JP3797693B2 - Sludge removal method in septic tank sludge - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for removing sludge in a pretreatment step of treating septic tank sludge with a biological method.
[0002]
[Prior art]
Human waste and septic tank sludge collected at the local treatment plant are released after biological treatment after passing through a pretreatment process to remove impurities and sand. In order to continue the biological treatment in a stable state, it is important to sufficiently perform a pretreatment for removing the sand and impurities contained in the stock solution in advance. That is, the collected human waste / septic tank sludge is first put into a sand settling tank to separate and separate the sand. Next, paper, cloth, plastic film, etc. are removed with a contaminant removal device such as a rotary screen. The sand that has settled in the sand settling tank is sucked with a vacuum pump and sent to the sand removal tank, where it is washed with water and then incinerated or used for landfill. The contaminants removed by the contaminant removal device are dehydrated and washed by a pressure dehydrator such as a screw press, and then subjected to the same final treatment.
[0003]
By the way, since the ratio of septic tank sludge to human waste was relatively small before, human waste and septic tank sludge were often treated together in the same equipment from the beginning. As the proportion of septic tank sludge gradually increased, the pretreatment process was divided into two lines, and human waste and septic tank sludge were often treated in separate systems. In the pretreatment process for treating human waste, the above-mentioned conventional method is used, but in the pretreatment process for treating septic tank sludge, it is possible to make the whole process more rational by removing the sludge after removing impurities. Because it can. The present invention relates to a method for removing sludge in a pretreatment process for treating septic tank sludge.
[0004]
As a method for removing sludge, sedimentation separation, flotation separation, centrifugation, and the like have been employed so far.
[0005]
[Problems to be solved by the invention]
The conventional removal methods have the following problems. The sedimentation separation method requires a large installation area and has poor concentration performance. The floating separation method is complicated in equipment, consumes a little power and has poor concentration performance. The centrifugal separation method has very high power consumption even though the concentration performance is good.
[0006]
Therefore, there has been a demand for a sludge removal method that is simple in equipment, low in equipment cost, easy in stable operation, low in operating cost, and excellent in separation performance. The problem to be solved by the present invention is to provide such a sludge removal method.
[0007]
[Means for Solving the Problems]
In the present invention, the sludge is captured by a gravity concentrator in which a cylindrical screen is vertically arranged in a pretreatment process in which the operation is only during the daytime. The next day, after dewatered sludge is removed, operation resumes. In other words, by effectively utilizing the time during which the operation was stopped, it was possible to use a gravity concentrator that was inexpensive and low in operating cost. Thereby, economical and efficient sludge removal is realizable.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The following two points are required for the sludge separation performance.
(1) Remove solids contained in the stock solution as completely as possible (removal performance)
(2) The water content in the removed solid is as low as possible (concentration performance)
[0009]
By the way, human waste and septic tank sludge are usually accepted only in the daytime. For this reason, the pretreatment process is intermittent operation only in the daytime. However, the biological treatment is naturally a continuous operation day and night.
[0010]
The inventor of the present invention has focused on the point that the operation of the pretreatment process is an intermittent operation only in the daytime. Then, it was confirmed that the object could be easily achieved with a very simple device by using a gravity type concentrator equipped with a cylindrical screen, and the present invention could be completed.
[0011]
The sludge removal method in the septic tank sludge according to the present invention is as follows. That is, in the pretreatment step of treating the septic tank sludge with a biological method, the step of removing the sludge with a gravity type concentrator in which a cylindrical screen is vertically arranged after injecting the flocculant into the stock solution from which contaminants have been removed. The pretreatment process is an intermittent operation only during the day, and in the gravity type concentrator, after the operation is stopped, the sludge is captured until the next day. The dehydration of the sludge is allowed to proceed, and the operation of the pretreatment process is resumed after removing the dewatered sludge from the gravity concentrator on the next day. In the gravity type concentrator, it is desirable to provide a cleaning pipe for ejecting the cleaning liquid at the center of the cylindrical screen.
[0012]
An embodiment of the present invention will be described. First, the outline | summary of the whole installation is demonstrated based on FIG. 1 about a sludge removal system. The stock solution is fed into the sand settling tank 1. Large sludge settles and the remainder flows over the cough and flows into the next receiving tank 2. The sludge that has settled at the bottom of the sand settling tank 1 is sent to the tank 12 by the vacuum pump 13 and eventually disposed of in landfill. The stock solution in the receiving tank 2 is sent to the contaminant removal device 4 by the crushing pump 3. The foreign matter separated by the foreign matter removing device 4 is transferred to the pressure dehydrator 5. The solid content after dehydration by the pressure dehydrator 5 is incinerated, and the liquid content is returned to the receiving tank 2. On the other hand, the remaining stock solution from which the contaminants have been removed by the contaminant removal device 4 is sent to the relay tank 6 and stored.
[0013]
