An efficient continuous flow device for water treatment using pulsed power technology, wherein untreated water flows as a thin film so that maximum surface area of untreated water gets exposed to plasma, and untreated water enters into plasma region and undergoes oxidation by different reactive oxygen species, then treated water is discharged through the reactor. Oxygen gas was purged into the reactor to decrease the nitrate concentration. With oxygen as the feed gas, the final nitrate concentration was found to satisfy the drinking water standards. To remove residual hydrogen peroxide, the plasma treated samples were incubated for 24 min with MnO2 catalyst.