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Reverse Osmosis (RO) Plants

KORGEN has a wealth of experience in manufacturing, erecting and commissioning a wide range of Reverse Osmosis Plants and RO Systems in Chennai, Tamil Nadu and select cities across South India.

While we have a wide range of pre-engineered and standard Reverse Osmosis (RO) Plants for homes and offices, we also design and manufacture large scale Reverse Osmosis (RO) Plants for commercial and industrial uses.

Our technical team analyses the raw water characteristics such as pH, Total Dissolved Solids (TDS), Hardness Content, Silt Density Index (SDI), Heavy Metals, Turbidity and Suspended Solids, BOD-COD Levels and other critical parameters, evaluates the site conditions and specific customer requirements before deciding on the specifications / plant configuration of the RO Plant. Even our standard units of RO Systems are selected / recommended based on key parameters of the feed water.

The efficacy, performance consistency and durability of a Reverse Osmosis (RO) Plant depend on the correctness of the design, pre-treatment and post-treatment modules, feed water temperature and key engineering factors such as Membrane Configuration, Permeate-Reject Ratio, Material of Construction besides complying with the prescribed usage, operational procedures and prompt preventive maintenance.

The design of the plant is of vital importance and KORGEN strictly adheres to the design guidelines issued by the respective membrane manufacturers to ensure long term performance stability, lowest downtime and reduced ownership costs.

Starting from raw water analysis to the selection of the right RO Plant that meets your requirements, KORGEN will closely guide you, at every stage, to take informed buying decisions.

After the erection, commissioning and process stabilization of our Reverse Osmosis (RO) Plants, we also offer various types of after-sales service packages at very competitive rates to make sure that the RO Systems deliver optimal performance and our customers get the maximum value out of their investment.

KORGEN Reverse Osmosis (RO) Plants are designed, manufactured / sourced under the most stringent quality control norms and tested to international quality standards in every aspect. All the components used in our RO Plants are from globally reputed and trusted companies.

Types of KORGEN Reverse Osmosis (RO) Water Purification Plants
i. Pre-Engineered and Standardized RO Purifiers for Tap and Brackish Water for homes, apartments, offices and institutions
ii. Custom-built Commercial and Industrial RO Plants for specific process requirements and large-scale water purification
iii. Reverse Osmosis Systems specially designed for Critical Processes (Cooling Towers, Boilers, Medical uses)
iv. Fully Automatic and Remote-controlled Sea Water Desalination Plant
v. Packaged Drinking Water (Mineral Water) Plants on turnkey basis Guidance and consultancy to set up labs and obtain regulatory approvals will also be provided

Our range of Reverse Osmosis (RO) Plants starts from a compact 100 LPH (Litres Per Hour) model and goes up to 500m3 LPD (Litres per day) plant. Both containerized and skid mounted RO Plants are made available based on specific requirements and site conditions.

Based on customer requirements, we supply manual, semi-automatic and fully automated Reverse Osmosis (RO) Systems using cutting-edge technological options that include Microprocessor-based PLCs (Programmable Logic Controllers) with Digital Display and Mimics, DCS, SCADA (Supervisory Control and Data Acquisition Modes) with real-time logging and remote communication facility. KORGEN offers very user-friendly and flexible automation options with various levels of control mechanisms.

Advantages of KORGEN Reverse Osmosis (RO) Systems

  • Removes all types of physical, chemical and biological contaminants from water
  • Pre-engineered and Easy-to-operate RO Plants for standard applications
  • Custom-built RO Systems for specific applications based on water characteristics and site conditions
  • Software-driven designs and time-tested practices that maximize performance, reduce costs, improve efficiencies and meet regulatory standards
  • Modular Designs and Optimized Plant Footprint
  • Can be operated for longer hours (up to 20 hours per day)
  • High-efficiency RO membranes and quality-tested premium components from reputed brands ensure durability and long-term performance stability
  • Wide range of models (Manual, Semi-automatic, Fully Automatic) that are competitively priced
  • Advanced accessories to facilitate easier operations, seamless automation and closely monitor various performance parameters. Eg., PLC, DCS, SCADA and Remote Monitoring Facility
  • Comes with 1-year warranty and Warranty Extension at minimal charges
  • Experienced and efficient after-sales service network
PLC - Programmable Logic Controllers with Digital Display and Mimic
DCS - Distributed Control System
SCADA - Supervisory Control and Data Acquisition

