I am new to this but is there any ideas on preventing tree roots growing in the septic system?
It depends on whether or not you have a septic system or municipal waste system.
You can google Copper Sulphate as a root control for municipal waste systems. If you have a septic you could use metam-sodium &/or diclobenil (foam) which sticks to the roots and walls of the pipe, killing the root within a few short hours. Then again, it can take up to a year for them (the roots) to decompose.
Alternatively, you can also REMOVE the offending tree from the proximity of your septic.