Experimental review of different plasma technologies for the degradation of cylindrospermopsin as model water pollutant

The challenge to remove more frequently occurring recalcitrant pollutants from drinking water has recently led to a rising interest for more advanced treatment. Non-thermal plasma was repeatedly introduced as a versatile method that can be adapted towards specific treatment needs. Nevertheless, investigations were so far focused on few or particular discharge configurations without thorough evaluation and comparison of their potential for different applications and especially the treatment of larger volumes. Therefore, we investigated six common but fundamentally different systems with respect to the degradation of a highly toxic compound of increasing concern, i.e. cylindrospermopsin. Accordingly, discharges either submerged in water, operated at the air-water interface or in air were appraised with respect to operating parameters and conditions. Their individual potential was assessed by the absolute degradation of the model compound and the time and energy required to remove 90 % of the toxin. The dissipated energy generally resulted in the generation of, to some extent, different reactive chemical species, which were found primarily responsible for the degradation. A dielectric barrier discharge in a water mist was the most versatile approach with the best performance regarding different criteria. A submerged corona-like discharge still offered a reasonable compromise between time and energy required to degrade the toxin by 90 % and even submerged spark discharges presented a viable option. The active discharge volume, describing the volume in which the dissipated energy can be effectively exploited, and the capacity to increase this volume was identified as a crucial scaling parameter for any configuration.

Automated summary

The challenge of removing frequently occurring recalcitrant pollutants from drinking water has led to a rising interest in more advanced treatment methods. This study investigated six different treatment systems and found that a dielectric barrier discharge in a water mist was the most versatile approach for degradation of cylindrospermopsin.