Other Membrane-Based Filtration Products

Based on specific applications and customer requirements, KORGEN also designs, manufactures and erects other environmentally-friendly membrane-based compact water filtration / purification plants such as UltraFiltration (UF) and NanoFiltration (NF) Plants where usage of chemicals is minimal.

Nano Filtration (NF) Plant

Nano Filtration Plants use spiral wound membranes and operate at a medium to high working pressure (90-150 psi). The nominal pore size of nanofiltration (NF) membranes is approximately 0.001 microns with a molecular weight cut off (MWCO) of 1,000 to 1,00,000 daltons. NF Plants can remove colour, cysts, bacteria, viruses and humic materials. Since NF membranes remove multi-valent ions, it can be used to remove hardness from water and hence is also known as softening membranes.

Ultra Filtration (UF) Plant

Ultrafiltration (UF) plants has a pore size of approximately 0.002 to 0.1 microns with a molecular weight cut off (MWCO) of approximately 10,000 to 1,00,000 daltons. Ultrafiltration Membranes operate at a working pressure of 30 to 100 psi and are capable of removing all microbiological contaminants from water. The primary advantages of low-pressure UF Membranes when compared with conventional clarification and disinfection processes are as follows:

  • Chemicals are not used (Coagulants, Flocculants, disinfectants)
  • Size-exclusion Filtration as opposed to media depth filtration
  • Constant quality of treated water in terms of particle and microbial removal
  • Compact Plants with lesser footprints
  • Learn More
Know more about Reverse Osmosis (RO) Water Purification Technology

Osmotic Process

Osmotic Process

Osmosis is a natural phenomenon and a vital mechanism in biological systems known for over 100 years. For example, the walls of the living cells are natural membranes with selective permeability wherein some materials can pass through and the others cannot. Osmosis provides the primary means for the transport of fluids into and out of cells of living organisms. Eg., Plants absorbing water from the soil, Kidneys absorb water for human body.

If two solutions (Liquids) with different ionic concentrations are separated by a semi-permeable membrane, then the solution with the lower concentration of ionic substances tend to flow towards the solution with higher concentration of ionic substances and tries to equalize the solute concentrations on the two sides. This is termed as the natural Osmotic Phenomenon. The osmotic pressure is a property of the solution proportional to the amount of dissolved minerals present in it.

This Osmotic Pressure generates a noticeable head difference between the two solutions and is referred to as the Osmotic Pressure Difference. Osmotic pressure can be defined as the potential energy difference that exists between two solutions of different ionic concentration on either side of a semi-permeable membrane.

Osmotic Process and Reverse Osmosis Process for water

Reverse Osmosis Process

Reverse Osmosis Process

Reverse Osmosis Process is a reversal of the natural osmosis pressure by exerting sufficient external pressure to the more concentrated solution. When pressure, that is greater than the osmotic pressure difference, is applied to the solution with higher concentration of ions, the direction of the water flow through the membrane is reversed and this process is known as the Reverse Osmosis Process. In the Reverse Osmosis (RO) Process, the ability of the membrane to selectively pass water is unchanged and only the direction of the water flow is changed.

When the water with higher concentration of ions is forced through a synthetic semi-permeable membrane that allows only water (H2O) molecules, the pure water passes through the membrane while the dissolved solids and other contaminants present in the water are rejected and left behind.

Contaminants Removed by RO Plants

Subject to certain limitations and the requirement of additional treatment schemes, Reverse Osmosis (RO) plants are capable of removing the following impurities | contaminants.

