The invention relates to a system, apparatus, pump unit, and method for purifying a liquid. More generally, the invention relates to an apparatus for pumping up a liquid, such as water.

According to the invention, the apparatus comprises a pump unit which works at least partly on the basis of a force generated by the pressing downwards of a portion of a road surface, by the weight of passing traffic, such as vehicles.

Optionally, the portion of the road surface is formed by a movable speed ramp.

Optionally, the pump unit is arranged for pumping up the Hquid from a hquid reservoir to a filter.

Optionally, the apparatus comprises a liquid tank.

Optionally, the apparatus comprises a supply conduit for supplying Hquid coming from the liquid reservoir and a discharge conduit for discharging liquid in the direction of the filter.

OptionaHy, the pump unit comprises a float which at least partly by the force generated by the weight of the passing traffic, is pushed into the Hquid in the Hquid tank or pushed further into the liquid, resulting in displacement of the Hquid present in the Hquid tank to the discharge conduit.

In another embodiment of the invention the pump unit can comprise a float which is movably received in the liquid tank, such that the float at least partly by the force generated by the weight of the passing traffic, is pushed into the liquid in the Hquid tank or pushed further into the Hquid, resulting in displacement of the Hquid from the Hquid tank, preferably via an overflow at an upper side of the Hquid tank, in the direction of the filter. The float can, for example, be of a material having a lower density than the density of the Hquid to be displaced, for example, of an EPS possibly provided with a watertight coating such as a resin coating. In another implementation the float can be a watertight tank, for example, a tank of stainless steel or plastic.

In a further elaboration of the invention, an inner tank may be provided in the liquid tank, with the float movably received in the inner tank. The inner tank can comprise, for example, a stainless steel inner tank. The inner tank may, for example, be fixedly provided in the liquid tank.

In a further elaboration of the invention, near an underside of the inner tank, preferably in a bottom thereof, a valve may be provided which is arranged to be brought into a closed condition upon the float being pressed in the inner tank and to permit supply of liquid to the inner tank upon the float moving in a direction opposite to the pressing direction.

According to a further elaboration of the invention, a collecting tank may be provided in the liquid tank downstream of the overflow for collecting liquid displaced by the float, which collecting tank is in fluid communication with the filter.

In a further elaboration of the invention, the road surface may be provided on the apparatus via two rotatable arms, such that an underside of the road surface is slidable relative to an upper side of the float. The rotatable arms may be biased to the initial position so that after passage of the vehicle the road surface moves back to the initial position again.

Optionally, the apparatus comprises a non-return valve in the supply conduit for at least partly hindering backflow of the liquid to the liquid reservoir upon the float being pushed into the liquid or pushed further into the liquid.

Optionally, the apparatus comprises a non-return valve in the discharge conduit for at least partly hindering backflow of the liquid from the filter to the liquid tank. Optionally, the pump unit comprises at least one liquid cup for taking up liquid from the liquid tank and driving means for driving the at least one liquid cup in upward direction, at least partly by the force generated by the weight of the passing traffic.

Optionally, the driving means are arranged for driving the at least one liquid cup into the vicinity of the discharge conduit for at least partly delivering the liquid coming from the liquid tank into the discharge conduit.

Optionally, the driving means are arranged for circulating a number of liquid cups from a position in the liquid for taking up the liquid to a position near the discharge conduit for delivering the liquid and vice versa.

Optionally, in use, the weight of the passing traffic generates a force on a toothed rod which by means of at least one gearwheel drives a chain with which the liquid cups are connected.

Optionally, the movement of the toothed rod is transferred to the at least one gearwheel by means of a ratchet so that a movement of the toothed rod in a first direction provides for rotation of the gearwheel and a movement of the rod in a second opposite direction does not provide or at least provides to a lesser extent for rotation of the gearwheel.

Optionally, the pump unit comprises driving means for converting the force generated by the weight of the passing traffic to a rotating movement of at least one unit resulting in the transport of the liquid present in the liquid tank to the discharge conduit.

Optionally, the at least one unit is a blade.

Optionally, the liquid tank comprises a circular segment having a radius substantially equal to the length of the blade.

