METHOD FOR DRAINING SLUDGE

Technical Field

The present invention relates to a method for draining sludge and transportation of sludge according to claim 1.

Background of the Invention

An underground station usually comprises one or more platforms and one or more station halls, which are connected to each other through galleries, passages, stairs, elevators, escalators, etc. Platforms and station halls may be situated on the same level or on different levels. Some may be situated under ground level and some above ground level.

Moreover, the underground station comprises a pipe system for waste water. The pipe system is connected to waste water pipes which in turn are connected to wells placed on platforms and in station halls. Furthermore, waste water pipes from elevator and escalator rooms are connected to the pipe system. The purpose of the pipe system is that water (and possibly other fluids), which for example is used when cleaning underground stations, will flow under the influence of the gravitational force of the earth to a lower level in the pipe system. With water follows sludge, for example in the form of gravel, to the lower level.

At said lower level, which is below the ground level, a sludge separator can often be found which separates water from sludge. The water is collected in a pump pit at which a pump is arranged to pump up the water from the pump pit to typically a surface water system. However, the sludge is collected in a sludge pit and therefore needs to be drained regularly to not be overfilled. A problem with draining sludge from sludge pits is that these cannot be drained by suction or by pumping to ground level since direct pipes up to ground level do not exist, and also due to the fact that the suction/pumping height is too high for this to be possible.

A serious complication when draining sludge in underground stations is that a large part of the sludge contains oil. This oil comes mainly from elevator and escalator rooms as a result of cleaning of the elevators and escalators, which is often done with high pressure cleaning. The amount of oil can be substantial and it floats with the water to the sludge pit, and furthermore

since the sludge separator is not arranged to separate oil from water a fraction of the oil follows the water over to the pump pit. This means that a water/oil mixture will be pumped up directly out into the surface water system, and hence will result in serious environmental consequences. Therefore, the pump pit should also be drained of sludge mixed with oil, which is not the case at present, and the result is that the oil is spread in the surface water system.

Further, draining sludge from sludge and pump pits is made more difficult because of the fact that oil is harmful to the environment and also due to its physical properties. Oil is on the one hand classified as a substance harmful to the environment which means that the handling of this organic substance is regulated according to existing law, why a number of provisions must be followed, and on the other hand oil forms together with other sludge substances (for example gravel) a type of sludge which is hard to drain from sludge and pump pits, respectively.

Moreover, the sludge mixed with oil must be handled for deposition or processing, which means that the sludge in a safe manner must be transported to a deposition or processing plant. This problem is not solved either.

Summary of the Invention The object of the present invention is to solve the above-mentioned problems. The object is achieved with a method for draining sludge from a sludge pit or a pump pit in an underground or railway station, and for transportation of the sludge to ground level according to claim 1.

The underground or railway station comprises: at least one platform below ground level in which at least one well is placed and with which at least one first waste water pipe is connected, at least one escalator with a corresponding escalator room to which at least one second waste water pipe is connected, at least one elevator with a corresponding elevator room to which at least one third waste water pipe is connected, and wherein the first, second and third waste water pipes lead to at least one common sludge pit and further to at least one pump pit, which are situated at a level below the platform. Sludge in the sludge or pump pit is sucked up with a mobile suction apparatus to a mobile container, wherein the mobile suction apparatus and the mobile container have dimensions suitable for transportation in the existing infrastructure of the underground or railway station. Further, the mobile suction apparatus and

the mobile container are arranged for suction and transportation of the sludge, respectively. The mobile container is transported to ground level where the sludge is forwarded, with a vehicle, for disposal or processing.

Embodiments of the method according to the present invention are found in the dependent claims 2-6.

Brief Description of the Drawings

In the following detailed description, the present invention will be explained with reference to the appended drawings, in which:

- Figure 1 schematically shows a vertical section of an underground station comprising a pipe system for waste water; and

- Figure 2 shows an example of how sludge is drained from a sludge pit.

