# US 10,864,481 B1 · Energy efficient low-fouling high-recovery reverse osmosis system for brackish water desalination

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- Number: US 10,864,481 B1
- Document ID: US10864481B1
- Status: Granted
- Kind: B1
- Application number: 16/105,103
- Filed: 2018-08-20
- Granted: 2020-12-15
- Earliest claimed: 2018-08-20
- Applicants: Dileep Kumar Agnihotri; John Joseph Barelli
- Inventors: Dileep Kumar Agnihotri; John Joseph Barelli
- Web page: https://patentgrep.com/patent/US10864481B1

## CPC

- B01D 61/029: {Multistep processes comprising different kinds of membrane processes selected from reverse osmosis, hyperfiltration or nanofiltration}
- B01D 61/025: {Reverse osmosis; Hyperfiltration}
- B01D 61/08: Apparatus therefor
- B01D 61/12: Controlling or regulating
- B01D 65/02: Membrane cleaning or sterilisation {; Membrane regeneration}
- B01D 65/08: Prevention of membrane fouling or of concentration polarisation
- C02F 1/441: {by reverse osmosis}
- 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)
- B01D 2311/04: Specific process operations in the feed stream; Feed pretreatment
- B01D 2311/06: Specific process operations in the permeate stream
- B01D 2311/18: pH control
- B01D 2313/18: Specific valves
- B01D 2313/48: Mechanisms for switching between regular separation operations and washing
- B01D 2317/022: Reject series
- B01D 2317/04: Elements in parallel
- B01D 2317/06: Use of membrane modules of the same kind
- B01D 2321/02: Forward flushing
- B01D 2321/10: Use of feed
- B01D 2321/167: Use of scale inhibitors
- C02F 2103/08: Seawater, e.g. for desalination
- C02F 2201/005: Valves
- C02F 2209/005: Processes using a programmable logic controller [PLC]
- C02F 2209/03: Pressure
- C02F 2301/08: Multistage treatments, e.g. repetition of the same process step under different conditions
- C02F 2303/14: Maintenance of water treatment installations
- C02F 2303/20: Prevention of biofouling
- C02F 2303/22: Eliminating or preventing deposits, scale removal, scale prevention (C02F1/042, C02F1/4602, C02F5/00 take precedence)
- Y02A 20/131: Reverse-osmosis
- 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)
- 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)
- Y02A: TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE

## Abstract

A novel multi-stage reverse osmosis system is proposed that allows for following benefits —a) reduction in pressure-loss while achieving optimum cross-flow velocities and therefore reducing energy consumption of 4-10%; —b) increased flux balance between stages resulting in reduced fouling of the first stage; —c) disruption of scale forming conditions resulting in reduced scaling of the last stage; —d) reduction in scale potential of the concentrate valve; —e) reduction in downtime for CIP by proactively disrupting scaling or fouling through several innovative methods; —f) ease-of and effectiveness-of CIP with reduced number of valves and —g) to keep system operational via isolation of the last stage for maintenance while the keeping remaining system in production mode. All the above improvements are achieved with process-flow and operational characteristics defined in the Specifications and Claims.

## Claims

### Claim 1

A desalination process for treating water using a three-stage reverse osmosis system comprising:
a first stage, a second stage, and a third stage; each stage having a feed inlet stream, a concentrate outlet stream, and a permeate outlet stream; wherein the number of pressure vessels decrease in subsequent stages;
wherein the three stages are configured to have the permeate stream flow in- parallel, and the concentrate stream flow in-series through subsequent stages;
a clean-in-place (CIP) system, wherein the CIP system receives combined permeate flow or combined concentrate flow or both from the three stages;
wherein using a plurality of valves and parallel piping, a first component of the feed stream is configured to flow to the first stage inlet, a second component of the feed stream is configured to flow to the second stage inlet, and a third component of the feed stream is configured to flow to the third stage inlet;
wherein the concentrate outlet stream of the first stage blends with the second component of the feed stream to make a blended feed inlet stream for the second stage and the concentrate outlet stream of the second stage blends with the third component of the feed stream to make a blended feed inlet stream for the third stage;
wherein the second component of the feed stream is 15-30% of the feed stream and the third component of the feed stream is 10-20% of the feed stream;
wherein, using a plurality of valves and parallel piping, the second stage and the third stage components of the feed inlet stream are controlled in both volume and duration, respectively, of the total feed stream;
wherein, during the normal operation, the components of the feed stream to the second and the third stage is continuous or intermittent;
and wherein the plurality of valves and parallel piping to the second and third stage used during the normal operation are also used for the offline CIP process.

### Claim 2 (depends on 1)

The desalination process of claim 1 wherein the three-stage reverse osmosis system has a staging ratio of 3:2:1.

### Claim 3 (depends on 1)

The desalination process of claim 1, wherein the third stage is taken offline intermittently and isolated for maintenance, while the rest of the stages are in the normal operation; wherein the period of isolation is 1-100 minutes and frequency of the isolation is once in 1-100 hours.

### Claim 4 (depends on 1)

The desalination process of claim 1, wherein the third stage of the system is a series combination of two pressure vessels connected in series and represents a combined third and fourth stage of the system.

### Claim 5 (depends on 1)

The process of claim 1, wherein, the process-flow is controlled via a programmable logic controller (PLC) and decisions to achieve novel process characteristics are programmed within PLC with adjustable periods, frequency, production rate, flowrate, % recovery, pressure, and flow conditions.

### Claim 6 (depends on 1)

The process of claim 1, wherein the third stage, as part of maintenance, receives intermittent injection of chemicals to disrupt fouling and to dissolve scale-forming seeds; the period of intermittent chemical injection is between 0.5-60 minutes and intermittency is between 1-100 hours and occurs either during normal operations or at the start of isolation of the third stage for maintenance.

### Claim 7 (depends on 1)

The process of claim 1, wherein, the third stage of the system is periodically flushed with 10-50% additional feed.