Your septic guy should have thought of that before he wasted your money on a new leach field.
He could have done a sand filter and put the outlet into the old field, or do it now and put it into the drain field.
There are aerobic systems that use air pumps to treat the sewage in the tank, what comes out is pretty clean. Call the guy in the phone book with the oldest license number that says he fixes bad systems. Google for systems info. Dont call your county guys for 'help' yet.
In the mean time, you can use LITTLE water, go to a laundromat, and pump the septic tank every few months. Check for toilet flapper leaks and any others.