Jeff:(posted 8488 days ago)If that's your main concern, then sodium sulfite is the least of your worries. SS is about the most benign chemical we use in the darkroom. Developing agents are the ones that will have the greatest effect on a septic system. You might want to try using human urine as your developing agent. It contains pyrocatechin, which was a popular developer many years ago. Let us know how it works.