Civic groups in Japan have urged the government to continue studying ways to dispose of treated water from the Fukushima Daiichi nuclear power plant other than releasing it into the ocean.
The groups met reporters in Tokyo on Monday before the government officially decides to release the treated water.
Wastewater produced by the crippled nuclear plant is stored in tanks in the compound that are set to fill up sometime next year.
The water has been treated with an Advanced Liquid Processing System, or ALPS, to remove most of the radioactive materials, but it still contains radioactive tritium.
The government plans to decide on Tuesday at the earliest to release the treated water into the ocean, after diluting it to levels far below national regulations.
The co-leader of the Citizens' Nuclear Information Center, Ban Hideyuki, said the government has not gained consent from citizens about the disposal method.
Ban also said releasing the water into the sea is likely to damage the reputations of the local fishery and tourism industries, and hamper recovery from the nuclear accident.
Other groups pointed out that the government has not fully considered alternative ways to dispose of the water on the grounds such as building additional large tanks for long-time storage or solidifying the water with cement.