With high DC voltage, electrochemical reactions can still be carried out even in distilled water with very low conductivity. Metal ions from the dissolution reaction at the anode can react with formed hydrogen gas from the cathode in aqueous medium to form metal and then interact for metal nanoparticles. The reaction processes on the electrodes to make metal nanoparticle solutions are controlled by high DC voltage, distance between anode and cathode electrodes and conductivity of the medium. The properties of metallic silver nanosolutions such as UV-Vis spectrum, TEM particle shape, particle size distribution, zeta potential as well as bactericidal ability have been determined and demonstrated. The obtained product has high purity because the nano solution does not contain Na+, NO3- ions as well as other reaction products and stabilizers, so it can be applied to many objects without affecting human health. In addition to silver, other metals such as Au, Cu, Fe, Al, etc. can also be fabricated in nano form by DC high-voltage technology. The gaseous environment created on the electrode by a DC high-voltage electrochemical reaction with a large electric field and high potential difference as well as the heating effect of the medium will be the right conditions to switch from the gaseous state to the plasma state. Indications of the presence of electrochemical plasma are the glow on the electrode as well as the amperage that spikes with time. It is also possible to control the electrochemical plasma appearance time when changing the DC high-voltage electrochemical reaction technology parameters. The electrochemical plasma state will generate H2O2 and free radicals such as OH• which are highly reactive. That is used to treat water contaminants like 2,4-D or 2,4,5-T into the final product CO2 very efficiently, especially on Fe electrode adding Fenton reaction. Similarly, methylene blue textile dyeing wastewater as well as high concentration hospital biochemical wastewater can also be treated with good results by high pressure DC with electrochemical plasma.