JP2001070997A - Treatment method of filtrate and washing wastewater in sludge dewatering machine - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To increase the recovery rate of sludge solids, prevent an increase in solids load of a water treatment system, and reduce the treatment cost by efficiently using a flocculant on sludge. To provide a method for treating filtrate and washing wastewater in a sludge dewatering machine capable of performing the treatment. SOLUTION: Filtrate discharged from a screen 9 of a sludge dewatering machine 6 for dewatering sludge and washing drainage D of a screen surface.
Is supplied to the stirring tank 11 and the sedimentation separation tank 13, and the solids in the wastewater are re-agglomerated, sedimented and separated, and the separated and collected solids are supplied to the sludge supply tank disposed in the preceding stage of the sludge dewatering machine 6. Return to 2.

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 filtrate and washing wastewater in a sludge dewatering machine, and more particularly to a method for removing solid matter from filtrate and the like generated when dewatering excess sludge generated from a facility for treating organic wastewater. The present invention relates to a method for treating filtrate and washing wastewater in a sludge dewatering machine capable of efficiently performing separation and collection, particularly separation and collection of solids from filtrate and the like generated during dewatering of sludge in a small-scale sewage treatment plant. is there.

[0002]

2. Description of the Related Art Conventionally, as a dehydrator for sludge generated from a small-scale sewage treatment facility, a screw press type dehydrator capable of continuously dehydrating has been adopted. In order to effectively dewater sludge by the screw press type dehydrator, a flocculant is added to the sludge in advance, and the aggregated sludge is supplied to the sludge dehydrator.

[0003]

However, even if a coagulant is added to the sludge, not all the sludge forms strong and large flocs, and the screen width (for example, 0.1 to 0) is not used. (About 0.5 mm), and further pressurized in the vicinity of the cake outlet, fragile sludge flocs were crushed and refined again, so that these sludge particles were placed on the outside of the screen. There was a problem of being pushed out.

Further, in order to eliminate clogging of the screen during sludge dewatering, cleaning water is sprayed from the outer periphery of the screen to perform cleaning. A large amount of solid matter is discharged together with the washing wastewater because sludge that has adhered to the screen is washed off from the screen by the washing water.Therefore, a large amount of solid matter is contained in the filtrate and washing wastewater by the screw press type dehydrator. May be included, and usually
All wastewater containing high-concentration solids is returned to the water treatment system for treatment.In that case, however, the solids load of the water treatment system increases, which has the problem of adversely affecting water treatment performance and treatment costs. there were.

The present invention has been made in view of the problems of a conventional method for treating filtrate and washing wastewater in a screw press type sludge dewatering machine, and has therefore improved the sludge solids recovery rate and increased the solids load of a water treatment system. It is an object of the present invention to provide a method for treating a filtrate and a washing wastewater in a sludge dewatering machine, which can reduce the treatment cost by preventing the flocculant from acting on the sludge efficiently.

[0006]

In order to achieve the above object, a method for treating filtrate and washing wastewater in a sludge dewatering machine according to the present invention comprises a method of treating a filtrate and a screen discharged from a screen of a sludge dewatering machine for dewatering sludge. The washing wastewater is supplied to a sedimentation separation tank, and solids in the wastewater are precipitated and separated, and the separated and recovered solids are returned to a sludge supply tank disposed in a preceding stage of the sludge dewatering machine. And

The method for treating the filtrate and the washing wastewater in this sludge dewatering machine is as follows. In the dewatering of the sludge, solids in the filtrate and the washing wastewater at the time of washing the screen are precipitated and separated, and the supernatant is returned to the water treatment system. The sludge solids separated and settled are returned to the sludge supply tank and dewatered again, so that the recovery rate of the sludge solids is increased to prevent an increase in the solids load of the water treatment system and to efficiently use the flocculant. By acting on sludge, treatment costs can be reduced.

[0008] In this case, the filtrate discharged from the screen and the washing wastewater of the screen surface can be supplied to the precipitation separation tank via the stirring tank.

As a result, the flocculation of the sludge contained in the filtrate and the washing wastewater can be promoted, and the gravity can be efficiently settled in a short time in the sedimentation / separation tank.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for treating filtrate and washing wastewater in a sludge dewatering machine according to the present invention will be described below with reference to the drawings.

