F Veglio
University of L’Aquila, Italy
Title: Treatment of wastewater from microelectronic industry: Process analysis of a combined process scheme
Biography
Biography: F Veglio
Abstract
The production of semiconductors requires a series of specific treatments in which a large amount of ultra-pure water is used. As a consequence of this, a large amount of polluted process water is produced that must be treated before discharged into the sewer. The treatment cost of the wastewater is a significant effect on the industrial total cost and the microelectronics industry is trying to adopt production processes accompanied by water treatment processes for production of ultra-pure water at a reasonable cost, involving water reuse. The principal pollutants are inorganic compounds such as mineral acids (sulfuric, nitric, hydrofluoric, phosphoric acids), ammonium hydroxide, heavy metals (copper, cobalt) and organic solvents. The mineral acids and the metals are successfully removed by most of the treatment processes of the semiconductor sewage industry. There are some problems in the treatment of organic compounds, among these is tetramethyl ammonium hydroxide (TMAH), (CH3)4NOH. This last is corrosive, slow to biodegrade and eutrophic to aquatic environments. Disposal of TMAH wastewaters from an industrial plant is a difficult and costly issue. The scientific literature shows that it is possible to remove this pollutant by using chemical/physical processes (e.g. advanced oxidation processes (AOP) and adsorption) as well as biological processes (e.g. anaerobic digestion). In this paper, an integrated process stream is proposed for the treatment of wastewater produced by electronic industry. A combination of chemical-physical and biological processes for the removal of TMAH and other pollutants as nitric and acetic acid is described in order to purify the water. Firstly, a series of experimental results obtained in the laboratory scale is reported, after in accordance with these results a process scheme is proposed and simulated with commercial software in order to investigate the technical feasibility and describe the overall mass balance of the whole scheme.