Nitrate is a chemical found in most fertilizers, manure, and septic tanks. It is a contaminant that can make drinking water unsafe when above a certain level (10mg/L as N). Nitrate: a tasteless, odorless chemical that you can’t boil out of your water, and at high levels it reduces your blood’s ability to absorb oxygen. Nitrates come from fertilizers, Dairies, Septic Tanks, Etc.