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.