JPH02277516A - Separator of suspended matter in liquid and operating method thereof - Google Patents

Abstract

PURPOSE:To efficiently remove suspended matter by rotatably and axially supporting a drum type screen and also circumscribing a rotary brush to the drum type screen. CONSTITUTION:Inflow drainage is introduced into a cushioning tank 1 and sent into a wedge wire drum type screen A by a storage pump 2 to perform solid-liquid separation. Separated sludge S is received in a sludge basket N provided to the terminal part of the drum A. Separated drainage is allowed to flow in an activated sludge aeration tank B to perform secondary treatment and chlorine disinfection is performed and then drainage is discharged to the water area for public. Thereby the removal efficiency of suspended matter is enhanced and clogging is prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a device for separating suspended substances in a liquid and a method for operating the same, and more particularly relates to a device for separating suspended substances in a liquid using a drum type screen and a method for operating the same. .

[Conventional technology]

Conventionally, in sewage treatment systems, a sedimentation separation system is well known as a basic means for removing sludge substances floating in sewage.

This precipitation separation method has the advantages of easy operation and relatively reliable solid-liquid separation, and is the most basic operation for solid-liquid separation. If the particle size and specific gravity of the sludge is small, a large-capacity and wide settling tank is required, and the separated sludge has a large amount of moisture. When attempting to separate the suspended solids, even if a large-capacity settling tank is used, the removal rate of suspended solids is only 30 to 40%, and the settled sludge easily rots in the settling tank, and the water content of the sludge is at most 98%.
There is a problem that it only becomes about %.

As a solid-liquid separation method capable of solving such problems, a screening method using a net-like sieve is known.

[Problems with conventional technology]

However, this screening method has the fatal disadvantage of clogging of the phloem, requires a washing method to prevent clogging, requires a lot of maintenance, and has extremely high physical properties of suspended particles. If the material is soft and easily destroyed, there is a problem in that the suspended matter comes into contact with the net-like sieve and is crushed to a size that can be seen through the eyes, resulting in an extremely low sludge removal rate.

In addition, as the sieve, a known drum type screen is used, in which annular wedge wires having a triangular cross section are arranged at minute intervals in the axial direction so that the inner surface is flat and formed into a cylindrical shape with a smooth inner surface. Attempts have also been made to remove suspended sludge.

In other words, when a known wedge wire drum type screen is held almost horizontally, a liquid containing suspended matter is continuously fed into one end, and the drum is rotated at a low speed, the liquid flows out from the slits between the wedge wires. As a result, floating matter remains on the inner surface of the cylinder. This floating material has a greater affinity with each other than with the metal or plastic that makes up the wedge wire, so the floating material remaining on the inner surface of the cylinder becomes lumpy sludge, and the other end of the drum It starts to fall down.

However, such action does not reach the extent of removing the gaps between the wedge wires and the floating matter on the outer surface, and the gaps eventually become closed.

Therefore, even if you try to put this type of drum type screen into practical use for removing suspended matter from sewage, it will take 1 to 2 months.
Maintenance to prevent clogging is required once every six months at most, which is still insufficient for practical use.

[Problem to be solved by the invention]

In view of the above-mentioned problems, the present invention provides an efficient suspended solids separation device and its operating method, in which the moisture content of removed sludge is kept low and maintenance work is required only once a year. It was done for the purpose of

[Technology that led to solving the problem]

That is, in the device for separating suspended substances in a liquid according to the present invention, annular bodies made of wedge wires having a triangular cross section are arranged at minute intervals in the axial direction, and a drum type screen formed into a cylindrical body with a smooth inner surface is arranged around a horizontal axis. A wiper is fixed to the base frame and has a uniform contact surface in the axial direction on the inner surface of the drum type screen, and a wiper having a diameter of at least the tip of the wiper on the outer periphery of the drum type screen is fixed to the base frame. The second invention is characterized in that a rotating brush made of a rigid fibrous body with a spacing smaller than a minute interval is rotatably supported in a circumscribed state so as to be able to rotate forward and backward. Regarding the operating method of the separation device, a drum type screen in which annular bodies made of wedge wires with a triangular cross section are arranged at minute intervals in the axial direction and has a smooth inner surface is horizontally operated at a circumferential speed of 30 Qcts for 7 minutes or less. The rotary brush is rotated around the shaft to allow the wastewater to be treated containing suspended matter to flow into the drum type screen, and the sludge adhering to the inner surface of the drum type screen is scraped off by a wiper. It is characterized by intermittent forward and reverse rotation at fixed time intervals at a circumferential speed of 300 cm and 7 minutes or less.

