When using UVC irradiation alone, the bulk of the A254-
absorbing species was slow reacting, with only a small proportion
of fast reacting components. Some material was refractory. When
the sample was treated with systems that generate hydroxyl radicals,
most of the A254-absorbing species reacted quickly, no material
was refractory and so the A254 was reduced to zero. The k1 values
were significantly enhanced by the addition of hydrogen peroxide,
and doubling its concentration effectively doubled the reaction
rate