WO1987000073A1

WO1987000073A1 - A device for the separation of solid substances from waste water

Info

Publication number: WO1987000073A1
Application number: PCT/FI1985/000066
Authority: WO
Inventors: Vilho Dunder
Original assignee: Insinooritoimisto Lujari Oy
Current assignee: Insinooritoimisto Lujari Oy
Priority date: 1985-07-11
Filing date: 1985-07-11
Publication date: 1987-01-15
Anticipated expiration: 1988-01-11
Also published as: GB8800218D0; NO870997D0; SE8800053L; DE3590820T1; CH663357A5; NO870997L; GB2199511A; SE8800053D0

Abstract

The device comprises a slowly rotating screening drum (1) which is provided with feeding devices for feeding waste water into the screening drum from one end (2) thereof and with devices for discharging solid substances out from the other end of the screening drum. The water is thereby filtered through a mantle (5) of the screening drum. The solid substances for their part are passed forwards inside the screening drum by means of transversal ribs (4) positioned slantingly with respect to the direction of rotation of the drum and, further, are agitated in the screening drum by the action of longitudinal ribs (3) extending over the length of the drum. In order to provide a filtration as effective as possible, at least some of the longitudinal ribs (3) are slanted with respect to the radial direction of the screening drum (1) in such a manner that an angle between that surface of the longitudinal rib (3) which faces in the direction of rotation of the screening drum and the inner surface of the screening drum mantle (5) is smaller than an angle between that surface of the longitudinal rib (3) which faces backwards with respect to the direction of rotation and the inner surface of the screening drum mantle (5).

Description

A device for the separation of solid substances from waste water

The invention relates to a device for the separation of solid substances from waste water, which device comprises a slowly rotating screening drum, which is provided with feeding devices for feeding waste water into the screening drum from one end thereof and with devices for discharging solid substances out from the other end of the screening drum, whereby water is filtered through a mantle of the screening drum and whereby the solid substances are passed forwards inside the screening drum by means of transversal ribs positioned slantingly with respect to the direction of rotation of the drum and, further, are agitated in the screening drum by the action of longi¬ tudinal ribs extending over the length of the drum.

This kind of devices are today extremely well- known and they are used in the purification of both industrial and community waste waters. The devices described in Swedish Published Specification 332,146 and German Offenlegungsschrift 2,711,528 may be mentioned as examples of known devices. A disadvantage of these known devices is their relatively complicated construction, because these devices must in practice be fitted in a slanting position in order to provide a sufficient separating capacity. If said devices are positioned in a horizontal position, so a flushing system of a great water demand and the recovering devices thereof must be fitted inside the drum.

Thereby it is uneconomical to stabilize the sludge formed of solid substances by means of polymers. Said stabilization is uneconomical due to the fact that the additives largely remain in the water on account of the great amount of flush water. Also centrifugal separators are used in the purification of waste waters. A disadvantage of these devices is their sensitivity to abrasive solid sub¬ stances of particles thereof. Also the operating costs of centrifugal separators are high. A further disadvan¬ tage is that lime or ash cannot be used in a centrifugal separator for controlling pH because of the effect wearing the device.

The object of the invention is to provide a 0 device which avoids the disadvantages of the previously used devices. This is achieved by means of a device according to the invention, which is characterized in that at least some of the longitudinal ribs are slanted with respect to the radial direction of the screening 5 drum in such a manner that an angle (^~zk _*. ) between that surface of the longitudinal rib which faces in the direction of rotation of the screening drum and the inner surface of the screening drum mantle is smaller than an angle (0.») between that surface of said 0 longitudinal rib which faces backwards with respect to the direction of rotation and the inner surface of the screening drum mantle.

