Cold Plasma as an Innovative Tool for Wastewater Pre-Treatment and Post-Treatment at Ravda WWTP: Bioindication by Means of Microbial Metabolic Potential

This study investigates the effectiveness of cold atmospheric plasma (CAP) treatment for improving the microbiological and physicochemical quality of wastewater generated in tourism-affected coastal regions. Experiments were performed on influent and effluent samples from the Ravda Wastewater Treatment Plant (WWTP) collected in April, August, and November 2024, representing different seasonal loading conditions. The plasma pre-treatment of influent aimed to minimize toxic micropollutants that inhibit activated sludge activity, reduce pathogenic and opportunistic microorganisms, and enhance oxidative potential before biological processing. The post-treatment of effluent focused on the elimination of residual pathogens, mainly Enterobacteriaceae, and the oxidative degradation of xenobiotics resistant to conventional treatment. Combined fluorescent (CTC/DAPI) and culture-based analyses were used to assess microbial viability and activity. Plasma exposure (1, 3 and 5 min) caused measurable changes in metabolic potential and bacterial abundance across all sampling periods. The results demonstrate that 1 min CAP treatment does not increase pathogen removal, but enhances oxidation capacity of the influent, while 3 min of CAP treatment ensures the disinfection of the effluent. Both can be combined to improve the effluent safety prior to Black Sea discharge. CAP is showing strong potential as a sustainable technology for wastewater management in tourism-intensive coastal zones.