JPH03114585A - Treatment of sludge - Google Patents

Abstract

PURPOSE:To enhance the dehydration efficiency of excessive sludge hard to dehydrate by inserting a self-cleaning type screen in the front stage of an ultrafiltration membrane and subjecting excretion to activated sludge treatment in a bioreactor and subsequently removing the excretion residue in the obtained mixed solution to withdraw the same along with the excessive sludge. CONSTITUTION:Since excretion residue containing fine fibers is removed by the self-cleaning type screen 7 inserted in the front stage of a UF membrane 4, the clogging of the UF membrane is prevented. The excretion residue containing fine fibers removed by the screen 7 is withdrawn along with excessive sludge 8 to be subjected to dehydration treatment but, since a large amount of fine fibers are mixed with the excessive sludge, dehydrating properties are drastically enhanced and the water content in a dehydration cake can be lowered. Further, since the excessive sludge 8 is withdrawn in the front stage of the UF membrane 4, the amount of the liquid to be treated passing through the UF membrane is reduced and the capacity of the UF membrane can be miniaturized and the life thereof can be extended in, the case of the same capacity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application 1] The present invention relates to a treatment method for a pretreatment step whose main purpose is removal of impurities and dehydration among a series of human waste treatment steps.

[Prior Art] Conventionally known human waste treatment methods involve separating treated water and sludge in a settling tank or centrifugal concentrator after activated sludge treatment, extracting a portion of the sludge as surplus sludge, and leaving the rest in an aeration tank. The mainstream was to send the sludge back to the factory and undergo activated sludge treatment again.
Ultrafiltration membranes (hereinafter referred to as UP membranes) have come to be used in place of the solid-liquid separation methods using sedimentation tanks, centrifugal concentrators, etc. described above.

The UF peritoneal method has the advantage of reliably obtaining treated water without turbidity, but the cross-sectional area through which the mixed liquid passes is small (3 to 5 mm slit for flat membranes, 11.5 mm for tube membranes).
φI! lI+), there is a problem that blockage occurs due to contaminants.

Therefore, as a preliminary treatment for human waste, chemicals are used to coagulate it and then screened or centrifuged. A method is used to remove contaminants using a machine or the like.

[Problems to be Solved by the Invention] By the way, surplus sludge obtained by treating human waste that has undergone such pre-treatment with activated sludge and then separating it with a UP membrane is
It does not contain fibers and has a high viscosity if, making it extremely difficult to dehydrate.

Therefore, the current practice is to use a special high-pressure press dehydrator, or to mix surplus sludge with human waste containing a lot of fibers, and after flocculation treatment, dewatering treatment is performed using a screen mosque press or centrifugal separator. The problem remains that a large amount of unhygienic dehydrated cake is generated at a high rate.

This invention aims to solve the above-mentioned problems, and aims to improve the dewatering rate of difficult-to-dewater surplus sludge by mixing fine fibers only into the surplus sludge to be dewatered. This is the purpose.

[Means for Solving the Problems] The present invention seeks to provide means for solving the above problems, and is to provide a means for solving the problems described above, in which a mixed liquid after treating human waste with activated sludge treatment in a biological reaction tank is passed through a circulation tank. In the activated sludge method, which separates sludge and treated water through an ultrafiltration membrane,
This method is characterized in that a self-cleaning screen is inserted in front of the ultrafiltration membrane, and the screen removes sludge from the mixed liquid and draws it out together with excess sludge. be.

[Example] The invention will be explained in detail by means of embodiments shown in the drawings.

In the figure, reference numeral 1 denotes a biological reaction tank, into which night soil A from which human sludge has been removed through a fine drum screen is inputted via a storage tank, where activated sludge treatment is performed.

After the treated mixed liquid flows into the circulation tank 2, it is sent to the UF membrane 4 by the pump 3, and is separated into treated water 5 and return sludge 6.

A self-cleaning screen 7 is inserted in front of the UF membrane 4, and removes scum from the mixed liquid sent by the pump 3 from the circulation tank 2 to prevent clogging of the UF membrane.

This self-cleaning screen 7 can be of any known type, but it is best to use a type that uses a sensor to detect clogging caused by scum in the passing liquid and automatically cleans it by backflow of the passing liquid. The cleaning waste liquid is extracted together with excess sludge 8 and subjected to dewatering treatment.

Since the surplus sludge 8 contains the residue removed by cleaning the screen 7 from clogging, the fine fibers in the liquid serve as a dewatering aid and improve the dewatering rate.

The fiber content in the excess sludge is shown in Table 1, and the results of the dewatering test of the excess sludge are shown in Table 2.

[Function] The human waste input into the biological reaction tank 1 has its human waste removed by a drum screen (not shown) in the preceding stage, but fine fibers pass through the slits and holes of the screen. flows into the processing system. These fine fibers intertwine with each other during the aeration mixing process in the biological reaction tank 1 to form a nucleus, and the activated sludge adheres to this nucleus and grows again as sludge.
Fl! This was the cause of 4 blockages.

However, according to the present invention, the residue containing these fine fibers is U
Since it is removed by the self-cleaning screen 7 inserted before the F membrane 4, clogging of the UF membrane 4 is prevented.

On the other hand, the residue containing fine fibers removed by the screen 7 is pulled out together with the surplus sludge 8 and subjected to dewatering treatment, but since a large amount of fine fibers are mixed in the surplus sludge,
Dehydration properties are dramatically improved and the water content in the dehydrated cake can be reduced.

In addition, in order to pull out excess sludge 8 before the UF membrane 4, the U
The amount of processing liquid that passes through the F membrane is reduced, and the capacity of the UF membrane can be reduced, and the life span is extended for the same capacity.

[Effect] According to the present invention, a self-cleaning screen is inserted in the front stage of the ultrafiltration membrane, and the screen removes the scum from the mixed liquid and draws it out together with the excess dirt. Since the fibers can be mixed only into the surplus sludge to be dewatered, it is possible to use these fine fibers as a dewatering aid to improve the dewatering rate of surplus sludge that is difficult to dewater. It is possible to reduce the amount of additive added and the moisture content of the dehydrated cake.
Processing costs can be saved.

In addition, since excess sludge is extracted at the stage before the UP membrane (the capacity of the JF membrane can be reduced, and the capacity is the same, its life can be extended).

[Brief explanation of drawings]

The drawings are process diagrams showing the method of this invention. 1: Biological reaction tank 2: Circulation tank 3: Pump ultrafiltration membrane treated water Returned sludge self-cleaning screen Excess sludge including residue

Claims (1)

[Claims] 1) In the activated sludge method, in which the mixed liquid after treating human waste with activated sludge in a biological reaction tank is guided to an ultrafiltration membrane through a circulation tank and separated into sludge and treated water, the pre-stage of the ultrafiltration membrane A sludge treatment method characterized in that a self-cleaning screen is inserted into the liquid mixture, and the screen removes sludge from the mixed liquid and draws it out together with excess sludge.