How Do You Choose the Best Reverse Osmosis and Nanofiltration Membrane System for an Industrial Facility?

As global demands for clean water increase, more and more industrial facilities are looking toward membrane filtration solutions, such as reverse osmosis (RO) and nanofiltration (NF), to help manage intake, process, and waste water treatment. Using membrane filtration can help your facility reuse wastewater and virtually eliminate discharge fees, and depending on the industry or required use, it can also help a facility efficiently treat raw and/or process water more efficiently than some conventional treatments.

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If you think an industrial plant needs to explore its options regarding RO/NF, you might be wondering “How Do You Choose the Best RO/NF System for an Industrial Facility?”

Since there are a variety of options that will depend on what industry the plant serves (oil and gas, petrochemical, food and beverage, etc.), along with which part of the process the filtration is needed and what contaminants need to be removed, this blog article breaks down what to consider when going through the process:

What is the stream characterization?

When a facility is looking to consider RO/NF membrane filtration as a water treatment solution, they first need to consider what the quality characterizations of the liquid stream are in addition to the purity requirements of the treated stream. For example, if a microelectronics facility is looking to use a raw water source, such as a river or lake, to feed their process stream (which requires extremely high-purity water), chances are you are looking at substantial pretreatment process preceding an RO system, followed by ion exchange, which can effectively remove nearly all suspended and colloidal contaminants. Since RO is the finest of all membrane filtration systems (with extremely small pores capable of removing particles as small as 0.1 nm), it is generally a great fit for microelectronics production, among other processes, such as desalination.

NF delivers slightly coarser filtration than RO, with the ability to remove particles as small as 0.002 to 0.005 μm in diameter, so it might be a better choice for softening hard water. NF is a relatively recent technology that was developed mainly for potable water generation, but it removes harmful contaminants, such as pesticide compounds and organic macromolecules, while retaining minerals that RO would otherwise remove. Nanofiltration membranes are capable of removing larger divalent ions such as calcium sulfate, while allowing smaller monovalent ions such as sodium chloride to pass through, which makes it a good choice for concentration and demineralization in some dairy-processing facilities.

What type of membrane should you use?

Membrane configurations can vary, but mostly spiral wound and hollow fiber membranes are used. The quality and overall efficiency of the unit can depend on the type of membrane chosen, which can include:

• Hollow fiber;more suitable for low-solid liquid streams, these membranes are constructed of thousands of hollow fibers that resemble spaghetti and can be efficiently kept clean with occasional backwashing and clean-in-place (CIP) technology.
• Plate and frame; these membranes are placed on top of plate-like structures that collect solids on the inside of the supporting plate. These have low packing densities and can be less efficient than other filtration methods, but they are generally easy to use and clean. Typically used on solutions difficult to filter. They are also among the lower-cost membranes but higher-cost systems.
• Spiral-wound; spiral-wound membranes are among the commonly used. They are composed of flat sheets of membrane between mesh-like spacers that are wound around a central tube (this tube collects the permeate after filtration) and placed within a casing. They are relatively compact and can be used in high-volume applications with low suspended solids.
• Tubular; several tube-like membranes are placed within a pipe/shell, and as the stream is passed through the tubes, it transfers the permeate to the pipe/shell side. These can be less permeable with a lower packing density and are generally used for hard-to-treat streams, such as those with high TDS, TSS, and oils, greases, and fats.

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Are there pre- or post-treatment needs for your RO/NF membrane treatment system?

RO and NF membrane systems are rarely used alone; they are generally part of a technology “train.” Since they can foul or scale pretty easily, they usually require some type of pretreatment, such as microfiltration, again, depending on the quality of the incoming stream versus the needed stream quality after filtration.

There is also usually some type of byproduct that needs to be recovered or disposed of after the filtration. When designing your RO/NF system, this should be taken into consideration, as well. For example, sometimes the byproduct might be something valuable (such as silver), or in other cases, it could be something expensive to dispose of. Byproducts are always important to keep in mind when developing a plan for filtration.

What is the result of a treatability study and/or pilot test?

A treatability study is a study or test that will determine if the water stream can be treated for your process and how it needs to be treated. If the study is done correctly, it will clearly identify the contaminants present in your water stream, helping ensure the proper treatment solutions are considered and implemented in your RO/NF membrane treatment system. It can help your facility understand what pre- and post-treatment might be needed, as well as the bypass ratio, amount of recovery the system will yield, and how efficient you can expect the process to be.

