JPH0788482A - Arsenic removal method by upward flow, continuously floating bed filtration in water purifying treatment - Google Patents

Abstract

PURPOSE:To lessen the installation surface area and suppress the arsenic concentration to wastewater standard or lower by filtering water in a prior stage by an upward flow, continuously floating bed way filtering method by which arsenic concentration can be adjusted and further carrying out final treatment of water filtration in a post stage by a quick filtration or a slow filtration apparatus. CONSTITUTION:Raw water, e.g. underground water, etc., is sent to an upward flow, continuously floating bed-way filtration apparatus 2 by a raw water pump 1. At that time, an oxidizing agent and a flocculant are poured to the apparatus from an oxidizing agent tank 3 and a flocculant tank 4, respectively, and they are mixed with the raw water by a pipe mixer 7. In the filtration apparatus 2, while being drawn out, a part of a filter medium is cleaned by carrying out air lift by a driving water pump 8 and a compressor 9 simultaneously with filtration. The treated water which comes out of the filtration apparatus 2 is stored temporarily in a pump pit 10 and then supplied to a finishing filtration apparatus 12 and finally treated by a quick filtration method or a slow filtration method. The arsenic concentration of the objective raw water to be treated is set to be 0.1mg/l or lower and the cleaned water discharge ratio to the raw water is set to be 5-20%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION This invention relates to arsenic and raw water containing the water quality of the standard items specified by the Water Supply Act that can be treated by the same removal method as arsenic, that is, a coprecipitation method with the addition of a coagulant (hereinafter referred to as coprecipitation method). It relates to water purification treatment as a water source.

[0002]

2. Description of the Related Art As a method of treating water containing arsenic, there are a coprecipitation method, an ion exchange resin method, a reverse osmosis membrane method, and the like. Except for the coprecipitation method, there are some examples of wastewater treatment. In terms of economical efficiency and maintenance, there are almost no examples of water purification treatment. Further, as for the coprecipitation method, conventionally, coagulation-precipitation treatment is generally performed.

[0003]

[Problems to be Solved by the Invention] In the coagulation-sedimentation method as a coprecipitation method, in the case of water having low turbidity such as groundwater, in addition to the amount of the coagulant necessary for coprecipitation, the coagulation flocs have a settling property. Because it is bad, a large amount of coagulant must be injected.

Arsenic is concentrated in the settled sludge produced by the coagulation settling process. Arsenic is designated as a hazardous substance in the Water Sludge Prevention Law, and it must be treated by a method different from normal purified water sludge treatment in order to meet the wastewater standards. The coagulation-sedimentation process requires a large installation area. In addition to coagulation sedimentation treatment, coagulation sedimentation treatment can be considered as a coprecipitation method. However, in the normal downflow filtration treatment alone, the filtration continuation time is shortened (increased cleaning frequency) due to an increase in turbidity accompanying the addition of a coagulant. ), The concentration of the filter media cleaning wastewater cannot be controlled, and the concentration of the cleaning wastewater varies with time during discharge, so wastewater treatment must be considered in order to meet the emission standards.

[0005]

In order to solve the above-mentioned problems, the present invention uses an upward flow continuous moving bed type filtration device. Further, as a finishing treatment, a rapid filtration device or a slow filtration device is provided in the latter stage to perform two stages of filtration. With this method, the following improvements were achieved. That is, the installation area is reduced as compared with the coagulation sedimentation method. Since the filter medium is continuously washed, the washing drainage is continuously discharged and the arsenic concentration is constant. The arsenic concentration in the wash drainage is controlled by adjusting the wash drainage ratio. As a finishing treatment, the load of down-flow filtration provided in the latter stage is reduced, and the concentration of waste water from filtration and washing is reduced. From the above, adjust the wastewater concentration below the wastewater standard without performing wastewater treatment.

[0006]

[Operation] Fig. 1 shows the relationship between the upflow continuous moving bed filter washing water discharge ratio and the arsenic concentration in the wastewater in a verification experiment conducted using arsenic-containing tap water (spring water). .
A correlation was observed between the wash drainage ratio and the arsenic concentration in the drainage, and it was confirmed that the arsenic concentration in the wash drain can be adjusted by adjusting the wash drainage ratio.

Example (1) (Arsenic Removal) FIG. 2 is a specific example of the present invention. Raw water is sent by a raw water pump 1 to an upward flow continuous moving bed type filtration device 2. In the meantime, from the oxidant (eg, sodium hypochlorite) tank 3 and the coagulant (PAC or iron salt) tank 4, the oxidant injection pump 5 and the coagulant injection pump 6 are used to oxidize the oxidizer in the pipeline. And coagulant injection,
Further, mixing is performed by the pipe mixer 7. In the upward flow continuous movement type filtration device 2, an operation of returning a part of the filter medium to the filter layer at the same time as the filtration is performed while extracting a part of the filter medium by an air-lift using the driving water pump 8 and the compressor 9 as an air source. It is performed continuously. For this reason,
Cleaning wastewater is also discharged continuously at a constant concentration. The amount of cleaning waste water is adjusted to a predetermined flow rate by the flow rate adjusting device in the device. The treated water of the upward flow continuous moving bed type filtration device 2 is temporarily stored in the pump pit 10 and then transferred by the pump 11 when the finishing filtration device 12 of the latter stage is a pressure type as in this example. In the case of an open type filter, it is transferred by gravity flow. The treated water is separately transferred as purified water to a water purification facility. Silica sand was used as the filter medium.