The stock solution in the relay tank 6 is sent to the gravity concentrator 8 by the pump 7, and a flocculant addition line is connected to the pipe line to the gravity concentrator 8. A cationic polymer flocculant is added through the addition line, and the sludge is aggregated in a floc form and supplied to the gravity concentrator 8. Details of the gravity concentrator 8 will be described later with reference to FIG.
[0014]
The filtrate that has passed through the screen of the gravity concentrator 8 is sent to the storage tank 10. The liquid in the reservoir 10 is routed to the biological treatment process by the reservoir pump 11.
[0015]
By the way, the above work continues during the day. The sludge in the stock solution gradually accumulates inside the gravity concentrator 8. The operation of these pretreatment steps is stopped at night, but the gravity concentrator 8 is left as it is. The sludge accumulated in the gravity concentrator 8 is further dehydrated at night. The dewatered sludge is discharged by the sludge pump 9 by opening the discharge valve of the gravity concentrator 8 before restarting the operation of the pretreatment process the next day. This sludge is incinerated with the sludge obtained in the biological treatment process.
[0016]
An example of the gravity concentrator 8 is shown in FIG. The main body 20 has a vertical container shape, and the lower part is formed in a cone. A double screen in which a slightly smaller inner screen 23 is provided concentrically inside the outer screen 22 is arranged in the center of the main body 20. It is desirable that the screens 22 and 23 are made of a resin net having excellent cleaning properties, and the opening is about 1 mm. You may make it with a wire mesh.
[0017]
Between the outer screen 22 and the inner screen 23, the upper and lower sides are closed to make the inside a filtrate chamber 24. A water collection container 30 having a U-shaped cross section and a ring shape as a whole is attached to the lower portion of the filtrate chamber 24. One end of the discharge pipe 28 is attached to the lower part of the water collecting container 30, and the other end of the discharge pipe 28 is extended out of the main body 20. In the center of the double screen, a cleaning tube 25 is arranged vertically from above. A rotary joint is provided above the cleaning pipe 25 and a bearing is provided at the lower end. And several spray nozzles 26 are attached at equal intervals up and down, giving an angle difference of about 30 degrees. Although it is designed to rotate by itself, it may be rotated by an electric motor or the like.
[0018]
An undiluted solution supply pipe 29 is inserted into the main body 20 from above, and the outlet of the undiluted solution supply pipe 29 is positioned at a position where the liquid passing through the screens 22 and 23 becomes as uniform as possible. A discharge port provided with a discharge valve 21 is provided at the lower end of the main body 20, and a cleaning liquid discharge port 31 is provided above the discharge port.
[0019]
The thing of FIG. 2 is used as follows. The discharge valve 21 and the cleaning liquid discharge port 31 are closed, and the raw solution is supplied from the raw solution supply pipe 29 into the main body 20. Although the structure is simple, the filtration area by the double screen is wide. Then, the filtered solid matter descends by gravity while sliding on the surface of the screen. Since the entire surface of the screen is constantly updated, filtration can be continued for a long time. When solid matter accumulates in the main body 20 to some extent, the supply of the stock solution is stopped and left as it is until the next day. Since the filtration through the screens 22 and 23 is continued even when left standing, the concentration of the solid matter further proceeds. On the next day, the discharge valve 21 is opened to discharge the solid matter. When the discharge is completed, the discharge valve is closed, the cleaning liquid discharge port 31 is opened, and the cleaning liquid is allowed to flow from the cleaning pipe 25. The spray nozzle 26 rotates while jetting the cleaning liquid, and the screens 22 and 23 are cleaned. When the cleaning is finished, the supply of the cleaning liquid is stopped, the cleaning liquid discharge port 31 is also closed, and the supply of the raw liquid from the raw liquid supply pipe 29 is resumed.
[0020]
The measurement results on the sludge separation performance obtained in the experiment are shown below.
Solid content concentration in relay tank 13000 mg / liter Solid content concentration in storage tank 760 mg / liter Solid content concentration in concentrated sludge 5%
[0021]
【The invention's effect】
According to the present invention, the equipment is inexpensive and the operation cost is low. And efficient sludge removal can be performed.
[Brief description of the drawings]
FIG. 1 is a flow sheet showing an embodiment of the invention.
FIG. 2 is a longitudinal sectional view showing a main part of what is shown in FIG.
[Explanation of symbols]
8 Gravity Type Concentrator 20 Main Body 21 Discharge Valve 22 Outer Screen 23 Inner Screen 24 Filtrate Chamber 25 Wash Pipe 26 Spray Nozzle 28 Discharge Pipe 29 Stock Solution Supply Pipe 30 Drainage Container 31 Wash Liquid Discharge Port

Claims (2)

In the pretreatment step of treating the septic tank sludge with a biological method, a step of removing the sludge with a gravity concentrator in which a cylindrical screen is vertically arranged after injecting the flocculant into the stock solution from which impurities have been removed is provided. The biological treatment process is a continuous operation all day, but the pretreatment process is an intermittent operation only during the daytime, and in the gravity concentrator, after the operation is stopped, the sludge is trapped and left until the next day. The method for removing sludge from the septic tank sludge is characterized in that the dewatering of the sludge is advanced and the operation of the pretreatment process is resumed after removing the dewatered sludge from the gravity concentrator the next day. The method for removing sludge in septic tank sludge according to claim 1, wherein the gravity type concentrator is provided with a cleaning pipe for ejecting a cleaning liquid in the center of the cylindrical screen.

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