JP2006255673A - Membrane evaluation method in membrane separation apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a membrane evaluation method in a membrane separation apparatus capable of being normally operated even if flux is reduced caused by fluctuation of water quality by a temperature in winter or the like. <P>SOLUTION: A filtration performance is measured using raw water added with colloidal silica and a separation membrane to be used is evaluated based on the measurement result. The colloidal silica is preferably added to raw water in an amount of 5-20 mg/L and is particularly preferably added thereto such that the total amount of colloidal silica in raw water becomes 10-20 mg/L. Thus, the evaluation test of the membrane is performed by previously adding the colloidal silica to raw water. Thereby, since the membrane separation apparatus is designed at the performance in response to reduction of the flux by fluctuation of the temperature, the membrane separation apparatus can always exhibit a predetermined function. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a membrane evaluation method in a membrane separation device, and more particularly to an optimum evaluation method for a membrane separation device such as a microfiltration membrane, an ultrafiltration membrane, and a reverse osmosis membrane.

  Membrane separation equipment is used to obtain high-purity water by separating industrial water obtained by subjecting surface water such as river water and lake water to water purification treatment such as coagulation and sedimentation, and suspended and dissolved substances in tap water. Or, it is widely used in fields such as purification equipment for separating and reusing suspended matter and dissolved matter in waste water discharged from factories, households, and sewage treatment plants.

  In the membrane separation apparatus as described above, a flocculant is added to river water, lake water, etc., and the separation water obtained by performing solid-liquid separation processing such as flocculation / precipitation / filtration is treated as raw water. At this time, membrane performance such as flux is evaluated using raw water, and a membrane separation apparatus is designed based on the evaluation result.

  At this time, since water is often heated in the latter stage of the membrane separation apparatus, preheated water is often passed, so the membrane is evaluated based on the raw water flux at 25 ° C. It was selected. However, the quality of the raw water varies depending on the water temperature, and the flux decreases in winter when the water temperature falls. Furthermore, some membrane separators may permeate unheated water.

  In such a case, if the membrane was evaluated based on the raw water flux at 25 ° C. and designed as the performance of the membrane separation device, the permeated water amount decreased in the winter, and the predetermined performance could not be exhibited. In other words, there is a risk that the treatment of the membrane separator may be hindered, and the operation of the membrane separator may be hindered.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a membrane evaluation method in a membrane separation apparatus that can be normally operated even when flux decreases due to fluctuations in water quality due to temperature such as in winter. And

  First, the present invention is a membrane evaluation method in a membrane separation apparatus for separating suspensions and dissolved substances in raw water using a separation membrane, and measures filtration performance using raw water to which colloidal silica is added. A membrane evaluation method in a membrane separation apparatus for evaluating a separation membrane to be used based on the results is provided. Colloidal silica in raw water increases with decreasing temperature and is difficult to agglomerate, so it is difficult to remove it by solid-liquid separation.If the membrane is evaluated at a high raw water temperature, the water temperature may decrease in winter. As the amount of colloidal silica in the raw water increases, the flux decreases and the membrane separator cannot perform its predetermined function.If the colloidal silica is added to the raw water in advance and the membrane is evaluated, Since the membrane separator is designed with the performance corresponding to the decrease in the flux due to the fluctuation, the membrane separator can always perform the predetermined function. Here, in this invention, the colloidal silica added to raw | natural water becomes a reference | standard which evaluates the filtration performance of a film | membrane.

  Secondly, the present invention provides a membrane evaluation method in a membrane separator in which 5 to 20 mg / L of the colloidal silica is added (Claim 2). Thereby, a membrane separator can be evaluated corresponding to the content of colloidal silica in raw water at a low temperature.

  3rdly, this invention provides the membrane evaluation method in the membrane separator which adds the said colloidal silica so that the total amount of the colloidal silica in raw | natural water may be 10-20 mg / L (Claim 3). Thereby, the membrane separator can be evaluated in accordance with the content of colloidal silica in the raw water at a low temperature.

  According to the membrane evaluation method in the membrane separation apparatus of the present invention, assuming the operation at a low water temperature, the flux is measured in advance in a state where colloidal silica which is an evaluation standard for filtration performance is added to the raw water, and based on this, the membrane is measured. Since the performance of the membrane separation device is set by evaluating the above, the membrane separation device can always be operated in a good state without being lower than the flux at the time of design due to fluctuations in temperature.

  Hereinafter, an embodiment of a membrane evaluation method in the membrane separation apparatus of the present invention will be described in detail. FIG. 1 is a schematic view showing an example of a flat membrane evaluated by the membrane evaluation method of the present embodiment. A membrane sheet 1 includes a polysulfone permeable support layer 2 that has been subjected to a polypropylene coating treatment and a polytetrasilane that performs filtration. A skin layer 4 made of fluoroethylene (PTFE) having a pore diameter of 0.2 μm is joined via a non-woven fabric layer 3 made of polypropylene, and this membrane sheet 1 is opposed to the skin layer 4 side so that a spacer (channel) In the state where the material 6 is disposed, the adhesive layer 5 is formed on the edge of the skin layer 4 and solidified and bonded to form a bag. And it processes by supplying the raw | natural water W to the inner surface side, permeate | transmitting the skin layer 4, and obtaining the treated water W1. The initial performance of this flat membrane is 80 mL / min with 25 ° C. RO treated water.

