reverse osmosis definition meaning example

What is Reverse Osmosis (RO) Definition

Reverse osmosis (RO) is basially the reverse of the osmosis process. Scientists found that all that is required to reverse the process of osmosis is a suitable semipermeable membrane and applying a pressure to the concentrated salt solution above the applied and osmotic back-pressures, thereby forcing pure water through the semipermeable membrane. In other words, reverse osmosis is the process where water containing inorganic salts (minerals), suspended solids, soluble and insoluble organics, aquatic microorganisms, and dissolved gases (collectively called source water constituents or contaminants) is forced under pressure through a semipermeable membrane. Semipermeable refers to a membrane that selectively allows water to pass through it at much higher rate than the transfer rate of any constituents contained in the water. Learn more about pressure driven membranes here. If water of high salinity is separated from water of low salinity via a semipermeable membrane, a natural process of transfer of water will occur from the low-salinity side to the high-salinity side of the membrane until the salinity on both sides reaches the same concentration. This natural process of water transfer through a membrane driven by the salinity gradient occurs in every living cell; it is known as osmosis.

The hydraulic pressure applied on the membrane by the water during its transfer from the low-salinity side of the membrane to the high-salinity side is termed osmotic pressure. Osmotic pressure is a natural force similar to gravity and is proportional to the difference in concentration of total dissolved solids (TDS) on both sides of the membrane, the source water temperature, and the types of ions that form the TDS content of the source water. This pressure is independent of the type of membrane itself. In order to remove fresh (low-salinity) water from a high-salinity source water using membrane separation, the natural osmosis-driven movement of water must be reversed, i.e., the freshwater has to be transferred from the high-salinity side of the membrane to the low-salinity side. For this reversal of the natural direction of freshwater flow to occur, the high-salinity source water must be pressurized at a level higher than the naturally occurring osmotic pressure.

If the high-salinity source water is continuously pressurized at a level higher than the osmotic pressure and the pressure losses for water transfer through the membrane, a steady-state flow of freshwater from the high-salinity side of the membrane to the low-salinity side will occur, resulting in a process of salt rejection and accumulation on one side of the membrane and freshwater production on the other. This process of forced movement of water through a membrane in the opposite direction to the osmotic force driven by the salinity gradient is known as reverse osmosis (RO).

The rate of water transport through the membrane is several orders of magnitude higher than the rate of passage of salts. This significant difference between water and salt passage rates allows membrane systems to produce freshwater of very low mineral content. The applied feed water pressure counters the osmotic pressure and overcomes the pressure losses that occur when the water travels through the membrane, thereby keeping the freshwater on the low-salinity (permeate) side of the membrane until this water exits the membrane vessel.

reverse osmosis definition meaning example

Osmosis and Reverse Osmosis Process

The salts contained on the source water (influent) side of the membrane are retained and concentrated; they are ultimately evacuated from the membrane vessel for disposal. As a result, the RO process results in two streams—one of freshwater of low salinity (permeate) and one of feed source water of elevated salinity (concentrate, brine or retentate), as shown in the figure above. While semipermeable RO membranes reject all suspended solids, they are not an absolute barrier to dissolved solids (minerals and organics alike). Some passage of dissolved solids will accompany the passage of freshwater through the membrane. The rates of water and salt passage are the two key performance characteristics of Reverse Osmosis membranes.

reverse osmosis process drawing

Reverse Osmosis Process Drawing

Reverse Osmosis System

An Industrial Reverse Osmosis System works the same way as illustrated. Net driving pressure (NDP) forces water through the membrane. In an operating RO system, feed water is pressurized by a high pressure pump. Due to NDP, a portion of the feed water is forced through the RO semipermeable membrane. The membrane is completely impermeable (won’t allow passage) to particles and only slightly permeable to dissolved substances. The water that passes through the membrane is called permeate. Permeate usually has very few particles in it. Unless there is a membrane defect (hole) or other problem, any particles found in the permeate were produced there (either from bacteria or equipment). Permeate is also low in dissolved substances (a small amount of dissolved solids does pass through the membrane). Permeate, therefore, is a relatively high purity water. Figure below illustrates an RO unit in the format we have been using so far.