An advantage of the invention is, above all, its simplicity and low operating costs. The operation is 5 economical among other things, due to the fact -that the amount of flush water required is small and that both conventional pH control agents and ash can be used in a highly advantageous manner. The device according to the invention is extremely simple in 0 construction, for no shaft, for instance, is needed for supporting the screening drum. The operation of the device according to the invention is not disturbed by the presence of abrasive solid substances. As a matter of fact, it has been found out in practice 5 that stones, for instance, have no effect on the operation of the device. Besides, the device according to the invention is effective, for, on account of an extremely efficient agitation, ash in place of polymers can be used as a means for neutralizing phosphor, which results in an ecologically beneficial waste and great savings. In comparison with the previously used methods, it is also more economical to rise the pH-value of the waste by means of lime or ash. This is due to the fact that said substances can be fed into the drum at a point as advantageous as possible.

The invention will be described in the following more closely by means of certain preferred embodiment examples shown in the attached drawings, whereby

Figure 1 is a perspective view of a screening drum of a device according to the invention as a partial section,

Figure 2 shows in principle the position of the screening drum of Figure 1 in a purification apparatus, Figure 3 shows the principal features of an axial cross-sectional view of the screening drum according to Figure 1 , and

Figure 4 shows the principal features of another advantageous form of the axial cross-section for the screening drum according to Figure 1. The invention relates to a water purification device, the essential part of which consists of a rotating screening drum 1. The waste water to be purified is passed inside the screening drum 1 through one end 2 of the drum, and as the drum rotates, the sludge is agitated during its progress longitudinally through the drum, water being discharged through a porous mantle 5 of the drum. When the screening drum 1 rotates, the sludge formed by solid substances rises upwards in the direction of the periphery of the drum by virtue of longitudinal ribs 3 fitted on the inner surface of the screening drum mantle 5 and extending over the whole length of the screening drum 1. When the drum rotates, the sludge rises upwards until it drops down on the sludge on the bottom of the screening drum on account of the gravity. Because the inner surface of the mantle of the screening drum 1 is further provided with transversal ribs 4 fastened on said longitudinal ribs 3, which ribs 4 are slantingly positioned with respect to the longitudinal axis of the drum, forming a screw line, so said dropping of the sludge partly takes place into a subsequent chamber defined by the transversal ribs. The screw line formed by the transversal ribs- 4 is intended to displace sludge in the longitudinal direction of the drum together with the rotation of the screening drum.

The dropping of the sludge lifted up by the longitudinal ribs 3 down on the sludge located in the lower portion of the drum is a matter of great importance, for the dropping of the sludge causes a pressure blow, which makes the discharge of water through the screening drum mantle 5 more efficient. In order to make said pressure blow more effective, at least some of the longitudinal ribs are fitted in a slanting position with respect to the radial direction of the drum in such a manner that an angle (X ₁ between the fo eward surface of each longitudinal rib 3 and the inner surface of the mantle 5 of the drum is smaller than an angle (X ₂ between the backward surface of said longitudinal rib and the inner surface of the drum mantle 5. The term "foreward surface" here means that surface of a longitudinal rib which during the rotation of the drum faces in the direction of the movement. Correspondingly, the term "backward surface" means the other surface of the same longitudinal rib 3, said surface facing backwards with respect to the direction of rotation of the drum. This matter particularly clearly appears from Figures 3 and 4. The direction of rotation of the drum is indicated in Figures 3 and 4 by means of an arrow. By virtue of said arrangement, the sludge rises higher before the dropping thereof than if it were lifted by means of radial ribs. So the pressure blow caused by the dropping is made considerably more effective as compared with the previously known devices. It is clear that the most efficient operation is obtained when all said longitudinal ribs are in the afore-mentioned position, as shown in Figures 3 and 4.

According to the invention, it is also advan¬ tageous to position the longitudinal ribs 3 in a slanting position with respect to the axial direction of the screening drum 1. Thereby the longitudinal ribs 3 for their part contribute to the displacing of the sludge in the longitudinal direction of the screening drum 1 towards the other end of the drum. The mantle 5 of the screening drum 1 can be advantageously manufactured of a resilient material, which leads in that the mantle 5 lives during the rotation of the drum, whereby the blinding of the mantle pores is reduced. The cross-section of the screening drum can be, for instance, round or polygonal, as shown in Figures 3 and 4.

