I took a class in septic system design last year and this information is from the class and workshop manual.
Houses with in-sink garbage disposal systems have a larger tank than houses without a disposal. If the house was built with a disposal, it is a pretty good assumption that the tank was designed with that in mind. It is not good to add a disposal to a house after the fact if one was not considered in the design.
Most of the human waste (feces and urine), residual food, and to a degree, toilet paper, will liquefy and can flow into the drain field where it is broken down by microbes. More solid stuff, such as washing machine lint, will stay in the tank and fill it up. That is what is pumped, generally every two years. While it is recommended not to flush tampons (see below) and pads, it will not hurt the system and will just need to be pumped more often. (My wife flushes her items and we have a septic system, but then again we haven’t lived there long either.) I would not worry about it, unless you are in a house with a number of women who are disposing that way. The tank has baffles that keep floating materials from getting into the drain field, and heavier stuff sinks to the bottom.
As for “food-type stuff” and soaps, they are included in what septic systems are designed for. Just use some sense and don’t go overboard. Same with bleach. Small, normal use amounts are diluted enough by water to not cause a problem with the bacteria. But I would not go and dump a whole gallon of bleach down the drain.
But, here is the official word from the University of Minnesota workshop manual:
“Do not deposit coffee grounds, wet-strength towels, disposable diapers, facial tissues, cigarette butts, feminine hygiene products, and similar non-decomposable materials into the sewage system. These Materials will not decompose, and will cause a rapid accumulation of solids in the septic system.
“Avoid dumping cooking fats or grease down the drain. This material may plug sewer pipes or build up in the septic tank and plug the inlet. Keep a separate container for waste grease and throw it out with the trash.
“If a garbage disposal is used, septic tank capacity must be at least 50 percent greater that that required for dwellings or other establishments without disposals…
“Detergents can cause problems with septic systems. It is very difficult to estimate the amount of cleaning power required for a load of laundry and people generally use more than is actually needed. If the automatic washer discharges a large amount of suds after the washing cycle, the amount of washing products should be reduced. Bleach is toxic to the bacteria in the septic tank, so excessive use may be harmful. One to three cups of bleach per week added to a residential system should not be a problem.”
Good luck and enjoy the new place!