Aerobic degradation of tetramethyl ammonium hydroxide (TMAH) from effluents of semiconductor industries: kinetic studies of laboratory and pilot experiments

Aerobic degradation of effluents contains tetramethylammonium hydroxide molecules (TMAH), coming from an electronic industry, were studied at laboratory and pilot scale. At the first, the preliminary experiments were conducted using a lab scale reactor inoculated with activated sludge coming from urban wastewater treatment. Several batches have been performed on real effluent, in which TMAH concentration was about 1800 mg/L. The results showed that after acclimation, the microorganisms removed 99% of TMAH in seven days. Kinetic studies have provided the following kinetic parameters able to describe the trends of TMAH, ammonium ions and biomass concentration as a function of time in the reactor: KS = 0.8 g/L; µmax = 0.042 h-1. Then, in a second phase the experiments were conducted at pilot scale using a pilot plant realized within Life Bitmpas project (LIFE15 ENV/IT/000332). The plant has three biological reactors of 1 m3 and it is possible to feed up to 25 L/h of TMAH effluent. The experiments were conducted in a continuous mode and the results showed that in 8 days the total degradation of TMAH was 99%; moreover, from kinetic study have been determined the following kinetic parameters: Ks = 0. 83 g/L and µmax = 0.0074 h-1.