What Is The Difference between Wet And Dry Reverse Osmosis Membrane Elements?

Reverse osmosis membrane elements play a key role at the heart of modern water treatment technology, with wet and dry reverse osmosis membrane elements demonstrating differentiated advantages in different application scenarios with their unique performance and characteristics. In-depth understanding of the differences between them is essential to optimize the design of water treatment systems, improve operational efficiency and reduce costs.

| Quality testing system

Wet reverse osmosis membrane elements

Wet reverse osmosis membrane element manufacturers strictly follow the quality control system of full volume testing. Every membrane element that is about to leave the factory must undergo rigorous testing of standard solutions. Only those membrane elements that meet or exceed the standard requirements in all performance indicators are allowed to leave the factory. This stringent testing process ensures the stable and reliable performance of each wet reverse osmosis membrane element, provides users with a high degree of quality assurance, and effectively reduces the risk of system failure due to product quality problems.

Dry reverse osmosis membrane element

Dry reverse osmosis membrane element manufacturers use product sampling system. In each production batch, randomly selected part of the membrane element for standard solution testing. After sampling and testing of qualified membrane elements present wet state, while not sampling to the dry state, as dry membrane elements factory. Although this sampling method to a certain extent to improve the production efficiency, but inevitably there is a certain quality risk, there may be substandard performance of the membrane element into the market, affecting the user's experience and system operation effect.

|Reverse osmosis membrane sheet manufacturing process differences

Conventional manufacturing process

At present, the conventional aromatic polyamide reverse osmosis composite membrane sheet manufacturing process has a high degree of consistency in the industry. First of all, the polyester nonwoven fabric is selected as the structural strength base layer of the membrane sheet, which provides a stable physical support for the whole membrane sheet. Next, a layer of highly permeable microporous polysulfone is uniformly coated on the nonwoven fabric as a support layer, which can effectively improve the water permeability of the membrane sheet and provide a good adhesion basis for the subsequent functional layer. Finally, a separated functional layer with an ultra-thin film structure is formed on the support layer by means of an advanced interfacial recondensation method.At the end of this conventional manufacturing process, the initially obtained diaphragm is usually in a moist state, or what we call a wet film.

Special process for dry film

A special drying process is required to convert a wet film into a dry film. Wet film is sent to a specialized drying unit, in the precise control of temperature, humidity and airflow conditions, and gradually remove the water in the film, so that it reaches a dry state. This drying process not only changes the physical state of the membrane, but also affects the microstructure and performance of the membrane to a certain extent, is the dry membrane and wet membrane in the manufacturing process of the significant difference.

Reverse osmosis membrane element rolling process

In the reverse osmosis membrane element rolling process, wet membrane element using wet film as raw materials, while dry membrane element using dry film.Although the two rolled process in the overall framework is not significantly different, follow the industry standard rolled specifications, but due to the wet and dry state of the membrane sheet is different, in the rolled process of the operational details, such as the flexibility of the membrane sheet, the degree of fit and the sensitivity of the environmental humidity, etc., the specific parameters of the rolled process and the operational skills may have a certain impact, and thus to a certain extent affect the membrane element of the final performance.

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 Advantages and disadvantages of comparison

  Wet reverse osmosis membrane element Advantages

Quality assurance: the full amount of testing before leaving the factory to ensure that the performance of each wet reverse osmosis membrane element can meet the strict standard requirements.This enables the user to obtain stable and reliable performance in the process of use, effectively avoiding the decline in performance or failure of the entire water treatment system due to the poor performance of individual membrane elements, providing a solid guarantee for the long-term stable operation of the system.

Fast start-up: Wet membrane elements have superior initial performance.After the installation is completed on-site, only a simple flushing step can quickly reach the membrane element ** performance state. This feature not only greatly saves the time required for system start-up, but also reduces the waste of water in the flushing process, which significantly improves efficiency and reduces operating costs.

Performance Advantage: In terms of the basic performance of reverse osmosis, wet membrane elements usually show better characteristics than dry membrane elements.Specifically embodied in its higher rate of desalination and water production, can more effectively remove the salt and impurities in the water, to meet the water quality and water requirements of higher application scenarios, such as electronic chip manufacturing, high-end pharmaceutical and other industries of ultrapure water preparation.

Disadvantages

Complicated maintenance: Due to their wetting characteristics, wet membrane elements require the use of specialized protective fluids or other protective measures to ensure that the membrane elements always remain wet, while preventing microbial growth and contamination on the membrane surface. This not only increases the difficulty and complexity of the maintenance process, but also raises maintenance costs, requiring users to have a certain degree of professional knowledge and maintenance skills.

Transportation constraints: The wet state of the wet membrane element makes it susceptible to freezing during transportation, especially at low temperatures in winter.In order to avoid damage to the membrane element due to freezing, under the transportation conditions below freezing point, ** use vehicles with heat preservation function for transportation.

After arriving at the destination, it is also necessary to store the membrane element in an environment above freezing point, which puts high demands on the transportation and storage conditions and limits the flexibility of its application.

Dry Reverse Osmosis Membrane Elements Advantages

Cost and Storage Advantage: Despite the relative complexity of the manufacturing technology and equipment for dry membrane elements, they offer significant cost advantages in subsequent use and maintenance. Because they require no protective fluids or special protective measures, they are relatively lightweight, which greatly reduces transportation costs. At the same time, dry membrane elements can be stored for a longer period of time, reducing the pressure brought about by inventory management and providing users with a more convenient experience.

Convenient transportation: Since the membrane elements are in a dry state, the transportation process is more convenient and quicker as no special insulated vehicles are required under the winter transportation conditions below freezing point. In addition, the environmental conditions of the storage place are less demanding, and the membrane elements can be safely stored either in room temperature warehouses or ordinary indoor environments, which greatly improves their scope of application and flexibility.

Disadvantages

Quality risk: Due to the quality testing method of sampling, it is not possible to ensure that the performance of every dry membrane element shipped from the factory can meet the standard requirements. This leads to the risk of substandard performance of individual membrane elements during actual use, which may affect the operational effectiveness and stability of the entire water treatment system and increase the cost of system maintenance and troubleshooting.

Slow performance start: dry membrane elements are often low in initial performance after being loaded into the system. Need to go through a long time of immersion and flushing process, the performance of the membrane element to gradually improve and reach ** state. This process not only wastes a lot of time and flushing water, reduces work efficiency, but also may have a certain impact on the normal operation of the system, users need to plan and prepare in advance.

Slightly lower performance: Compared to wet membrane elements, dry membrane elements usually perform slightly lower in the basic performance of reverse osmosis, i.e., water production and desalination rate. This makes the dry membrane element may not be able to fully meet the user's needs in application scenarios with more stringent water quality and quantity requirements, limiting its application in some high-end fields.

In summary, wet and dry reverse osmosis membrane elements have their own advantages and disadvantages, the user should be based on the specific application scenarios, budgetary constraints, maintenance capabilities, and water quality and water requirements and other factors for comprehensive consideration to ensure that the selection of the most suitable for their own needs of the membrane element, to achieve efficient and stable operation of the water treatment system.