Should you feel bad about using STPP?
Here's an overview of the entire phosphorus control issue:
If your wastewater discharges into a body of water not affected by eutrophication, we can probably agree that you can use STPP without feeling guilty.
Now, what if your wastewater is treated to remove phosphorus, and the treatment facility has it under control because the phosphate detergent ban has reduced the amount of phosphorus it has to handle? Your bit of STPP isn't going to pollute the water, and it won't require construction of new treatment facilities. Should you feel guilty about using STPP? Opinions might differ on this question. I'd say you shouldn't feel guilty.