JPH1043796A - Water cleaning device and its method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce good source water for city water so that even when trichloroethylene or the like is mixed in the water, trichloroethylene can be decomposed, by using a fiber contact material as a filter bed in a first stage to remove lots of algae and then removing the residual algae and org. matter by irradiation of UV rays and using a biological filter in a second stage. SOLUTION: The cleaning device is composed of almost two stages. A treating tank 3 filled with a fiber contact material 2 is disposed in the first stage. The source water 1 is made to flow into the treating tank 3 filled with the fiber contact material 2 such as a thread-type filter and slowly passed through the fiber. In this process, algae and org. matter are trapped around the fiber and the water is cleaned. Then the water is introduced into the second stage of the bed, where the water is treated in a UV irradiation device 4 and in a biological filter 5. In this process, the water is first irradiated with UV rays and then introduced into the biological filter 5. In the biological filter bed 5, the org. matter is decomposed and as a result, productivity for trihalomethane in the water can be decreased. The obtd. treated water 6 is used as the source water for city water, which is supplied after filtering and adding chlorine.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an apparatus and a method for purifying polluted water from rivers, ponds, lakes and moats, and to reducing a power required to remove algae, suspended solids, soluble organic substances and the like in water. On pre-treatment of tap water and purification for tap water. Further, the present invention relates to a technique for preserving water environment.

[0002]

BACKGROUND OF THE INVENTION The main pollutants of river, pond, lake and moat water are algae, zooplankton, bacteria and organic matter. When purifying and treating these waters, if the pollution is severe, it will be difficult to use tap water as raw water or middle tap water. When raw tap water is polluted, tap water contains a large amount of harmful substances and odorous substances such as trihalomethane. Therefore, an activated carbon treatment or an ozone treatment is performed as a pretreatment. However, each of these methods is costly and has a limit in reducing trihalomethane.

[0003] More recently, purification with potassium permanganate or aqueous hydrogen peroxide has been studied, but there are many points to be solved in the future, such as cost and safety, and it has not been put to practical use.

[0004] Purification methods using biological filters have also been studied. This method is used for wastewater treatment and is safe because it decomposes organic matter biologically and does not use chemicals.
However, the treatment of algae, which is a major contaminant in ponds and lakes, with ordinary biological filters is not efficient and is not an excellent method.

[0005] As a method for solving the problems of the biological filter bed, a method using a fiber contact material as a filter material has been proposed. According to this method, when water is flowed at a flow rate of 20 mm / sec or less through the fiber contact material, 50 to 80% of the algae can be aggregated on the fiber surface. If a sufficient treatment time is taken, the aggregated algae are gradually decomposed and purified. However, in order to increase the algae removal rate, it is necessary to lengthen the treatment time, and there is a disadvantage that the treatment facility becomes large.

An ultraviolet irradiation method is a method for more reliably stopping the growth of algae. This method utilizes the property of ultraviolet rays to change the chemical bonds of organic substances, and it is also known that biodegradable organic substances can be converted to organic substances that can be easily decomposed by living organisms. Although it has been used, it has recently been used to purify ornamental ponds because it can be killed with ultraviolet light. The disadvantage is high running costs.

[0007]

In the biological filter method, algae can be removed by using a fiber contact material as a filter, but the algae removal rate is increased, the treatment time is shortened, and the cost is reduced. It is desired.

[0008] Further, the water contains organic substances that are hardly decomposable. When these components are present, the trihalomethane-producing ability is high, and there is a problem in using them as tap water.

If the treatment is carried out using chemicals, it is not impossible to decompose organic substances which are hardly decomposable, but much attention must be paid to safety. In addition, there is a problem in cost.

[0010]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems by using a plurality of methods.
In the first stage, the fiber contact material is used as a filter bed to remove most of the algae, and in the second stage, by UV irradiation and biological filter,
It removes residual algae and organic matter.

That is, in the first stage, algae are aggregated on the surface of the fiber, and the algae are peeled off by aeration or vibration to remove the algae, thereby removing most of the algae in the raw water. It is necessary that the falling flow rate be as slow as 20 mm / sec or less, and the length of the filter bed needs to be at least about 1 m. Therefore, the processing time needs to be at least about 10 minutes. If the treatment is performed for a sufficient time, the aggregated algae are gradually decomposed into bacteria. However, since the treatment is performed in the latter stage, the treatment does not need to be performed as long as in the case of the wastewater treatment.

In the latter stage, the remaining algae are killed by performing ultraviolet treatment first, and the biodegradable organic matter is easily biodegraded. Algae killed algae are easily broken down by bacteria. The required amount of UV irradiation varies depending on the type of algae.
00 mW · sec / cm ² .

The water irradiated with ultraviolet rays is treated by a biological filter. This is similar to biological treatment of sewage treatment, but B
Since the OD is about 1/10 to 1/100 of the sewage and is hardly blocked by excess sludge, a fixed bed method is used. That is, a natural flow immersion biological filter bed or a water circulation type immersion biological filter bed in a tank is used. The former has a filter floor attached to the long waterway, through which water flows. In the latter, a filter bed is placed in a water tank, and water is flowed by air, a water pump or a stirrer.
Either method may be used, but the flow rate of water in the filter bed is set to 10 cm / sec or less because the BOD is low. When the air volume is sent, since the BOD is low, the air volume should be 1/3 or less of that of similar facilities for sewage treatment. The treatment time is shorter than that of the wastewater treatment, and is set to 30 minutes to 7 hours.

The arrangement in the latter stage may be a method in which not only the biological filter treatment is performed after the ultraviolet treatment, but also the two treatments are repeated. Also in this case, the treatment time of the biological filter is 30 minutes to 7 hours in total of the repeated treatment.

