Answers to common questions about reverse osmosis membrane and ion exchange resin (51-60)

51. How to replace the new series of nanofiltration elements NF90-400, NF270-400 and NF200-400 with a larger water pipe for the original system using old-style nanofiltration (NF) membrane elements?

You can put all the old components in the same pressure vessel. If you only want to replace one of the old components, please order a 1.125”~1.5” component coupling. Please contact the nearest Dow personnel for processing dimensions.

52. How to remove silicon from water?

Silicon in water exists in two forms, active silicon (monomer silicon) and colloidal silicon (polysilicon):

  • Colloidal silicon does not have the characteristics of ions, but the scale is relatively large. Colloidal silicon can be intercepted by fine physical filtration processes, such as reverse osmosis, and the content of water can also be reduced by coagulation techniques, such as coagulation clarification tanks, but those need to rely on Separation techniques for ionic charge characteristics, such as ion exchange resins and continuous electrodeionization process (CDI), have very limited effect on the removal of colloidal silicon.
  • The size of active silicon is much smaller than that of colloidal silicon, so most physical filtration technologies such as coagulation, clarification, filtration and air flotation cannot remove active silicon. The processes that can effectively remove active silicon are reverse osmosis, ion exchange and Continuous electrodeionization process.

53. Can ROSA5 be equipped with water holding pressure and inter-stage pressure lift pumps?

In ROSA5, the product water holding pressure can be set in the first section, and the inter-section pressure lift pump can be set between the second and third sections. This is a new design function of ROSA5.

54. Can the membrane element be exposed to sunlight?

No, not even in the original box. It is recommended to store indoors, and prevent the sunlight coming in from windows and other places from being exposed for a long time, and the ambient temperature should not exceed 45℃.

55. How about the packaging of Dow FILMTEC membrane elements?

For 8” components, Dow’s standard packaging is: 1) 1 corrugated carton (outer shape 10 inches × 10 inches × 44.5 inches); 2) 2 layers of polyethylene bags; 3) 2 polystyrene end protection covers; 4) If it is a wet component, the protective fluid in the sealed bag is less than 250mL.
For 4” components, Dow’s standard packaging is: 1) Each component is packed in a separate plastic bag; 2) The components are packaged in a large carton containing 70 individual plastic bags, and there is no separate corrugated carton*.
* This is because many 4″ component systems use unit components. For the purpose of environmental protection, no inter-component internal connectors are provided.

56. How to choose the model when replacing NF70-400 components?

The NF70-400 component has been modified. If the desalination rate is similar to NF70-400, please replace it with NF90-400. If you want more hardness and other salts to pass through, please replace it with NF270-400.

57. How does pH affect the removal rate, water production and membrane life?

Dow FILMTEC™ brand membrane element is characterized by its proprietary fully aromatic high crosslinking desalination layer chemical structure, as long as it is within the specified product corresponding pH range, generally 2 to 11, pH has little effect on membrane performance itself This is one of the distinguishing features that are different from other membrane products, but the characteristics of many ions themselves in water are greatly affected by pH. For example, when weak acids such as citric acid are in a low pH condition, they are mainly in non-ionic state, while in high Dissociation occurs at pH and appears ionic. Due to the same ion, the degree of charge is high, the removal rate of the membrane is high, and the degree of charge is low or uncharged, the removal rate of the membrane is low, so pH has a great influence on the removal rate of certain impurities.

58. How does the water inlet grid (water inlet channel) in the membrane element affect the generation of dirt plugs and the cleanability of the dirt plugs?

The function of the water inlet grid (flow channel) is to provide a channel for the inlet water to flow from the inlet end of the element to the concentrated water end. It must be able to provide turbulence promotion to the membrane surface, so as to prevent concentration polarization and fouling. The wider flow channel can greatly prevent the formation of fouling, while improving cleaning performance, which is why many membrane module structures used for concentration separation always use a wider and thicker grid (flow channel). Some membrane element manufacturers still use the old but low-investment element manufacturing process, and cannot use a wide and thick grid under the condition of ensuring the effective membrane area of ​​the element, so that the fouling of their membrane products will continue to increase after several months of use. The cleaning efficiency is low. For the same components, the Dow membrane grid is 10-20% thick.

59. In ROSA5, how to view the various design solutions without opening the workbook?

The easiest way is to design each plan, in the Project Information column (Project Information) fill in the description of each design plan, so that you can quickly browse when needed. You can also create a database to accommodate 1 or more projects. In ROSA5, the file must be renamed after a real design operation.

60. How can I e-mail the calculation results of ROSA5 to others who do not have ROSA5 software installed?

The print file of the calculation result is displayed as an .html file on the screen. It can be sent to others as an E-mail attachment. In addition, it can be made into pdf software using Acrobat Writer software (software that converts it into pdf). It will not change when displayed and printed on any computer. But this software is not free. When Adobe® Acrobat® Writer is set as the default printer in ROSA5, ROSA5 will automatically generate a file containing pdf, and then you can send it to others.

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