I'm sorry to say the only proven method to revive a failing leaching field is to give it a break. All of the "alternative" methods are temporary at best. You do need to install another leaching field. However, that said provide a method of alternating back to the old field. In a few short years that old field barring a mechanical failure if the piping will be ready for use again as the bio-matt breaks up and the soil becomes ready to accept water again. With 2 alternating fields you will be all set!