JPS63137708A - Treated water turbidity control device in purification facilities - Google Patents

Abstract

PURPOSE:To maintain water quality stably at high level and save flocculant consumption significantly by mixing flocculant-added sedimentation treated water and non-flocculant added natural sedimentation treated water. CONSTITUTION:In a treatment process having a plurality of systems, a chemical treatment system 4 for applying chemical treatment (flocculant) and precipitation treatment to water, and a non-chemical treatment system 12 for applying natural sedimentation treatment without chemical treatment are provided. Further, in order to reach a target turbidity, a mixing part for adjusting a mixture ratio of chemically treated water (low turbidity water) of the above-mentioned chemical treatment system 4 and non-chemically treated water (high turbidity water) of the above-mentioned non-chemical treatment system 12 are provided. Subsequently, the stable supply of purified water at a proper turbidity required by the user can be ensured without consideration of complicated intermediate treatment processes (flocculation process, sedimentation process), and flocculant consumption can be saved significantly.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a device for controlling the turbidity of treated water discharged from a sedimentation tank outlet in industrial water purification equipment, and particularly to a device for controlling turbidity contained in raw water. The present invention relates to a turbidity control device suitable for reducing the injection amount of flocculant used for removing turbidity.

[Conventional technology]

A common method for improving water quality in industrial water facilities, that is, reducing turbidity, is to inject a raw water flocculant and purify the water by sedimentation treatment.

The mainstream of turbidity control by chemical injection is chemical injection control proportional to raw water turbidity.

By the way, the standard value of turbidity for industrial water is generally set at 10 degrees or less, but in reality, many water purification facilities produce industrial water of higher quality than necessary. . This seems to be due to the fact that industrial water facilities are considered as an extension of water supply facilities. In this way, unnecessarily purifying industrial water to a level exceeding the standard value results in the use of a large amount of wasteful flocculant.

Therefore, a system has been proposed in which the injection of a flocculant is controlled intermittently for the purpose of saving the flocculant (Japanese Patent Laid-Open No. 17889/1989).

[Problem that the invention seeks to solve]

According to the above-mentioned conventional technology (Japanese Unexamined Patent Publication No. 58-17889), even if the customer's required turbidity can be satisfied at a water quality standard of 10 degrees or less, the settling tank outlet turbidity does not equal the target turbidity, and the flocculant There is still some leeway in terms of reducing the amount of injection, and since the turbidity of the raw water continues for a certain period of time, a coagulation tester is required.

As described above, the conventional technology does not take into account that the turbidity of the treated water at the outlet of the settling tank meets the turbidity required by the customer, and the problem remains that the production cost of industrial water cannot be reduced much. . In other words, since factors other than turbidity subtly influence the block formation and chemical precipitation process, operators tend to be lenient in their settings to ensure safety and end up using a large number of flocculants. This is because it does not lead to a significant reduction in production costs.

The purpose of the present invention is to realize purified water with an appropriate turbidity without considering complicated intermediate treatment processes (coagulation process, sedimentation process) so that the turbidity of treated water = the turbidity required by customers. It is to do so.

[Means for solving problems]

The purpose of the above is that coagulant injection is not performed in some processes in a treatment process that has multiple lines, and in the final stage of the treatment process, treated water that has undergone chemical coagulation precipitation and untreated water that is not injected with chemicals. By mixing to achieve the turbidity required by the customer.

This ensures stable water quality and significantly reduces the amount of flocculant used.

In other words, the present invention provides a chemical treatment process in which chemical-treated water is discharged by subjecting raw water to chemical treatment and precipitation treatment, a precipitation treatment process in which chemical-untreated water is discharged by subjecting raw water to precipitation treatment, and The present invention is characterized by comprising a mixing section that mixes treated water and non-chemically treated water, and a mixing ratio control device that controls the mixing ratio of both treated waters.

[Effect]

It is difficult to keep the turbidity of treated water constant only by controlling chemical injection because of the degree of floc formation and sedimentation efficiency caused by physical factors other than turbidity. Therefore, by adding a non-treatment process that does not involve coagulant injection to some processes in a treatment process that has multiple lines (flocculation pond, chemical sedimentation basin), it is possible to improve the quality of raw water (turbidity, etc.) in the treatment process. By injecting coagulant based on chemical sedimentation tank.

Suspended matter can be almost completely removed.

Here, the required function of the chemical sedimentation tank is to almost completely remove inflow flocs and suspended solids within a residence time of around 3 hours relative to the treated flow rate. However, the standard is an average flow rate of 40 am/min or less.

On the other hand, in the non-treatment process, although there is a design value of raw water turbidity of 30 degrees or less, by using the chemical sedimentation tank as a normal sedimentation tank and increasing the residence time (average flow rate 3
01/min), a considerable precipitation effect is obtained.

Treatments produced in this manner generally have a turbidity of 2
The temperature will be around 3 degrees, and the untreated turbidity will be lower than the raw water turbidity due to natural precipitation. By mixing these low-turbidity treated water and high-turbidity untreated water, the target turbidity can be achieved as required by the customer, and the amount of chemical injection can be changed from the required treated water volume to the untreated water volume. It is sufficient to inject flocculant according to the amount of water after subtracting the amount of water, and it is possible to significantly reduce the amount of flocculant.

〔Example〕

Next, two embodiments of the present invention will be described based on the drawings.

FIG. 1 shows an embodiment of water purification equipment according to the present invention.

