CH618147A5 - Process for sterilising water by irradiation with ultraviolet light and device for carrying out the process - Google Patents

Description

The invention relates to a method for sterilizing 30 water by irradiation with ultra-violet light.

The germicidal effect of ultra-violet light is known from a number of possible uses, e.g. in the food and packaging industry. For the disinfection of water, especially drinking water, this process has so far only been used in small drinking water disinfection systems on board seagoing vessels. Here, a tubular UV lamp was inserted coaxially into a tube with a nominal width of about 300 mm, through which the water to be sterilized was pumped. In order to ensure a reasonably reliable disinfection, several tubes of this type must be arranged one behind the other, since the relatively small flow cross sections mean that relatively high flow velocities and thus a short dwell time of the water in the area of the UV lamps have to be used. This process can be used for the disinfection of drinking water, i.e. So use an already prepared water that is suitable for drinking purposes. The known method is unsuitable for the treatment of large amounts of water, for example in the treatment of swimming pool water, the production of drinking water from surface water or contaminated groundwater, since much larger amounts of water have to be treated here. In addition, a significantly higher disinfection rate must be achieved, 55 since in these cases water has to be treated that is much more contaminated than is the case in the area of application of the known method.

The invention is therefore based on the object of providing a process for the disinfection of water by means of ultra-violet Be-60 radiation which can be used universally and which provides the required disinfection performance both with large amounts of water and with heavily polluted water.

According to the invention, this object is achieved in that the water to be sterilized is passed through a container at a flow rate of 0.5 to 50 cm / sec and is thereby exposed to the irradiation by ultra-violet light. A mean flow rate of about 0.5 to 50 cm / sec is particularly advantageous.

3rd

618 147

Depending on the throughput and thus the size of the container, one or more UV lamps can be immersed directly in the water in the container. The distance between the individual UV lamps is determined by the degree of penetration of the radiation component effective for disinfection with a wavelength of approx. 2530 Â, i.e. thus on the optical density of the water to be sterilized. The optical density is essentially dependent on the turbidity and the number of ingredients dissolved in the water. The distance should therefore be selected so that there is sufficient radiation energy in the middle between two neighboring tubes to kill or sustainably damage the germs in the water.

The term germs is not only understood to mean bacteria, but also highly organized organisms such as spores, fungi, etc.

While the implementation of the method with immersed UV lamps places considerable design requirements, particularly with regard to electrical safety, in one embodiment of the method according to the invention it is provided that the water to be sterilized is passed through an open container, during the flow a practically wave-free surface is maintained and that the free water surface is irradiated with ultra-violet light. This method has the advantage that the UV lamps do not come into direct contact with the water to be disinfected, which is particularly important for the treatment of swimming pool water, but without the radiation energy penetrating into the water being significantly reduced by reflection on the water surface becomes. The dimensions of the container are to be determined in such a way that a sufficiently lower flow rate and therefore a long residence time of the water in the UV radiation range are achieved. The depth of the container in turn depends essentially on the optical properties of the water to be treated.

In an embodiment of the method according to the invention, it is further provided that the water is circulated through the container. This procedure makes it possible to work with greater tank depths, since the overall residence time of the water to be treated in the region of UV radiation is increased further by the circulation and the long residence time caused by the low flow rate. In the treatment of swimming pool water, for example, this allows tank depths in the order of 80 to 100 cm, whereby the respective permissible maximum levels for the content of germs and chloramines are also nowhere near reached.

In a special embodiment of the method according to the invention it is provided that the water surface is mechanically cleaned of floating solids at predetermined time intervals. It is particularly advantageous if the water surface is cleaned by removing water in the area of the water surface. This ensures that the entry of UV radiation into the water is not impaired by a contaminated water surface, even in continuous operation.

While it is generally expedient to pass the water through a filter in order to mechanically remove contaminants and coarse contaminants, it is particularly advantageous if the water is removed from the container via a filter surface. Depending on the type of water to be treated, the filter surface can be the main filter surface, as is possible, for example, in the treatment of swimming pool water, or it can also be an additional filter that is preceded by a pre-filter in front of the tank, as is the case, for example, in the treatment of drinking water Surface water is required. In addition to the purely technical advantages in terms of cleaning, this procedure has the further advantage that a large-area and uniform removal of the water from the container takes place over such a filter surface, so that a uniform and low flow is ensured over the cross-section of the container.

