JPH06343999A - Sludge dewatering method - Google Patents

Abstract

PURPOSE:To dehydrate effectively difficultly by dehydrating sludge without shortening the life of a dehydrator main body and its filter material in a belt press type dehydrator. CONSTITUTION:In the pretreatment process for supplying sludge to a belt press type dehydrator 3, a high molecular weight cation polymeric coagulant 6 is added and sludge 4 is turned into the bulky flock shape, and then concentrated by a gravity dehydrator 11. The high cation degree polymeric coagulant is added to the concentrated sludge 8. Thus the polymeric coagulant is applied effectively in the pretreatment process to dehydrate the sludge easily.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for dehydrating sludge produced as a residue in a wastewater treatment plant.

[0002]

2. Description of the Related Art Sludge is an aggregate of organic and inorganic substances having a complicated structure. Since the particle size is small and the affinity with water is strong, sludge cannot be filtered or centrifuged without appropriate pretreatment. It is difficult to separate water by a dehydration operation. Therefore, dewatering is performed by improving the dewatering characteristics of sludge by adding a flocculant. For example, when a polymer flocculant is used, sludge and the polymer flocculant are directly mixed to form flocs capable of weight dehydration and shearing / squeezing, and the floc-like sludge is supplied to a belt press type dehydrator. Squeezed by rolls.

[0003]

Generally, in order to dehydrate sludge by using a polymer flocculant, the effect of acting on the active points of the sludge to make the sludge particles hydrophobic (easy dehydration) and the sludge particles The effect of facilitating gravity dehydration by cross-linking to form coarse flocs is required, but in the case of hardly dehydratable sludge such as sludge having a high organic matter content, these effects may not be sufficient. Although the dewaterability of sludge can be improved by adding an inorganic flocculant such as polyiron or PAC in some form, this inorganic flocculant causes clogging in a belt press type dehydrator and has a short life. Change or pH
There is a problem in that the dehydrator main body is corroded due to the decrease of the water content.

The present invention is intended to solve the above problems, and it is an object of the present invention to effectively dehydrate non-dewatering sludge without shortening the life of the dehydrator body or its filter cloth.

[0005]

In order to solve the above-mentioned problems, the sludge dewatering method of the present invention comprises coagulating sludge with a polymer coagulant and supplying the coagulated sludge to a belt press type dehydrator. In the method of dehydrating sludge to be dehydrated by adding a high molecular weight cationic polymer flocculant to the sludge in the previous step of supplying to a belt press type dehydrator, the obtained coarse floc sludge is concentrated by gravity dehydration, A feature is that a high cationic polymer flocculant is added to this concentrated sludge.

[0006]

By adding a high molecular weight cationic polymer flocculant in the above constitution, sludge forms coarse flocs capable of gravity dehydration due to the excellent flocculating action of this flocculant. After gravity dehydration of this coarse floc-like sludge, by adding a high cationic polymer flocculant,
The surface hydrophilic layer of the sludge is destroyed by the action of the coagulant, and the sludge is hydrophobized to further coagulate. The obtained coagulated sludge can be easily squeezed with a belt press type dehydrator.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. In FIG. 1, 1 is a drum, 2 is a gravity dehydrator, and 3 is a belt press type dehydrator. The drum 1 is supplied with sludge 4 to be dehydrated and a high-molecular weight cationic polymer flocculant 5 of DAM type (methacrylate type) or DAA type (acrylate type). The sludge 6 is supplied to the gravity dehydrator 2 after being stirred and mixed. The gravity dehydrator 2 has a filter cloth 7 or a filter material in the form of a drum screen or multiple discs, and can easily perform solid-liquid separation by gravity. After dehydrating the sludge 6, it is mixed as a concentrated sludge 8 in a mixing tank 9 Is configured to be sent to. The mixing tank 9 is provided with a stirring means such as a stirring blade 10 inside the tank, and a means for supplying a polyamine-based or polyethyleneimine-based high cation polymer flocculant 11 outside the tank, so that the concentration in the tank is increased. After mixing sludge 8 and coagulant 11, coagulated sludge 1
2 is supplied to the belt press type dehydrator 3. The belt press type dehydrator 3 dehydrates the supplied coagulated sludge 12 and discharges it as a dehydrated cake 13.