The splashing of the mantle 5 of the screening drum 1 can be effected by means of a high pressure spray 6, the amount of water required by said spray being small. The need of splash water is less than 2 % out of the amount of sludge passed inside. The position of said high pressure spray 6 appears from the example of Figure 2. By virtue of the small amount of splash water and the extremely efficient agitation, the polymer amount required for the stabilization of the sludge remains very low, being approximately one half of the amount used in connection with the known devices. The lime used for rising the pH can be fed into the screening drum 1 in about the middle of it, whereby the washoff into the spraying water is insignificant. Ash, on the contrary, can be fed into the screening drum 1 immediately at the inlet end thereof.

As appears from the figures, the construction of the drum is extremely compact. The transversal ribs 4 and the longitudinal ribs 3 form a bearing structure, in which the mantle 5 is fastened. Thus the drum does not require any shaft, but it can be supported on rolls 7 secured on the ends of the drum, whereby it is ex- tremely simple to remove the drum for maintenance, for instance. In addition, it is of advantage that the mantle 5 has such a shape that it does not extend over the whole length of the drum, but a discharge opening 9 can be left in the outlet end. Thereby the rolls 7 can be positioned directly at the ends of the drum. The position of the rolls 7 clearly appears from Figures 1 and 2. The rotation of the screening drum 1 can be effected, for example, in such a manner that one pair of the rolls is driving. The power required for the rotation of the drum and for the pumping of the splash water is small as compared with the previously used devices.

The sludge discharged from one end of the screening drum 1 can be further dewatered in a highly advantageous manner by means of a fabric press 8.

The principal features of said fabric press 8 are shown in Figure 2. The screening drum 1, the fabric press 8 and the pumps with the motors thereof can be highly advantageously positioned in a closed casing 10, whereby the whole system is completely closed. odourless and essentially noiseless, whereby it is particularly well adapted to be used also in densely populated areas for emptying drains sumps, for instance. Thereby it is advantageous to position the whole system, the principal features of which are shown in Figure 2, on a displaceable base, whereby the apparatus can be transported to the place of operation in an extremely simple manner.

The above embodiment examples are by no means intended to restrict the invention, but the invention can be modified within the scope of the claims in various ways. So it is fully possible to manufacture a system comprising e.g. two screening drums positioned side by side or one above the other. The screening drum 1 can be used for various purposes, such as e.g., for removing solid substances of community garbage, industrial waste waters or industrial processes and for treating a fibre suspension. It is also clear that the screening drum or parts thereof do not need to be exactly similar to those shown in the figures, but other kinds of embodiments are possible, too.

Claims

Claims:

1. Device for the separation of solid substances from waste water, which device comprises a slowly rotating screening drum (1), which is provided with feeding devices for feeding waste water into the screening drum from one end (2) thereof and with devices for discharging solid substances out from 0 the other end of the screening drum, whereby water is filtered through a mantle (5) of the screening drum and whereby the solid substances are passed forwards inside the screening drum by means of transversal ribs (4) positioned slantingly with respect to the direction 5 of rotation of the drum and, further, are agitated in the screening drum by the action of longitudinal ribs (3) extending over the length of the drum, c h a r ¬ a c t e r i z e d in that at least some of the longi¬ tudinal ribs (3) are slanted with respect to the radial 0 direction of the screening drum (1) in such a manner that an angle (Λ₁) between that surface of the longi¬ tudinal rib (3) which faces in the direction of rotation of the screening drum (1) and the inner surface of the screening drum mantle (5) is smaller 5 than an angle ( -^'" „) between that surface of said longitudinal rib (3) which faces backwards with respect to the direction of rotation and the inner surface of the screening drum mantle (5) .

2. Device according to Claim 1, c h a r a c - 0 t e r i z e d in that said longitudinal ribs (3) are fitted in a slanting position with respect to the axial direction of the screening drum (1) in order to make the displacing effect of the solid substance more effective.