Optionally, the apparatus comprises a counterweight or spring for returning the blade and the ramp to a starting position after passage of the traffic.

Optionally, a number of blades are arranged in a blade wheel. Optionally, the blade wheel is rotated by a gearwheel associated with a shaft around which the blades are arranged.

Optionally, in use, the weight of the passing traffic generates a force on a toothed rod which drives the gearwheel.

Optionally, the movement of the toothed rod is transferred to the at least one gearwheel by means of a ratchet so that a movement of the toothed rod in a first direction provides for rotation of the gearwheel and a movement of the rod in a second opposite direction does not provide or at least provides to a lesser extent for rotation of the gearwheel.

The invention further relates to a pump unit of an apparatus according to the invention.

The invention further relates to a system comprising an apparatus according to the invention and a liquid reservoir, such as a water reservoir with potentially polluted water, such as a canal or pond, and a filter for purification of the liquid.

Optionally, the filter comprises a helophyte filter for purification of the water.

Optionally, the filter is connected with the liquid reservoir, such that the liquid after purification flows back into the liquid reservoir.

The invention further relates to a method for purifying a liquid, such as water, utilizing a system according to the invention.

The present invention will be further clarified on the basis of different exemplary embodiments, with reference to the different drawings, in which:

Figure 1 shows a schematic widthwise cross section of a first exemplary embodiment of the apparatus according to the invention;

Figure 2 shows a schematic lengthwise cross section of the first exemplary embodiment of the invention; Figure 3 shows an exemplary embodiment of a system provided with an apparatus according to the invention;

Figure 4 shows a schematic lengthwise cross section of a second exemplary embodiment of the apparatus according to the invention;

Figure 5 shows a schematic lengthwise cross section of a third exemplary embodiment of the apparatus according to the invention;

Figure 6A shows a schematic lengthwise cross section of a fourth exemplary embodiment of the apparatus according to the invention;

Figure 6B shows a further schematic lengthwise cross section of the fourth exemplary embodiment of the apparatus according to the invention;

Figure 7 shows a schematic lengthwise cross section of a detail of a fifth exemplary embodiment of the apparatus according to the invention.

It is noted that like elements in the different figures are indicated with like reference numerals.

Fig. 3 shows an example of a system 1 according to the invention. The system according to the invention particularly enables realization, for example without further costs of energy, of a continuous filtering of water present in a reservoir 22, such as a canal or pond. For this purpose, the water may be supplied by means of an apparatus 2 provided with a pump unit, from the reservoir to a filter 24, such as a helophyte filter. In this way, the water (of the canal or pond) becomes increasingly cleaner, resulting in a constant improvement of the quality.

The working of the purification is preferably based on the proven and known process of a natural helophyte filter.

A portion of grassland next to the canal or pond can then be laid out as helophyte filter. It is sufficient to create a small dike (preferably being level) on an existing grassland and to connect it with the canal or pond by means of an overflow, weir, and/or check dam. The water from the canal or pond is pumped up by the apparatus as a vehicle passes, out of the canal or pond, and into the helophyte filter. It will be clear that it is possible that by the time enough vehicles have passed, the helophyte filter can get filled up with water. In an

embodiment, all the excess supplied water flows back into the canal or pond again, e.g., via an overflow.

The residence time of the, possibly polluted, water in the helophyte filter is preferably such that the pollutants that may be present are left behind in the helophyte filter and are taken up by plants of the helophyte filter. The water flowing via the helophyte filter back into the canal or pond will therefore be cleaner than at the time it was pumped up.

The system keeps working upon every passage of a vehicle and in the course of time the result will be appreciable, e.g., visible. Evidently, the operation of the system can be improved by having several apparatuses at the same time pump water from the reservoir to one or more helophyte filters. It will be clear that the size and or the number of the helophyte filters needs to be attuned accordingly.

In this example, the liquid, here water, is pumped up from a reservoir, here formed by a canal or pond. Pumping up is carried out by an apparatus. The apparatus is preferably operated by means of a force, such as gravitational force, exerted by a vehicle on the apparatus. In this example, the apparatus is operated by gravity acting on a passing vehicle. This provides the advantage that, if desired, no external energy needs to be employed to operate the apparatus.

