JPH0645029B2 - Steel wastewater treatment method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a steel wastewater treatment method for easily and economically removing suspended particles from a steel wastewater containing ferromagnetic suspended particles having a specific gravity of 3 or more. Is.

(Prior Art) Conventional treatment of steel wastewater containing suspended solids (suspended solids, hereinafter referred to as ss) containing ferromagnetic materials (FeO, Fe ₃ O ₄ ) as main components is described in, for example, “New Systematic Civil Engineering Water Treatment (Steel Drainage) ”(Showa 57-3-20), Gihodo, p.29
3 to 297.

A general example of the conventional method will be described with reference to FIG. Factory 1
The steel wastewater generated from the steel flows through the scale rule 2 into the scale pit 4.

Usually, coarse particles of about 100 μm or more are precipitated and treated by the scale pit 4. After that, the particles are sent to a coagulation tank 6, where chemicals such as a coagulant and a polymer coagulation aid are added to form fine particles, and then the particles are subjected to a precipitation treatment in a coagulation sedimentation tank such as a clarifier 13.

The sludge that has settled is sent to the Schuckner coagulation tank 14, and is dehydrated by the dehydrator 17 after passing through the Schuckner 15 and the dehydrator stirring tank 16. The treated water is sent to the treated water tank 9 and circulated for use.

As described above, the conventional method is to remove the suspended particles by combining the precipitation treatments of the coarse particles and the fine particles.

(Problems to be solved by the invention) However, in this method, since the precipitation treatment in the primary treatment equipment such as scale pits and clarifiers is performed by the gravity action of precipitation, other external disturbances (for example, wind and temperature) ) And the structural problem of the settling tank itself, there is a drawback that the scale of the treatment equipment does not become smaller than a certain level even if the amount of steel drainage decreases.

Therefore, especially when the steel drainage is very small, the space occupied by the treatment equipment and the equipment cost become large.

In addition, this method requires a secondary treatment facility for further treating the precipitated suspended particles, for example, a large-scale facility such as a Schuckner or a dehydrator.

(Means for Solving Problems) The present invention solves the problems of the conventional method and provides an effective method that occupies a smaller space than steel drainage and has a low equipment cost. To a high-concentration steel wastewater containing, first, the coarse particles are separated by a centrifuge, the wastewater containing the coarse particles is directly sent to a magnetic separator,
Wastewater containing the remaining fine particles is added with a chemical to aggregate the fine particles to form flocs, and then sent to the magnetic separator,
Coagulate coarse particles and flocs until the final water content is 50.
% Of the low water content sludge is separated and processed, and the steel wastewater treatment method is characterized.

(Operation) In other words, paying attention to the fact that the coarse particles in the iron and steel wastewater contain a large amount of ferromagnetic material, separating the coarse particles from the steel and wastewater by a centrifuge and sending the water directly to the magnetic separator, while containing the remaining fine particles. After adding chemicals such as flocculants and polymer flocculation aids to the waste water to flocculate the fine particles to form flocs, send them to the magnetic separator to coaggregate the coarse particles and the flocs, and The magnetic substance is attracted to the magnet and removed. By doing so, the coagulating sedimentation basin can be omitted, the space occupied by the primary treatment equipment and the equipment cost can be reduced, and the magnetic separation lowers the water content of the sludge compared to the conventional method. The secondary treatment equipment can also be omitted.

Next, the mechanism by which the coaggregate is adsorbed by the magnet will be described with reference to FIG. The coarse particles 10 and the flocks 11, which are ferromagnetic materials, co-aggregate due to the extremely high magnetic field gradient of the coarse particles 10, and the co-aggregates are magnetized by the co-aggregates themselves to form permanent magnets 12 arranged in the magnetic separator. Adsorbed.

