Description of Diagram:
You've got an enclosed reservoir for your water with a water inlet and outlet. You have two electrodes inside the tank/reservoir. One is the cup you see in the picture and that is an open ended beer can. One end is closed and the other is open. The closed end is anchored to the side of the tank. At the open side of the beer can is a metal ring/strap, that fits around the top outside of the beer can without touching it. The strap/metal ring comes close to the beer can but does not touch it. The metal ring/strap is anchored to the side of the tank/reservoir. The beer can is tuned to 60 Hz and is the anode. The ring/metal strap is the cathode electrode.
Dimensions of the ring/strap:
Ring 5mm wide and .2mm thickness. It needs to be just long enough to fit around the beer can and still have a space between it and the beer can.
I need to ask my contact about the 400 Hz scenario with the cathode.