Physical Contaminants Turbidity, Suspended Solids, Silt, Colloids
Chemical Contaminants Inorganic (TDS) Solids. Eg. Sodium, Calcium, Magnesium, Chlorides,
Nitrates, Fluorides, Sulphates, Heavy metals and Organics
Biological Contaminants Bacteria, Virus, Pyrogens, Protozoa and all others micro-organisms

The Origin of RO Technology

Origin of Reverse Osmosis (RO) Technology

Reverse Osmosis (RO) Filtration, also known as hyperfiltration, is a very advanced water purification technology. First developed in the late 1950s with the successful invention of semi-permeable membranes, it was initially used by the US Government for their armed forces.

This semi-permeable membrane rejected dissolved solids (salts |inorganics) present in the water in ionic form but allowed the passage of water molecules and was therefore considered a revolutionary separation process.

Initially, this technology was applied to desalinate sea water as an alternative technology to the energy-intensive, thermal-based separation (Heating-Evaporation-Condensation). With the progress of the space race, NASA invested heavily in the membrane technology as a solution for providing drinkable water during space flight.

In the early 1970s, the first commercial low-pressure semi-permeable membrane was developed and was capable of producing 1 to 5 gallons of clean and safe drinking water per day for small households. Later, as a result of technological advancements, the capacity of membrane systems was augmented to produce sufficient pure water for whole communities.

However, one issue that had remained a challenge was scaling. Scaling is the physical process that occurs when sparingly soluble salts come out of the solution to form a solid scale on the membrane surface. This occured in membrane filtration due to the fact that when salty water entered the membrane, most of the water molecules were removed, leaving behind many salts in a reduced quantity of water. As fresh water source reduced and the demand for higher recovery systems increased, the likelihood for membrane-scaling also increased.

When polyamide membranes, also known as thin film composite (TFC) membranes were introduced, Sodium Hexametaphosphate (SHMP) was used to control the scaling potential. Due to the limitations of SHMP such as quick degradation, limited control of carbonate scaling, liquid anti-scalants primarily made of polyacrylic acid (borrowed from cooling tower technology) was introduced and this was found to be much more stable than SHMP. However, this too had limitations such as limited control of carbonate scaling and precipitation in the presence of metal hydroxides.

In the mid-to-late 80s, advanced research resulted in the introduction of phosphate-based anti-scalants and many formulations even today are derived from phosphate-based materials. These too carry many limitations like overdosing (which can exacerbate phosphate scaling and have limited control over silica precipitation) along with increased prohibitions by US and many other countries.

Phosphate being the primary ingredient in many fertilizers greatly increased the risk of algal blooms and bacterial proliferation in the discharge stream.

The new generation of anti-scalants is unique in molecular structure. Phosphate-free and made in concentrated form, this technology is an evolutionary step in the operation of RO Plants. This technology eliminates the concern of membrane fouling caused by overdosing and adheres to most discharge regulations of various countries.

Today, RO Technology accounts for 80% of the desalination plants worldwide and are used for thousands of different processes and applications. With the continuing depletion of naturally clean water sources, Reverse Osmosis (RO) Plants are now most sought after than ever before.

Technology and Process Description

Technology and Process Description

RO is a reliable and time-tested water treatment methodology to desalinate the water by reducing / removing total dissolved solids (TDS) and other undesirable organic and inorganic chemicals, heavy metals present in the raw water. This technology is today globally acclaimed as the most advanced level of liquid filtration system and is used for a wide variety of applications.

How does Reverse Osmosis work?

In conventional water filtration systems, the entire water is pumped through the filter medium and this is known as ‘dead-end’ filtration. In the RO process, raw water (high TDS/salt) after necessary pretreatment - is passed through a semi-permeable membrane under external pressure created using a high-pressure pump. The amount of required pressure depends on the TDS/Salt concentration of the raw water.

This filtration is called as crossflow or tangential flow filtrations since the raw water flows over and parallel to the membrane surface. In the process, this crossflow creates two streams called the Permeate (or Product) Water and the Concentrate (or Reject) Water. The permeate stream (pure water) is collected separately whereas the reject stream creates a certain amount of turbulence to sweep away the solids/contaminants filtered by the membrane to the reject port and thereby minimizing the accumulation of contaminants on the membrane surface and facilitates smooth operation of the RO Plant.

