Cold atmospheric plasma discharges in air above air–water surface interface and discharges inside water with injection of air bubbles, show interesting properties for water purifca- tion. Water parameters during plasma treatment get diferent values depending on dis- charge schemes. Detailed measurements of water parameters during plasma applications as pH, oxidation–reduction potential, total dissolved solids and conductivity are essential in understanding micropollutants degradation mechanisms in water. E. coli bacteria in water have been eliminated faster by plasma discharges produced in water than in air above it. Degradations of two antibiotics oxytetracycline hydrochloride (OTC) and doxycycline hyclate (DXC) in water solution are faster for plasma generated below solution surface than above it with appearance of one degradation product for OTC and two for DXC along plasma treatment time. Degradations are enhanced in the solution after 200  h following plasma treatment for the two antibiotics. H2O2 concentration can give a good indication of plasma efectiveness on diferent pollutants as it is a relatively stable compound. For water purifcation, contributions of two factors have to be identifed namely water acidity with certain pH value and concentrations of reactive species generated in water. For plasma dis- charges inside water with air bubbles the most pronounced efect is the increasing value of H2O2 generated in water, while for plasma discharges above water the efect of water acid- ity induced by low pH is more dominant regarding pollutants degradations.