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: KS = 0.8 g/L; μmax = 0.42 h-1; YX/S = 0.34 gS/gX.