# US 10,870,591 B2 · Water treatment system for removing hexavalent chromium

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- Number: US 10,870,591 B2
- Document ID: US10870591B2
- Status: Granted
- Kind: B2
- Application number: 16/407,495
- Filed: 2019-05-09
- Published: 2019-08-29
- Granted: 2020-12-22
- Earliest claimed: 2015-06-05
- Assignees: U.S. Water Services, Inc.
- Applicants: U.S. Water Services, Inc.
- Inventors: Michael D. Kelly
- Web page: https://patentgrep.com/patent/US10870591B2

## CPC

- C02F 1/42: by ion-exchange (ion-exchange in general B01J)
- C02F 1/285: {using synthetic organic sorbents}
- C02F 1/66: by neutralisation; pH adjustment (for degassing C02F1/20; using ion-exchange C02F1/42; for flocculation or precipitation of suspended impurities C02F1/52; for removing dissolved compounds C02F1/58)
- C02F 1/70: by reduction {(C02F1/4676 takes precedence)}
- C02F 2001/422: {using anionic exchangers}
- C02F 2101/22: Chromium or chromium compounds, e.g. chromates
- C02F 2303/16: Regeneration of sorbents, filters
- C02F: TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE (separation in general B01D; special arrangements on waterborne vessels of installations for treating water, waste water or sewage, e.g. for producing fresh water, B63J; adding materials to water to prevent corrosion C23F; treating radioactively-contaminated liquids G21F9/04; regeneration of reactants for recirculation into processes, see the relevant places for the processes)

## Abstract

A method for removing chromium from a water source can include delivering source water having a hexavalent chromium oxyanion into contact with an ion exchange resin to exchange the hexavalent chromium oxyanion for an anion and convert the source water to treated water, discharging the treated water, rinsing the ion exchange resin with a brine solution to remove the hexavalent chromium oxyanion from the ion exchange resin, converting the hexavalent chromium oxyanion to a trivalent chromium cation, binding the trivalent chromium cation to a chelating resin, and removing the trivalent chromium cation bound to the chelating resin.

## Claims

### Claim 1

A system comprising:
a first vessel containing an ion exchange resin, the first vessel configured to receive source water and exchange an hexavalent chromium oxyanion for an anion and convert the source water to treated water, and configured to receive a brine solution to remove the hexavalent chromium oxyanion from the ion exchange resin;
a second vessel for receiving the brine solution with the hexavalent chromium oxyanion from the first vessel;
a third vessel containing a reducing agent for converting the hexavalent chromium oxyanion in the brine solution to a trivalent chromium cation; and
a fourth vessel containing a chelating resin for binding the trivalent chromium cation in the brine solution, the fourth vessel configured to discharge the trivalent chromium cation bound to the chelating resin.

### Claim 2 (depends on 1)

The system of claim 1, wherein the second vessel is configured to adjust the pH of the brine solution.

### Claim 3 (depends on 1)

The system of claim 1, further comprising:
a fifth vessel for receiving the brine solution from the fourth vessel, adjusting the pH of the brine solution, and recycling the brine solution to the first vessel.

### Claim 4 (depends on 1)

The system of the claim 1, further comprising:
a sixth vessel and a seventh vessel configured to re-concentrate the brine solution with the hexavalent chromium from the first vessel;
wherein the sixth vessel is configured to receive the brine solution from the first vessel, cycle the brine solution through the seventh vessel, and deliver a concentrated brine solution to the second vessel; and
wherein the seventh vessel contains a reverse osmosis system for producing the concentrated brine solution.

### Claim 5 (depends on 1)

The system of claim 1, wherein the ion exchange resin is a basic anionic ion exchange resin.

### Claim 6 (depends on 1)

The system of claim 1, wherein the ion exchange resin includes at least one of an acrylic, a styrenic, or a phenolic cross-linked co-polymer.

### Claim 7 (depends on 1)

The system of claim 1, wherein the ion exchange resin includes a quaternary amine functional group.

### Claim 8 (depends on 1)

The system of claim 1, wherein the anion is selected from the group consisting of a sulfate and a chloride.

### Claim 9 (depends on 1)

The system of claim 1, wherein the brine solution includes a salt selected from the group consisting of sodium sulfate, potassium sulfate, and magnesium sulfate.

### Claim 10 (depends on 1)

The system of claim 1, wherein the reducing agent includes a granular activated carbon.

### Claim 11 (depends on 1)

The system of claim 1, wherein the chelating resin includes a functional group selected from the group consisting of iminodiacetic, aminophosphonate, thiouronium, and thiol.