###### Abstract  
Various advanced oxidation processes have been used to degrade perfluorooctane sulfonate (PFOS), one of the persistent organic pollutants that dissolves in aquatic ecosystems, but these processes suffer from inherent limitations. This study proposes aeration-assisted cold plasma (CP) technology as an alternative. PFOS removal via CP treatment reached 62.5% after 1 h of exposure, with a degradation rate constant of 3.1 h\({}^{-1}\). The detection of sulfate (SO4\({}^{2-}\)) in the solution provides evidence of effective PFOS degradation. The close agreement between the measured and estimated fluoride concentrations further confirms mass balance after degradation. Acute toxicity tests indicate that PFOS degradation may initially increase the acute toxicity, possibly due to the formation of degradation by-products. However, this increased toxicity can be mitigated through additional exposure to the reactive species generated by CP. Furthermore, investigations into the energy per order of CP and the quantification of hydroxyl radicals support its operational effectiveness. This study confirms that aeration-assisted CP has the potential to serve as a viable treatment option for mitigating the environmental threats posed by PFOS. perfluorooctane sulfonate; aeration-assisted cold plasma; ecotoxicity; degradation kinetics 2020 IEEE/RSJ Web Conference 202  
In particular, PFOS has been found not only in surface water and sediment downstream of production facilities but also in wastewater treatment plant effluent, sewage sludge, and landfill leachate [6; 7; 8], and it comes as no surprise that many people have been exposed to it through the consumption of normal water or by exposure to contaminated soil and sediment [9; 10]. Although the amount of PFOS detected in many studies is very small, the environmental persistence, tendency to bioaccumulate, and potential toxicity of PFOS have generated great concern [11]. Due to its high biological resistance, PFOS is not naturally biodegradable, leading to its bioaccumulation and persistence in organisms [6; 12; 13; 14; 15]. The estimated half-life of PFOS in the environment is 41-97 years, but in adult human bodies it decreases to 4-5 years due to excretion [16; 17]. These characteristics have led to the discontinuation of PFOS production in North America and Europe [18]. Moreover, PFOS has been added to Annex B of the Stockholm Convention on persistent organic pollutants (POPs) [19]. Several studies have been conducted to identify the most effective means of destroying PFOS in water to ensure the safety of water, humans, and ecosystems. Activated carbon and ion exchanges have been the primary means used to remove PFOS dissolved in water [1; 20; 21; 22]. However, the generation of by-products that can only be cleaned with adsorbents and the concentrated brine solution used to regenerate the ion exchange resin limit the usage of these means, respectively [23]. Various advanced oxidation processes (AOPs) have been proposed as alternatives [24], primarily because hydroxyl radicals, key agents in the degradation of organic pollutants when using AOPs, can oxidize PFOS [25]. The literature indicates that electrochemical oxidation [26], photocatalysis [27], electrocatalytic oxidation [28], sonolysis [29], and electron beam irradiation [30] may be applicable. These technologies, however, are economically inefficient, as they require additional chemicals and electrical energy [24]. Also, after these treatments by-products still remain, and residual halogen compounds may be harmful to humans [31; 32]. To overcome the limitations of conventional AOPs in PFOS treatment, aeration-assisted cold plasma (CP) technology has been applied instead. CP is one of the AOPs that has been examined as being potentially beneficial in wastewater treatment [33; 34].