The operator of the crippled Fukushima No. 1 nuclear plant on Thursday powered up an additional water treatment facility to scrub contamination from the massive quantities of radioactive water stored there.

The new, mobile facility filters radioactive strontium from water used to cool three reactors that partially melted down in March 2011, said operator Tokyo Electric Power Co., and can handle 300 tons of water a day.

The facility could help to “drastically reduce the risks of radioactive water,” said a Tepco official.

The operator plans initially to process 23,000 tons of water from which radioactive cesium has already been removed. That water is held in tanks at the plant.

The procedure will reduce radioactive strontium in the water to about one-thousandth of its current level, the utility said.

However, removing strontium will not in itself render the water safe. It then needs to be treated by another system at the plant which filters out around 60 kinds of radioactive materials.

But there is an important reason why the strontium takes precedence. Removing that isotope before the others will make the water far less of a hazard in the event of a major leak into the ocean.

Meanwhile, an estimated 400 tons of groundwater continues to seep into the reactor basements every day, forcing the utility to find ways to store it. Tepco already has 400,000 tons of toxic water stored at the site, which will all need to be treated one day.