JPH10202269A - Treatment of waste liquid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease the chemical oxygen demand and biochemical oxygen demand in a waste liq. with high efficiency by preventing the floc from being broken and micronized, supplying the floc having a desired diameter to a solid- liq. separation part on the downstream side along with the waste liq. and removing the pollutant. SOLUTION: A flocculant is added to a waste liq. at a flocculation part to flocculate the pollutant in the waste liq. into a solid floc, then a cross-linking and adsorbing flocculant is added at the inlet of a liq. feed pipe connected to the lower part of the flocculation part, and the waste liq. is supplied to a solid-liq. separation part on the downstream side through the liq. feed pipe by this method. The solid in the waste liq. is separated from liq. at the solid-liq. separation part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating industrial waste liquid containing polluting components such as suspended substances and dissolved substances.

[0002]

2. Description of the Related Art Generally, industrial waste liquids include polymer substances, metals,
Various polluting components such as coarse or colloidal particle suspensions composed of metal compounds, sparingly soluble salts and oils, and dissolved substances in the form of ions or molecules composed of water-soluble high-molecular substances and low-molecular substances Wastewater treatment, such as separation of water from these substances or conversion to water, carbon dioxide, or other stable and harmless substances, to improve the quality of wastewater to the permissible limit when used as service water The waste liquid must be treated to preserve the environment at the discharge destination. In the waste liquid treatment, the physical properties, chemical properties, physicochemical properties, biological properties, and the like of the pollutant components are applied.

[0003] As a waste liquid treatment method utilizing the above-mentioned physical properties, a filtration method, a sedimentation method, a floating method, an evaporation method, a drying method, an electrolytic method, a magnetic separation method, and the like are used. Methods include oxidation, reduction, and neutralization methods.
Coagulation method, adsorption method, ion exchange method, distillation method, etc. are used as waste liquid treatment methods applying physicochemical properties, and activated sludge method, biological oxidation pond method, etc. are used as waste liquid treatment methods applying biological properties. A contact aeration method or the like is exemplified. As a practical application of the above-described waste liquid treatment method, as shown in FIG. 2, a flocculant (7) and a crosslinking agent are added to a waste liquid (6) in a flocculation tank (5). An aggregating section (2) that adds an adsorbent flocculant (11) to coagulate and precipitate contaminants in the waste liquid (6) to form solid aggregated particles, and a feed for sending the waste liquid (6) downstream. 2. Description of the Related Art A method using a waste liquid treatment apparatus (1) having a liquid-tube (3) and a solid-liquid separation part (4) for subjecting the waste liquid (6) to a solid-liquid separation treatment to remove a pollutant component as a core component is widely used. I have.

[0004] Here, the above-mentioned aggregation means that colloidal particles or coarse particles larger than colloidal particles dispersed in a liquid are aggregated and adhered to form flocs, which are aggregates of larger aggregated particles. is there.

A liquid in which colloid particles or a group of particles larger than colloid particles are dispersed in a liquid is called a suspension. When the particles are colloid particles, they are also called a colloid solution. In order to aggregate the particles in this suspension, it is necessary to prepare conditions for the surface properties that can be adhered when the particles collide, collision between the particles, and that the adhered particles stably exist in the movement in the liquid. Is necessary.

[0006] In order to optimize the above conditions necessary for the aggregation, an aggregation agent (7) is used. As the flocculant (7), aluminum sulfate (sulfuric acid band),
7. Inorganic coagulants such as ferric sulfate, ferrous sulfate, ferric chloride, sodium aluminate, and polyaluminum chloride.
An aqueous solution containing 0 to 12.0% by weight is used. The flocculant (7) is used in an amount of 400 to 800 mg with respect to the waste liquid.
/ L.

In the above-mentioned coagulation, a flocculant (7) is added to the waste liquid (6), and then the flocculant (7) and the waste liquid (6) are rapidly dissolved and mixed, and the particles are collided. Agitation is required to form flocs by collective bonding.

