In this study, anaerobic treatability of domestic wastewater contaminated with two different types of aircraft deicing fluids (ADFs) at different ratios (i.e., Type 1: 0.9%-9.7% and Type 2: 1.8%-12.5%) were comparatively investigated with the control reactors using batch systems operated at mesophilic temperature (35 degrees C). In this respect, the threshold Type 1_ and Type 2_ADF ratios indicated inhibition on the microbial cultures were determined according to the biogas yields during the incubation time. The highest biogas yields were calculated as about 0.22 and 0.25 m(3)/kg tCOD(fed) in the bioreactors having 0.9% Type 1_ADF and 1.8% Type 2_ADF, respectively. However, when tCOD removals were also taken into account; 3.4% Type 1_ADF and 1.8% Type 2_ADF represented the upper concentration limits excluding the control reactors. Because the reactors with more than 3.5% Type 1_ADF and 2.0% Type 2_ADF indicated significant inhibition on microbial cultures with considerable reductions in biogas yields and organic material removals. Hence, ADF-contaminated wastewaters are of great concern for anaerobic reactors that require careful control at full-scale treatment facilities.