The invention further relates to a device for carrying out the method, which is characterized by a container open at the top with an inlet chamber for water calming, a drain device and UV lamps arranged in the upper region of the container. Such a device makes it possible to build systems for the greatest throughput rates with the simplest of means, and such an i5 system can be expanded practically as desired. While the UV lamps can in principle be immersed in the containers, a preferred embodiment of the invention provides that preferably tubular UV lamps are used in a cover for the container opening 20, which run approximately parallel to the free water surface. Such an arrangement is not only structurally simpler, easier to maintain, but also offers significantly higher electrical safety, since the water on the one hand and the radiator part on the other hand are not in direct contact with one another and are therefore much easier to isolate electrically from one another.

In order to largely utilize the radiation energy in such an arrangement, it is expedient if the UV emitters are provided with reflectors. In the simplest embodiment, this can be done by designing the surfaces of the cover facing the UV emitters to be reflective.

In an advantageous embodiment of the invention, it is further provided that the drain device has a collecting space which is adjacent to the container and is connected to it by a plurality of through openings. This ensures that practically no dead zones form in the container on the outlet side, with the water flowing through practically the entire container cross-section at the same flow speed and thus practically identical residence times are achieved for each imaginary water particle. It when the passage between the container and the collecting space is designed as a filter surface is particularly advantageous. As a result, in addition to the disinfection, a filtration can also be carried out, with highly organized organisms, such as spores, fungi or the like, killed by the disinfection process being retained by the filter and thus perfect water being withdrawn from the container. A further advantage of this arrangement is if, in the normal case, the filter surface is simultaneously exposed to UV radiation, so that bacteria, germs, spores, fungi or the like settle on the filter regardless of the flow rate of the water over a very long time are exposed to UV radiation for a long period of time and are therefore certain to be killed.

In a particularly preferred embodiment, it is provided that the filter surface is formed by a plurality of vertically extending filter plates which are spaced apart and parallel to one another, and that at least part of the UV jet 60 1 is arranged above the water surface in such a way that it is in each case above the water surface Gaps between the filter plate and run parallel to this. This arrangement represents an optimal combination between the filter system and the disinfection system, since a large filter area can be accommodated in the smallest space, the desired low flow rate through the container and thus the long dwell time of the water in the area of the filter due to the large drainage area formed by the filter UV

618 147

4th

Radiation can be maintained. At the same time, it is ensured that the filter surfaces are exposed to UV radiation on the inlet side, so that germs that settle on the filter surfaces are reliably killed.

In order to prevent components floating on the free water surface from accumulating over time, it is further provided that a discharge opening, which is connected to a discharge line, is preferably arranged in the inlet region of the container, approximately at the height of the water surface. The water can either be drawn off in such a way that the level of the water surface is kept constant by means of a corresponding control device, so that a partial flow is continuously discharged via the discharge opening and discharged into the receiving water or, in the case of water treatment plants, is added to the raw water again. However, it is particularly advantageous if, according to another embodiment of the invention, a valve is arranged in the exhaust line, the actuator of which is connected to a time switch. As a result, water can be drawn off from the free surface at predeterminable time intervals via the drain opening, regardless of any level control, so that metered, i.e. Predeterminable amounts of water are withdrawn from the process that is usually carried out in a circuit. A complicated level control or a complicated setting of a weir in front of the drain opening can thus be omitted.

In an advantageous embodiment of the invention, it is further provided that a valve is arranged in the feed line to the container, the actuator of which is connected to a level measuring device for determining a lower and an upper level of the water surface, the valve opening when and when the lower level is reached When the upper level is reached the valve closes. This configuration means that with constant water drainage after the closing. sen of the inlet valve, the water surface is slowly lowered by the predetermined amount, but at the same time the water surface calms down in a very short time, so that losses of radiation energy due to total reflection are practically excluded. If, in a further embodiment, the lower edge of the discharge opening, which is preferably designed as an overflow weir, is formed so that it is slightly below the upper level, there is a periodic removal of water in the area of the surface even without additional valves in the discharge line and without an additional time switch device , so that any accumulating floating components are periodically removed from the water surface.

Exemplary embodiments of the invention are explained in more detail with the aid of schematic drawings. Show it:

1 is a treatment and disinfection system for a swimming pool in vertical section,

2 the arrangement according to FIG. 1 in supervision,

3 shows a treatment plant for drinking water as a block diagram,

4 shows a section through the sterilization container of the plant according to FIG. 3.

