The water gets contaminated with radioactivity and must be stored on site. A new system to decontaminate this water was unsuccessfully tested on Friday.
NHK World reports here:
Contaminated water is increasing by 500 tons a day as fresh water is continuously being injected into the reactors to cool them down.
The storage facilities for the contaminated water are filling up and a delay in restarting the system could cause the water to overflow [into the sea] in about a week.
A story via Reuters here says 110,000 tons of the stuff has already accumulated since 3/11 and that space is running out.
