How Wells Work? – EPA
https://www3.epa.gov/safewater/kids/flash/flash_watercycle.html
Groundwater Treatment Resources
https://www3.epa.gov/safewater/kids/flash/flash_watercycle.html
Keystone Clean Water Team – Pennsylvania
https://www.who.int/water_sanitation_health/bathing/recreadischap6.pdf