Japan has announced plans to release wastewater from the stricken Fukushima-Daiichi nuclear plant into the ocean starting Thursday. Here is what we know about the release, how the water has been treated and concerns around the safety of the exercise. Why the release? Around 100,000 litres (26,500 gallons) of contaminated water – from cooling the crippled plant's reactors as well as groundwater and rain seeping in – is collected at the site in northeast Japan every day. Some 1.34 million tonnes – equivalent to almost 540 Olympic pools – are now stored in around a thousand steel containers at the…