Example (2) (removing arsenic, iron and manganese) The device configuration is the same as in Example (1). However, as a filter medium,
Both filters used manganese sand.

Example (3) (arsenic and iron, manganese, removal of organic chromaticity) The device configuration is the same as in Example (1). However, as a filter medium,
Both filter devices used a filter material for removing organic chromaticity.

Table 1 shows the respective water qualities of raw water, purified water, and cleaning waste water when arsenic was removed using the apparatus shown in FIG. Fig. 3 shows the change over time in the concentration of arsenic in the cleaning wastewater of the rapid filtration equipment as a finishing treatment by the latter-stage filtration equipment.
(Example (1)).

[0011]

[Table 1]

From Table 1 and FIG. 3, treated water was obtained that sufficiently satisfied the new water quality standard, and the cleaning and drainage of both filtration devices had water quality far below the drainage standard. From this, it was confirmed that good clean water and washable waste water that could be discharged were obtained without providing waste water treatment equipment, and that this is an excellent treatment method for arsenic removal. Table 2 shows the respective water qualities of raw water, purified water, and washing drainage when the apparatus shown in FIG. 2 was used to operate for the purpose of removing arsenic, iron, and manganese (Example (2)).

[0013]

[Table 1]

As can be seen from Table 2, treated water was obtained which fully satisfied the new water quality standards. From this, it was confirmed that the present invention is an excellent treatment method not only for removing arsenic but also for removing iron and manganese.

Using the device shown in FIG. 3, arsenic and
Table 3 shows the respective water qualities of raw water, purified water, and washing wastewater when the operation was performed for the purpose of removing iron, manganese, and organic chromaticity (Example (3)).

[0016]

[Table 3]

As can be seen from Table 3, treated water sufficiently satisfying the new water quality standard was obtained. From this, it was confirmed that the present invention is a processing method excellent not only in removing arsenic, iron and manganese but also in removing chromaticity.

[0018]

The following effects can be obtained by carrying out the method of the present invention described above. That is, the installation area can be reduced as compared with the coagulation sedimentation method. Since the filter medium is continuously washed, the washing drainage is continuously discharged and the arsenic concentration can be kept constant. The arsenic concentration in the cleaning drainage can be controlled by adjusting the cleaning drainage ratio. Since the load of the downward flow filtration provided in the latter stage as the finishing treatment is reduced, the concentration of the filtered and washed waste water can be lowered. From the above, the wastewater concentration can be adjusted to below the wastewater standard without performing wastewater treatment.

[Brief description of drawings]

[Fig. 1] Upflow continuous moving bed filtration device washing drainage ratio,
It is a graph which shows the relationship with the arsenic concentration in wastewater.

FIG. 2 is a flow chart of an example of an apparatus for carrying out the method of the present invention.

FIG. 3 is a graph showing changes over time in the concentration of arsenic in the cleaning wastewater of a rapid filtration device.

[Table 2]

Claims (6)

[Claims] 1. A method for removing arsenic and the like in the purification treatment of raw water having surface water, groundwater, spring water, underground water, lake water, etc. containing arsenic etc. A front-stage up-flow continuous moving bed filtration method that can handle turbidity water, continuously discharges wash wastewater, and can control the amount of wastewater to adjust the concentration of arsenic, etc. in the wash wastewater. And, as a finishing treatment, not only good water purification by the latter stage filtration equipment that uses the rapid filtration method or slow filtration method, but also the wastewater from both filtration equipment is mixed so that the drainage standard without wastewater treatment is performed. A method for removing arsenic and the like by an upflow continuous moving bed filtration method in water purification treatment, characterized in that 2. The raw water arsenic concentration to be treated is 0.1.
mg / l or less, and the ratio of cleaning wastewater to raw water is 5 to
In the range of 20%, one or two kinds of filter media for removing organic chromaticity including silica sand and activated carbon are used as the filter media of the filtering device, depending on the removal target other than arsenic. The method of claim 1, wherein 3. The method according to claim 1, wherein when the object to be removed is arsenic, silica sand is used in both the front and rear filtration devices. 4. When the object to be removed is arsenic, iron or manganese,
The method according to claim 1, characterized in that silica sand or manganese sand is used for the first stage filtration device and manganese sand is used for the second stage filtration device. 5. When the object to be removed is arsenic, iron, manganese, or organic chromaticity, silica sand or a filter material for removing organic chromaticity is used in the former filter, and organic color is used in the latter filter. The method according to claim 1, characterized in that a filter medium for removing the degree is used. 6. The method according to claim 1 for the water quality items that can be treated by the coprecipitation method with a coagulant among the water quality items specified in the Water Quality Standards of the Water Supply Act and the discharge standards of the Water Pollution Control Act at the same time as arsenic. Removal method.