It depends where you are located. In PA, USA, you will have predischarge limits on critical parameters (in your case, I'm guessing BOD, DO and temp; possibly pH) which will dictate how much you have to pretreat. These will be set with respect to the existing loadings in the system, as well as the capacity and process at the recieving treatment facility.
Contact the permitting agency, they will probably give you preliminary limits, upon which you can base your design/discharge proposal.
Remember: The Chinese ideogram for “crisis” is comprised of the characters for “danger” and “opportunity.”
-Steve