Methods for treating water using iron
View Patent ↗Systems and associated methods for treating contaminant-containing wastewater are provided. The systems generally include a reducing zone for reducing the oxidation-reduction potential of the water and a clean-up zone comprising zero valent iron for removing at least a portion of the contaminant from the contaminant-containing water. The systems are operable to remove one or more contaminants from the contaminant-containing water and are operable for extended durations without clogging due to the formation of iron hydroxides.
1. A method for purifying water, the method, comprising:
passing contaminant-containing water through a reducing zone having a reducing agent present in an amount of less than about 10 wt % of the reducing zone at a pH of at least about 5, wherein the reducing agent comprises an iron-containing media, wherein the contaminant-containing water comprises at least one of cyanide, arsenic, chromium and selenium;
reducing the oxidation-reduction potential of the contaminant-containing water in the reducing zone to not greater than about 0 mV, and restricting Fe 3+ and iron hydroxide production;
flowing the contaminant-containing water from the reducing zone to a clean-up zone, the clean-up zone comprising at least 50 wt % zero valent iron; and
removing contaminants from the contaminant-containing water, wherein the removing step comprises: corroding zero valent iron into Fe 2+ using the contaminant-containing water; forming precipitates from the Fe 2+ and contaminants of the contaminant-containing water; and removing precipitates from the water.
2. The method of claim 1 , wherein the reducing step comprises:
corroding zero valent iron into at Fe 2+ using the contaminant-containing water.
3. The method of claim 2 , wherein the contaminant-containing water exiting the reducing zone comprises an insubstantial Fe 3+ concentration.
4. The method of claim 2 , wherein the contaminant-containing water exiting the reducing zone has a oxidation-reduction potential of not greater than about zero millivolts.
5. The method of claim 2 , wherein the flowing step occurs before a substantial amount of Fe 3+ is produced within the water.
6. The method of claim 1 , wherein water exiting the clean-up zone comprises less than 30 ppb total cyanide.
7. The method of claim 1 , wherein the removing step occurs during both the passing and flowing steps.
8. The method of claim 1 , further comprising:
flowing the water from the clean-up zone to a bio-treatment zone.