As an example of such a coagulation treatment, a coagulant (7) such as a sulfuric acid band is added from the upper part of the coagulation tank (5) of the coagulation part (2), and then stirred by a stirrer (8). A water-soluble natural polymer or a denatured product thereof, a synthetic polymer substance, etc. were dissolved in water in an amount of 0.05 to 0.2% by weight from a crosslinking adsorption coagulant adding means (10) at the lower part of the coagulation tank (5). 1. The cross-linking adsorbent (11) is added to the waste liquid.
There is a method in which the particles are added at a ratio of 0 to 3.0 mg / l to form large particles having a particle diameter of 2 to 3 mm by the crosslinking adsorption action.

The waste liquid (6) containing flocs formed by the coagulation is sent to a solid-liquid separation section (4) on the downstream side through a liquid sending pipe (3), and concentrated by sedimentation separation, flotation separation, etc. Solids (flocs) and liquids are separated by applying solid-liquid separation techniques such as treatment, dehydration filtration, centrifugation, and dehydration treatment such as dehydration screening, or clarification treatment such as clarification filtration and clarification screening.

However, as described above, the cross-linking and adsorbing agent adding means (10) for adding the cross-linking and adsorbing agent (11)
Is disposed below the flocculation tank (5) of the flocculation section (2), so that the floc once formed is broken and fragmented by the liquid flow of the stirring device (8), and the particle size is again 10 to 100 μm.
The fine particles are contained in the waste liquid in that state and supplied to the solid-liquid separation section (4) on the downstream side. As a result, the physical action acting on the fine particles having a smaller surface area than flocs becomes smaller, and solid-liquid separation processes such as floating and sedimentation are not performed sufficiently, making it difficult to remove the pollutant component (SS). As a result, there is a problem in that the chemical oxygen demand (COD) and the biochemical oxygen demand (BOD), which indicate the degree of organic contamination in the waste liquid, cannot be reduced efficiently. This has made it possible to cause the problem that the liquid containing the harmful component is discharged again to the outside.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and it is an object of the present invention to prevent the destruction and fragmentation of flocs, and to maintain the desired floc diameter in the downstream side together with the waste liquid. It is an object of the present invention to provide a waste liquid treatment method for supplying a solid-liquid separation section to remove pollutant components and reducing the amount of chemical oxygen required and the amount of biochemical oxygen required in the waste liquid with high efficiency.

[0012]

The above object is achieved by adding a flocculant to a waste liquid in a flocculation section to aggregate pollutant components in the waste liquid into solid aggregated particles, and then connecting to a lower portion of the flocculation section. Add the cross-linking adsorbent to the waste liquid at the inlet of the liquid sending pipe
This is achieved by a waste liquid treatment method, wherein the waste liquid is sent to a solid-liquid separation section on the downstream side through the liquid sending pipe, and then the waste liquid is subjected to a solid-liquid separation process in the solid-liquid separation section. Things.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a side sectional view of a waste liquid processing apparatus (1) for realizing an example of the method of the present invention. As shown in FIG. As described above, the aggregation section (2), the liquid sending pipe (3), and the solid-liquid separation section (4) have a core structure.

After the coagulant (7) is added to the waste liquid (6) in the coagulation tank (5), the coagulation part (2) is powered by a driving device such as a motor, and the power is applied to the waste liquid (120) per minute. The waste liquid (6) containing the flocculant (7) is stirred for about 3 minutes using a stirring device (8) rotating at 150 rotations, and the contaminant component in the waste liquid (6) is flocculated and settled. 3 mm solid particles (flock).

The coagulant (7) is added from the coagulant adding means (9) on the upstream side of the coagulation tank (5). An aqueous solution containing 8.0 to 12.0% by weight of an inorganic coagulant such as aluminum sulfate (sulfuric acid band), ferric sulfate, ferrous sulfate, ferric chloride, sodium aluminate, polyaluminum chloride, etc. This was added to the waste liquid (6) by 30%.
It is added at a rate of 0-400 mg / l.

Next, the waste liquid (6) in which flocs are formed in the liquid is supplied to a liquid feed pipe (3) connected to the lower part of the flocculation tank (5) of the flocculation part (2). The cross-linking and aggregating agent (11) is added from the cross-linking and aggregating agent adding means (10) provided at the inlet of the liquid sending pipe (3).

