JPH0592198A - Softening treatment of hard water - Google Patents

Abstract

PURPOSE:To reduce the injection amount of chemicals and the amount of discharged matter in the softening treatment of hard water by the treatment of water containing 100ppm or more of a hardness component. CONSTITUTION:Alkali is added to water containing 100ppm or more of a hardness component to adjust the pH of the water to 10 or more and a flocculant is further arbitrarily added to this water. Next, the water immediately before entering a flocculation/sedimentation process is mixed with air (oxygen) by a gas-liquid mixing means 10.

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to a method of softening hard water by treating water containing a hardness component of 100 ppm or more to soften the water.

[0002]

2. Description of the Related Art Softening of hard water has been performed for a long time.
The coagulation-sedimentation method, the ion exchange method, the electrodialysis method, the reverse osmosis method, etc. exist as the method.

The latter three methods are generally called advanced processing methods,
Because of its high treatment cost, it is used only for special purposes such as the production of pure water.

The coagulation-sedimentation method is a soft water treatment method for hard water that has been used for the longest time because it has a relatively low treatment cost and can easily treat a large amount of water. There is.

And, US Pat. No. 3,238,12
No. 8 describes the processing method and apparatus.

[0006]

However, in the above-mentioned conventional coagulating sedimentation method, a large amount of chemical injection and a large amount of sludge are required.
It is desired to reduce this amount.

In particular, in recent years, the demand for sludge treatment plants has become more and more intense as the shortage of sludge treatment plants has become serious.

Generally, in the method of softening hard water by coagulation and precipitation, it is described that insoluble calcium and magnesium salts produced by the reaction shown in FIG. 4 are removed by precipitation.

Thus, calcium hydroxide Ca (O
H) 2 is added to the raw water, which reacts with calcium hydrogen carbonate or magnesium hydrogen carbonate dissolved in the water to form calcium carbonate and magnesium hydroxide, and to remove the precipitate thus formed. It is described that softening is performed.

According to the above reaction equation, theoretically,
To remove 1 mol of Ca (HCO3) 3 dissolved by reaction by precipitation, 1 mol of Ca (OH) 2 is needed, and further 1 mol of Mg (HCO3) 2 is removed. Two moles of Ca (HCO3) 2 are needed.

Thus, to simply add Ca (OH) 2 to the raw water and remove the hardness component by the reaction,
A large amount of chemicals is required, and at the same time, a large amount of sediment (sludge) is discharged.

The present invention was devised to solve the above conventional problems, and provides a softening treatment method for hard water capable of reducing the amount of chemical injection and reducing the amount of discharged substances. To do.

[0013]

In order to achieve the above object, the present invention is constructed as follows.

That is, the pH of water is adjusted to 10 or more by adding an alkali to water containing 100 ppm or more of hardness component,

Next, an aggregating agent is optionally added, and further, the gas-liquid mixing means 10 is used to mix water and air (oxygen) immediately before entering the aggregating and precipitating step,

Alternatively, the pH of water is adjusted to 1 by adding an alkali to water containing a hardness component of 100 ppm or more.
0 or more,

Next, a flocculant is optionally added, and further, the gas-liquid mixing means 10 is used to mix water and air (oxygen) immediately before entering the floc formation step and the flocculation-precipitation step,

Alternatively, the gas-liquid mixing means 10 is of an aspirator type.

[0019]

In the present invention, the pH is raised to 10 or more by adding an alkali to water containing a hardness component,
It has been found that the hardness component is insolubilized by optionally adding some amount of a conventional flocculant and mixing the mixture with air.

At the present stage, it is unknown for what reason the hardness component is insolubilized by mixing the air, but it is considered that oxygen in the air has some action.

Examples of alkalis that can be used in the present invention include alkali metal or alkaline earth metal hydroxides, carbonates and hydrogen carbonates such as sodium hydroxide, calcium hydroxide, sodium carbonate and sodium hydrogen carbonate. , Potassium hydrogen carbonate and the like.

Examples of the aggregating agent include aluminum chloride, aluminum sulfate, ferric sulfate, and acrylic aggregating agents such as polyacrylamide, sodium polyacrylate, and cationic polyacrylamide.