Reverse Osmosis System Illustration

Reverse Osmosis System Illustration

We know that when we pressurize the feed water and water passes through the membrane , the feed water is concentrated. If the concentration in the feed water gets high enough, the osmotic back pressure will rise to eventually give us an NDP of zero and the flow will stop. In an RO system, then, we must flush away the dissolved substances from the membrane surface so that the osmotic back pressure won’t keep going up. This is different from the other filters that we’re used to working with. Most of the filters that we have dealt with in our lives have been “full flow”, “accumulative” types of filters. “Full flow” means that there is one stream in (feed water) and one stream out (filtrate). “Accumulative” means that the “stuff” that is filtered accumulates in or on the filter.

From coffee filters, to cartridge filters, to multimedia filters, this has been the case. The feed water goes in, the “stuff” that we want to take out is removed by the filter. When the filter gets full, we backwash or replace the filter. Membrane systems can’t be full flow or accumulative. With an RO membrane, we are filtering out ions which have an osmotic pressure. What would happen if we continue to filter out dissolved substances which produce an osmotic back pressure? Answer: The process would stop.

An RO unit therefore, must have a flushing flow which carries away the dissolved and suspended substances. This waste stream is called concentrate. An RO unit, therefore, has one stream going into it (Feed Water), and two streams coming out (Permeate & Concentrate).
The following illustration also shows an RO unit with a 100 gpm (22.7 m3/hr) feed water flow. Due to NDP supplied by a high pressure pump, around 75% of the feed water is forced through the membrane. The water, suspended particles, and dissolved substances which don’t go through the membrane are concentrated and exit the RO unit as concentrate.

reverse osmosis unit example flush

Reverse Osmosis Unit Example

Depending on their size and electric charge, most water constituents are retained (rejected) on the feed side of the Reverse Osmosis membrane while the purified water (permeate) passes through the membrane. Figure below illustrates the sizes and types of solids removed by Reverse Osmosis membranes as compared to other commonly used filtration technologies. RO membranes can reject particulate and dissolved solids of practically any size. However, they do not reject well gases, because of their small molecular size. Usually Reverse Osmosis membranes remove over 90 percent of compounds of 200 daltons (Da) or more. One Da is equal to 1.666054 × 10−24 g. In terms of physical size, RO membranes can reject well solids larger than 1 (Angstrom) Å. This means that they can remove practically all suspended solids, protozoa (i.e., Giardia and Cryptosporidium), bacteria, viruses, and other human pathogens contained in the source water. While Reverse Osmosis membranes can retain both particulate and dissolved solids, they are designed to primarily reject soluble compounds (mineral ions).

bqua reverse osmosis RO membrane contaminant removal

BQUA Reverse Osmosis RO Membrane Contaminant Removal

The structure and configuration of Reverse Osmosis membranes is such that they cannot store and remove from their surface large amounts of suspended solids. If left in the source water, the solid particulates would accumulate and quickly plug (foul) the surface of the Reverse Osmosis membranes, not allowing the membranes to maintain a continuous steady-state desalination process. Therefore, the suspended solids (particulates) contained in source water used for desalination have to be removed before they reach the RO membranes. The following chapters of this book focus exclusively on the planning and engineering of RO membrane desalination systems.

