An apparatus subjects water to waves from an RF plasma. This allows continuous production of "activated water" characterized by cluster sizes below about 4 molecules per cluster, substantially bacteria free water and controlled pH. The basic frequency of the plasma is preferably between 0.44 MHz and 40.68 MHz, and the plasma is preferably modulated at a frequency between 10 kHz and 35 kHz. Flow rates typically range from 20 l/hr to about 2000 l/hr. Activated water can be used for many purposes, including antimicrobial treatment of drinking water, antimicrobial cleaning of worktables, floors, walls, knives, and other surfaces, for example, in meat processing facilities and hospitals.