For pumping up the water, in this example an existing speed ramp is converted - or a new speed ramp is constructed if such is desirable with a view to traffic safety. Preferably, no additional speed ramps that are not desirable from a traffic point of view are constructed especially for the purpose of this idea. In this way, the aspect of traffic safety and the cleaning action of traffic can be combined in a positive manner. The water is pumped up by passing traffic, by configuring a speed ramp as a kind of pumping device. In this example, that is done as follows.

Fig. 1 shows a widthwise cross section of a first exemplary

embodiment of an apparatus 2 according to the invention. Fig. 2 shows a lengthwise cross section of this first exemplary embodiment.

The apparatus comprises an energization unit and a pump unit. The energization unit in this example comprises a road surface 15 as is described below.

The pump unit in this example comprises a concrete tank 4

(preferably watertight) with an inlet 6 and an outlet 8. The inlet 6 is in fluid communication with the reservoir (not shown in Fig. 1), here the canal or the pond. In the tank 4, in this example, the water level 10 is at the same height as in the canal or pond. Floating on the water 12 is a big float 14. The float 14 is also part of the pump unit. In this example the float 14 is guided in the tank 4 by means of guide rollers 21. As soon as a vehicle drives up the road surface 15 of the speed ramp (of course, the speed ramp can comprise an oblique adapter/gradient member 7, see Fig. 2), the weight of such vehicle causes the road surface of the speed ramp to come down. The float 14 is thereby pushed down. It will be clear that in this example the road surface is configured to hinge about an axis 19. The gradient members 17 can be hingedly connected with the road surface 15.

The amount of displaced water can flow exclusively to the outlet pipe 8, due to a first non-return valve 16 arranged in the supply conduit. As soon as the vehicle has passed, a second non-return valve 18 in the outlet pipe ensures that water cannot flow back from the outlet pipe into the tank 4 anymore, while water from the canal or pond can. As a result, the water level in the tank 4 will be adjusted to the level of the canal or pond again with water from the canal or pond, as a result of which the speed ramp goes back up again. A next vehicle repeats this process and thus every time a predetermined amount of water is pumped into the helophyte filter.

In this example the apparatus comprises sealing elements, here rubber flaps 20, which are arranged to prevent water being forced upwards alongside the float 14.

The non-return valve 16 in the supply conduit 6 ensures that the water can only flow from the canal or pond to the tank 4, but not directly from the tank 4 to the canal or pond. The non-return valve 18 in the discharge conduit 8 ensures that the water cannot flow from the discharge conduit back into the tank 4. In this manner, the water is pumped.

Fig. 3 shows an example of a system 1 according to the invention. The system 1 comprises an apparatus 2 according to the invention, for example an apparatus 2 as described hereinabove. The system further comprises a liquid reservoir 22, such as the above-mentioned canal or pond. In addition, the system comprises a filter 24, such as the above- mentioned helophyte filter.

In this example, the apparatus 2 is incorporated in a (public) road 26. Every time a vehicle passes the apparatus 2, the latter will be operated. Every time, water will thereby be passed through, and this water will end up in the helophyte filter, where it is purified.

Without wishing to be bound to any theory, the inventor believes that the efficiency depends on a driving speed of the energizing vehicle. The lower the speed, the longer the residence time on the speed ramp, the more water will be pumped (or the larger the float can be).

In the examples described so far, the apparatus is incorporated in a

(public) road. Clearly, it is also possible to deploy the apparatus, or the system, at other locations. An example is in and/or at car parks in (busy) cities where, for example, city canals, or other surface water, are present which traditionally often had a sewerage (overflow) function and hence are often polluted. In the examples, the apparatus is provided with a pump unit on one side of the road surface, that is, merely at the drive-on or drive-off part. It is also possible to provide a pump unit at both the drive-on and drive-off part.

Efficiency at a car park may be greater than in the case of a speed ramp in a road or property access, because at the car park it is possible that every car comes to a practically complete halt to obtain a card or ticket, or to insert the same when exiting the car park.