As can be seen from Fig. 1, water purification equipment is roughly divided into two types: a chemical treatment process system that uses flocculant injection, and a precipitation treatment process system that uses only sedimentation without using a flocculant. It consists of a process of mixing and distributing treated water and non-chemically treated water, and the mixing ratio is adjusted to the treated water having a desired turbidity by a control device W (FIG. 2), which will be described later.

Multiple chemical treatment process systems are installed in parallel, including a rapid stirring pond 1 that takes in raw water and rapidly stirs it together with a flocculant, followed by a floc formation pond 2 that gently stirs it.
, a chemical sedimentation tank 4 following this, and a flocculant injection device 3 for injecting a flocculant into the rapid stirring tank 1 . 7 is a raw water turbidity meter for detecting the turbidity of raw water, 6 is a raw water flow meter, 8 is a treated water turbidity meter for detecting the turbidity of treated water on the outflow side of the chemical sedimentation tank 4, and 9 is a raw water turbidity meter for detecting the turbidity of the treated water. This is a treated water flow meter.

The above equipment has the same configuration for each treatment process.

The sedimentation process system does not include a chemical treatment process, and simply removes suspended matter in raw water by sedimentation in the sedimentation tank 12. In addition, raw water flow meter 6. Treated water turbidity meter8. They are the same in that a treated water flow meter 9 is provided. When the present invention is applied to existing water purification equipment, the rapid stirring basin 1 and the flocculation basin 2 may be bypassed, and the settling basin 12 may be formed by using the chemical settling basin 4 as a normal settling basin.

The outflow ports of each of the chemical sedimentation tanks 4 in the above chemical treatment process system and the sedimentation tank 12 in the sedimentation treatment process system are collected in the mixing section 16 and led to the water purification tank 5.

The treated water pooled in the water purification pond 5 is distributed to consumers as industrial water.

Next, a mixing ratio control device for obtaining a desired turbidity will be explained. A specific example is shown in FIG.

In FIG. 2, 13 is a treated water flow rate control valve, 14 is an untreated water flow rate control valve, and 15 is a control circuit that determines the flow rate distribution of treated water and untreated water in order to achieve optimal mixing. The treated water turbidity meter 8 outputs the detected turbidity value Tub1 of the treated water flowing out from the chemical sedimentation tank 4, and the treated water flow meter 9 outputs the flow rate value Q1 of the treated water. On the other hand, sedimentation tank 1
Similarly, on the second side, a turbidity detection value Tubz is output from the turbidity meter 8 for untreated water that has not been treated with chemicals, and a flow rate value Q2 is output from the treated water flow meter 9. Further, in the water purification pond 5, the turbidity meter 10 outputs the turbidity detection value Tubδ, and at the outlet, the flow meter 11 outputs the flow rate value Qa, each of one or more detected values Tub1~Tubδ+Qi~
Q8 is input to the control circuit 15, and the control circuit 15 receives the following (
The opening degrees of the flow control valves 13 and 14 are adjusted so as to achieve the optimum mixing ratio expressed by equations 1) and 2).

In this way, the treated water treated with chemicals and the untreated water that is not treated with chemicals are mixed in the mixing section 16 in a desired proportion, and the mixed water is distributed via the water purification pond 5, which results in unnecessary excessive quality. It is possible to save on flocculants and electricity, etc. associated with chemical treatment without producing industrial water.

As mentioned above, there is no regulation value for the turbidity required by consumers, especially in industrial water, and the value varies depending on the use, but it is often 10 degrees or less on average. However, with the conventional treatment process that involves injecting a coagulant and precipitating chemicals, it is difficult to predict the turbidity of the treated water based on the jar test results, and ultimately the amount of chemicals injected is determined based on the safety factor. It was decided to use the amount that could be expected to reach the bottom price, and it was forced to produce treated water of unnecessary excessive quality.

However, according to this embodiment, by adding a normal settling tank, the treated water and untreated water are mixed by performing optimal flow control so that the target turbidity is achieved at the exit of the settling tank. By doing this, water distribution flow rate to consumers - untreated flow rate =
By injecting the flocculant into the amount of water to be treated, the amount of flocculant can be reduced.

Although the above embodiments are based on industrial water purification, the present invention can also be applied to water supply facilities for the purpose of removing extremely small amounts of turbidity. In other words, in the example shown in Figure 2, it is sufficient to install a filter suitable for removing extremely small turbidity at the inlet of the water purification pond 5, and in this case, It is only necessary to take into consideration the negative part of the suitable ground when calculating the mixing ratio.

〔Effect of the invention〕

As described above, according to the present invention, water having the desired turbidity required by consumers can be produced without using complicated intermediate treatment processes or controls.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of water purification equipment according to the present invention, and FIG. 2 is a block diagram showing an example of a mixing control device. 1... Rapid stirring pond, 2... Block forming pond, 3...
- Coagulant injection equipment, 4... Chemical sedimentation tank, 5... Water purification pond, 6... Raw water flow meter, 7... Raw water turbidity meter, 8...
・Sedimentation basin outflow turbidity meter, 9...Sedimentation basin outflow flow meter, 10
...Sedimentation basin outlet turbidity meter, 11...Water distribution flow rate, 12.
・・Ordinary sedimentation tank, 13 ・・Treatment flow rate control valve, 14・・
- Untreated water flow rate control valve, 15... control circuit.

Claims (1)

[Claims] 1. A chemical treatment process in which chemically treated water is discharged by subjecting raw water to chemical treatment and precipitation, a precipitation process in which chemical-untreated water is discharged by subjecting raw water to precipitation, and the chemically treated water and chemicals A treated water turbidity control device in a water purification facility, comprising: a mixing section that mixes untreated water; and a mixing ratio control device that controls a mixing ratio of both treated water.