Over the past 20 years, RO membrane separation has evolved more rapidly than any other desalination technology, mainly because of its competitive energy consumption and water production costs. The energy and cost analysis presented in Table 1.3 indicates that the all-inclusive energy consumption for freshwater production of thermal desalination plants is typically much higher than that for brackish or seawater desalination. BWRO desalination yields the lowest overall production costs of all the desalination technologies. It is also important to note that the latest Multi-Effect Distillation MED projects built over the last 5 years have been completed at costs comparable to those for similarly sized SWRO plants. For the majority of medium and large projects, however, SWRO desalination usually is more cost competitive than thermal desalination technologies.

industrial brackish water reverse osmosis system bwro

Industrial Brackish Water Reverse Osmosis System (BWRO)

The BQIX-BW Series of industrial brackish water reverse osmosis systems is a durable, future-proof and compact Reverse Osmosis System. It is designed ideally for both city water and brackish water treatment applications. BQUA designs Reverse Osmosis Systems capable of reaching maximum and highest recovery rates depending on each water condition.

BQUA is a proud manufacturer of reverse osmosis systems. Our technical sales engineers and water treatment specialists are capable of designing and executing these systems no matter how harsh the condition or application is. BQUA will always find a solution to your tough water pollution.

 

industrial brackish water reverse osmosis system bwro

   BQIX-BW Industrial Brackish Water Reverse Osmosis System BWRO

Customized Reverse Osmosis System

BQUA’s Industrial BQIX-BW Reverse Osmosis System is integrated and manufactured to exceed expectations and solve your toughest water problems. Our future-proof series is well known for its durable construction, user friendly operating system, environmental friendly materials, plug and play turnkey operation and hassle-free operation.

All BQUA RO Systems series including the BQIX-BW is customizable based on each individual water contaminants and design. Additional equipment is added if necessary based on each case to include water softener, media filter, chemical dosing, iron removal, cleaning skids, anti-scalant, etc. The BQIX-BW series has capacities ranging from as low as 200,000 GPD to 900,000 GPD, with feed water TDS ranging from 1000 ppm to 10,000 ppm. These features have the capability of removing hardness, arsenic, chlorine, odor, taste, smell, color, iron, sulfur, fluoride and a lot more. BQUA industrial brackish water reverse osmosis system represents the latest technologies in the water treatment industry and is capable of removing dissolved salts, particles, organics, minerals, solids and other contaminants from water with a molecular weight greater than 150-250 Dalton. We partner with major market players in the field of water treatment and only use top quality brands and the most reputable manufacturers; Pentair, Dow, Hydrodex and Siemens.

Industrial Brackish Water Reverse Osmosis Product Specifications

Operation Specifications
  • Maximum feed water temperature: 42°C
  • Hydrogen Sulfide must be removed
  • Maximum Silica tolerance: 25 ppm at 60% recovery
  • Feed water TDS: 0-2,000 ppm
  • Operating pressure: 150 to 250 psi
  • pH tolerance range: 3-11
  • Max. Iron content: 0.05 ppm
  • Feed water pressure: 20 to 80 psi
  • Hardness over 1 GPG requires water softener
  • Turbidity should be removed
  • Operate at higher TDS by lowering recovery

BQUA BQIX-BW Series Product Specifications by model number

Industrial Brackish Reverse Osmosis System BQIX-BW Series
Model Number Permeate Flow Rate Membranes Motor Rating at 1,000 ppm
GPD M3/Day Size Qty. 60Hz (hp) 50Hz (kw)
BQ200K-BW 200,000 758 8″ X 40″ 28 30 22
BQ225K-BW 225,000 852 8″ X 40″ 30 30 22
BQ270K-BW 270,000 1,023 8″ X 40″ 36 40 30
BQ320K-BW 320,000 1,212 8″ X 40″ 42 40 30
BQ360K-BW 360,000 1,364 8″ X 40″ 48 50 37
BQ410K-BW 410,000 1,553 8″ X 40″ 54 60 37
BQ450K-BW 450,000 1,705 8″ X 40″ 60 60 45
BQ500K-BW 500,000 1,894 8″ X 40″ 66 60 45
BQ550K-BW 550,000 2,083 8″ X 40″ 77 75 45
BQ600K-BW 600,000 2,273 8″ X 40″ 91 100 55
BQ700K-BW 700,000 2,652 8″ X 40″ 98 100 75
BQ800K-BW 800,000 3,030 8″ X 40″ 112 2 X 60 2 X 37
BQ900K-BW 900,000 3,409 8″ X 40″ 126 2 X 60 2 X 37
For more information, please feel free to ask a BQUA specialist