  The membrane evaluation method of this embodiment is performed by adding a predetermined amount of colloidal silica to raw water, introducing the raw water into a membrane separator, and measuring the filtration performance. Here, the colloidal silica added to the raw water is not particularly limited as long as it becomes an evaluation standard for the filtration performance of the membrane, and for example, Snowtex 20 (trade name, manufactured by Nissan Chemical Industries, Ltd.) or the like is used. be able to. The amount of colloidal silica added is preferably 5 to 20 mg / L, and is preferably added so that the total amount of colloidal silica in the raw water is 10 to 20 mg / L.

  In the membrane sheet 1 as described above, first, a coagulant (PAC) 60 mg / L and a sodium hypochlorite (12% concentration) 35 mg / L were added to suppress slime, followed by a coagulation precipitation treatment. Water was used as industrial water. The pH of this raw water was 6.2, and the colloidal silica concentration at 25 ° C. was 5 mg / L. The transition of flux from the start of operation of such raw water to 6 hours later was measured. The result is shown by a solid line in FIG.

  As can be seen from FIG. 2, in the flat membrane of this embodiment, the permeated water amount of about 35 mL / min is maintained substantially at a water temperature of 25 ° C. with a colloidal silica concentration of 5 mg / L. Conventionally, based on the flux at such a high water temperature, the membrane separator was designed with the flux of the flat membrane set to 35 mL / min. However, in such a design, when the water temperature is lowered in winter, the flux is lowered, which causes a disadvantage that performance as designed cannot be exhibited. Therefore, in the present invention, the decrease in flux accompanying the decrease in water temperature is due to the increase in the concentration of colloidal silica due to the decrease in solubility, and this was used to cope with the decrease in flux associated with the decrease in water temperature. The membrane separator was evaluated.

  That is, by using 15 mg / L of colloidal silica (trade name: Snowtex 20, manufactured by Nissan Chemical Industries, Ltd.), which is an evaluation standard for filtration performance, with respect to raw water, the total colloidal silica is 20 mg / L. The change in flux from the start of operation to 6 hours after the start was measured under the same conditions. The results are shown by broken lines in FIG. From this result, it is understood that when the colloidal silica concentration is 20 mg / L, the flux (permeated water amount) gradually decreases from about 35 mL / min to about 15 mL / min. Therefore, in this embodiment, by setting the performance of the membrane separation device by evaluating the flux of this flat membrane as 15 mL / min, even if the water temperature is lowered and the flux is lowered, the membrane separation device is set. It becomes possible to drive based on the performance.

  However, since the amount of the colloidal silica added is too much, it is not practical to evaluate the membrane separation apparatus as an excessively low flux, so it corresponds to the content of the colloidal silica in the raw water at a low temperature. Therefore, it is preferable to add 5 to 20 mg / L. Specifically, the colloidal silica may be added so that the total amount of colloidal silica in the raw water is 10 to 20 mg / L, and the membrane in the membrane separation apparatus may be evaluated.

  Although the present invention has been described based on the above embodiment, the present invention is not limited to a flat membrane, and can be applied to a membrane separation apparatus using various membranes such as an ultrafiltration membrane, a microfiltration membrane, and a reverse osmosis membrane. is there.

  According to the membrane evaluation method in the membrane separation apparatus of the present invention, since the membrane separation apparatus is designed with performance corresponding to the decrease in flux due to temperature fluctuations, the membrane separation apparatus always exhibits a function exceeding the design value. Can continue.

It is the schematic which shows a structure of the flat membrane which can apply the membrane evaluation method in the membrane separator of this invention. It is a graph which shows the relationship between a colloidal silica density | concentration and permeation | transmission amount.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Membrane sheet 2 ... Permeable support layer 3 ... Nonwoven fabric layer 4 ... Skin layer 5 ... Adhesive layer 6 ... Spacer (channel material)

Claims (3)

  A membrane evaluation method in a membrane separator that separates suspensions and dissolved substances in raw water using a separation membrane, and the filtration performance is measured using raw water added with colloidal silica, and the separation membrane used based on the measurement results A membrane evaluation method in a membrane separator characterized by the above.   The membrane evaluation method for a membrane separator according to claim 1, wherein 5 to 20 mg / L of the colloidal silica is added. The membrane evaluation method for a membrane separator according to claim 1, wherein the colloidal silica is added so that the total amount of colloidal silica in the raw water is 10 to 20 mg / L.

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