1 and 2, provided for a swimming pool, combined filter and sterilization device, has an open, rectangular container 1, from which an inlet chamber 3 is separated by a partition wall 2 for calming the water. The partition 2 is arranged such that a passage gap 5 remains in the bottom area. Furthermore, it has a plurality of passage openings 6 in the region of the container side walls, which extend over the entire partition wall height. The bottom 7 of the container 1 is sloping downwards from the inlet chamber 3 in the direction of the filter chamber 4 and has, at the deepest point, a channel 8 which runs transversely to the incline of the floor. As can be seen from the top view according to FIG. 2, the channel has a closable discharge opening 9 on one side, while a flushing nozzle 10 is arranged on the opposite side, the mouth of which is directed in the direction of the channel 8 against the exhaust opening 9 is. In the bottom area 7 there are also two rows of nozzles 11, 12 running approximately parallel to the channel 8, the nozzle openings of which point in the direction of the channel 8. The rows of nozzles 11, 12 are connected to a pressurized water line 13 as well as the flushing nozzle 10. ' io Valves 14, 15 can be used to apply pressurized water to the rows of nozzles 11, 12 or the nozzle 10 of your choice. In the bottom area of the filter chamber 4 there are also two supports 16,

17 arranged, on which filter plates 18 are upright. The cross members are provided with spacers 19, which ensure a precise distance between the filter plates 18, which are arranged next to one another in parallel. The filter plates can be hollow in a known manner and are provided with a filter cloth and a filter auxiliary layer of diatomite, activated carbon, mixtures of both substances or other filter auxiliary layer materials to be applied thereon.

The filter plates 18 are each provided at their upper end with a suction nozzle 20 which opens into a pressure compensation chamber 21. The connection between the pressure compensation chamber and the filter plates is preferably detachable, for example via a screw connection or a flange connection. A suction line 23, which leads to a pump 24, is connected to the pressure compensation chamber 21 at the lower end. This arrangement practically achieves the same pressure distribution at the orifices 26 of the suction ports of the filter plates, so that the liquid is drawn off from the filter chamber 4 over a large area and uniformly.

The lying between the partition 2 and the pressure compensation chamber 21 container part, which also serves as a filter-35 chamber, is provided on its top with a cover 27 in which a plurality of tubular UV lamps 28 are arranged side by side in parallel. The UV lamps are installed in the cover so that they are as close as possible above the free water surface. 2, which shows the device without the cover 27, the position of the UV lamps with respect to the filter plates is shown by the dash-dotted lines 28 '

18 drawn.

In the inlet area of the filter chamber 4 there is also a drain opening 29 on a side wall, which is connected to a drain line 30 leading to the receiving water. The lower edge of the drain opening 29 is designed in the manner of a weir and its height is such that, as will be explained below, when the upper level of the water surface reaches water, water drains from the area of the water surface via the drain opening 29 and such as floating components are subtracted from the water surface. The facility works as follows:

55 The water to be cleaned, which is pumped out of the swimming pool, is pumped via the pipeline 31 into the inlet chamber 3, while the filtered and sterilized water is pressed back into the swimming pool by the pump 24 via the pipeline 32. Since the pump 24 sucks the water from 60 of the pressure compensation chamber 21, practically the same negative pressure is created as a result of the negative pressure that forms at the suction nozzle 20 of each filter plate, so that water is sucked out uniformly over all filter plates. The pump 24 delivers continuously. Via a Ni-65 vacuum measuring device 33, a valve 34 in the feed line 31 is controlled in such a way that the actuator 35 opens the valve when a lower level (arrow 37) is reached and when an upper level (arrow

5

618 147

36) the valve is closed. Since the water inlet via the pipeline 31 is somewhat larger than the water outlet via the pump 24, the surface fluctuates between the lower and the upper level at certain time intervals, so that during the time in which the valve 34 is closed, there is practically complete calming of water enters the filter chamber 4. During the inflow time, a uniform overflow of the water from the calming chamber 3 into the filter chamber 4 is achieved due to the influence of the partition wall 2, whereby a disturbance of the free water surface in the filter chamber 4 is prevented. As long as the water level is in the area of the upper level, water is simultaneously withdrawn from the surface area for a short time via the opening 29 and parts floating on the surface, such as hair or the like, are flushed out into the receiving water.

