JPS5940488B2 - Filter media and filtration methods for water treatment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a water treatment filter medium having excellent filtration performance and a filtration method using the same.

Generally, wastewater treatment of organic matter-containing wastewater such as sewage is carried out using BOD
In order to remove organic substances, nitrogen compounds, etc., which are the target of the Suspended substances such as finer biological fragments
Solid id1 and below are abbreviated as ss.

) is removed by filtration to purify the SS concentration to about 5 to 3000 pI)m.

In addition, if you want to reduce the SS concentration to 1 ppI or less in order to reuse the treated water for various purposes, add a flocculant to the sand filtration layer to flocculate fine SS to make them larger particles before applying them to sand filtration. The following methods have been adopted.

The mechanism of sand filtration in water treatment as described above is similar to the method of scooping up SS floating in water with a sieve and removing it.

That is, the system traps SS in the gaps in the sand layer and allows only water to pass through.

In sand filtration, the grain size of sand corresponds to sieve size, and in order to capture more SS in the treated water, it is necessary to use finer sand.

However, as the sand becomes finer, the trapping performance of SS increases, but it not only increases the filtration resistance and decreases the filtration rate, but also causes the filtration layer to become clogged with SS because the pore size of the filtration layer becomes narrower. The major drawback is that the filtration time (filtration cycle) until cleaning is shortened.

Conventionally, in order to improve the above drawbacks, coarse sand and fine sand were used together, and the coarse sand was placed on the water inlet side.
A method is adopted in which large SS is first captured on the water inlet side, and the SS retention space in the filtration layer is utilized as effectively as possible.

However, in this filtration method, the above-mentioned drawbacks are still not sufficiently improved, and in order to automatically restore the original arrangement after the cleaning operation, it is necessary to mix sands with significantly different specific gravity. Another drawback is that the filter media is expensive.

In view of the above-mentioned current situation, the present inventor has realized that the SS capture performance is high,
As a result of intensive research to develop a filter medium for water treatment that has a long filtration cycle, low filtration resistance, and is inexpensive, it was discovered that the objective could be achieved by coating the filtration layer with a cationic polymer, and the present invention was developed. It was completed.

That is, the present invention provides a water treatment filter medium characterized in that a filtration layer is coated with a cationic polymer, and a water treatment filter medium in which a filter layer is coated with a cationic polymer. It relates to a filtration method characterized by filtration.

As the filtration layer in the present invention, any material that is normally used for this type of purpose can be used, such as river sand, sea sand,
Examples include silica sand.

Although the particle size is not particularly limited, it is suitably about 0.1 to 5 mm.

In addition, the cationic polymer used in the present invention is a polymer whose particle charge is cationic and a polymer having a cationic structure in the molecule, which adheres well to sand and is sparingly soluble in water (according to JIS K-6828). In the twice-dissolved portion test, it forms a film with a six-times dissolved portion of 5 or less.

Examples of such cationic polymers include the following.

In the following examples, (meth)acrylate refers to both acrylate and methacrylate.

The same is true for (meth)acrylic. (1)
Methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, etc. (meth)acrylic acid esters, (meth)acrylic acid amide and its methylolated products, styrenic monomers such as styrene, vinyltoluene and α-methylstyrene, fatty acid vinyl esters such as vinyl acetate and vinyl propionate, acrylonitrile , ethylene, vinyl chloride, vinylidene chloride, butadiene, isoprene, chloroprene, etc.
A polymer with a cationic structure introduced at the polymer end by polymerization using a cationic initiator such as 2-aminodipropane) hydrochloride.

(2) The vinyl monomer (5) has an amine group such as dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, t-butylaminoethyl (meth)acrylate, 2-aminoethyl vinyl ether, vinylpyridine, etc. A polymer obtained by copolymerizing at least one vinyl monomer having 1 mole φ or more.

(3) A polymer obtained by emulsion polymerization of the above vinyl monomer in an aqueous solution of a water-soluble cationic thermosetting resin (manufacturing method disclosed in Japanese Patent Publication No. 46-22922).

(4) A polymer obtained by emulsion polymerization of the vinyl monomer (5) in an aqueous cationic oligomer solution (manufacturing method disclosed in JP-A-54-21485).

(5) Thermosetting polymers such as cationic urea resins, cationic melamine resins, cationic polyurea polyamide cocondensation resins, and cationic epoxy resins.