RO Membranes

The RO Membrane has a pore diameter of 0.0001 micron which is smaller than a bacteria (0.5 mm to 1 mm) and virus (0.02 mm to 0.04 mm) and these fine pores ensure effective filtration (99%) of microbial load in addition to the removal of ions in the water. The passage of water through the membrane depends on factors such as molecular size and diffusability co-efficients.

RO Membranes are made of thin, multi-layered polyamide sheets. These polyamide sheets are layered on top of a polyethersulfone or polysulfone porous layer supported by a non-woven fabric support sheet. This multi-layer configuration gives RO membranes high filtration rates and good mechanical strength. The polyamide layer is responsible for the high rejection rate of solids and is chosen for its permeability to water and relative impermeability to various dissolved impurities.

RO - Design Basis

The basic design and configuration of RO Plants and requisite pre and post treatment modules are highly formula-driven and should be primarily based on the following factors to ensure optimal performance and durability of the RO Plant.

i Source of Water
ii Feed Water Characteristics
iii Water Temperature
iv Desired Flux Rates and hydraulic balancing
v Scaling Potential and LSI
vi Permeate Flow Rate (LPH) required
vii Recovery-Reject Ratio
viii Operating Pressure (Feed | Permeate | Concentrate)
ix Volume of water to be treated per day
x End-use applications of the output water
xi Automation Requirements for the Plant
xii Site Conditions and Specific Customer Preferences

Percentages and Equations

The basic design and configuration of RO Plants and requisite pre and post treatment modules are highly formula-driven and should be primarily based on the following factors to ensure optimal performance and durability of the RO Plant.

Rejection of Solids (TDS) in Feed Water

This equation determines the efficacy of RO Membranes in removing the desired contaminants. While it does not reveal the performance of the individual membranes, it shows the overall performance of the RO Plant.

Rejection % =

Conductivity of Feed Water – Conductivity of Permeate Water × 100

Conductivity of Feed

RO Systems with high efficiency membranes are designed to reject 95-99% of the feed water contaminants. Higher the salt rejection, better is the performance of the system. A low salt rejection may be an indication that the RO Membranes either require cleaning or replacement.

Permeate Recovery Ratio

Permeate Recovery is the quantity of water that passes through the membrane to the filtered side. ie., water that is not sent to the drain port but collected as product water. Higher recovery results in lower water wastage. However, high recovery percentage may also lead to frequent scaling / fouling of the membranes. The recovery percentage for an RO Plant is determined based on numerous factors including the feed water characteristics, pre-treatment modules and the number of arrays and stages. The formula for recovery percentage is

Recovery % =

Permeate Flow Rate

Feed Flow Rate

x 100

If the permeate recovery is at 75%, it means that for every 100 litres of feed water, the RO Plant recovers 75 litres of water as usable product water and the balance 25 litres of water is sent to reject port as concentrate. Based on the design, the recovery percentage of an RO Plant can be set anywhere between 25% to 85%.

Concentration Factor

The is an important parameter for the design of an RO System. Higher the permeate, more will be the concentration of salts and contaminants in the reject stream. If the concentration factor is too high, the scaling | fouling potential of the RO membranes also will increase.

Concentration Factor =


1 – Recovery %

If the feed flow is 100 litres and the permeate flow is 75 litres, then the recovery is 75%. The Formula to find the concentration factor is 1 ÷ (1- 75%) = 4

Note: If the permeate recovery surges above the designed ratio, it may be possibly an indicator of membrane damage or enlargement of membrane pores.


Flux is used to express the rate at which water permeates a reverse osmosis membrane. ie., total water volume per area per unit of time. Flux of an RO membrane is directly proportional to temperature and pressure.

Flux Formula (GFD) =

LPM of Permeate x 1,440 mins/day

Number of membranes in RO System x Surface Area of per RO Element

Flux differs for different sources of water and can be determined with the help of an RO Design Software.