This step is critically important when choosing the best treatment system for your plant. After having a roadmap of maybe two or three technology platforms that meet your base and operating cost, running an efficient treatability test will help validate the assumptions you’ve made about possible contaminations and solutions to remove them. This streamlines to process and takes out any guesswork, ensuring your facility is getting the best possible solution for your unique situation.

Also keep in mind that even though the study might seem thorough on paper, there’s nothing better than running pilot testing in the field to validate the treatment/technology assumptions, optimize design, because during this phase, other problems can arise and be found prior to choosing the components of your system, which can help save you from any process water hiccups or effluent violations down the line.

How can SAMCO help?

SAMCO has over 40 years’ experience custom-designing and manufacturing RO/NF systems for a range of industries and solutions, so please feel free to reach out to us with your questions.

For more information or to get in touch, contact us here to set up a consultation with an engineer or request a quote. We can walk you through the steps for developing the proper solution and realistic cost for your RO/NF treatment system needs.

Head on over to our blog to learn more about industrial filtration and process separation technology. Some articles that might be of specific interest to you include:

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• Does Your Facility Need a Reverse Osmosis or Nanofiltration System?
• Reverse Osmosis and Nanofiltration Membrane Filtration Systems: Common Problems and How to Fix Them
• What Are the Best Companies for Reverse Osmosis and Nanofiltration Membrane Systems?
• Reverse Osmosis vs Nanofiltration Membrane Process: What Is the Difference?
• What Are Reverse Osmosis and Nanofiltration and How Do They Work?

Clean and safe water is essential, but ensuring its availability requires advanced filtration methods capable of removing harmful contaminants. Traditional methods may not suffice for today’s water quality demands, making ultrafiltration and nanofiltration two of the most valuable solutions in water treatment. These technologies each address different types of contaminants, so understanding their distinctions is critical to choosing the right technology based on water quality needs.

As a leading water treatment company, Ion Exchange has been pivotal in promoting efficient filtration methods in various industries. With innovative membrane technology, Ion Exchange helps clients determine whether ultrafiltration or nanofiltration best suits their specific water treatment needs, ensuring clean water with optimal efficiency.

What is Ultrafiltration in Water Treatment?

Ultrafiltration (UF) is a membrane filtration process that removes particles, bacteria, and other contaminants from water. Ultrafiltration membranes have pore sizes typically ranging from 0.01 to 0.1 microns, which allows them to effectively filter out suspended solids, bacteria, and certain viruses, without affecting dissolved salts and minerals.

Ultrafiltration is commonly used in drinking water treatment, industrial processing, and wastewater treatment. In drinking water applications, ultrafiltration removes harmful microorganisms and improves clarity, making water safe for consumption. Industrial applications include pre-treating water for more advanced filtration methods like reverse osmosis, while wastewater treatment facilities use UF to clarify and disinfect effluent before discharge or reuse.

Advantages and Limitations of Ultrafiltration

Ultrafiltration offers several benefits, particularly for applications where the goal is to remove larger particles and improve water clarity:

• Advantages: Ultrafiltration operates at low pressure, meaning it requires less energy, reducing operational costs. It’s highly effective at removing bacteria, suspended solids, and some viruses, making it ideal for municipal and industrial applications where clarity and microorganism removal are key.
• Limitations: Ultrafiltration cannot remove dissolved salts or smaller organic molecules, limiting its effectiveness in applications that require water softening or removal of specific contaminants. This limitation highlights the distinction between ultrafiltration vs. nanofiltration, where nanofiltration is needed for finer filtration.

What is Nanofiltration in Water Treatment?

Nanofiltration (NF) is a more selective filtration process than ultrafiltration, with membrane pore sizes typically around 0.001 microns. Nanofiltration targets dissolved ions, organic molecules, and other contaminants that ultrafiltration cannot remove. It is effective in removing divalent and multivalent ions, making it ideal for applications such as water softening and treating industrial wastewater that contains specific chemical pollutants.

In water softening, nanofiltration removes hardness ions such as calcium and magnesium, making the water suitable for various industrial processes. It is also commonly used in the food and beverage industry to remove salts and pesticides and in pharmaceutical applications where a high level of water purity is essential.

