A comparative study has been conducted for differentiating between attached and suspended growth represented by a lab-scale biotrickling filter and bio-scrubber under anoxic conditions, respectively. However, malodorous Ethanethiol gas (ET) that categorized as one of the volatile organic sulfur compounds (VOSCs) was studied using a variety of settings and parameters. In contrast, NO3− can be used as an electron acceptor in the bioconversion of ET gas to elemental sulphur and/or sulphate when there is no oxygen around. Empty bed residence times (EBRTs), gas to liquid ratios (G/Ls) (40, 60, 80, 100, 150), and inlet concentrations (150, 300, 800, and 1500 mg/m3) were all investigated in relation to ET's removal efficiency (RE) (30, 60, 90, and 120 s). While the G/L ratio of 80 resulted in efficient ET removal (more than 90.8% for 150 mg/m3 of inlet concentration), it could only achieve the extraction of 80.6% for 1500 mg/m3 of inlet concentration at a fixed EBRT of 60 s. These results were based on the performance of a lab-scale anoxic biotrickling filter. Even though mass transfer constraints and poor solubility of ET were factors, the biotrickling filter's performance under anoxic settings was superior to that of the bio-scrubber and improved the low oxidation rates of ET.