Standard and Available Features:

Standard Features: Available Options:
  • NEMA 4x enclosure.
  • Pressure switch.
  • Liquid filled pressure gauges.
  • Permeate conductivity monitor.
  • Permeate & concentrate flow meters.
  • Powder coated aluminum, stainless steel or carbon steel frame.
  • 8” Thin Film Composite spiral wound membrane.
  • Stainless steel multi-stage pump.
  • FRP membrane housing.
  • 5 micron cartridge pre-filter.
  • 380-415V/3Ph/50Hz power supply.
  • Microprocessor based control panel. Conventional control panel also available.
  • Programmable time delay and set points.
  • Status indicators.
  • Motor starter.
  • Concentrate Recycle.
  • Export crate.
  • 460V/3Ph/60Hz power supply.
  • 220V/Single phase/50Hz power supply.
  • Iron removal filter.
  • Ozone / UV sterilization systems.
  • Water softener.
  • Media Filter.
  • De-ionization post filter.
  • Product tank level controller switch.
  • Feed pH monitor with sensor.
  • Feed water conductivity monitor.
  • Membrane cleaning skid.
  • Automatic hourly flush.
  • ORP monitor with sensor.
  • Water and hour meters.
  • Chemical dosing systems.
bqua brackish water reverse osmosis water treatment system

Light Industrial Brackish Water Reverse Osmosis System (BWRO)

The BQLIX-BW Series of light industrial brackish water reverse osmosis systems is a durable, future-proof and compact Reverse Osmosis System. It is designed ideally for both city water and brackish water treatment applications. BQUA designs Reverse Osmosis Systems capable of reaching maximum and highest recovery rates depending on each water condition.

BQUA is a proud manufacturer of reverse osmosis systems. Our technical sales engineers and water treatment specialists are capable of designing and executing these systems no matter how harsh the condition or application is. BQUA will always find a solution to your tough water pollution.

 

BQUA BQLIX-BW Light Industrial Reverse Osmosis Water Treatment System

BQUA BQLIX-BW Light Industrial Reverse Osmosis Water Treatment System

Customized Reverse Osmosis System

BQUA’s Light Industrial BQLIX-BW Reverse Osmosis System is integrated and manufactured to exceed expectations and solve your toughest water problems. Our future-proof series is well known for its durable construction, user friendly operating system, environmental friendly materials, plug and play turnkey operation and hassle-free operation.

All BQUA RO Systems series including the BQLIX-BW is customizable based on each individual water contaminants and design. Additional equipment is added if necessary based on each case to include water softener, media filter, chemical dosing, iron remval, cleaning skids, anti-scalant, etc. The BQLIX-BW series has capacities ranging from as low as 28,000 GPD to 173,000 GPD, with feed water TDS ranging from 1000 ppm to 10,000 ppm. These features have the capability of removing hardness, arsenic, chlorine, odor, taste, smell, color, iron, sulfur, fluoride and a lot more. BQUA light industrial brackish water reverse osmosis system represents the latest technologies in the water treatment industry and is capable of removing dissolved salts, particles, organics, minerals, solids and other contaminants from water with a molecular weight greater than 150-250 Dalton. We partner with major market players in the field of water treatment and only use top quality brands and the most reputable manufacturers; Pentair, Dow, Hydrodex and Siemens.

