.


Original languageEnglish
Publication statusPublished - 28 Jun 2023
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Sustainable Development Goals


  • Silicon-containing wastewater, sludge dewatering, silicon recovery