I grew up sometimes having them (and dealing w. them most summers when we went to the family farm), and every spring the damn things flooded with the spring rains. So for several weeks, we were very, very, very water conscious, taking tiny and less frequent showers, washing clothes at the washateria, that kind of thing. Basically, the concept was to reduce waste water production to as low as possible until the field had a chance to pick itself up and get back with the program.
There are bacteria boosters that you can flush, but if you're having it pumped out (and that's relatively inexpensive - $150 or so, compared to several thou to replace or enlarge the system) and the bacteria replaced, and you're careful for a few weeks to let everything get established, you should be okay (but I am not an expert.)
My grandfather's house has this book, and it's pretty much the bible. You might look into it.
http://www.shelterpub.com/_shelter/ssom_book.html