The operation of the above structure will be described below.
The sludge 4 and the high molecular weight cationic polymer flocculant 5 are supplied to the drum 1, and the mixture is slowly stirred and mixed in the drum 1. Then, the sludge 4 is satisfactorily aggregated by the excellent aggregating action of the aggregating agent 5 to form coarse flocs capable of gravity dehydration. Therefore, the coarse floc-like sludge 6 is taken out and sent to the gravity dehydrator 2. Then, in the gravity dehydrator 2, the free water in the sludge 6 is separated by the filter cloth 7 and concentrated to a sludge solid matter concentration of 4 to 10%. The concentrated sludge 8 thus obtained is sent to the mixing tank 9, and the high cation polymer flocculant 11 is supplied while being sufficiently stirred by the stirring blade 10. Concentrated sludge 8 is coagulant 1
By the action of 1, the surface hydrophilic layer is destroyed and hydrophobized,
This flocculate sludge 1 because it flocculates easily to dehydration
2 is supplied to the belt press type dehydrator 3 for dehydration. The coagulated sludge 12 supplied to the belt press type dehydrator 3 moves according to the movement of the belt shown by the arrow, and is dehydrated between the roll a and the roll b by gravity or capillary action until the sludge 12 loses its fluidity. Then, between rolls b and c, the rolls are gradually squeezed. The sludge 12 is dehydrated and then discharged as a dehydrated cake 13.

[0009]

As described above, according to the present invention, after the formation of coarse floc-like sludge by adding a high molecular weight cationic polymer flocculant for the purpose of sludge concentration, the sludge solid content concentration is determined by gravity dehydration. Concentrate to 4-10%. A high cationic polymer flocculant for the purpose of dehydration, that is, hydrophobization of sludge particles, is added to the concentrated sludge, and the obtained flocculated sludge is supplied to a belt press type dehydrator. That is, the sludge can be easily dehydrated by effectively acting the polymer coagulant in the previous step of supplying the sludge to the belt press type dehydrator. As a result, the difficult-to-dewater sludge, which has been difficult to dewater in the past, can be easily dewatered by the belt press type dewatering machine. Shortening the life of the dehydrator body and its filter medium is also prevented.

Table 1 below shows the results of the sludge dewatering test. In Table 1, test numbers 1, 2, 3, 4, 5,
9 shows the conventional dehydration method, and test numbers 6, 7, and 8 show the dehydration method of the present invention. From this table, it can be seen that the dehydration method of the present invention has a lower water content of sludge than the conventional dehydration method, and the dehydration method of the present invention is a very excellent method.
At this time, neither the pH of the filtrate was lowered nor the life of the filter cloth was shortened.

[0011]

[Table 1]

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a flow of a sludge dewatering method of the present invention.

[Explanation of symbols]

 2 Gravity dehydrator 3 Belt press type dehydrator 4 Sludge 5 High molecular weight cationic polymer flocculant 6 Coarse floc sludge 8 Concentrated sludge 11 High cationic polymer flocculant 12 Flocculated sludge

Claims (1)

[Claims] 1. A sludge is coagulated using a polymer coagulant,
In the sludge dewatering method of supplying coagulated sludge to a belt press type dehydrator for dewatering, a high molecular weight cationic polymer coagulant is added to the sludge in the previous step of supplying to the belt press type dehydrator to obtain A method for dewatering sludge, characterized in that coarse floc-like sludge is concentrated by gravity dehydration, and a high cationic polymer flocculant is added to the concentrated sludge.