The salt in the waste of the softener will not be detrimental to your septic system. In fact, it has been proven to improve the bacterial action in the septic system. Regarding the amount of water going to the septic tank, that would depend upon how large your septic tank is. Obviously, if it is too small then the additional waste from the softener could be a problem. You should check with your septic system supplier to find out if the amount of water from the softener will be a problem for your system. If it is you can redirect the softener waste to a dry well or to an area on the surface that will not be affected by the salt content. Ion exchange water softeners are the only proven technology to soften water.