Some info on the Electron Affinity of bulk water:
"Using cluster studies to approach the electronic structure of bulk water:
Reassessing the vacuum level, conduction band edge, and bandgap of water."
Some Electron Affinities (eV) from CRC:
H 0.754
C 1.26
O 1.46
Na 0.547
K...0.50
Cr 0.66
Fe 0.15
Ni 1.16
Pd 0.56
CrO 1.22
FeO 1.50
O2 0.45
OH 1.83
HOO 1.08
O2Ar 0.52
OH(H2O) < 2.95
WO3 3.33
"Since substances which dissolve (dissociate) are electrically neutral to begin with, they will generate equal numbers of positive and negative charges. Electrification occurs only if either the positive or the negative charges preferentially adhere to the solids surface. If this occurs, a very compact layer, known as the Helmholtz layer is formed. Because the Helmholtz layer is charged, it will attract ions of the opposite polarity to it. These ions will cluster into a more diffuse layer, known as the Gouy layer, which rests on top of the surface of the compact Helmholtz layer. The thickness of the Gouy layer increases with the resistivity of the liquid. Conducting liquids form very thin Gouy layers.
This double layer will separate if the liquid flows, with the Helmholtz layer remaining bound to the interface and the Gouy layer becoming entrained by the flowing liquid. The movement of these charged layers produces a difference in potential (the zeta potential), and the current induced by the moving charges is known as the streaming current. The amount of charge that accumulates in the liquid depends on the rate at which the ions diffuse towards the interface and on the liquids resistivity (r). The streaming current is, however, constant over time.
Neither highly insulating nor conducting liquids will become charged-the first because very few ions are present, and the second because in liquids which conduct electricity very well, the ions will recombine very rapidly"