According to the present invention, the same action as filtration is performed by aggregating and removing most of the algae on the fiber by a tank using a low-power fiber contact material in the first stage. Next, in the latter stage, the remaining algae are killed by ultraviolet rays, and the biodegradable organic matter is converted to biodegradable, and then decomposed by bacteria through a biofilter.

The first-stage fiber contact material treatment and the second-stage biological filter bed treatment have very low running costs, and the second-stage ultraviolet treatment surely modifies algae and organic matter. Safe and high quality water treatment can be performed.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment according to the present invention will be described with reference to the accompanying drawings of FIG. As shown in FIG. 1, the purification device is roughly divided into two stages. First, at the first stage, a treatment tank 3 filled with the fiber contact material 2 is arranged. Raw water 1 is allowed to flow into a treatment tank 3 provided with a fiber contact material 2 such as a string filter medium,
Gently pass between the fibers. Algae and organic matter gather around the fibers and the water is purified. When the fiber contact material becomes clogged, it is peeled off by a method such as aeration from a lower part, a jet, or vibration of the contact material, and the excess sludge is removed by drainage or sedimentation.

Next, water is guided to the latter stage of the filter bed, and treated with the ultraviolet irradiation device 4 and the biological filter bed 5. First, after ultraviolet irradiation, the treated water is led to the biological filter 5. Organic substances are decomposed in the biological filter 5 and, as a result, trihalomethane production ability is also reduced.

The finally obtained treated water 6 becomes raw water of tap water, and after undergoing a PAC-rapid filtration treatment or a slow filtration treatment, chlorine is injected and supplied. In the case of middle water supply, the subsequent treatment varies depending on the required water quality. In the case of pond water or water sprinkling, the treated water 6 is used as it is.

[0020]

EXPERIMENTAL EXAMPLE 1 Water containing algae was placed in a shallow container having a thickness of 2 cm, and irradiated with ultraviolet rays. Thereafter, the photosynthetic amount was measured using a manometer-type BOD measuring device. From this experiment, the irradiation amount at which the photosynthetic rate becomes の of that of the unirradiated sample was defined as the half-lethal irradiation amount.

Table 1 shows the ultraviolet irradiation dose at which half of the algae are killed.

[Table 1] According to Table 1, the irradiation amount of half-lethal ultraviolet rays differs greatly depending on the algae. Therefore, it is necessary to change the irradiation amount depending on the type of algae. To perform 100% algicidal treatment, several times to 10 times the irradiation of Table 1 is required. It was also confirmed that the irradiation amount could be reduced when the algal concentration was low.

[0022]

[Experimental example 2] Using a UV lamp, 240 mW · s / c of pond water of a 44 m ³ ornamental pond where carps are fed daily.
Treated at m ³ / day. Treatment was performed at 5 m ³ / hour, and a circulating treatment was performed in which treated water was returned to the pond. The results are shown in FIGS.
Shown in The suspended solids SS and dissolved oxygen DO in the pond water gradually decreased. On the fifth day, the pond water showed abnormal bacterial growth, and the aeration was started because the DO became 1 mg / l or less.

From the above, it can be seen that algae are rapidly killed by ultraviolet light and decomposed by BOD bacteria.

[0024]

EXAMPLE After the same ultraviolet irradiation as in Example 2 was performed,
Further treatment was carried out by a biological filter using a 4 m ³ corrugated plate. The filter bed residence time is 48 minutes. FIG. 4 shows the results. In the experiment, SS was 1 mg / or less, and there was no abnormal growth of algae and bacteria.

From the above experimental examples, it has been found that algae are converted into easily decomposable organic substances by irradiation with ultraviolet rays, and that they are easily decomposed by placing a biological filter after irradiation with ultraviolet rays.

As is clear from the above description, it can be seen that good water can be obtained by treating the water from which most of the algae have been removed by the fiber contact material in the first stage with ultraviolet irradiation and biological filtration. Although the present invention can be used as it is for purification of pond water, it can be used not only as a middle water system for treating water such as lakes and rivers polluted by algae, but also effective as a pretreatment for waterworks. Since the ultraviolet irradiation is performed, even when trichlorethylene, tetrachloroethylene, or the like is mixed in the raw water, it can be decomposed and made into good tap water.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a processing method of the present invention.

FIG. 2 is a diagram showing measurement results of Experimental Example 2.

FIG. 3 is a view showing measurement results of Experimental Example 2.

FIG. 4 is a diagram showing measurement results of Experimental Example 3.

[Description of sign]

1 ... raw water, 2 ... fiber contact material, 3 ... treatment tank filled with fiber contact material, 4 ... ultraviolet irradiation device, 5 ...
・ Biological filter bed, 6 ... treated water.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical indication location C02F 1/32 C02F 1/32 3/06 ZAB 3/06 ZAB

Claims (3)

[Claims] 1. A water purification apparatus in which a treatment tank 3 filled with a fiber contact material 2 is arranged in a front stage, and an ultraviolet irradiation device 4 and a biological filter bed 5 are arranged in a rear stage. 2. The biological filter bed 5 is a natural flow immersion biological filter bed or a water circulation type immersion biological filter bed in a tank. A water purification method for obtaining purified water 6 by performing the method. 3. The water treatment conditions are as follows: the treatment time in the first stage apparatus is 10 minutes or more and 4 hours or less, the amount of water irradiation by an ultraviolet irradiation device is 3 to 2000 mW · sec / cm ² , and the biological filter 5 3. The method for removing algae according to claim 2, wherein the treatment time is 30 minutes or more and 7 hours or less.