JPH03101900A - Method for dehydrating sewage sludge - Google Patents

Abstract

PURPOSE:To simply treat hardly filterable sewage sludge with high operation efficiency by adding crushed chaff to the sludge after concentration, mixing them and carrying out dehydiation with a screw press. CONSTITUTION:A small amt. of a flocculant is added to sludge fed into a sludge concentrator 1 and the concd. sludge is discharged from the opening of a trommel 1a and sent to a mixing tank 3, where crushed chaff is added from a hopper 2 and mixed with the sludge. This mixture is sent to a screw press 5 by a pump 4, dehydrated and stored in a cake hopper 6. The crushed chaff contained in the sludge acts as a nucleus to prevent the sludge from escaping from pressure applied by the carrying blade of the press 5, only the water is separated in the filter tube 5a of the press 5 and a highly dehydrated cake is obtd.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to an improvement in a method for dewatering sewage sludge, and proposes a method that has good dewatering properties and allows easy disposal of the cake after dewatering. .

[Conventional technology]

Conventionally, methods for dewatering this type of sewage sludge include methods of concentrating the sewage sludge, adding a polymer flocculant to the thickened sludge to further lengthen the flocs, and dewatering the flocs using a belt press or centrifugal dehydrator. It is known that a filtering aid such as coal powder or diatomaceous earth is added to concentrated sludge and the sludge is dewatered using a filter press or belt press. Japanese Patent Publication No. 59-24879 is an example of adding a polymer flocculant, and Japanese Patent Publication No. 39-70
No. 44 and Japanese Patent Publication No. 56-24600 are examples of adding slaked lime and carbon powder to sludge.

[Problem that the invention seeks to develop]

However, in the conventional method of adding a polymer flocculant,
The flocs are relatively weak, and if they are pressurized and over-dehydrated in the furnace, it is difficult to separate the cake from the sludge, etc. Therefore, dehydration of sludge added with a polymer flocculant makes it easier to recycle and clean the sludge. The process is carried out using a belt press or a centrifugal dewatering machine that does not regenerate the p-material, and the pressure applied during dewatering is low, and the cake dewatered using these machines has a high moisture content. Therefore, there is a difference between incineration and dumping after the fact. In addition, with the method of adding auxiliary materials such as lime, the moisture content can be lowered, but the cake increases by the amount of the added auxiliary material, and its disposal not only requires expense, but also If these are added, they will not burn, so when disposing of them by incineration, there is a time limit.

[Means to solve problems]

? The invention solves the above-mentioned problems by selecting additives that improve the dewatering properties and devising means for dewatering the added sludge. Crushed rice husks are added to and mixed with the thickened sludge, and this mixed sludge is dehydrated under pressure using a screw press.

[Effect]

In the sludge to which this crushed rice husk is added, the fine solid matter is connected by the rice husk powder and separated from water to form a strong core. Therefore, when pressurizing with a screw press, strong pressure can be applied without causing flocs to escape, and only moisture is separated by the metal mesh of the screw press. In other words, in a screw press, sludge is gradually fed inside a cylindrical P-tube by a cone-shaped feeder and dehydrated under pressure by a feeder blade, and the sludge is strongly pressurized in a sealed chamber. Unlike belt presses, sludge does not escape, and a highly dehydrated cake can be obtained.

In addition, compared to the furnace cloth of belt presses and filter presses, the thinly stretched metal mesh of this screw press is less susceptible to cake adhesion, and the metal mesh has more rigidity even if it becomes clogged with adhesion. It also has high strength and can be washed under high pressure. Furthermore, since the cake obtained by this dehydration method contains rice husks, it is of course easy to dispose of them afterward, such as incineration, and since the rice husks are composed of inorganic and organic substances such as silica, they can be returned to fields as dung posts. is also safe.

〔Example〕

The figure shows a general flowchart of the sewage sludge dewatering method according to the present invention, in which reference numeral 1 is a trommel type thickener, 2 is a hopper for crushed rice husks, 3 is a mixing tank for thickened sludge and rice husks,
4 is a transfer pump, 5 is a screw press for dewatering, 6
The cake hopper 7 is a screw for taking out the dehydrated cake. In the apparatus arranged in this way, the sludge supplied to the sludge thickener 1 is mixed with a small amount of flocculant, the concentrated sludge is taken out from the opening of the trommel a, and then transferred to the mixing tank 3.
sent to. Then, in the mixing tank 3, rice husks crushed by a rice husk hopper are added and mixed, and this mixed sludge is dehydrated by a screw press 5 by a transfer bomb 4 and stored in a cake hopper 6. During dewatering in this screw press 5, the mixed sludge contains crushed rice husks, so this becomes a nucleus and does not escape against the pressure of the feed blades of the screw press 5, and only the water is transferred to the screw press 5.
A highly dehydrated cake can be obtained. If the metal mesh becomes clogged by continuing such operation, the clogging can be easily eliminated using high-pressure cleaning water or the like, since the metal mesh has strength. The cake accumulated in the cake hopper as described above is taken out by the take-out screw 7 and can be subjected to subsequent processing such as incineration or composting.

〔Effect of the invention〕

As is clear from the above explanation, this invention adds rice husks obtained by crushing sewage sludge, which conventionally only yielded a cake with high moisture content using a belt press or centrifugal dehydrator, and dehydrated it using a screw press. By doing so, a highly dehydrated cake can be obtained.Because a screw press is used, the sludge to which rice husks have been added can be strongly pressurized. Of course,
Conventional problems in processing difficult-to-permeate sewage sludge, such as continuous operation, high operating efficiency, simple structure compared to conventional filter presses, and comparable dewatering rate. This completely eliminates the problem.

[Brief explanation of drawings]

The drawing is a schematic flow sheet of the dehydration method according to the present invention.

Claims (1)

[Claims] (1) Add and mix crushed rice husks to concentrated sewage sludge,
A sewage sludge dewatering method characterized by dewatering this mixed sludge using a screw press.