JPH0810777A - Bubbling device for waste water of backwashing of portable water forming device - Google Patents

Abstract

PURPOSE:To suppress backwashing water to alkaline concn. and to shorten the time for treating waste water of backwashing by bubbling a vent gas contg. carbon dioxide in the waste water of backwashing of a thickening tank of a device for forming raw water into potable water by supplying of the carbon dioxide into the raw water and treating in a limestone filter. CONSTITUTION:The raw water for the potable water is fed from a feed water line 6 and is partly sent to a carbon dioxide absorption column 1 where the carbon dioxide is absorbed in the raw water and thereafter, the water is again joined with the feed water line 6. Next, the raw water is sent to a limestone absorption filter column 20 and is passed through the limestone filter 2 by which the raw water is filtered. The supply of the raw water is stopped and the backwashing water is supplied by starting a backwashing pump 5 to backwash the filter 2 when the limestone filter 2 is clogged. At this time, a gas supply valve 8 is opened to supply the vent gas contg. some carbon dioxide into the thickening tank 3 through an acidic gas line 4 and to eject the carbon dioxide into the waste water of backwashing, by which the waste water of backwashing is neutralized to pH <=7.9 with the carbon dioxide and the suspended solids are rapidly settled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bubbling device for backwash drainage of a limestone filter in a device for converting raw water into drinking water by supplying carbon dioxide gas to raw water and treating with a limestone filter.

[0002]

2. Description of the Related Art An outline of a conventional raw water drinking water conversion apparatus is shown in FIG. The raw water is sent from the water supply line 6, a part of the raw water is sent to the carbon dioxide absorption tower 1, where the carbon dioxide is absorbed and returned to the water supply line 6 again to be mixed with the raw water. The raw water that has absorbed this carbon dioxide is sent to a limestone filter tower 20 filled with calcium carbonate, where the limestone filter 2
Calcium carbonate is dissolved during passage through the treated water, so that treated water (drinking water) containing calcium carbonate is discharged from the treated water line 17 connected to the lower portion of the limestone filter tower 20. On the other hand, the limestone filter 2 needs to be backwashed about once a week in order to remove adhered dust and supplement calcium carbonate. Therefore, the limestone filter tower 20
After stopping the passage of the raw water to the drinking water, the backwash pump 5 is activated to feed backwash water from the backwash water supply line 13 connected to the lower portion of the limestone filter tower 20 to backwash the limestone filter 2. The backwash water is supplied by switching the valves installed in the treated water line 17 and the backwash water supply line 13 connected to the lower part of the limestone filter tower 20. The backwash drainage discharged from the upper part of the limestone filter tower 20 is sent to the concentration tank 3 through the backwash drainage line 18. The backwash drainage is allowed to stand for several hours in the concentrating tank 3, the extraction valve 10 is sequentially opened from top to bottom, and only the supernatant liquid is extracted from the recovery line 15 by the recovery pump 7 and recovered, and then passed through the sand filter 12. After that, it is returned to the water supply line 6 as drinking water raw water again. On the other hand, the sediment deposited in the concentration tank 3 is separately discharged by the slurry pump 14. Generally, such a drinking water liquefying device is composed of a plurality of limestone filter towers 20 and one concentrating tank 3.

[0003]

In such a drinking water conversion process of raw water, the backwash drainage dissolves calcium carbonate to a substantially saturated state after a while after the start of backwashing, and the pH of the drainage reaches about 8.2. As a result, milky white floating solids (mainly calcium carbonate) are generated. Although this suspended solid is not a harmful substance, it cannot be used as drinking water as it is because the water is white and turbid, so it is necessary to precipitate the suspended solid in the concentration tank and collect only the supernatant. However, when the pH of the suspended solids is 7.9 or less, the sedimentation speed is fast, but when the pH exceeds 7.9, the sedimentation speed is significantly slowed. Therefore, it took a long time of 5 to 6 hours to stand still in the concentration tank. If it takes a long time to stand, only one limestone filter tower can be processed per day, and it is impossible to backwash a plurality of limestone filter towers at a time (for example, if the limestone filter tower is 14 The base installed process requires two backwashes each day). Further, a plurality of withdrawal valves 10 were installed in the concentration tank 3 in the depth direction, and the supernatant liquid was withdrawn by opening and closing with a timer from the upper part to the lower part with the passage of standing time. Furthermore, in order to speed up recovery, it was necessary to use a special chemical (acid solution) for pH adjustment. However, if the recovery is accelerated, the sedimentation is insufficient, and thus some of the suspended solids may be mixed in the recovered liquid, and it was necessary to install the sand filter 12 on the downstream side of the supernatant water recovery pump.

The present invention solves the above-mentioned problems in the prior art, requires only a short residence time in the concentrating tank, does not require a chemical for neutralization, and simplifies the equipment. The purpose is to provide a device.