[Function] As mentioned above, in a solid-liquid separation system using a drum type screen, prevention of clogging is a very important issue.

A natural method to prevent clogging is to install a rotating brush in the upper half of the outer periphery of the drum, parallel to its long side, and rotate it in the same direction as the drum rotates or in the opposite direction. Rotate the wire and brush to remove any obstructions in the gaps between the wires.

When the wedge wire gap is large, it is relatively easy to prevent clogging using this method, but according to the experiments of the present inventors, in the case of a very narrow gap close to 0.1 mI++, the following conditions should be met. It became clear that the requirements had to be met.

■ The tips of the bristles of the rotating brush are thinner than the gaps in the wear wire, and their rotation continuously reaches the inner surface of the drum.

■ The bristles of the rotating brush must be long enough to meet the conditions in ■, but if the bristles are too soft and the bristles are too long,
During long-term use, the bristles will become flattened and the effectiveness of brushing will be diminished. Therefore, you should make the bristles thin and strong, or shorten the bristles to the extent that brushing is not hindered, or make sure that the tips of the bristles are very thin ( Care must be taken to make the hair look like it is.

■ If the bristles of the rotating brush are made of a hydrophilic material such as nylon, the bristles will peck each other during long-term use, and even though the individual bristles are thin, they will not easily pass through the gaps between the wedge wires. The hair must be made of a strong, hydrophobic material like polyester, as the 1 or 2 substances that are removed by storing or brushing will stick to the hair and make it difficult to separate.

However, a Ufuji wire screen with a diameter of 20 cm and a length of 30 cr using a rotating brush that satisfies these conditions (it is installed so as to be lightly pressed against the rotating brush drum, and the rotating brush is reversely rotated just by the rotation of the drum) We conducted an experiment on solid-liquid separation of sewage using the brushing method, but although the screening was successful for the first few weeks, it gradually became clogged and became completely clogged in about two months. . A detailed investigation into the cause of such blockage revealed that it was caused by the following phenomenon.

+11 In order to fix the wedge wire ring with a certain gap, a thin linear or plate-shaped support loft is placed on the outer periphery at right angles to the ring and welded. During rotation, floating particles adhere to the side parts of the support loft and wedge wire that are on the rear side in that direction, making it difficult to remove with such brushing, and which may over time fill some of the gaps. occlusion, reducing the effective filtration area for separation.

(2) Even if the bristles of the rotating brush are made to be quite strong, if they are kept in one direction for a long time, the wedge wire drum,
In particular, when it comes into contact with the support loft mentioned in (1) and receives a force in a certain direction, the bristles will lie in a certain direction, and as in the initial stage, the bristles will move from the gap between the wedge wires to the inner surface of the drum. becomes difficult to reach.

Based on the results of elucidating such causes, the rotation direction of the rotating brush is changed at fixed time intervals (every 15 minutes, every 30 minutes, every 6 minutes).
A solid-liquid separation experiment similar to that described above was carried out by brushing by reversing the plate in the forward and reverse directions (every 0 minutes). There was no significant difference in the brushing effect whether the rotating brush was rotated by a motor separate from the drum or by transmitting the rotation of the drum to the brush.

Changing the time interval for forward and reverse reversal did not change the effect. As a result of such experiments, the phenomena (1) and (2) above were significantly alleviated, and it became possible to perform solid-liquid separation without clogging for several months. One element of the present invention is that the rotating brush installed on the outer periphery of the wedge wire drum type screen is brushed by reversing it in forward and reverse directions at regular intervals.

