Or evaporation mineral collection ponds or something of that nature. The facility in Wendover on the salt flats is pretty large too though there's no ponds like these images appear to show. There's lots mineral collection ponds like this in California and Nevada.

Wendover: http://maps.google.com/?ll=40.696778,-113.939209&spn=0.4...

Owens lake has evaporative collection ponds that can be really bright red some times, the salt itself is pink: http://maps.google.com/?ll=36.411336,-117.892742&spn=0.1...

That's the Gobi desert. There isn't a whole lot of water to treat, let alone polluted water. It looks like salt production on a truly massive scale.