[0005]

According to the present invention, a raw water supply line for drinking water having a carbon dioxide absorption tower, a limestone filter tower connected to the water supply line, and treated water discharged from the filter tower are discharged. A drinking water system consisting of treated water lines,
A backwash water supply line connected to the treated water line side of the filter tower, a backwash drainage line connected to the upper part of the filter tower, and a concentrating tank that receives backwash drainage to concentrate and separate solid matter,
In a drinking water hydration apparatus for raw water constituted by a limestone filter backwash system consisting of a supernatant recovery line and a slurry discharge line connected to the concentrating tank, the carbon dioxide-containing gas discharged from the carbon dioxide absorption tower is converted into the concentrating tank. Backwash drainage of a drinking water treatment apparatus, characterized by comprising an acid gas line leading to the tank, a gas supply valve for adjusting the supply amount of acid gas, and a bubbling pipe for bubbling the acid gas during backwash drainage in the concentration tank. Bubbling device.

The device of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a system diagram showing an outline of a drinking water conversion device for raw water incorporating the bubbling device for backwash drainage of the present invention. In the apparatus of FIG. 1, the raw water for drinking water is supplied to the water supply line 6
Water from. A part of this raw water is sent to the carbon dioxide absorption tower 1 on the way, absorbs the carbon dioxide and joins the water supply line 6 again. Next, the raw drinking water is sent to a limestone filter tower 20, where it is filtered through a limestone filter 2 filled with calcium carbonate. At this time, calcium carbonate is dissolved to form treated water containing calcium carbonate, which is discharged from the lower part of the tower 20 and discharged from the treated water line 17.

On the other hand, when the limestone filter 2 is clogged or the elution amount of calcium carbonate becomes small, the supply of raw water is stopped and the backwash pump 5 is started to reverse the backwash water supply line 13. Wash water is supplied to backwash the limestone filter 2 of the limestone filter tower 20. The backwash water is injected from the lower part of the limestone filter tower 20 by adjusting the valve connected to the limestone filter tower 20, and discharged from the upper part. The discharged backwash water is sent to the concentration tank 3 through the backwash drain line 18. In the present invention, the gas supply valve 8 and the gas release valve 9 are provided in the vent line at the top of the carbon dioxide absorption tower 1, and the gas supply valve 8 is opened immediately before the backwash drainage of the concentration tank 3 is allowed to stand. The gas release valve 9 is closed, and a vent gas containing a small amount of carbon dioxide is supplied to the lower part of the concentration tank 3 through the acid gas line 4 and is supplied to the backwash drainage from the lower bubbling pipe 11. There is. The backwash wastewater bubbled in the concentrating tank 3 is neutralized with carbon dioxide gas to have a pH of 7.9 or less, so that suspended solids can be settled in a short standing time. After the suspended solids are settled, the extraction valve 10 is opened, and only the supernatant water is extracted from the recovery line 15 by the recovery pump 7. This recovered water can be returned to the drinking water raw water line again. On the other hand, the sediment deposited in the concentration tank 3 is separately discharged by the slurry pump 14.

[0008]

By bubbling a vent gas containing carbon dioxide gas in the backwash water of the concentration tank 3, the pH of the backwash water can be suppressed to 7.9 or less. When the pH is suppressed to 7.9 or less, the sedimentation rate of the suspended solids in the wastewater is increased, and the calcium carbonate in the suspended solids is eluted by the bubbled carbon dioxide gas to become calcium bicarbonate. Is significantly purified compared to the case where the pH exceeds 7.9.

[0009]

The following effects can be obtained by using the device of the present invention. It is possible to increase the sedimentation rate of the backwash drainage, and it is possible to backwash a plurality of units per day even with one concentration tank. In order to lower the pH of the wastewater, bubbling carbon dioxide gas in the released gas, the pH of the wastewater can be lowered to 7.9 or less, and it is not necessary to use a special chemical (acid solution), and the chemical cost is low. It is unnecessary. Since the backwash drainage from the concentrating tank is completely stationary, the sand filter, which was required in the past, is not required, and the equipment cost can be reduced. Since settling is fast, the number of drainage extraction valves can be reduced, and equipment costs can be reduced.

[Brief description of drawings]

FIG. 1 is a system diagram showing an outline of a drinking water conversion device for raw water incorporating a bubbling device for backwash drainage of the present invention.

FIG. 2 is a schematic system diagram showing one example of a conventional raw water drinking water conversion device.

Claims (1)

[Claims] 1. A drinking water conversion system comprising a raw water supply line for drinking water provided with a carbon dioxide absorption tower, a limestone filter tower connected to the water supply line, and a treated water line for discharging treated water from the filter tower. A system, a backwash water supply line connected to the treated water line side of the filter tower, a backwash drain line connected to the upper part of the filter tower, and a concentration tank for concentrating and separating solid matter by receiving backwash drainage. In a drinking water hydration apparatus for raw water constituted by a limestone filter backwash system consisting of a supernatant recovery line connected to the concentration tank and a slurry discharge line, the carbon dioxide-containing gas discharged from the carbon dioxide absorption tower is concentrated as described above. A beverage characterized by comprising an acid gas line leading to a tank, a gas supply valve for adjusting the supply amount of the acid gas, and a bubbling pipe for bubbling the acid gas into the backwash drainage in the concentration tank. Bubbling device for backwash drainage of hydration equipment.