Further, the apparatus or the system is also applicable on any company premises. Preferably, the apparatus is then positioned and configured in a manner as is considered necessary or desirable for reasons of safety. Since it is possible that such locations are mainly entered by trucks, having a much higher weight than passenger cars, the pump unit can accordingly be made much larger and hence efficiency per passage will be higher.

If there is no room in the vicinity of the canal or pond to create a helophyte filter, there is always a possibility of solving this by means of a floating tank. On this floating tank a green 'roof may be created, for example, from Xerofioor or the like. For the rest, operation is the same. By means of the pump unit and the discharge conduit (pressure pipe) the water is forced up to this floating tank, where it flows over and through the plants. On the other side of the tank, it flows down again into the canal.

The system may be further expanded with a facility generating electricity from the liquid being pressed away. Such electricity can then be employed to strip the inlet of dirt, or to pump up extra water so that still more water is purified. Preferably, the apparatus is prevented from causing nuisance of noise due to any banging. Conceivably, the guide rollers 21 can be made of plastic or rubber. Further, the drive-up plates can be made of plastic (or metal clad with a sound-damping material). Since an open communication between the pump unit and the reservoir is possible, influences of frost may play a role. Frost damage can be hindered, for example, by adding a. winter position. In the winter position, the supply conduit can be shut off by means of a valve. In addition, the float may be placed in a fixed position (for example, at a particular measure above the surfacing or even flush with ground level). After the winter, simply opening the valve of the supply conduit (and, where applicable, undoing the locking of the float) is sufficient to start the system up again.

In case of frost, any rainwater that is present on the side of the construction is relevant. For this purpose, it may suffice to arrange for the outer side of the speed ramp to be an oblique surface up to a particular height.

Preferably, at the inlet of the tank, a typically fine -meshed grid is placed. This can keep floating and/or suspended dirt and/or water plants out of the non-return valves of both the supply conduit and the discharge conduit. Further, preferably, a maintenance space is provided where the non-return valves can be cleaned.

The operation of the above-described system benefits from a substantially fixed water level (in non-operated condition). At some locations this cannot be (fully) ensured (think, for example, of differences between summer and winter levels, which often differ by some 20 cm). Especially the up fluctuations are more problematic than the down fluctuations (these can often be combined with the above-described 'winter position').

For the up fluctuations, for example, a maximum may be fixed. This can be realized by means of a stop beam within the construction. In doing so, however, account needs to be taken of the forces that are exerted on this construction. The pump unit pumps the liquid out of the tank, which involves a pressure being created in the liquid in the tank. This pressure determines a maximum height to which the liquid can be pumped up by means of the pump unit at nominal load. The height to which the liquid can be pumped up is herein also designated as lift or raising height.

The needed raising height is determinative of the magnitude of the float (a float having a water surface of 2.5 x 0.4 meters = 1 m ² , has a maximum raising height of approximately 1 meter given a 1,000 kg top load). If the needed raising height is limited, a larger ramp can be chosen which lowers only to a limited extent at a load of a passenger car (every centimeter of lowering gives 10 liters of water), if the needed raising height is greater, the water surface needs to be limited and the ramp will come down more upon a passage of a vehicle.

As soon as the level fluctuations are such that the maximum lock construction enters into operation or as soon as the supply conduit is shut off in connection with frost and the ground water level is at a higher level than the bottom height of the construction, the buoyant force on the overall construction also needs to be taken into account. Most simply, the apparatus is provided with a bottom plate which is made somewhat larger than the dimensions of the tank 4, as a result of which an amount of active ground pressure on the construction occurs which with the construction's inherent weight minimally equalizes the buoyant force.

For the capacity of the apparatus, various factors are relevant.

Factors that may be varied are, for example, ramp height (e.g., 0.20 m), height difference between water surface and outflow facility, diameter of discharge conduit, diameter of supply conduit, dimension of water tank float, length of the movable road surface, ramp length, wheel base, shaft pressure front, shaft pressure rear, factor for compensation of line losses. On account of the relatively short residence time of the vehicle on the speed ramp, a kind a pressure surge may occur in the water mass in the conduit. As a consequence, possibly, not all gravitational energy of the passing vehicle is utilized to pump water. In an embodiment a first additional water tank is placed directly before the inlet and/or a second additional water tank is placed directly after the outlet. The additional water tank before the inlet ensures that the rebound speed of the float is greater. Certainly so, if the float is so designed that in its extreme position it does not float on the water but is pressed about 0.05 m under water.