However, after a few months, some of the gaps in the drum-type screen began to become clogged, and it became clear that it was difficult to continue solid-liquid separation without maintenance. As a result of a detailed investigation into the causes and phenomena, we found that even if the rotating brush prevents the gap between the wedge wires from clogging, floating matter gradually accumulates on the smooth inner surface of the wedge wire, and some of it accumulates in the gap. It was found that it became stuck and could not be easily removed with a rotating brush. Furthermore, it has been found that this phenomenon occurs more easily as the amount of oil in the liquid to be treated increases.

As a means to prevent such a phenomenon, a wiper or brush is installed vertically in contact with the upper edge of the inner periphery of the wedge wire/drum type screen, so that even the slightest amount of floating matter adhering to the smooth inner surface can be scraped off. That's what I do. Thus, the installation of a fixed wiper or brush on the inner surface of the drum is another element of the invention.

By installing a fixed wiper or brush in combination with the above-mentioned forward and reverse rotation of the rotating brush, solid-liquid separation of ordinary sewage can be carried out for a long period of one year or more even in the case of a very narrow wedge wire gap of 0.11111 mm. We were able to experimentally demonstrate that this can be done completely maintenance-free.

In addition to the above conditions, we also tried using two or three rotating brushes installed on the outer periphery of the drum instead of just one as described above, but we found that they were better at preventing clogging. too,
This increased the rotational resistance of the drum and brushes. In addition, the rotational speed of the rotating brush on the outer periphery is approximately the same as the peripheral speed of the drum when the brush is moved by transmitting the rotation of the drum, and the peripheral speed of the drum suitable for solid-liquid separation is 300 cm/min. It was sufficient that the brush was also linked to the following. If the rotating brush is driven by a separate motor, if the rotating direction is the same as the drum, it will likely suppress the drum's rotation, and if it is in the opposite direction, it will likely promote the drum's rotation. In that case as well, it is desirable that the rotational circumferential speed of the brush be the same as, or close to, the circumferential speed of the drum as much as possible. The installation angle of the drum is almost horizontal or 1 to 3 degrees in the direction of movement of the sludge mass.
It should be a downward slope of ″′.

〔Example〕

Example 1 In order to further clarify the application method and effects of the present invention described above, the following example is shown.

As shown in Figure 1, 50 people, 1110I wastewater
lff 7 days (B00 approx. 20 (lag/l, suspended solids approx. 200 mg/l) in domestic wastewater treatment equipment,
The inflow wastewater is received in a cushion tank 1 of approximately 7C, and from there the wastewater is sent to the wedge wire drum type screen A according to the present invention by a water pump 2 of 81/min, where it is separated into solid and liquid. The separated sludge S is received in a basket N installed at the end of the drum A, and the separated wastewater flows into the activated sludge aeration tank B installed at the bottom of the device, where it is subjected to secondary treatment and disinfected with chlorine. The water was released into public waters.

The drum type screen A in the above has a triangular cross section as shown in Figure 2, and has a diameter of approximately 3 mm with a smooth inner surface.
Ring A of 0cm stainless steel edge wire-A! Arrange them at intervals of O, l, about 70 cm deep, and 50 cm.
Height at m position? A ring-shaped weir A of
It is welded into a drum shape. The drum A is placed on a horizontally arranged roller R, a gear (not shown) is provided on the outer periphery of the inflow end of the drum A, and a gear (not shown) is connected to a reduction motor with a chain 7, so that the drum A is rotated at a speed of 1.5 rpm (peripheral speed The rotation speed was approximately 135 clIIZ minutes) and rotated in forward and reverse directions every 30 minutes. A scraper C, in which polyester bristles were grafted in a straight line so as to have a length of approximately Ion's length, was vertically fixed so as to contact the upper end of the inner circumferential portion of the drum A.

Furthermore, by lightly pressing the ring A2 of the wedge wire parallel to the drum A diagonally above the outer periphery of the drum, a polyester wire with a tip thickness of O, O1l+am, a base thickness of 0.25 mm, and a length of 30 mm is placed. A rotating brush D was installed, which had hairs planted on a rotating shaft with a diameter of 50+ mm. The rotation of the rotating brush D was caused by the movement of the rotation of the drum, and no separate driving equipment was provided.