RO Flow Separation and Membrane Structure - Illustration

Product Features and Technical Information

Product Features and Technical Information of RO Plants

Unless warranted under special conditions, Reverse Osmosis (RO) Plants generally comprise the following major parts

i. Pre-Treatment Modules iv. Control Panel and Accessories
ii. RO Membranes & Housings v. Mounting Skid (MS | SS)
iii. Hign Pressure Pumps vi. Post-Treatment Modules
Process Illustration

Pre-Treatment Stage

The efficacy, long-term performance stability and lower maintenance costs for a Reverse Osmosis (RO) plant largely depend on the feed water quality. Certain contaminants in the feed water, if not eliminated, can quickly lead to a decline in membrane performance and, in worst cases, can even irreparably damage the RO membranes leading to premature membrane failure. Eg., Silt, Suspended Solids, Colloidal Particles, Chlorine, Hardness (Ca,Mg), Microbes, Algae, Organics etc. Faulty or partial pre-treatment schemes can result in frequent membrane cleaning requirements that increases the running costs, plant downtime and also adversely affects the membrane life.

Therefore, the purpose of pre-treatment of feed water is to make sure that such contaminants are reduced, neutralized or removed from the water and thereby improve the life and performance of the RO Membrane.

While the pre-treatment module for an RO plant is dependent on the feed water characteristics and the desired output water, generally it is a selection from the following treatment schemes.

i. Multimedia Filters v. pH Boosters
ii. Activated Carbon Filters vi. Anti-Scalants and Scale Inhibitors
iii. UV Sterilizers vii. Micron Filters
iv. Chlorination | De-chlorination Systems viii. Ultra Filteration Units

Note: In case of chlorination of feed water, ORP meters need to be used to monitor the residual chlorine levels in the feed.

Additional pre-treatment may be warranted in the event of feed water having heavy metals, oil and grease, BOD-COD. For sea water applications, clarifiers and flocculators are used before the feed water is sent to the pre-treatment module.

Main Treatment Stage

This stage consists of the full RO module. ie., Reverse Osmosis (RO) Membranes with Housings, High Pressure Pumps, Control Panel with critical accessories and the skid.

The RO Membrane is chosen based on the TDS (Total Dissolved Solids) in the water, required permeate output and the desired operating pressure. Selection factors for membranes include total surface area, pH stability, fouling factors, working life, mechanical strength, operating pressure and selectivity for solutes. The RO Housings come in both SS (Stainless Steel) and FRP (Fibre Reinforced Polymer)

Types of RO Membranes
Tap Water Membranes (TDS Range: < 2000 ppm)
Brackish Water Membranes (TDS Range: 2000 ppm to 8000 ppm)
Sea Water Membranes (TDS Range: >8000 ppm)

Korgen uses membranes made by trusted global brands like GE Osmonics, Dow-Filmtec, Hydranautics, Koch and Toray reputed for their high efficiency, ruggedness and energy-saving designs

Types of high-pressure pumps
Rotary Vane Pumps
Multi-stage Centrifugal Pumps
Piston Pumps
Plunger Pumps

Pumps are chosen based on the TDS content in water. Grundfos, Danfoss, Wilo and KSB are our preferred pumps.

Mechanical Damage to RO Membrane

While proper pre-treatment schemes can prevent membrane damage, the pre and post-system plumbing and controls used in the RO Plant also play a role in the life of a membrane. For instance, a ‘hard start’ can lead to mechanical damage to the RO membranes. Excessive backpressure on the RO Plant can also result in membrane damage. Such issues can be addressed by using pumps with VFDs, installing check valve(s) and/or pressure relief valve(s) etc.

Standard Instrumentation for RO Plants
Low-Pressure and High-Pressure Switches Treatment Status – Indicator Lamps
Pressure Gauges Intermediary Pipes and Fittings (SS 316 | UPVC | CPVC)
Membrane Cleaning Pump and Tank Flow Switches
Conductivity Meters Electrical Panels
Flow Meters for Feed | Permeate | Reject Pre-wired Control Panel
Reject Control Valves Time-delayed Startup Device

The entire RO Plant is mounted on a compact skid made up of MS or SS with easy to the control panel.

