# US 11,027,989 B2 · Membrane filtration system with concentrate staging and concentrate recirculation, switchable stages, or both

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- Number: US 11,027,989 B2
- Document ID: US11027989B2
- Status: Granted
- Kind: B2
- Application number: 16/653,615
- Filed: 2019-10-15
- Published: 2020-02-06
- Granted: 2021-06-08
- Earliest claimed: 2019-10-15
- Assignees: Bl Technologies, Inc.
- Applicants: Bl Technologies, Inc.
- Inventors: Jianwen Zhai
- Web page: https://patentgrep.com/patent/US11027989B2

## CPC

- C02F 1/44: by dialysis, osmosis or reverse osmosis {(general membrane separation processes B01D61/00, membrane modules B01D63/00, electrodialysis C02F1/4693, combination of membrane modules and bioreactors C02F3/1268)}
- B01D 61/58: Multistep processes
- B01D 65/08: Prevention of membrane fouling or of concentration polarisation
- C02F 1/441: {by reverse osmosis}
- C02F 1/442: {by nanofiltration}
- B01D 61/025: {Reverse osmosis; Hyperfiltration}
- B01D 61/145: {Ultrafiltration}
- B01D 2311/08: Specific process operations in the concentrate stream
- B01D 2311/2523: to feed side
- B01D 2313/243: Pumps
- B01D 2317/022: Reject series
- 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

A membrane filtration system with reverse osmosis (RO) or nanofiltration (NF) elements is adapted to provide high recovery from difficult wastewater. The system has a plurality of stages. The system is configured to provide concentrate staging. The last stage also has concentrate recirculation. The valves and pumps of the system are arranged such that the order of flow and a recirculation pump may be switched between the first stage and the last stage at some times.

## Claims

### Claim 1

A process of treating a feed water comprising the steps of:
flowing the feed water through a plurality of stages of membrane filtration with concentrate staging between the stages and concentrate recirculation in the last stage,
wherein the concentrate recirculation in the last stage comprises recirculating concentrate from the last stage back to the last stage.

### Claim 2 (depends on 1)

The process of claim 1 further comprising the step of periodically flowing the feed water through the plurality of stages of membrane filtration with the order of flow and concentrate recirculation switched between a portion of the first stage and the last stage.

### Claim 3 (depends on 1)

The process of claim 1 wherein the stages comprise nominal 8 inch spiral wound modules and the feed or concentrate flow rate through each stage is at least 6 m3/h.

### Claim 4

The process of cairn 1 wherein the process is operated at a recovery rate of 80% or more.

### Claim 5

The process of cairn 1 wherein the feed water has at least 200 mg/L of chemical oxygen demand.