Detailed Description of Preferred Embodiments of the Invention

Figure 1 shows, in vertical section, an underground station 1 comprising a station hall 2, in this case on ground level 4, and one or more platforms 3 below ground level. The station hall and the platform are connected to each other vertically by escalators 7, elevators 10, stairs and passages (stairs and passages are not shown in figure 1).

The underground station, in this example, further comprises a pipe system for waste water 13 to which one or more wells 5 are connected via a first waste water pipe 6. These wells can be placed in the station hall, on the platform or in other suitable areas. A second 9 and third 12 waste water pipe is further connected to the pipe system. The second waste water pipe 9 is connected to at least one escalator room 8, and the third waste water pipe 12 is connected to at least one elevator room 11.

Water (possibly mixed with a cleaner) is commonly used when cleaning an underground station. Further, it is common to use high pressure cleaning to flush galleries, underground stations and platforms. The water that is used for cleaning is flowing under the influence of the gravitational force, via said wells 5, to a lower level in the pipe system. With the water follows sludge in the form of e.g. gravel and other small particles.

A sludge separator 16, which separates water from sludge, can be found at the lower level in the pipe system. The sludge is collected in a sludge pit 14, which needs to be drained regularly to not be overfilled. However, the water is collected in a pump pit 15 at which a pump 17 is arranged and whose function is to pump up the water from the pump pit to, in this case, a surface water system.

Similarly, water is used when cleaning escalators and elevators, often in combination with high pressure cleaning. Oil used for lubrication of different mechanical parts of escalators and elevators follows with the cleaning water, through the second 9 and third 12 waste water pipes, to a lower level in the system. The amount of oil that follows with the water in the pipes can be substantial, and the oil together with other sludge particles forms a sludge mixed with oil in the pipe system.

The sludge mixed with oil forms a sludge coating inside the pipes in the pipe system, and also follows with the water to the sludge pit. A certain fraction of the oil in the sludge mixed with oil also follows with the water further to the pump pit, since the sludge separator is not arranged to separate water from oil.

As mentioned earlier, the water in the pump pit is pumped up to the surface water system, which in this case means that water/oil mixture is pumped out directly in the surface water system with serious environmental consequences as the result. However, part of the oil that has ended up in the pump pit is left on its bottom and inner walls, which means that also the pump pit needs to be drained from the sludge mixed with oil.

Sludge mixed with oil that follows with the water down to the lower level cannot be pumped up or sucked up of from this lower level. The reason for this is that pipes do not exist for this purpose, and also that the suction/pumping height is too high to make it possible for suction or pumping to ground level. Further, the draining of sludge is made substantially more difficult as the sludge to a large extent contains oil.

Oil is classified as harmful for the environment, which means that a number of environmental and working environmental regulations apply when handling this organic substance. Therefore, oil must be taken care of in a safe and approved way according to existing

provisions. Furthermore, the oil due to its physical qualities together with other sludge substances forms a mucky sludge, with sticky consistency which tends to stick in pipes and containers. These two factors make sludge draining substantially more difficult, but also the further handling of the sludge such as transportation and final processing.

As shown in the example in figure 2, the sludge is sucked up from a sludge pit 14 or a pump pit 15 with a first suction hose 22. The first suction hose 22 is connected to a mobile container 21, which in turn is connected to a mobile suction apparatus 20 through a second suction hose 23. With suction force acting from the suction apparatus 20 through said suction hoses 22, 23, the sludge is sucked from the sludge pit 14 or the pump pit 15 through the first suction hose 22 to the mobile container 21.

Due to the fact that the sludge mostly contains oil, the suction apparatus and container are both arranged to be used in a method according to the invention.

Regarding the suction apparatus 20, the fan blades of the fan engine has been adjusted by arranging suitable washers on the fastening means of the fan blades. Hence, the suction effect of the suction apparatus is adjusted to the special physical qualities of the sludge mixed with oil, and therefore makes it possible to suck up the sludge in an effective and safe way.

