Sodium hypochlorite is bleach, plain and simple. In large quantities it will cause problems with a septic tank.
Brewers do not generally sterilise, they sanitise, and that is generally good enough. The most important step by far is cleaning, and ideally cleaning before anything gets hold. Simply thoroughly washing with something such as non perfumed household washing up liquid, and allowing to dry, is the most important step you can take.
Do not leave anything damp for example. A cleaned and sealed, damp fermenter will breed all kinds of nasties. I only use three piece ball valves, unless it is just on a boiler that is delivering hot or boiling water. Having seen the crap that can harbour in valves I ensure I take them apart after every use.
Starsan (a sanitiser not steriliser) is something that I use quite a lot of. I always have some in a spray bottle close to hand. This gets sprayed on just about everything. It, however, does not clean and should only be used on previously cleaned surfaces.
I do have bleach (sodium hypochlorite) in my brewery, but it is a rare occasion that I use it. If you have a biofilm (a load of crap in everyday parlance) hiding away on some part of your equipment due to inadequate cleaning, bleach on its own will not always remove the threat.
I also have a septic tank and I take basic precautions when disposing of something like bleach. If I had a fermenter full of bleach for example I would empty this into some sort of holding tank outside. Bleach will not last very long in the presence of sunlight and will revert back to something that could safely be put down the drain.
As has already been mentioned, boiling water or steam can be used on previously cleaned equipment to effectively sanitise it. A high pressure steam cleaner is really useful for spraying down corny dip tubes and silicon tubing and other hard to clean places, but can be done without.
In essence then, you shouldn't really normally need to use anything that will be detrimental to your septic tank if you follow a good cleaning regime. In exceptional circumstances take the appropriate steps to protect it.