You can find out a lot about state rules pertaining to septic systems and water wells here:
http://des.nh.gov/organization/divis.../ssb/index.htm
I note the site also addresses discharge of backwash from water treatment facilities in residences. You can jump to that from the site above or just go here:
http://des.nh.gov/organization/commi...dwgb-22-17.pdf