The additional water tank directly after the outlet ensures that hardly any water mass needs to be set in motion and the water which is pumped is pumped into the tank next to it. Thence, the water flows slowly into the helophyte filter.

To muster public understanding regarding the ramp and regarding the system, a digital signboard could be set up next to it displaying how many liters of water have been purified by the operation of the pump unit resulting from the passage of the vehicle in question, for example:

Thank you for being here. Thanks to you,

xx more liters of water of the canal or pond

are now being purified

Fig. 4 shows a lengthwise cross section of a second example of an apparatus 2 according to the invention. The apparatus broadly corresponds to the apparatus as described with reference to Figs. 1 and 2.

In this example the apparatus 2 comprises an alternative pump unit, provided with a float 14. The float 14 is of a material having a lower density than the density of water, for example, of EPS possibly provided with a watertight coating such as a resin coating. In another embodiment of the invention the float 14 can also be a watertight tank of, for example, stainless steel or plastic. The pump unit in this example comprises an inner tank 5 which is provided in the concrete tank 4 (preferably

watertight). The inner tank 5 is, for example, a stainless steel tank 5 which is fixedly connected with the concrete tank 4. The inner tank 5 is arranged to receive the float 14, such that the latter can move in this inner tank 5 in a direction substantially perpendicular to the surface of the ramp. In use, the float 14 is moved in the direction of the bottom 5a of the inner tank 5, so that the water that is under and/or next to the float 14 is forced out of the inner tank 5 and, via an overflow 11 provided at the edge of the inner tank 5, ends up in a collecting tank 13. Near an underside of the inner tank 5 - in the exemplary embodiment shown, in the bottom 5a of the inner tank - a non-return valve 7 is provided. The non-return valve 7 is movable with respect to the bottom 5a, such that, as the float 14 moves back in the direction of the ramp, an opening 9 can be obtained in the bottom 5a of the inner tank 5 for forming a fluid communication between the inner space 4a of the concrete tank 4 and the inner space 5b of the inner tank 5. The tank 4 is provided with an inlet 6 which is in fluid communication with the reservoir (not shown in Fig. 4), here the canal or the pond. In the tank 4, in this example, the water level 10 is at the same height as in the canal or pond. The float 14 floats on or partly in the water 12 which is in the inner tank 5. The float 14 is part of the pump unit. In this example the float 14 is guided in the inner tank 5 by means of guide rollers 21. As soon as a vehicle drives up the road surface 15 of the ramp (of course, the ramp can comprise an oblique adapter/ gradient member 17, which may be hingedly connected with the road surface 15), the weight of that vehicle causes the road surface 15 of the ramp to descend. In the exemplary embodiment shown in Fig. 4, the road surface is movably arranged with respect to the apparatus 2 with the help of two rotating arms 23. The rotating arms 23 can rotate in a rotation direction R around the respective hinge points 23 a. The road surface 15 will thereby move both in a direction Rl substantially perpendicular to the road surface 15 and in a direction Rp substantially parallel to the road surface 15, so that an underside of the road surface 15 will slide over an upper side 14a of the float. At the same time, the float 14 in the water in the inner tank 5 is thereby pressed towards the bottom 5a. Due to the pressure in the inner tank 5 the non-return valve 7 will seal the opening 9 in the bottom of the inner tank 5. The water pressed away by the float 14 will move up along the circumferential sides of the float 14 and via the overflow 11 end up in the collecting tank 13. Via the outlet 8 the collecting tank 13 is in fluid communication with the helophyte filter 24, so that the water level in the collecting tank 13 is equal to the water level in the helophyte filter 24.