As the air mixing means which can be used in the present invention,
Although any kind of gas-liquid mixing means 10 can be used, preferably, an aspirator type gas-liquid mixing means 10 can be used.

This aspirator type gas-liquid mixing means 10
1 has a structure as shown in FIG. 1, and when raw water mixed with an alkali and optionally added with a flocculant is sent to the gas-liquid mixing means 10 by a pump, the inlet 12 to the outlet 13
It is designed so that air flows through the air introduction port 14 as the water flows in, and the water and air are mixed near the water outlet 3.

The sizes of the water inlet 12 and the outlet 13 and the air inlet 4 are important, but vary depending on the amount of water to be treated, viscosity and flow rate.

Therefore, although the size cannot be limited here, good gas-liquid mixing can be obtained when a white layer is observed, which is caused by mixing of air and water at the water outlet 13. can get.

[0027]

EXAMPLES Preferred examples of the method for softening water by water according to the present invention will be described below.

First, the processing method according to the present invention will be described with reference to the simple schematic diagram of FIG. In FIG. 2, raw water, alkali and optionally a flocculant are mixed in a mixing tank 15.

Here, the mixing tank 15 is not limited in any way, and alternatively, the alkali or the coagulant may be directly fed to the pipe for feeding the raw water to the gas-liquid mixing means 10.

Raw water mixed with an alkali and optionally a flocculant is preferably pumped to a gas-liquid mixing means, where water and air (oxygen) are mixed, and then the flocculation-precipitation tank 1
Sent to 6.

Here, the device shown in FIG. 1 is preferably used as the gas-liquid mixing means 10, but the invention is not limited to this, and other gas-liquid mixing means 10, for example, an ordinary aeration device is also used. it can.

Then, the insolubilized hardness component is settled and removed in the coagulating sedimentation tank 16, and the overflowed water is sent to the treated water tank.

In this specific example, only the softening process of hard water is briefly shown. However, in actual use, it is possible to add various other steps, for example, it is possible to provide a floc forming tank before the coagulation-sedimentation tank 16, and after the coagulation-sedimentation, perform slow filtration or rapid filtration. It is also possible to incorporate a filtration system or the like.

Here, a test showing the effect of the method of the present invention was conducted, and an explanation of the contents is shown in FIG.

As raw water containing hardness component, CaCO
Well water containing a hardness component of 320 ppm in terms of 3 was used. The gas-liquid mixing means is made of hard glass,
The flow rate was adjusted to create a white band at the water outlet (2.0 l / min). The coagulation / sedimentation tank is made by processing a polyethylene tube with an outer diameter of 267 mm into a U shape as shown in FIG.
The height was 1.5 m and the width was 1.0 m.

As a comparative example, the same conditions and processing apparatus as described above were used except that the gas-liquid mixing means was removed.

[0037]

[Brief description of drawings]

FIG. 1 is a schematic explanatory diagram of gas-liquid mixing means.

FIG. 2 is a schematic explanatory diagram of an example.

FIG. 3 is an explanatory diagram showing the contents of a test according to an example.

FIG. 4 is an explanatory diagram illustrating a reaction.

[Explanation of symbols]

 10 gas-liquid mixing means 12 inlet 13 outlet 14 air inlet 15 mixing tank 16 coagulating sedimentation tank

Claims (3)

[Claims] 1. The pH of the water is adjusted to 1 by adding an alkali to water containing a hardness component of 100 ppm or more.
0 or more, and further, an aggregating agent is optionally added to the water, and then the water just before entering the aggregating and precipitating step and air (oxygen) are mixed by a gas-liquid mixing means (10). A method for softening hard water. 2. The pH of the water is adjusted to 1 by adding an alkali to water containing a hardness component of 100 ppm or more.
0 or more, and further optionally adding a flocculant to the water, and then mixing the water just before entering the floc forming step and the flocculation and precipitation step with air (oxygen) by a gas-liquid mixing means (10), A method for softening hard water, which is characterized in that 3. The softening treatment method for hard water according to claim 1, wherein the gas-liquid mixing means (10) is of an aspirator type.