The US EPA seems to disagree. They state "Wastewater treatment facilities in the United States process approximately 34 billion gallons of wastewater every day. Wastewater contains nitrogen and phosphorus from human waste, food and certain soaps and detergents."
https://www.epa.gov/nutrientpollutio...ons-wastewater
Most homes and businesses in the US handle their waste water this way.
In contrast all the desalination plants worldwide produce less than 23 billion gallons a day. USA water treatment alone processes one third more water than all desalination plants combined.
Interesting that you have to "guess" about the waste products at Carlsbad. Why don't they explain on their site more about this important issue?
Desalination is just not ready for prime time yet...
The Roaring River plant makes much more economic sense.
And waste water MUST be treated anyway. You can't just pump into the rivers or sea untreated. That is a dangerous lesson mankind learned the hard way.