The leaching fields do all of the wastewater treatment in your septic system. The larger the field and conversely the smaller the family, the better the treatment, (less odors). Periodically all home septic tank systems get overloaded, (the hiccups). The reasons are plentiful. What you need to do when this happens is make sure your tank is pumped to prevent solids from entering the leaching system and make sure your leaching system is large enough for your useage.