Aerobic treatment of wastewater containing Tetramethylammonium hydroxide (TMAH) and photoresist was investigated using a lab scale reactor inoculated with activated sludge coming from urban wastewater treatment that never received TMAH before. The consumption of TMAH was monitored by liquid ion chromatography. Biodiversity indices were calculated from Denaturing Gradient Gel Electrophoresis (DGGE) bands distribution and used to estimate changes in community composition related to adaptation to the new feeding compound. The first week of adaptation was crucial, and it was analyzed in detail: many organisms died, and the microbial community suffered a great shock. TMAH levels remained constant through the first four days, and then suddenly dropped to undetectable, and at the same time NH4+ increased. When the community showed complete adaptation, predominant groups of bacteria were obtained by the Illumina sequencing of 16s rDNA amplicons, to provide insights on ecology of the adapted community, focusing on the main actors of TMAH abatement. Richness of species (Rr) peaks suggest that the development of TMAH-consuming bacteria leads to persistent consortia that maintain toxicity resistance over time. This showed adaptation and changes of the population to the different feeding conditions, and it opens new perspectives in the in situ treatment of these important residues of industrial processes without relying on external processing plants.

Tetramethylammonium hydroxide is used in the electronic industry during the photolithography process to produce memories. The effluent produced in this process must be treated before discharging due its toxicity. The aim of this research is to evaluate the feasibility of biological treatment to remove this molecule from the effluent by aerobic process at room. Experiments were carried out on real effluent, in which TMAH concentration was about 1800 mg/L. Like C-source for microorganisms another effluent coming from the same industries was used. Batch reactor tests have showed an efficiency of TMAH removal of about 99%. Kinetic studies have provided the following kinetic parameters able to describe the trends vs time of TMAH, ammonium ions and biomass concentration in the reactor: K S = 0.8 g/L; µ max = 0.42 h -1 ; Y X/S = 0.34 g S /g X.