JPH05317899A - Treatment of sludge - Google Patents

Abstract

PURPOSE:To improve the handleability of sludge by adding an aq. PVA soln. to the sludge, preparing a uniform liq. mixture, adding inorg. salts to the mixture, flocculating and treating the sludge. CONSTITUTION:An aq. PVA soln. and inorg. salts are added to raw sludge or excess sludge produced at the time of treating sewage to rapidly flocculate the sludge. This sludge is allowed to stand and kneaded. By this kneading, the shrinking action of the sludge is promoted and the sludge solidifies to a rubbery state and becomes nonsticky. The water content of the sludge is reduced to about 76.4% corresponding to a degree attained by dehydration with a dehydrator such as a centrifugal dehydrator or a belt press. The malodor of the sludge is removed and excellent handleability can be imparted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sludge treatment method for producing raw sludge, surplus sludge, particularly flocculation of sludge, collecting sludge, solid-liquid separation, and sludge having good handleability.

[0002]

2. Description of the Related Art Sewage sludge, which is a solid after the water and sludge are dynamically separated and the supernatant water is separated and removed during sewage treatment, has an extremely high water content and cannot be used as it is for landfilling. Therefore, sludge generated in sewage treatment, etc.
After concentrating, it is further dehydrated by centrifugal dehydration or a belt press dehydrator to a desired water content.

[0003]

However, in the treatment of sewage, it takes time and is inefficient to simply separate water and solids. Therefore, when the solid-liquid is separated, a polymer flocculant is added to the concentrated sludge to increase sludge flocs, which is then used for dehydration. In this case, it is necessary to select a flocculant suitable for each property of the sludge, and to inject the chemical into the sludge in a very limited concentration range for proper use, and if this technique is not sufficient, The water content of the dehydrated cake becomes high,
Stickiness and poor handleability in the subsequent dehydration treatment.

An object of the present invention is to improve the handleability by simply coagulating the sewage sludge and simply dehydrating the obtained sludge.

[0005]

Means for Solving the Problems The present invention has been made to achieve the above object, and an aqueous solution of polyvinyl alcohol (hereinafter abbreviated as PVA) is added to sludge such as raw sludge and excess sludge generated in water treatment. The gist is that the sludge is treated by adding inorganic salts to the mixed solution which has been made uniform by adding inorganic salts.

[0006]

The sewage sludge is rapidly aggregated by simply adding inorganic salts to an aqueous polyvinyl alcohol solution that can be obtained at low cost from raw sludge and surplus sludge generated during sewage treatment. When this is left to stand still and then kneaded, the contraction action of the sludge is promoted and the sludge is solidified into a rubber-like form, and stickiness disappears. Since the water content is about 76.4%, it is about dehydrated by a dewatering machine such as a concentric dewatering machine or a belt press machine, and sludge can be treated quickly and easily.

[0007]

EXAMPLES The present invention will be described below with reference to examples.

[Example 1] 15% per 100 ml of activated sludge
After adding 10 ml of an aqueous PVA solution and subsequently adding 400 ml of a 10% sodium sulfate solution, the mixture is allowed to stand for 60 minutes. After that, after collecting and kneading the mud and draining the sludge,
When the water content was measured, the water content was 76.4%. In the above operation, when the sodium sulfate aqueous solution is added, the sludge rapidly flocculates and floats. In the next sludge collection operation stage after standing for 60 minutes, the sludge is sufficiently shrunk, and in terms of strength, it reaches a state where it can be taken out by being sandwiched with tweezers or the like. Further, when the sludge is kneaded to promote the contraction action, the sludge is solidified into a rubber-like state, and the sludge is improved to a property that is not sticky and has no bad odor and is excellent in handleability. The water content of the sludge drained from the surface water is 76.4%.
Therefore, it has almost the same performance as the circle-center dehydration and the belt press dehydration.

[Example 2] 50 ml of activated sludge (estimated ML
5% PVA aqueous solution was added to SS3000mg / l) from 2ml to 12ml in 2ml increments, and the addition amount was changed, and 200ml of 10% sodium sulfate was further added to the mixture. confirmed. In Example 2, high-viscosity PVA having a degree of polymerization of 4000 was used, and the amount used was 4/5 to 2/15 as compared with Example 1.
The amount was reduced to 0 and the cohesiveness of the sludge was observed. As a result, the sludge aggregated even in the 2 ml addition test area where the amount of PVA used was the smallest, and the sludge formed was larger than the floc obtained by the polymer flocculant. Further, it was possible to produce rubbery sludge in the subsequent operation in a test area of 4 ml or more. The amount of PVA used per 50 ml of waste water is 4 ml,
The amount was as small as 0.2 g.

Since the conventional polymer flocculant decomposes molecules when dissolved in water to reduce the coagulability of sludge, it is necessary to adjust the coagulant for each use and according to the concentration and properties of the sludge. The PVA used in the invention is chemically stable even in an aqueous solution, can be stored for 30 days or more without gelation even when made into an aqueous solution of about several%, and can be obtained at low cost. In that case, it is suitable.

Example 3 With respect to 50 ml of MLSS 3000 mg / l sludge, the addition amount of PVA was changed as shown in Table 1, and then, as inorganic salts other than sodium sulfate,
Potassium sulfate [K2SO4], ammonium sulfate [(NH
a) 2SO4] is adjusted to various concentrations, and 200m
1 was added to confirm sludge cohesiveness and solidification.

[0012]

[Table 1]

From this test, it was confirmed that the combination of PVA and sulfate is effective for agglomeration or solidification of sludge, although the amount used varies depending on the type of inorganic salt. The water content of the solidified sludge after draining is 10 m of PVA.
In the 1 addition test section, in the case of 15% sodium sulfate,
78.2% for 76.8% and 25% ammonium sulfate
%, Which was almost equivalent to that of sodium sulfate.

[0014]

INDUSTRIAL APPLICABILITY According to the sludge treatment method of the present invention, inorganic salts are added to a mixed solution which is made uniform by adding an aqueous solution of polyvinyl alcohol (hereinafter abbreviated as PVA) to sludge such as raw sludge and surplus sludge generated in water treatment. Since the sludge is treated by aggregating the sludge by using the MLSS300, the unit cost of the chemicals used is lower than that of the polymer flocculant, and the running cost of the sewage treatment is kept low and the MLSS300 is used.
Since it can be used for a liquid having a relatively low sludge concentration of about 0 mg / l, the sludge drawn out from the final settling tank can be directly treated, and the conventional sludge thickening tank and storage tank are unnecessary. In addition, PVA needs to control only the lower limit necessary for aggregation, and is chemically stable, as compared with polymer flocculants that must maintain the upper and lower limits accurately, and therefore is extremely stable. Easy to use, sewage treatment can be performed easily and surely without the need for advanced special technology. Furthermore, the sludge obtained by adding PVA can be easily drained to achieve a water content of 76.4%, and since a conventional dehydrator is not required, the device is simple and the cost is low. Is a rubber-like substance that is not sticky or has a bad odor, so it is advantageous for transportation, and because it is a substance composed of carbon, hydrogen, and oxygen, it does not produce harmful substances even when incinerated. ..

Claims (2)

[Claims] 1. An inorganic salt is added to a mixed solution obtained by adding an aqueous solution of polyvinyl alcohol (hereinafter abbreviated as PVA) to a sludge such as raw sludge and surplus sludge generated in water treatment to aggregate the sludge. A sludge treatment method characterized by treating the sludge. 2. The sludge treatment method according to claim 1, wherein the inorganic salts are sulfates such as sodium sulfate and potassium sulfate.