Hidehiko Nishiyama, spokesman for the Nuclear and Industrial Safety Agency (NISA) under the Ministry of Economy, Trade and Industry, said, "We'll have to keep solving the problems as they arise. If the system doesn't work, we'll have to look for other alternatives."
I take it to mean that they are not considering alternatives now.
There's a more fundamental problem beyond decontaminating the water at the plant.
One reason for setting up the water treatment system was to decontaminate the water enough so that it can be used as coolant that circulates back into the Reactor Pressure Vessels. But now that it's been admitted by TEPCO that the melted fuel (with other things melted with it, forming the "corium") may be out of the RPVs and possibly out of the Containment Vessels, what will the water be cooling? How can you cool the corium that's eating the concrete foundation?