Advantages and Limitations of Nanofiltration

Nanofiltration offers several unique advantages for applications that require high-quality water with minimal dissolved salts and organic molecules:

• Advantages: Nanofiltration effectively removes dissolved salts, organic molecules, and pesticides, making it ideal for water softening and treating chemically contaminated water. It requires fewer chemicals than traditional methods and is more environmentally friendly.
• Limitations: Nanofiltration membranes require higher pressure than ultrafiltration, resulting in greater energy consumption and operational costs. This limitation is a key consideration when choosing between nanofiltration and ultrafiltration; nanofiltration is only suitable when the water quality demands justify the increased cost.

Ultrafiltration vs. Nanofiltration: Key Differences

When comparing ultrafiltration vs. nanofiltration, several factors distinguish these technologies:

• Pore Size: Ultrafiltration has larger pores (0.01 to 0.1 microns), removing bacteria and suspended solids, while nanofiltration’s smaller pores (around 0.001 microns) target dissolved ions and organic molecules.
• Filtration Mechanism: Ultrafiltration relies on size exclusion to remove larger particles, whereas nanofiltration uses both size exclusion and selective retention, allowing it to remove specific dissolved salts and organic compounds.
• Contaminants Removed: Ultrafiltration effectively removes bacteria, suspended solids, and some viruses, while nanofiltration can remove dissolved ions, organic molecules, and pesticides, providing a finer level of filtration.

How to Choose Between Ultrafiltration vs. Nanofiltration

Selecting between ultrafiltration vs. nanofiltration requires consideration of several factors, including water quality requirements, contaminant types, and operational costs:

• Water Quality Requirements: Ultrafiltration is ideal when the primary goal is to remove microorganisms and suspended solids, whereas nanofiltration is preferable for applications that require water softening or removal of dissolved ions.
• Contaminants: If the water contains high levels of bacteria or turbidity, ultrafiltration may suffice. However, if the water has dissolved salts or organic pollutants, nanofiltration is a better choice.
• Energy and Cost: Ultrafiltration is generally more energy-efficient and cost-effective, making it suitable for large-scale applications. Nanofiltration’s higher operational costs are justifiable in specialized applications where its selective filtration capabilities are necessary.

Ion Exchange’s Impact on Water Treatment with HYDRAMEM Membrane Technology

Ion Exchange has been at the forefront of water treatment innovation with its HYDRAMEM membrane technology, providing tailored ultrafiltration and nanofiltration solutions to address complex water treatment needs.

• HYDRAMEM UF Membranes

Hydramem Ultrafiltration (UF) Modules are advanced hollow fiber membranes engineered to handle a wide range of applications, including the treatment of brackish water (ground, river, and surface), municipal waste, industrial effluents, and seawater, catering to both potable and process water needs. These cutting-edge modules are available in two configurations: modified PES fibers (in to out) and PVDF fibers (out to in), offering flexibility and efficiency for diverse operational requirements. With a molecular weight cut-off (MWCO) of 100,000 Daltons (100 KD), Hydramem UF modules ensure optimal energy usage while delivering consistent permeate quality with an SDI of less than 3, making them a reliable solution for superior water treatment.  

• HYDRAMEM NF Membranes

Hydramem Cross-Linked Fully Aromatic Polyamide (Thin Film) Composite Nano Filtration Elements (NFE) are meticulously designed with a robust outer shell, ensuring high stability in industrial applications even under challenging temperature and pH conditions. These advanced elements deliver exceptional performance with higher rejection rates for bivalent ion removal, brackish water softening, dye desalting, and the treatment of textile brine, making them ideal for chemical salt recovery processes. Tailored for demanding environments, Hydramem NFE elements provide reliable and efficient solutions for a wide array of water treatment and recovery applications.

Conclusion

Choosing between ultrafiltration vs nanofiltration is crucial to ensuring that water treatment systems are effective, energy-efficient, and economically feasible. Ultrafiltration is ideal for applications that require the removal of bacteria and suspended solids, while nanofiltration is best for applications involving dissolved salts, organic molecules, or specific chemical pollutants.

Contact us to discuss your requirements of nanofiltration system. Our experienced sales team can help you identify the options that best suit your needs.