Ah yes, because the only danger of nuclear meltdown industrial wastewater is tritium.
One big concern is that the ALPS system is imperfect: it supposedly removes other radioactive contaminants to within legal limits, but those legal limits ARE higher than that of seawater. The ALPS has also been custom-designed for this project: it is a bespoke system that hasn’t been tested in production.
Plus, this is coming from the same private entity that mismanaged the Fukushima plant enough to cause the disaster… How much faith do you have in them to not fuck up again? Tepco’s optimizing for their bottom line, not for what’s best for society.