Among the above cationic polymers, usually (1) and (2)
) as a solid, emulsion or solution in an organic solvent (
3) and (4) are used as emulsions, and (5) is used as an aqueous solution to coat sand.

The coating amount of the cationic polymer in the present invention is as follows:
It is selected from a wide range without particular limitation, and varies depending on the type of the polymer used, but it is usually about 0.005 to 10 parts by weight, preferably 0.01 to 5 parts by weight, based on 100 parts by weight of the filtration layer. Department.

If the amount is less than 0.005 parts by weight, the desired effect of the present invention cannot be obtained, and if it is used in excess of 10 parts by weight, no further effect can be expected and it is not economically preferable.

In the present invention, the method for coating sand with a cationic polymer may be appropriately selected from known methods depending on the properties of the polymer used.

Examples of coating treatment methods depending on the properties of the polymer are shown below.

When the polymer used is an emulsion or an aqueous solution of a thermosetting resin, the polymer is added to the sand and heated while stirring and mixing uniformly to evaporate the water and deposit the polymer on the surface of the sand grains. Forms a film.

The heating temperature depends on the curing temperature and moisture content of the polymer, but is usually about 100 to 180°C.

In addition, when the polymer used is solid, the sand is heated in advance to a temperature above the melting point of the polymer, and after the polymer is added thereto, a film of the polymer is formed on the surface of the sand grains while stirring and mixing uniformly. Form.

When the solid polymer is soluble in an organic solvent such as benzene, acetone, or hexane, the polymer dissolved in the organic solvent is added to the sand, and the organic solvent is evaporated off by heating while stirring and mixing uniformly. , a film of the polymer may be formed on the surface of the sand grains.

In the present invention, equipment for coating filter sand with a cationic polymer includes a ribbon blender equipped with a heating device, a planetary mixer, a Henschel type high-speed mixer, a solid air type fluidized dryer, and other devices capable of stirring, mixing and heating. Any device that has both functions can be used.

As a method of filtration using the thus obtained filter medium for water treatment of the present invention, both a downward flow method and an upward flow method can be adopted, but in the case of the former, the filtration resistance is greater than the latter; The latter method is particularly effective because clogging occurs quickly.

The rapid sand filtration performance by the upward flow method using the water treatment filter medium of the present invention will be explained with reference to the drawings.

FIG. 1 shows an example of a filtration tower used for filtration using the water treatment filter medium of the present invention.

In FIG. 1, water to be filtered (raw water) is introduced from one side of an inflow pipe 1, and is passed through a filter medium 6 for water treatment of the present invention supported by a wire mesh 4 fixed with a flange 2 and a packing 3 in an upward flow manner. Filter.

The filtered water (treated water) flows out from the overflow pipe 7.

Filtration is 1-3 kg LCR! 120~ under pressure
It is preferable to carry out at a speed of about 300 m/day.

During filtration, the filtration resistance is measured with a pressure gauge connected to the pressure gauge connection pipe 5, and when the filtration resistance reaches a certain value, the raw water is stopped and cleaning water is introduced from the other end of the inflow pipe 1. Wash at a pressure of about 1.5 to 5 kg/ffl for about 20 to 90 minutes.

The water treatment filter medium of the present invention is suitable for use in general sand filtration devices, such as slow and rapid crushing filtration devices for sewage treatment, industrial wastewater treatment, gray water systems, etc. Compared to this, the SS removal rate is higher.

At that time, as mentioned above, if the upward flow method is used, the SS
Not only does it have a high removal rate, but it also has remarkable effects such as low filtration resistance and a long filtration cycle.

Moreover, the water treatment filter medium of the present invention is inexpensive and can be satisfied in terms of cost.

The reason why the filter medium for water treatment of the present invention exhibits the excellent filtration performance as described above is that SS in wastewater is mainly negatively charged. to be electrostatically adsorbed to the filter media;
This is thought to be due to the fact that the adsorption occurs uniformly within the filtration layer.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

Example 1 900 parts by weight of water, 100 parts by weight of ethyl acrylate, 2,
Add 50 parts by weight of 2'-azobis(aminodibuO/'?n) hydrochloride, and while stirring at 70°C under a nitrogen atmosphere,
Emulsion polymerization was carried out for 4 hours to obtain a cationic emulsion polymer.

