How Japan is dumping 1m tonnes of radioactive water in the ocean | It's Complicated

Since the 2011 Fukushima nuclear disaster, more than 1m tonnes of radioactive water has been building up at the power plant in central Japan. Soon the plant will run out of space to store the water, which is a big problem. The plan at the moment is to dump it all in the sea. So how do you go about making 1m tonnes of radioactive water, safe to drink?