JP2007181772A - Filtering treatment method for waste cleaning water of plant including vegetable and/or fruit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a filtering treatment method in which waste cleaning water of plants including vegetables and/or fruits is subjected to filtering treatment to reutilize the same as a cleaning water. <P>SOLUTION: In the filtering treatment method, the waste cleaning water of plants including vegetables and/or fruits is filtered with an ultrafiltration membrane in which at least the part in contact with the waste cleaning water is formed of a hydrophilic material. As the ultrafiltration membrane, an internal pressure type hollow fiber membrane made of cellulose acetate is preferably used. The treated water after the filtering treatment can be recycled as cleaning water for plants including vegetables and/or fruits. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a filtration method for filtering washing wastewater of a plant containing vegetables and / or fruits so that it can be reused as washing water, and vegetables and / or fruits using the treated water by the filtration method. It is related with the washing | cleaning method of the containing plant.

  Conventionally, a large amount of clean water is required for washing vegetables and fruits, and tap water is generally used. The washed waste water after washing is drained as it is, or a large foreign matter is removed with a rough mesh or the like, and a part is reused.

  In recent years, so-called cut vegetables that have been cut into sizes that are easy to eat vegetables and fruits, and salads and mixed fruits that are mixed with several types of cut products have been sold at convenience stores and supermarkets.

  Since such cut vegetables and fruits need to be sterilized and washed sufficiently, they require a large amount of washing water. In addition, vegetable juice and fruit juice are transferred to cleaning and sterilizing liquids (tap water mixed with sodium hypochlorite) from fine cuts and cuts of cut vegetables and fruits. .

  It is conceivable to use a separation membrane frequently used as a wastewater treatment means for the treatment of washing wastewater such as vegetables. The turbid component can be removed with a microfiltration membrane, but the organic matter can hardly be removed. Therefore, a reverse osmosis membrane treatment is required. The ultrafiltration membrane can be removed if it is a high molecular weight organic substance, but depending on the nature of the foreign matter in the waste water, it may not be removed.

  For this reason, a technique that combines separation by a membrane, agglomeration, activated carbon treatment, and the like has been studied. Patent Document 1 discloses a technique in which washing water for agricultural products such as vegetables and fruits is filtered through a microfiltration membrane and reused.

In the present invention, coagulation and activated carbon treatment are used in combination for removing organic substances. However, the use of technologies other than membranes increases the processing cost, which is not an economical method. Further, back pressure cleaning is performed at a high pressure to maintain the performance of the membrane, and the membrane may be damaged. When the membrane is broken, leakage occurs from the portion and deteriorates the quality of the treated water. Therefore, there is a sanitary problem especially when the membrane is reused for food-related washing water.
Japanese Patent Laid-Open No. 11-055081

  This invention makes it a subject to provide the filtration processing method which makes it possible to recycle the treated water which processed the washing waste_water | drain of the plant containing vegetables and / or fruits.

  Moreover, this invention makes it another subject to provide the washing | cleaning method of the plant containing the vegetable and / or fruit which reuses the treated water by the said filtration method as a solution means of another subject.

  As a means for solving the problems, the present invention provides a filtration treatment method for filtering washing wastewater of plants containing vegetables and / or fruits with an ultrafiltration membrane in which at least a portion in contact with the washing wastewater is formed of a hydrophilic material. I will provide a.

  As a means for solving other problems, the present invention circulates and uses treated water obtained by the filtration method according to any one of claims 1 to 3 as washing water for plants containing vegetables and / or fruits. And / or a method for cleaning a plant containing fruit.

  The treated water obtained by treating with the filtration method of the present invention can be recycled as washing water for plants containing vegetables and / or fruits, so that water resources can be saved and washing is required. Cost can also be reduced.

  The treatment target of the filtration method of the present invention is washing wastewater generated when washing various vegetables, various fruits, flowers, other plants, and processed products thereof (cut or crushed).

  In the filtration method of the present invention, before the filtration treatment with an ultrafiltration membrane, if necessary, a pretreatment for removing large foreign matters such as leaf and stem fragments, sand and pebbles is performed using a strainer or the like. Also good.

  If necessary, the pre-treated washing wastewater is stored directly in the washing line or once stored in the raw water tank, and then the pressure pump is operated, and from the washing line or the raw water tank through the pipe, It is sent to an ultrafiltration membrane module housed in a module case and filtered.

  Since the ultrafiltration membrane used in the present invention is formed of a hydrophilic material at least in contact with the cleaning wastewater, the portion not in contact with the cleaning wastewater may be a hydrophobic material. Is preferably made of a hydrophilic material.

  Examples of the hydrophilic material include cellulose materials such as cellulose acetate, cellulose propionate, cellulose butyrate, regenerated cellulose, and a mixture thereof. Moreover, polyvinyl alcohol etc. can also be used.

  Examples of hydrophobic materials that can be combined with hydrophilic materials include polysulfone resins, polyether sulfone resins, polyvinylidene fluoride resins, polyacrylonitrile resins, polyimide resins, polyaramid resins, polypropylene resins, and polyethylene resins. Can do.

  The ultrafiltration membrane used in the present invention is preferably a hollow fiber membrane made entirely of cellulose acetate, and particularly preferably an internal pressure type hollow fiber membrane.