5 kg of filter sand with average particle size of 0.8 and ytw uniformity coefficient of 1.5
and 1 kg of sand with an average particle size of 2 mm as coarse sand are placed in a ribbon blender, and after mixing until uniform, add the cationic emulsion polymer obtained above while stirring to give a polymer component amount of 12 g. about 6k of filter sand coated with cationic polymer.
I got g.

This was designated as treated sand I.

Example 2 A commercially available cationic emulsion polymer (trade name: VONCOATSFC7) was added to the premixed sand in the same manner as in Example 1.
-50, manufactured by Dainippon Ink Chemical ■) was added by spraying in an amount to give a polymer component of 12 g, mixed until homogeneous, heated at 110°C for 30 minutes to remove water, and the cationic polymer Approximately 6 g of coated filter sand was obtained.

This was treated as treated sand ■. Example 3 A commercially available cationic urea resin aqueous solution (trade name Newlamin P-1500,
Mitsui Toatsu ■) was added in an amount to give a polymer component of 12 g, and while stirring and mixing, the mixture was heated at 140°C for 30 minutes to remove water, and about 6 kg of cationic polymer-coated filter sand was obtained. Ta.

This was treated as treated sand ■. Comparative Example 1 For comparison, 5 kg of filter sand with an average particle size of 0.8 mm and a uniformity coefficient of 1.5 and 1 kg of coarse grain sand with an average particle size of 2 mm were mixed uniformly using a ribbon blender and coated. Approximately 6 kg of unfiltered sand was obtained.

This was used as untreated sand.

Example 4 Treated sand 1. n, III and untreated sand in a filtration tower similar to that shown in Fig. 1 (height from wire mesh to overflow pipe: 900 mm, inner diameter: 2
00 mm) were filled to a filling height of 600 mm, and the secondary treated wastewater from a sewage treatment plant (SS concentration 9.0
ppm) was filtered at a filtration rate of 300 m/day using an upward flow method in which the flow flows from the bottom to the top.

Table 1 shows the filtration resistance at the start of filtration and 4 hours after the start of filtration.

In this experiment, cleaning was performed when the filtration resistance reached 2000 imAq.

Table 2 shows the time until washing, ie, the time of the filtration cycle.

Next, as secondary treated wastewater (raw water) from the sewage treatment plant,
Two types of sand with SS concentrations of 2.4 ppm and 9.0 ppm were used as treated sand 1, 1. III and untreated sand.

Table 3 shows the SS concentration and SS removal rate (a) of raw water and filtered water (treated water).

As is clear from Tables 1, 2, and 3, the water treatment filter medium of the present invention has excellent filtration performance such as high SS removal rate, low filtration resistance, and long filtration cycle. I understand.

Example 5 Treated sand ■ and untreated sand were filled into the filtration tower used in Example 4 to a filling height of 600 mm, and secondary treated wastewater (SS Concentration 20p
pm) was filtered at a filtration speed of 300 m/day.

Table 4 shows the filtration resistance at the start of filtration and 150 minutes after the start of filtration, and the SS concentration of the water after filtration.

As is clear from Table 4, when the water treatment filter medium of the present invention is used in the downward flow method, the SS removal rate is slightly higher than in the upward flow method, but the filtration resistance is higher than that of untreated sand. As a result, the filtration cycle is shorter than that of untreated sand.

On the other hand, when the upflow method is used, the SS removal rate is as high as the downflow method, and the filtration resistance is also considerably lower than that of untreated sand, resulting in a longer filtration cycle.

[Brief explanation of the drawing]

FIG. 1 shows an example of a filtration tower used in filtration using the water treatment filter medium of the present invention. Each symbol in the figure indicates the following. 1... Inflow pipe, 2... Flange, 3.
...Patzkin, 4...Wire mesh, 5...
... Pressure gauge connection pipe, 6 ... Filter medium for water treatment of the present invention, 7 ... Overflow pipe.

Claims (1)

[Scope of Claims] 1. A filter medium for water treatment, characterized in that a filtration layer is coated with a cationic polymer. 2. The water treatment filter medium according to claim 1, wherein the cationic polymer is coated in an amount of 0.005 to 10 parts by weight based on 100 parts by weight of the filtration layer. 3. A filtration method characterized by carrying out upward flow filtration using a water treatment filter material whose filtration layer is coated with a cationic polymer.