Light Industrial Brackish Water Reverse Osmosis Product Specifications

Operation Specifications
  • Maximum feed water temperature: 42°C
  • Hydrogen Sulfide must be removed
  • Maximum Silica tolerance: 25 ppm at 60% recovery
  • Feed water TDS: 0-2,000 ppm
  • Operating pressure: 150 to 250 psi
  • pH tolerance range: 3-11
  • Max. Iron content: 0.05 ppm
  • Feed water pressure: 20 to 80 psi
  • Hardness over 1 GPG requires water softener
  • Turbidity should be removed
  • Operate at higher TDS by lowering recovery

BQUA BQLIX-BW Series Product Specifications by model number

Light Industrial Brackish Reverse Osmosis System BQLIX-BW Series
Model Number Permeate Flow Rate Membranes Motor Rating at 1,000 ppm
GPD M3/Day Size Qty. 60Hz (hp) 50Hz (kw)
BQ28K-BW 28,000 109 8″ X 40″ 4 5 4
BQ36K-BW 36,000 136 8″ X 40″ 5 7.5 4
BQ43K-BW 43,000 164 8″ X 40″ 6 7.5 5.5
BQ57K-BW 57,000 218 8″ X 40″ 8 7.5 7.5
BQ72K-BW 72,000 273 8″ X 40″ 10 10 7.5
BQ87K-BW 87,000 327 8″ X 40″ 12 15 11
BQ108K-BW 108,000 409 8″ X 40″ 15 20 15
BQ130K-BW 130,000 491 8″ X 40″ 18 20 15
BQ144K-BW 144,000 545 8″ X 40″ 20 20 15
BQ173K-BW 173,000 655 8″ X 40″ 24 20 18.5
For more information, please feel free to ask a BQUA specialist

Standard and Available Features:

Standard Features: Available Options:
  • NEMA 4x enclosure.
  • Pressure switch.
  • Liquid filled pressure gauges.
  • Permeate conductivity monitor.
  • Permeate & concentrate flow meters.
  • Powder coated aluminum, stainless steel or carbon steel frame.
  • 8” Thin Film Composite spiral wound membrane.
  • Stainless steel multi-stage pump.
  • FRP membrane housing.
  • 5 micron cartridge pre-filter.
  • 380-415V/3Ph/50Hz power supply.
  • Microprocessor based control panel. Conventional control panel also available.
  • Programmable time delay and set points.
  • Status indicators.
  • Motor starter.
  • Concentrate Recycle.
  • Export crate.
  • 460V/3Ph/60Hz power supply.
  • 220V/Single phase/50Hz power supply.
  • Iron removal filter.
  • Ozone / UV sterilization systems.
  • Water softener.
  • Media Filter.
  • De-ionization post filter.
  • Product tank level controller switch.
  • Feed pH monitor with sensor.
  • Feed water conductivity monitor.
  • Membrane cleaning skid.
  • Automatic hourly flush.
  • ORP monitor with sensor.
  • Water and hour meters.
  • Chemical dosing systems.
bqua bwro industrial brackish water reverse osmosis system

Commercial Brackish Water Reverse Osmosis System (BWRO)

The BQCX-BW Series of commercial brackish water reverse osmosis systems is a durable, future-proof and compact Reverse Osmosis System designed ideally for tap and brackish water treatment applications. BQUA designs RO systems that are capable of reaching maximum and highest recovery rates depending on the water condition.

BQUA is a proud supplier of standard and customized reverse osmosis systems. Our technical sales engineers and water treatment specialists are capable of designing these systems no matter how harsh was the condition or application. BQUA will always find a solution to your tough water pollution.

 

bqua bwro industrial brackish water reverse osmosis system

BQUA BQCX Series of Commercial Brackish Water Reverse Osmosis System

Customized Reverse Osmosis System

BQUA’s Commercial BQCX-BW Reverse Osmosis System is integrated and manufactured to exceed expectations and solve your toughest water problems. Our future-proof series is well known for its durable construction, user friendly operating system, environmental friendly materials, plug and play turnkey operation and hassle-free operation.