According to the present invention, sludge generated from a wastewater treatment facility such as a sewage treatment plant is supplied to a screw press type sludge dewatering machine for continuously dewatering, and dewatered, and the dewatered cake is discharged from a cake discharge port of the dewatering machine. While draining, the filtrate discharged from the screen of the sludge dewatering machine during dewatering, and the screen is periodically cleaned when the dewatering machine is operated for a long period of time, and the cleaning drainage when the sludge adhering to the screen is washed off is removed. By guiding to a stirring tank arranged in the latter stage of the dehydrator and performing slow mixing using a stirrer arranged in the stirring tank,
The solids in the filtrate and the washing wastewater are coagulated again, so that solid-liquid separation becomes easy.Then, this flocculent floc is guided to a sedimentation separation tank arranged at the subsequent stage, and is included in the sedimentation separation tank in the wastewater. The re-agglomerated solids are gravity precipitated, and the sedimented and separated solids are transferred to a sludge supply tank disposed in the former stage of the dehydrator and subjected to the dehydration treatment again, thus circulating the solids in the drainage water. The supernatant liquid that has been removed and contains almost no sludge solids is returned to a water treatment system such as an aeration tank or a pump tank.

FIG. 1 is a schematic explanatory view of an example of a wastewater treatment facility such as a sewage treatment plant for implementing a method for treating filtrate and washing wastewater in a sludge dewatering machine according to the present invention.
The excess sludge generated in the aeration tank 1 is drawn out of the aeration tank 1, and is supplied to the sludge supply tank 2 by a sludge transfer pump 21. To be supplied. In this sludge supply tank 2, a stirrer 3 is installed to stir the excess sludge so that the excess sludge is temporarily stored. In addition to the method of extracting the excess sludge from the aeration tank 1, it is also possible to extract the sludge subjected to precipitation and concentration from the concentration tank or the storage tank based on a normal flow.

Reference numeral 4 denotes a mixing tank, and a sludge supply pump 22
Is connected to the sludge supply tank 2 by the sludge supply pipe 16 provided with the coagulant C supplied into the mixing tank 4 and mixed with the sludge fed to the mixing tank 4 provided with the stirrer 5. Is done. As a result, the sludge forms flocculated flocs with the flocculant C. Further, a sludge dewatering machine, for example, a screw-type sludge dewatering machine 6 as shown in the figure is disposed downstream of the sludge supply tank 2 and the mixing tank 4, and the flocculated flocs flocculated in the preceding mixing tank 4 are dewatered. To the machine 6.

The screw type sludge dewatering machine 6 comprises a screw 8 rotated by a driving device 7, a screen 9 disposed around the screw 8, and a back pressure plate 10 disposed at the tip of the screw 8. The flocculated floc is supplied to a supply port of the sludge dewatering machine 6. The dewatered cake B of the flocculated floc dewatered by the sludge dewatering machine 6 is supplied to the dewatered cake discharge port 1 which is a gap between the screen 9 and the back pressure plate 10.
Filtrate D discharged from the screen 5 and flowing out of the screen 9 through the slit of the screen 9 is disposed so as to be guided to the stirring tank 11.

A washing device (not shown) such as a nozzle for spraying washing water for washing the screen surface is provided outside the screen 9, and the washing wastewater after washing the screen 9 is similar to the filtrate. Then, it is drained into the stirring tank 11. The structure and shape of the screen surface cleaning device are not particularly limited.

The stirring tank 11 is provided with a stirrer 12,
The filtrate of the screen 9 and the washing wastewater of the screen 9 are guided to the stirring tank 11 and are stirred by the stirrer 12. This stirring is performed without using the stirrer 12, for example, by utilizing a flowing flow. It is also possible to use a method other than the conventional means. In the stirring tank 11, the solid matter in the wastewater which has been gently stirred by the stirrer 12 and re-agglomerated is guided to the sedimentation separation tank 13 provided at the subsequent stage, where it is allowed to stand and separated. In this sedimentation separation tank 13,
It is also possible to arrange the sludge interface meter 14.

The solid precipitated in the sedimentation / separation tank 13 is returned to the sludge supply tank 2 via a sludge return pipe 17 provided with a sludge return pump 23.
The supernatant is returned to the aeration tank 1 or a water treatment system such as a pump tank via the return water pump 24 and the return water pipe 18. In this manner, the sewage containing the sludge is circulated through the sludge supply tank 2, the sludge dewatering machine 6, the sedimentation separation tank 13, and the like to remove solids.

Next, a method of treating filtrate and washing wastewater by a wastewater treatment facility such as a sewage treatment plant will be described. Organic substances contained in the sewage A flowing into the aeration tank 1 are decomposed and mineralized by activated sludge microorganisms. Although excess sludge is generated due to this decomposition, it is necessary to periodically pull out this sludge in order to keep the sludge concentration in the aeration tank 1 constant. Sludge can be pulled out through a sedimentation tank and a sludge concentration tank at the subsequent stage of the aeration tank 1 as in a normal flow, and the precipitated and concentrated sludge can be pulled out from a sludge storage tank or the like and supplied to a dehydrator. However, as shown in FIG. 1, a method in which the sludge in the aeration tank 1 is pulled out by the sludge transfer pump 21 to perform dehydration is more desirable from the viewpoint of the stability of the sludge concentration. The sludge transferred to the sludge supply tank 2 prevents concentration change due to settling of the sludge,
Stir with stirrer 3.