As soon as the vehicle has passed, the road surface 15 will move back up again, i.e., in a direction opposite to the directions of movement Rl and Rp, and the float 14 moves in upward direction. This allows the non- return valve 7 to come off the bottom 5a, as a result of which liquid is sucked from the tank 4 via the opening 9 to an inner side 5b of the inner tank 5. At the same time the tank 4 will be filled with water from the canal or pond, so that the water levels in the tank and the canal or pond end up at the same level again. Upon passage of a next car this process repeats itself, whereby, in turn, a next amount of water is pumped into the helophyte filter 24. It may be that the successive car already ends up on the road surface 15 before the float 14 has returned to the initial position again. As a result, the float 14, due to that car, will move over a smaller distance in the inner tank 5 and therefore displace less water. By choosing the dimensions of the float 14 favorably, it can be arranged that a first passing car presses the float 14 down over a particular distance, for example 10 cm, and a next passing car, even when the float 14 has not returned to the initial position yet, can also move it over a particular distance. In this way, also in case of rapid succession of cars, a high efficiency can be obtained. In this example the apparatus does not comprise any sealing elements between the float 14 and the inner tank 5, since the water is to be driven upwards between them.

Compared with the system as described with respect to Figs. 1 and 2, the system according to Fig. 4 has the following advantages:

• The apparatus has a simple construction with few moving parts, so that the apparatus is hardly maintenance-prone;

• Non-return valves in the supply and discharge conduits are not needed;

· Since the whole circumference of the float is utilized, a large outflow opening is created, thus enabling the required fast operation of the system;

• Supply conduit can be dimensioned to be thinner;

• Discharge conduit can be dimensioned to be thinner;

· Less sensitive to level fluctuations in the water pond;

• The apparatus can easily be prefab manufactured and easily be installed on site.

In this system the road surface can be returned to the initial position after passage of a vehicle, for example by means of springs and/or a counterweight.

In an alternative embodiment of the apparatus 2 according to the invention (not shown), the float 14 may also be movably provided in the liquid tank 4. Such an embodiment works substantially similarly to the apparatus as described in relation to Fig. 4. The difference with respect to the embodiment of the apparatus shown in Fig. 4 is that the liquid in such an alternative embodiment is introduced into the liquid tank 4 via a supply conduit 6 which is provided with a non-return valve 16. When the float 14 is pressed downwards by the passing traffic, the liquid in the liquid tank 4 is driven up via the sides of the float 14, such that the liquid via an outflow at an upper side of the liquid tank 4 is moved in the direction of the filter 24.

It is noted that the term Outflow' in this application should be interpreted broadly. Outflow can mean an upper edge of the liquid tank and/or of the inner tank. However, the outflow can also comprise an additional component which is provided at an upper side of the liquid tank and/or the inner tank to enable movement of the liquid which has been moved up, from the liquid tank and/or the inner tank in the direction of the filter.

Fig. 5 shows a lengthwise cross section of a third example of an apparatus 2 according to the invention. The apparatus broadly corresponds to the apparatus as described on the basis of Figs. 1 and 2.

In this example the apparatus 2 comprises an alternative pump unit in lieu of the embodiment with the float 14 . In this example the pump unit comprises the water tank 4, having included therein a mechanism 26 which raises the water by means of cups 28 (comparable to a dredger). It will be clear that the term cup is not limiting, and any form of cup, bucket, reservoir, holder, etc., can be suitable.

The cups 28 in this example are suspended from two chains 30 (on either side of the cups).

For the rest, operation is comparable. The passing vehicle applies a downward force on a toothed rod 32 which, by means of one or more gearwheels 34, drives the chain 30 with the cups 28 thereon. The cups 28 are filled under water (A) and each time pushed further up by a vehicle. As soon as the cup has arrived at the top and reverses (B) it will deliver the water. This water is collected, for example, in a channel 36, and, for example by motion under gravity, transported to the helophyte filter.

Compared with the system as described with respect to Figs. 1 and 2, the system according to Fig. 5 has the following advantages. • The cups can be made of frost-insensitive design (gradient of about 10° provides sufficient protection from breaking by frost). Of course, this also applies to the large water tank 4 under the ramp.

• Non-return valves are not needed;

· Supply conduit can be dimensioned to be thinner;

• Discharge conduit can be dimensioned to be thinner;

• Not sensitive to level fluctuations in the water pond.