All BQUA RO series including the BQCX-BW is customizable based on each individual water contaminants and design. Additional equipment is added if necessary based on each case to include water softener, media filter, chemical dosing, iron remval, cleaning skids, anti-scalant, etc. The BQCX-BW series has capacities ranging from as low as 13,000 GPD to 32,000 GPD, with feed water TDS ranging from 1000 ppm to 10,000 ppm. These features have the capability of removing hardness, arsenic, chlorine, odor, taste, smell, color, iron, sulfur, fluoride and a lot more. BQUA commercial brackish water reverse osmosis system represents the latest technologies in the water treatment industry and is capable of removing dissolved salts, particles, organics, minerals, solids and other contaminants from water with a molecular weight greater than 150-250 Dalton. We partner with major market players in the field of water treatment and only use top quality brands and the most reputable manufacturers; Pentair, Dow, Hydrodex and Siemens.

Commercial Brackish Water Reverse Osmosis Product Specifications

Operation Specifications
  • Maximum feed water temperature: 42°C
  • Hydrogen Sulfide must be removed
  • Maximum Silica tolerance: 25 ppm at 60% recovery
  • Feed water TDS: 0-2,000 ppm
  • Operating pressure: 150 to 250 psi
  • pH tolerance range: 3-11
  • Max. Iron content: 0.05 ppm
  • Feed water pressure: 20 to 80 psi
  • Hardness over 1 GPG requires water softener
  • Turbidity should be removed
  • Operate at higher TDS by lowering recovery

BQUA BQCX-BW Series Product Specifications by model number

Commercial Brackish Reverse Osmosis System BQCX-BW Series
Model Number Permeate Flow Rate Membranes Motor Rating at 1,000 ppm
GPD M3/Day Size Qty. 60Hz (hp) 50Hz (kw)
BQ13K-BW 13,000 50 4″ X 40″ 9 3 2.2
BQ15K-BW 15,000 57 4″ X 40″ 10 5 2.2
BQ18K-BW 18,000 68 4″ X 40″ 12 5 3
BQ22K-BW 22,000 85 4″ X 40″ 15 5 3
BQ24K-BW 24,000 91 4″ X 40″ 16 5 3
BQ27K-BW 27,000 102 4″ X 40″ 18 5 3
BQ32K-BW 32,000 121 4″ X 40″ 21 5 4
For more information, please feel free to ask a BQUA specialist

Standard and Available Features:

Standard Features: Available Options:
  • NEMA 4x enclosure.
  • Pressure switch.
  • Liquid filled pressure gauges.
  • Permeate conductivity monitor.
  • Permeate & concentrate flow meters.
  • Powder coated aluminum, stainless steel or carbon steel frame.
  • 4” Thin Film Composite spiral wound membrane.
  • Stainless steel multi-stage pump.
  • FRP membrane housing.
  • 5 micron cartridge pre-filter.
  • 380-415V/3Ph/50Hz power supply.
  • Microprocessor based control panel. Conventional control panel also available.
  • Programmable time delay and set points.
  • Status indicators.
  • Motor starter.
  • Concentrate Recycle.
  • Export crate.
  • 460V/3Ph/60Hz power supply.
  • 220V/Single phase/50Hz power supply.
  • Iron removal filter.
  • Ozone / UV sterilization systems.
  • Water softener.
  • Media Filter.
  • De-ionization post filter.
  • Product tank level controller switch.
  • Feed pH monitor with sensor.
  • Feed water conductivity monitor.
  • Membrane cleaning skid.
  • Automatic hourly flush.
  • ORP monitor with sensor.
  • Water and hour meters.
  • Chemical dosing systems.
bqua light commercial brackish water reverse osmosis system bwro

Light Commercial Brackish Water Reverse Osmosis System (BWRO)

The BQLCX-BW Series of light commercial brackish water reverse osmosis systems is a durable, future-proof and compact Reverse Osmosis System designed ideally for tap and brackish water treatment applications. Even our small compact RO systems are capable of reaching high recovery rates depending on the water condition.

BQUA is a proud supplier of standard and customized reverse osmosis systems. Our technical sales engineers and water treatment specialists are capable of designing these systems no matter how harsh was the condition or application. BQUA will always find a solution to your tough water pollution.