Sarcasm aside, your comment actually works: you can use the freshwater from desalination!

Just wait for the saltwater to come back around in the sewer.

Globally about 70% of freshwater is used for agriculture so less than a third of it will come back around, if it's exclusively for residential/commercial use you might do better but overall not a strategy that balances out

70% of desalinated water wont ever go to agriculture because its too expensive to use for corn. Only very high value crops need apply.

But, so what? 30% sewage is still a strong dilluant... especially when mixed with more seawater

Im shocked how many people cannot grasp that you can dilute brine's salinity arbitrarily close to seawater's with energetically cheap pumps.