The device continued to operate by sending domestic wastewater to it for over a year, but
During that time, there were no problems and it was always working normally. Both the fixed brush of scraper C and the rotating brush D were somewhat dirty after one year of use, but they were not damaged to the point that they needed to be replaced. The removal rate of suspended solids was 33 to 45%, with an average of about 37%, and the removal rate of BOD was 27 to 38%, with an average of 31%. The solid-liquid separated water undergoes activated sludge treatment, resulting in 5rsg/j of suspended solids! below,
BOD 15mg/j! It was discharged at the following levels. The sludge mass discharged from the end of the drum had a moisture content of approximately 89% immediately after discharge, but as it gradually accumulated in the basket, it underwent drying and aerobic fermentation, and the average moisture content decreased to approximately 65% after one month. (There was little odor).

〔effect〕

Although this invention can easily be seen as a well-known wedge wire drum type screen with only a few additional devices and operations added, it is clear from the detailed description that it can be used for solid-liquid separation including suspended matter. This means that we have provided a new technology that can demonstrate the following remarkable effects in the technical field of technology.

(1) When ordinary household sewage is fed into the drum-type screen of the present invention with a wedge wire gap of 0.11 mm and solid-liquid separation is performed, approximately 35% of suspended solids are removed (
0.25 s+m (approximately 25% removal), which is comparable to the removal rate of suspended solids in a normal sewage primary sedimentation tank.

(21 (Even with a screen with fine gaps like 11, 1
It can operate completely maintenance-free and perform solid-liquid separation for more than a year without clogging (if the rotating and fixed brushes become worn out after a year or more, just replace them).

(3) Even in cases where there is a lot of organic content, such as in sewage, the separated suspended solids can be separated as sludge with a moisture content of 90% or less, compared to conventional sedimentation separation, which only accounts for 98% at most. , you will be severely dehydrated. It serves to reduce the amount of sludge handled and facilitate subsequent sludge treatment.

(4) Sedimentation separation requires a certain sedimentation tank area (water area load) and a certain residence time for the amount of liquid fed, but in the device of the present invention, the required area is 1/3 of the sedimentation tank. ~1
/2 In addition, the volume is 1/25 to 1/15 of that of a sedimentation tank, making it extremely compact.

Furthermore, since it does not carry a large load, it can be easily installed in a building built on top of a processing facility for the liquid part after solid-liquid separation, so the entire facility can be installed in a significantly narrow space. become.

(5) The power required for solid-liquid separation is extremely small because it only rotates the drum and brushes at low speed.

(6) Although the main focus was on solid-liquid separation of sewage without clogging, this technology has a wide range of applications.For example, in the industrial field, raw materials such as water, acid, etc.
It can also be used when dissolving with an alkali, solvent, etc. and attempting to separate the dissolved and undissolved parts.

It is also versatile, as it can be used to separate coarse and fine particles, such as making strained bean paste by steaming, grinding, and sifting adzuki beans.

[Brief explanation of drawings]

FIG. 1 is a side view showing an embodiment of the present invention, FIG. 2 is a sectional view of a wedge wire, and FIG. 3 is a perspective view of a device for separating suspended substances in a liquid. ln

Claims (2)

[Claims] (1) A drum-type screen in which annular bodies made of wedge wires having a triangular cross section are arranged at minute intervals in the axial direction and has a smooth inner surface is rotatably supported around a horizontal axis, and the drum On the inner surface of the type screen, a wiper having a uniform contact surface in the axial direction is fixed to the base frame, and on the outer periphery of the drum type screen there is a wiper with a rigid wiper whose bristles have a diameter smaller than the minute interval. A device for separating suspended matter in a liquid, characterized in that a rotating brush made of a fibrous material is pivotally supported in a circumscribed state so as to be able to rotate forward and backward. (2) A drum type screen in which annular bodies made of wedge wires with a triangular cross section are arranged at minute intervals in the axial direction and has a smooth inner surface is rotated around a horizontal axis at a circumferential speed of 300 cm/min or less. , the sewage to be treated containing suspended matter is allowed to flow into the drum-type screen, and the sludge adhering to the inner surface of the drum-type screen is scraped off by a wiper, while the rotating brush circumscribing the outer surface of the drum-type screen is moved at a circumferential speed of 300 cm/min. A method of operating a device for separating suspended substances in a liquid, which is characterized by performing forward and reverse rotation intermittently at regular time intervals.