(Example) Below, a test result is demonstrated. FIG. 3 shows that the iron and steel wastewater is sent to the centrifuge 5, the coarse particles are separated and directly sent to the magnetic separator 7, and the wastewater containing the other fine particles is sent to the coagulation tank 6 to add chemicals to the floc. An application example (method A) of the present invention, in which water is sent to the magnetic separator 7 after forming, is shown. Fig. 4 shows iron and steel wastewater sent to the centrifuge 5 to separate coarse particles and
The wastewater containing the remaining fine particles sent to the next treatment facility is agglomerated tank 6
A comparative example (B) method is shown in which water is fed to the magnetic separator 7 after adding a chemical to form a block. The test results are shown in Table 1.

From Table 1, the ss concentration in the treated water of Method A is 18-29 mg / l
However, the ss concentration in the treated water of Method B is 40 to 52
It is found to be mg / l, Method A is reduced to about half compared with Method B, and it is understood that it is comparable to the ss concentration of 20 to 50 mg / l in the treated water of the conventional method.

Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an embodiment of the present invention. Iron and steel wastewater containing ss generated from the factory 1 is collected in the water collecting pit 3, pumped up from this, and sent to the centrifugal separator 5.

The coarse particles of 100 μm or more separated by the centrifuge 5 are
The water is directly sent to the magnetic separator 7, and the waste water containing the other fine particles is sent to the aggregating tank 6, and the fine particles are added with a chemical in the aggregating tank 6 to form a block and then sent to the magnetic separator 7.

Coarse particles and particles after addition of chemicals (floats) are processed by the magnetic separator 7. The treated water is collected in the treated water tank 9 and reused again in the factory 1, while the separated sludge is collected in the hopper 8 and discharged.

It was found that the separated sludge had a water content of 36 to 50%, which was less than the conventional method of 80 to 95%, and did not require a secondary treatment facility.

(Effects of the Invention) By applying the present invention, (1) it is not necessary to dredge the sludge accumulated at the bottom of the sedimentation basin.

(2) Since the generated sludge is handled by a storage tank such as a hopper or bucket, it does not require a large-scale secondary treatment facility such as a Schipper or a dehydrator. (3) A centrifugal separator, a magnetic separator, etc. The equipment is very compact and occupies almost half the space compared to conventional precipitation methods.

(4) By reducing the number of secondary treatment facilities, the facility cost can be significantly reduced compared to the conventional method, and if the steel drainage is small, the facility cost can be further reduced.

[Brief description of drawings]

FIG. 1 is an overall view showing an embodiment of the present invention, FIG. 2 is a view showing how a co-aggregate is adsorbed by a magnet, FIG. 3 is a view showing a test apparatus of the present invention, and FIG. The figure which shows the test apparatus of a comparative example, and FIG. 5 is a figure which shows the conventional steel wastewater treatment equipment. 1 ... Factory, 2 ... Scale sluice, 3 ... Water collecting pit, 4 ... Scale pit, 5 ... Centrifuge, 6 ...
Coagulation tank, 7 ... Magnetic separator, 8 ... Hopper, 9 ... Treated water tank, 10 ... Coarse particles, 11 ... Float, 12 ...
Permanent magnets, 13 ... Clarifier, 14 ... Shuckner coagulation tank, 15 ... Schuckner, 16 ... dehydrator stirring tank, 17 ... dehydrator.

Continuation of the front page (56) Reference JP-A-59-6918 (JP, A) JP-A-51-76852 (JP, A) JP-A-58-95578 (JP, A) Actual development Sho-57-95294 (JP , U) "Industrial water", July 1992, No. 406 PP. 15-20

Claims (1)

[Claims] 1. A high-concentration iron and steel wastewater containing a ferromagnetic material is first subjected to separation of coarse particles by a centrifuge, and the wastewater containing the coarse particles is directly sent to a magnetic separator to leave the remaining fine particles. Wastewater containing water is added with a chemical to agglomerate fine particles to form flocs, and then sent to the magnetic separator to coaggregate coarse particles and flocs, and finally a low water content sludge having a water content of 50% or less. A steel wastewater treatment method, characterized in that the steel is separated.