Further, the mobile container 21 is provided with an oil cup arranged on its lid which prevents the container from being overfilled, and therefore the sludge from being spread around the container with the risk that persons (for example people working with draining sludge) are getting in contact with the environmentally harmful sludge in an inappropriate way, and there will be no need for clearing the area around the container from the sludge. The design of said oil cup consists of a frame that is arranged on the inside of the lid of the container, and in which a floatable ball is placed. When the level of sludge in the container rises, the ball follows with the rising level due to its floating characteristic to finally seal against the suction side (that is against the first suction hose 22), with the result that no more sludge can be fed to the container since there is no longer any suction force in the first suction hose 22.

Also, the mobile suction apparatus 20 and the mobile container 21 have been given dimensions so that they can be transported in the existing infrastructure for transportation in

the underground station. The suction apparatus and container are provided with wheels to further facilitate transportation in the underground station.

After that the sludge has been sucked into the mobile container, the container is transported manually or with a small transportation vehicle through the existing infrastructure to ground level. Examples of existing infrastructure for transportation in an underground station may be: galleries, stairs, escalators or elevators. A great advantage with using the existing infrastructure is that no new infrastructure has to be constructed especially for draining sludge and/or transportation of sludge, which means saving in cost.

When the container has been transported up to ground level, the sludge is reloaded from the container to a specially adapted vehicle which receives the sludge mixed with oil for forward transportation to a disposal or processing plant. However, it is realized that instead of reloading the sludge, the whole container may be transported (with the sludge still in the container) to a disposal or processing plant where the container is emptied on its content.

In a second embodiment of the invention the method further comprises the steps: suction of sludge in the escalator room, and flushing the escalator room and the second pipe. That is, the floor drain and inner walls of the escalator room is sucked off from sludge with the mobile suction apparatus. Thereafter, the escalator room and the second waste water pipe are flushed clean with a mobile flushing apparatus especially arranged for the method.

Also, the mobile flushing apparatus has been given dimensions suited to be transported in the existing infrastructure of underground stations. To be able to remove sludge mixed with oil in an effective manner, the flushing apparatus has been adjusted to deliver suitable pressure and water flow. The water flow is reduced with water flow pipes having smaller dimensions than commonly used to raise the water pressure. However, risk for blowing the pipes is increased with increased water pressure, and therefore a pressure regulator has been arranged on the mobile flushing apparatus to be triggered if the water pressure is reaching too high levels. Further, a pressure equalizing regulator, i.e. a start regulator, has been arranged on the mobile flushing apparatus, and the function of the pressure equalizing regulator is to prevent that the mobile flushing apparatus starts with full rotational speed with the risk that the electrical system of the mobile flushing apparatus is overloaded.

In addition, the nozzle of the mobile flushing apparatus has been drilled with a suitable drilling angle so that water hitting a surface to be cleaned hits with an appropriate angle, and hence the operation of the nozzle is substantially improved. Borings between 10 to 30 degrees have been shown to be effective against sludge mixed with oil of the kind that can be found in pipes, sludge pits and pump pits.

A person skilled in the art also realizes that the elevator room can be sucked clean of sludge according to the second embodiment above. Furthermore, the skilled person realizes that the elevator room and a first and third waste water pipes can be flushed clean with said mobile flushing apparatus in order to remove sludge mixed with oil.

Also, the additional method steps according to the second embodiment can be performed either before or after the sludge has been drained from the sludge or pump pit. Usually, it is preferable to suck the sludge in the escalator room and flush the second waste water pipe before draining sludge from the sludge and/or the pump pit. However, a situation may arise when the sludge or pump pit is so full of sludge that no more sludge should be provided. In a situation like that, it is preferable that draining of sludge from the sludge or pump pit is performed before the method steps according to the second embodiment of the invention, a fact that is realized by a person skilled in the art.

Further, a person skilled in the art realizes that a method according to the present invention also is applicable in a railway station comprising: one or more platforms below ground level, a pipe system for waste water, and wherein the pipe system leads to a sludge and/or a pump pit at a lower level where sludge mixed with oil can be collected.