Selection of a Very Active Microbial Community for the Coupled Treatment of Tetramethylammonium Hydroxide and Photoresist in Aqueous Solutions

Abstract

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.

Aerobic Treatment of Waste Process Solutions from the Semiconductor Industry: From Lab to Pilot Scale

“…The experimental reactor was kept at room temperature (20 ± 2 • C), stirred at 70 rpm with air-oxygen saturation. Colony counts, Lowry's protein assay, and the biodiversity indexes were calculated according to the methods detailed in Moretti et al [22]. Colony count was performed on Luria-Bertani enriched medium and AGAR-TMAH selective medium.…”

“…(3) Batch M, from day 25 to day 30, where 1 L of activated sludge resulting from Batch M was added to 2 L of distilled water and 50 mL of mineral culture medium [22].…”

“…The microorganism community was inoculated and adapted quickly to the change of nutrients, and stabilized over a new equilibrium state within a week when in the constant presence of TMAH and any further perturbation did not change the community structure. The biomass enrichment was obtained by means of some sequential batches, according to the sequence: 1) Batch T, from day 1 to day 6 (2 L of inoculum and 2 L of feeding solution); 2) Batch R, from day 7 to day 12, Batch A from day 13 to day 18, and Batch M from day 19 to day 24: at the beginning of each batch from the 7-24th day, 1 L of activated sludge coming from the previous batch was left in the reactor and fed with 2 L of feeding solution; 3) Batch M, from day 25 to day 30, where 1 L of activated sludge resulting from Batch M was added to 2 L of distilled water and 50 mL of mineral culture medium [22].…”