The crosslinking adsorptive component used in the crosslinking adsorptive agent (11) has a number of hydrophilic groups and hydrophobic groups in the molecule and has a property of adsorbing particles dispersed in water. Any substance having a property of dissolving in water may be used, but generally, a water-soluble natural polymer or a modified product thereof, a synthetic polymer substance, and specifically, an acrylamide compound,
Agar, gelatin, polyethyleneimine, etc. are exemplified.
Dissolve to obtain a cross-linked adsorptive flocculant (11).

When the above cross-linking and adsorbing agent (11) is added to the waste liquid in an amount exceeding 2.0 mg / l, the flocculating effect has reached a saturated state, and there is no further improvement effect. This hinders purification of water, and wastes costs. Also, 1.0m
If the addition amount is less than g / l, sufficient crosslinking adsorption is not performed, causing the same problem as in the prior art.
It is preferred to use g / l.

In the method of the present invention, since the cross-linking and adsorbing agent (11) is added at the inlet of the liquid sending tube (3) as described above, the inside of the aggregating tank (5) by the stirring device (8) is used. Hardly affected by the liquid flow of the
The fragmentation is prevented, and the particles are supplied downstream while maintaining the desired particle size.

Further, the waste liquid (6) is sent to the solid-liquid separation section (4) on the downstream side via the above-mentioned liquid sending pipe (3), and sedimentation and floating separation of solid contaminants and water are performed. Is separated by the above processing. In general, the structure is simple,
The construction cost is low, there is no need for driving, the driving cost is low,
Flotation processing equipment, which has features such as easy maintenance, few failures, and no repair costs, is widely used.

The above-mentioned levitation separation processing includes a normal pressure levitation method and a pressurized levitation method. In contrast to the normal pressure levitation method in which a floc floats and separates under normal pressure due to a difference in specific gravity with water, The pressurized levitation method uses air in water at a pressure of about 3 to 5 kg.
/ Cm ² to give air-dissolved water, which is returned to normal pressure and mixed with waste liquid to float flocs. Generally, the amount of air-dissolved water added to waste liquid is about 30%. At this time, a foaming agent, a collecting agent, and the like may be appropriately added.

In addition, there is a filtration treatment, which generates a pressure difference (filtration pressure) before and after a porous body (filter material) as a separation surface, and the vicinity of or inside the filter material surface. This is a process in which the contaminant component is captured as filter residue in step (a), and at the same time, the filtrate obtained by permeating the contaminant component particles and the flow path group formed of the filter medium is taken out of the system.

The polluted components separated in the solid-liquid separation section (4) as described above are further concentrated to thick sludge, and are reused as feed and fertilizer, or subjected to final disposal such as incineration. At the same time, the water that has been removed to a stable and harmless state by removing the pollutant components is discharged out of the system.

[0025]

As described above, according to the waste liquid treatment method of the present invention, the destruction and fragmentation of flocs obtained by aggregating pollutants can be suppressed, and the floc can be supplied downstream with a large particle size. This makes it possible to efficiently separate and remove the polluted components in the solid-liquid separation section on the downstream side, and at the same time, it is possible to reduce BOD and COD in the liquid. Furthermore, since it becomes possible to efficiently separate and remove the pollutant components as described above, it is possible to save the addition amount of the flocculant and the cross-linking adsorbent flocculant, which also has the effect of improving economic efficiency. .

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a side cross section of a waste liquid treatment apparatus according to an example of the present invention.

FIG. 2 is an explanatory view showing a side cross section of a conventional general waste liquid treatment apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Waste liquid processing apparatus 2 Aggregation part 3 Liquid sending pipe 4 Solid-liquid separation part 5 Coagulation tank 6 Waste liquid 7 Flocculant 8 Stirrer 9 Flocculant addition means 10 Crosslinking adsorption flocculant addition means 11 Crosslinking adsorption flocculant

Claims (1)

[Claims] Claims: 1. A flocculant is added to a waste liquid in a flocculation section to aggregate pollutants in the waste liquid into solid aggregated particles.
A cross-linking adsorbent is added to the waste liquid at the inlet of the liquid feed pipe connected to the lower part of the flocculation section, and the waste liquid is sent to the solid-liquid separation section on the downstream side through the liquid feed pipe, and then the solidified liquid is discharged. A waste liquid treatment method comprising subjecting a waste liquid to a solid-liquid separation process in a liquid separation unit.