Actually it will kill/impact aquatic life up to 150 miles downstream. That brine you talk of is not just sodium chloride, but many types of salts, acids, and other contaminants or processing agents. The reason they aren't Superfund sites is because they exist in less developed nations that dont have the same laws.

It's probably a step in the right direction, but I'm looking forward to supercapacitors or alternative battery tech.