Next, the sludge kept homogeneous is supplied to the mixing tank 4 by a sludge supply pump 22. In the mixing tank 4, the mixture is stirred and mixed with a flocculant by a stirrer 5 set to a desired number of revolutions to form a flocculant floc.

The flocculation floc is filtered and dewatered while being sent through the cylindrical screen 9 toward the dewatering cake discharge port 15 by the screw 8 rotated by the driving device 7. The flocculated floc of the sludge is finally pressurized by the back pressure plate 10 and discharged as the dewatered cake B from the dewatered cake outlet 15. At this time, not all of the supplied sludge solids form strong and large flocs, but contain particles finer than the mesh width (about 0.1 to 0.5 mm) of the screen 9 or the cake outlet. These fine sludge particles are extruded to the outside of the screen 9 because they are pressurized in the vicinity and the fragile flocculated flocs are refined.

Further, when the screen 9 is washed from the surroundings, after passing through the screen 9, the sludge adhering to the outer periphery is washed off the screen 9 by the washing water.
A large amount of solid matter is discharged together with the washing wastewater.

The filtrate and the washing wastewater are introduced into the stirring tank 11 and gently stirred by the stirrer 12, whereby the sludge contained in the filtrate and the washing wastewater is adsorbed on the sludge particles or contained in the filtrate. By reacting with the flocculant, flocculated flocs of sludge are formed again. Although the flocculated floc has a smaller particle size than the flocculated floc formed in the mixing tank 4, the sedimentation of the sludge is increased in the sedimentation separation tank 13 at the subsequent stage due to re-coagulation, so that gravity sedimentation can be efficiently performed in a short time. it can.

The sludge solids precipitated in the precipitation separation tank 13 are:
The sludge is transferred to the sludge supply tank at a predetermined flow rate by the sludge transfer pump 23. In addition, when there is a height difference in the water level, it is possible to return the water without power, and the sludge may be returned intermittently by a timer or the like. Alternatively, it is also possible to install a sludge interface meter 14 or the like in the sedimentation separation tank 13, detect the rise of the sludge interface position, and automatically extract the sludge intermittently.

On the other hand, the supernatant water of the sedimentation separation tank is returned to the water treatment system such as the aeration tank 1 by the return water pump 24, and it is more preferable that the supernatant water flow naturally by utilizing the difference in water level.

Although the case where the sludge in the aeration tank is dehydrated has been described above, the present invention is not limited to this case, and the present invention is not limited to this case. The same can be applied to the case where the sludge solids in the filtrate and the washing wastewater are to be recovered by the machine.

[0026]

According to the method for treating filtrate and washing wastewater in the sludge dewatering machine of the present invention, in the dewatering of sludge, solids in the filtrate and washing wastewater at the time of screen washing are precipitated and separated, and the supernatant is water. The sludge solids that have been returned to the treatment system and settled and separated are returned to the sludge supply tank and dehydrated again, thereby increasing the sludge solids recovery rate and preventing the solid matter load in the water treatment system from increasing. In addition, by making the flocculant act on the sludge efficiently, the treatment cost can be reduced.

Further, by supplying the filtrate discharged from the screen and the washing wastewater of the screen surface to the sedimentation / separation tank via the stirring tank, the flocculation of the sludge contained in the filtrate and the washing wastewater is promoted. Gravitational precipitation can be performed efficiently in a short time in the precipitation separation tank.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view showing an example of a wastewater treatment facility such as a sewage treatment plant for performing a method for treating a filtrate and washing wastewater in a sludge dewatering machine of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Aeration tank 2 Sludge supply tank 3 Stirrer 4 Mixing tank 5 Stirrer 6 Sludge dewatering machine 7 Drive device 8 Screw 9 Screen 10 Back pressure plate 11 Stirring tank 12 Stirrer 13 Sedimentation separation tank 14 Sludge interface meter 15 Dewatering cake discharge port 16 Sludge supply pipe 17 Sludge return pipe 18 Return water pipe 21 Sludge transfer pump 22 Sludge supply pump 23 Sludge return pump 24 Return water pump A Sewage B Dewatering cake C Coagulant D Filtrate

Claims (2)

[Claims] 1. Filtrate discharged from a screen of a sludge dewatering machine for dewatering sludge and washing wastewater on a screen surface are supplied to a sedimentation separation tank, and solid matter in the wastewater is sedimented and separated. Of the filtrate and the washing and drainage in the sludge dewatering machine, wherein the wastewater is returned to a sludge supply tank provided in a preceding stage of the sludge dewatering machine. 2. The sludge dewatering machine according to claim 1, wherein the filtrate discharged from the screen and the washing wastewater of the screen surface are supplied to a sedimentation separation tank via a stirring tank. Processing method.