Post-Treatment Stage

While the post-treatment module required for an RO Plant depends on the permeate quality, intended applications of the product water and the distribution method chosen for the product water, generally it is a selection from the following options.

pH Boosters Neutralizes the pH in the product water
Remineralization Systems Increases the dissolved solids in the product
De-gasser Towers Removes the free CO2 in the permeate
UV Sterilizers Eliminates storage recontamination issues
Ozonators Eliminates storage recontamination issues and increases shelf life
Point-of-use Purifiers Disinfection just before consumption

Stages and Passes in RO Plants

Stages and Passes in RO Plants

Reverse Osmosis (RO) Plants are configured in a variety of ways based on the permeate quality required, desired recovery ratio and related environmental issues. There are single stage RO plants and Multi-stage RO Plants with single or multiple passes. A few examples are here below.

Single Stage RO System

In this single stage RO System, the feed water enters the RO Plant as a single stream and exits the RO Plant as permeate and concentrate.

Pictorial Illustration

Two-Stage RO System

In a two-stage RO System, the concentrate (or reject) from the first stage becomes the feed stream to the second stage. The permeate water collected from the first stage is combined with the permeate water from the second stage. Additional stages will increase the recovery from the system.

Pictorial Illustration


In an RO System, an array describes the physical arrangement of the pressure vessels in a multi-stage system. Pressure Vessels may contain multiple RO membranes (1 to 6 in a single vessel). The reject of each stage becomes the feed stream for the successive stage. In the above illustration, it is a 2:1 array which means that the concentrate of the first two RO membranes is fed to the next membrane.

RO Plant with Concentrate Recycling

If the feed water characteristics allow for it, concentrate recycling is possible wherein a portion of the concentrate stream is fed back to the feed water at the first stage. This helps in increasing the system recovery ratio.

Pictorial Illustration

Single Pass RO Vs Double Pass RO

The difference between a single pass RO Plant and double pass RO Plant is that with a double pass RO, the permeate from the first pass becomes the feed water to the second pass. This results in a much higher quality of permeate water.

Maintenance of RO Plants

Maintenance of RO Plants

The filtration units in the pre-treatment module will have to be periodically backwashed and rinsed to remove the accumulated physical impurities. The quantity of anti-scalant chemical available in the tank will have to be monitored and periodically refilled. The UV lamp has to be checked for any drop in intensity.

Even the best pre-treatment cannot completely eliminate the decline of membrane performance over time and hence periodical cleaning of the membranes is necessary to maintain the RO membrane’s peak performance. As a general rule, if there is a drop in the permeate flow or permeate quality (increase in salt passage), it is an indicator that the membrane needs to be cleaned. Membranes can also be cleaned onsite using specialized devices / cleaning skids.

Automated RO Plants are equipped with devices that backflush the membrane at a pre-set frequency. Beside this routine backflushing, chemical cleaning may be required and the periodicity of the same depends on the fouling potential of the feed stream and other related factors. Generally it is any where between 1 to 4 times a year depending on the age and condition of the membrane/s.

General Applications

General Applications of Reverse Osmosis (RO) Water Treatment Plants

  • Purification of drinking water for homes, institutions, commercial establishments and industries
  • Ultrapure water for medical uses. Eg. Feed for Renal Dialysis Units, Instrument Sterilization, Production of Medicines and Pharmaceutical Formulations.
  • Desalination of sea water
  • Packaged Drinking Water for commercial sales
  • Pre-treatment to Demineralizer (DM/MB) Plants
  • Recirculation of industrial and process water
  • Used in Cooling Towers, Boiler Plants and other process water requirements
  • Tertiary treatment for STP, ETP and Recycling Plants
  • Industrial Uses - Power Generation | Food & Beverage Processing | Pharmaceutical Production | Biotechnology | semiconductor manufacturing




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