In this system, the road surface can be returned to the initial position again upon passage of a vehicle, for example, by means of springs and/or a counterweight.

Figs. 6A and 6B show a lengthwise cross section of a third example of an apparatus 2 according to the invention. The apparatus broadly corresponds to the apparatus as described on the basis of Figs. 1, 2, and 4.

In this example, the apparatus 2 comprises an alternative pump unit in lieu of the embodiment with the float 14, or the cups 28.

In this example the pump unit comprises the water tank 4, having therein a blade 38. In this example, the blade 38 in an unloaded position (see Fig. 6A) is virtually perpendicular to and a few centimeters from a stop beam 40 of the concrete tank 4. The tank 4 in this example is provided with a part 39 partly in the form of a circular segment. The blade 38 is suspended rotatably about an axis R. The blade 38 in this example is provided with an actuation surface 41. The movable road surface 15 of the apparatus 2 in this example rests on the actuation surface 41.

In front of the blade 38 there is an amount of water (water level in this example is equal to the pond level).

The construction in this example is practically in equilibrium. The inherent weight of the ramp construction (with point of application 19 in this example being about 2.5 meters before the blade 38) is compensated by a counterweight 42 (with point of application in this example being about 0.20 m behind the blade 38). Due to the difference in point of application the counterweight can be limited to about l/20 ^th part of the weight of the ramp construction.

As soon as a vehicle drives up the movable road surface 15 of the ramp, the weight of the vehicle is converted to an (eccentric) force on the blade 38 (via the actuation surface 41). The eccentricity in this example is about 0.20 m. Given a total blade length of about 1-1.50 m, from the part 39 to the axis R, the force is still amply sufficient for the amount of water in front of the blade 38 to be pushed forwards, and also a few decimeters upwards because of the circular shape of the part 39 of the tank 4 (with the radius of the part 39 being substantially equal to the blade length). The water thereby flows over a threshold 44 into a collecting tank 46 and thence, by motion under gravity, to the helophyte filter.

As soon as the vehicle is off the movable road surface 15 of the ramp, the counterweight 42 ensures that the ramp rapidly returns to the starting position (possibly provided with a delay (as in the manner of a door- spring)).

The shape of the overall tank 4 provides for a large stock of water, so that a next vehicle directly yields the same amount of water again.

Further advantages of this embodiment include:

• Basically all walls that are in contact with water can be designed with a gradient, so that no sensitivity to frost is to be expected;

• Construction is much less sensitive to level difference in the pond (though output diminishes as a result of less water before the blade);

· Overall construction is reasonably uniform and independent of the location and hence easier to make in prefab;

• Greater efficiency owing to: a) more water before the blade (up to as many as 150 liters/passage, compared to about 40 with the float) and b) quicker readiness for the next vehicle (i.e., no half yield if one vehicle is quickly succeeded by the next);

• Hardly maintenance-prone (no non-return valves).

Fig. 7 shows a lengthwise cross section of a detail of a fifth example of an apparatus 2 according to the invention. The apparatus broadly corresponds to the apparatus as described on the basis of Figs. 1, 2, 4, 5, 6A and 6B.

In this example, the apparatus 2 comprises an alternative pump unit in lieu of the embodiment with the float 14, the cups 28, or the blade 38.

In this example, the pump unit comprises the water tank 4 (not shown), having included therein a blade wheel 48 provided with a plurality of blades 38. The blade wheel 48 is so positioned in the tank 4 that each blade 38 of the blade wheel 48 will consecutively move along the circular part 39 of the tank 4. The blade wheel 48 in this example is driven through a toothed rod 32 and a gearwheel 34 associated with the blade wheel. The gearwheel 34 is coupled with the blade wheel through a ratchet

mechanism, so that upon the toothed rod 32 coming down, the blade wheel is driven, and upon the toothed rod going up, the blade wheel is clear. As a result, each time a vehicle passes, the blade wheel will be rotated through a particular angle (clockwise in this example) so that an amount of water is pushed up and can flow over the threshold 44.

It will be clear that the apparatus in the system 1 shown in Fig. 3 can also be configured as an apparatus according to any one of Figs. 4, 5, 6A, 6B, or 7.