  When a hollow fiber membrane is used as the ultrafiltration membrane, for example, an inner diameter of 0.3 to 3.0 mm (preferably 0.5 to 1.0 mm), an outer diameter of 0.4 to 5.0 mm (preferably 0.7). And a molecular weight cutoff of 3,000 or more (preferably 100,000 or more) can be used.

  The hollow fiber membrane can be used as one bundle or two or more bundles of hollow fiber membranes in which a necessary number is bundled according to the amount of treated water and the concentration of turbid components in the treated water.

  The filtration operation conditions (water permeability rate, etc.) can be appropriately set according to the amount of treated water and the concentration of turbid components in the treated water. For example, the water permeability rate is 0.5 to 5.0 m / day, 10 A method of repeating this by setting the operation of carrying out the filtration operation for ˜1500 minutes and then performing the reverse pressure washing for 0.5 to 5 minutes as one cycle can be applied. You may add chemical | medical solutions, such as a well-known sodium hypochlorite, to backwashing water. Further, instead of back pressure cleaning, only filtration during operation may be stopped, and flush cleaning in which only the raw water side is passed may be performed, or flash cleaning and back pressure cleaning may be combined.

  The filtration treatment method of the present invention can be combined with any of the known flocculant treatment, microfiltration, and activated carbon treatment as necessary, but the filtration treatment method of the present invention can be combined with each of the above treatments. The treated water obtained by treating with can be circulated as it is as washing water for plants containing vegetables and / or fruits. In addition, when reusing the said treated water as washing water, you may add disinfectants, such as sodium hypochlorite, if necessary, and you may mix with tap water.

(Pure water permeability)
The produced module was subjected to dead-end filtration of pure water at an internal pressure under a pressure of 98 kPa, and the amount of pure water permeating per unit time and unit membrane area (internal surface area conversion) was measured. Furthermore, the water temperature of the filtrate was measured, and based on the viscosity of water at a water temperature of 25 ° C., the ratio of the viscosity of the measured water temperature was applied to the amount of pure water to obtain the pure water permeability.

Example 1
A bundle of 20 cellulose acetate hollow fiber membranes (FUC1582; inner diameter 0.8mm, outer diameter 1.3mm, molecular weight cut off 150,000 Dalton), stored in a module case with an inner diameter of 20mm and a length of 30cm, both ends with urethane adhesive A sealed module was produced. The membrane area of this module was 0.0132 m ² . It was 601 L / m ² · hr (25 ° C., converted to 98 kPa) when the pure water permeation ability of this module was measured by internal pressure total amount filtration.

Tap water with 1000ppm of vegetable juice (product name; one vegetable per day, manufactured by Kagome Co., Ltd.), which assumes vegetable juice in this module, is partially filtered (80% filtrate, concentrated solution) at an internal pressure of 50kPa or less. 20%). The filtrate and concentrate were discharged out of the system. When the filtration amount per membrane area reached 100 L / m ² , the filtration was stopped, and after replacing with tap water, the pure water permeation ability of the module was measured in the same manner as before the filtration of vegetable juice. m ² · hr.

This was 70% of the initial pure water permeation capacity. Furthermore, when tap water was used and backwashing was performed at a pressure of 50 kPa, the pure water permeation ability recovered to 547 L / m ² · hr. This was 91% of the initial pure water permeation capacity.

Comparative Example 1
Except that the membrane was changed to polyethersulfone (FUS1582; inner diameter 0.8 mm, outer diameter 1.3 mm, molecular weight cut off 150,000 dalton), the module was produced in exactly the same way, and the same filtration treatment was performed. went. As a result, it decreased to 34% immediately after filtration with respect to the initial pure water permeation ability, and recovered to only 38% after back pressure washing.

Example 2
50 liters of cut lettuce was added to 2 liters of the filtrate obtained in Example 1 and stirred for 20 minutes to bring the filtrate and cut lettuce into contact. Thereafter, the number of lettuce bacteria immediately after cutting off the filtrate and the number of lettuce bacteria after storage in a refrigerator for 72 hours were evaluated by the number of general bacteria and the number of coliforms. The number of general bacteria was cultured by the standard agar plate culture method, and the number of coliforms was cultured by the desoxycholate agar plate culture method.

As a result, the number of bacteria per lettuce was 6.2 × 10 ⁵ immediately after storage, and 1.6 × 10 ⁷ after storage for 72 hours. The number of coliforms was 1.5 × 10 ³ immediately after and 1.7 × 10 ⁵ after storage for 72 hours.

Comparative Example 2
Evaluation was performed in the same manner except that tap water was used instead of the filtrate obtained in Example 1. As a result, the number of bacteria per lettuce was 7.8 × 10 ⁵ immediately after general bacteria and 1.9 × 10 ⁷ after storage for 72 hours. The number of coliforms was 2.2 × 10 ³ immediately after and 1.9 × 10 ⁵ after 72 hours storage.

Claims (4)

  A filtration treatment method of filtering washing wastewater of a plant containing vegetables and / or fruits with an ultrafiltration membrane in which at least a portion in contact with the washing wastewater is formed of a hydrophilic material.   The filtration method according to claim 1, wherein the hydrophilic material contained in the ultrafiltration membrane is a cellulosic material.   The filtration method according to claim 1 or 2, wherein the ultrafiltration membrane uses an internal pressure type hollow fiber membrane made of cellulose acetate. A method for washing a plant containing vegetables and / or fruits, wherein the treated water obtained by the filtration method according to any one of claims 1 to 3 is circulated and used as washing water for plants containing vegetables and / or fruits.