# US 10,766,800 B2 · Removal of nitrates from ground water

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- Number: US 10,766,800 B2
- Document ID: US10766800B2
- Status: Granted
- Kind: B2
- Application number: 15/571,162
- Filed: 2016-05-03
- Published: 2018-09-13
- Granted: 2020-09-08
- Earliest claimed: 2015-05-05
- Assignees: Technion Research & Development Foundation Limited
- Applicants: Technion Research & Development Foundation Limited
- Inventors: Michal Green; Ori Lahav; Razi Epsztein; Oded Nir
- Web page: https://patentgrep.com/patent/US10766800B2

## CPC

- C02F 9/00: Multistage treatment of water, waste water or sewage
- B01D 61/029: {Multistep processes comprising different kinds of membrane processes selected from reverse osmosis, hyperfiltration or nanofiltration}
- C02F 1/441: {by reverse osmosis}
- C02F 1/442: {by nanofiltration}
- B01D 61/025: {Reverse osmosis; Hyperfiltration}
- B01D 61/027: {Nanofiltration}
- B01D 2311/2531: to permeate side
- B01D 2315/10: Cross-flow filtration
- B01D 2317/025: Permeate series
- C02F 2101/163: {Nitrates}
- C02F 2103/06: Contaminated groundwater or leachate
- C02F 2301/043: Treatment of partial or bypass streams
- C02F 2301/08: Multistage treatments, e.g. repetition of the same process step under different conditions
- 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)
- B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28)

## Abstract

The present invention relates to a process for the selective removal of nitrates from ground water using a hybrid nanofiltration (NF)—reverse osmosis (RO) filtration system. The process generates product water that is low in nitrate and can be used for drinking, irrigation and other purposes, as well as waste water that is relatively low in salinity and can be safely discarded to sewage systems and recycled, e.g., for irrigation purposes.

## Claims

### Claim 1

A process for removal of nitrates from water, to produce (i) product water and (ii) a waste brine comprising sodium (Na+) concentration below about 250 mg/L and a chloride (Cl−) concentration below about 450 mg/, the process comprising the steps of:
a. passing a sample of water through a nanofiltration (NF) membrane to obtain a NF permeate and a NF retentate;
b. passing the NF permeate obtained in step (a) through a reverse osmosis (RO) membrane to obtain an RO permeate and an RO retentate;
wherein steps (a) and (b) further comprise controlling NF and RO recovery ratios to result in RO retentate comprising waste brine having sodium (Na+) concentration below about 250 mg/L and a chloride (CI−) concentration below about 450 mg/L;
c. combining the NF retentate obtained in step (a) with the RO permeate obtained in step (b) so as to produce product water; and
d. discarding the RO retentate obtained in step (b).

### Claim 2 (depends on 1)

The process according to claim 1, further comprising a step of passing the NF permeate obtained in step (a) through at least one additional NF membrane prior to performing step (b).

### Claim 3 (depends on 2)

The process according to claim 2, wherein the NF retentates resulting from each NF step are combined.

### Claim 4 (depends on 3)

The process according to claim 3, wherein the combined NF retentates are mixed with the RO permeate.

### Claim 5 (depends on 2)

The process according to claim 2, comprising the steps of:
a. passing a sample of water through a first NF membrane to obtain a first NF permeate and a first NF retentate;
b. passing the first NF permeate obtained in step (a) through a second NF membrane to obtain a second NF permeate and a second NF retentate;
c. combining the first and second NF retentates;
d. passing the second NF permeate obtained in step (b) through an RO membrane to obtain an RO permeate and an RO retentate;
wherein steps (a) - (d) further comprise controlling NF and RO recovery ratios to result in RO retentate comprising waste brine having sodium (Na+) concentration below about 250 mg/L and a chloride (CI−) concentration below about 450 mg/L;
e. combining the combined NF retentate obtained in step (c) with the RO permeate obtained in step (d) so as to produce product water; and
f. discarding the RO retentate obtained step (d).

### Claim 6 (depends on 1)

The process according to claim 1, wherein the NF membrane preferentially rejects Na+, Cl−, Ca+2 and/or Mg2+ ions over NO3− ions.

### Claim 7 (depends on 1)

The process according to claim 1, wherein the NF membrane rejects divalent ions selected from Ca+2 and Mg+2 thereby preventing precipitation of said ions in the RO stage.

### Claim 8 (depends on 1)

The process according to claim 1, wherein the product water in step (c) has a nitrate concentration below about 16.0 mgN/l.

### Claim 9 (depends on 8)

The process according to claim 8, wherein the product water in step (c) has a nitrate concentration below about 13.5 mgN/l.

### Claim 10 (depends on 1)

The process according to claim 1, wherein the brine has a sodium (Na+) concentration below about 230 mg/L and a chloride (Cl−) concentration below about 430 mg/L.

### Claim 11 (depends on 1)

The process according to claim 1, wherein the NF recovery ratio is about 70% or higher.

### Claim 12 (depends on 1)

The process according to claim 1, wherein the RO recovery ratio is about 90% or higher.