It is very easy to see that the flow rate of the water within the filter chamber 4 is very low and is in the range of approximately 1.2 cm / sec. This results in a long dwell time for the water inside the filter chamber, even with large throughputs, and therefore a correspondingly long dwell time in the radiation area of the UV lamps 28. Since the swimming pool water is constantly circulated through the filter and disinfection device, the water quality can be reduced be kept constant and well below the permissible tolerance limits with regard to the number of bacteria, etc. The long residence time in the area of UV radiation also allows a relatively large container depth to be used, since sufficient radiation exposure is also achieved in the lower zones of the container.

Another advantage arises in connection with the chlorination that is mandatory for swimming pool water. The chloramines that form in the swimming pool, in particular due to the reaction with the ureas, are decomposed in the filter chamber under the influence of UV radiation, so that the chlorine dissolved in the water is practically regenerated. The addition of chlorine can thus be considerably reduced compared to the previous processes. Since the UV radiation also kills diatoms, there is also no need to add algicides to swimming pools that are exposed to strong sunlight. Flocculants to support the filtering process can also be dispensed with.

The device shown in Fig. 1 and 2 works with a radiation power of 330 watts on an area of about 1.4 square meters, with a filter passage of about 1.2 cm / sec. This results in a theoretical length of stay in the UV radiation range of about 2.2 to 2.4 minutes, so that even germs that are present in a water depth of more than 30 cm are killed, but are certainly damaged so that they be completely killed in another run.

Since, as can be seen from FIG. 2, the UV emitters are arranged above the spaces between the individual filter plates, the filter surface is also exposed to UV radiation, so that germs which settle on the filter surface are also killed and the formation of bacteria or germ nests in the filter auxiliary layer is completely prevented. This is important insofar as when replacing the filter auxiliary layer, which is usually done by rinsing or backwashing, the used filter auxiliary layer material removed from the filter chamber is completely germ-free and can be removed or processed much more easily,

The above embodiment is provided specifically for the treatment of swimming pool water, wherein a schematically illustrated heat exchanger 38 for heating the swimming pool water can optionally be provided in the area of the inlet chamber 3.

In Fig. 3, a system is provided in the form of a block diagram as it can be used, for example, for the treatment of drinking water from surface water or groundwater or also for the treatment of waste water which contains dissolved substances which can be decomposed by means of UV radiation. In the scheme shown in FIG. 3, for example, river water to be treated is first pumped through a filter 39, which can either be a sand filter or a plate filter, as shown in FIG. 1. The water passes from the filter into a container 40 through which it flows at a flow rate in the range of approximately 0.5 to 50 cm / sec. The container 40 is provided with UV lamps, through which the water is sterilized. The water is conveyed into a collecting container 42 via a three-way valve 41. Once the container

42 is filled, the supply of raw water to the container 40 is shut off and the water from the container 42 is circulated through the container 40 by a corresponding changeover of the valve 44 until the desired degree of disinfection is reached. Then the completely treated water is pumped out of the container 42 and fed to the consumption point. During this time, raw water is again drawn into the container 40 via the filter and into the container by the corresponding position of the valve 41

43 pumped, and then, with the valve 44 in the appropriate position, the water which has already been filtered is in turn circulated several times through the container 40 and thus through the UV radiation.

Depending on the type of water to be treated, it may be expedient to pass the water through an ion exchange system 45 after passing through the filter 39, for example to remove dissolved salts.

The system described above is based on a design for the container 40 as shown in FIG. 4. Here, the open container 40 is provided with a partition 46 with a lower passage 47, which separates an inlet and settling chamber 48 from the container. On the outlet side, a partition 49 is provided with a large number of through openings, which allows an outlet into a discharge chamber 50 practically over the entire cross section of the container. The area between the partition wall 46 and 49 is covered by a cover 51, in which UV lamps 52 are arranged in accordance with the required radiation power. Instead of UV lamps, which act on the contents of the container 40 via the free water surface, UV lamps immersed in the container contents can also be used with a corresponding structural design. However, the design effort required for this is considerable and the replacement of used UV lamps is difficult.

However, it is particularly advantageous if the container 40 is designed in accordance with FIG. the water is drawn off from the container via a corresponding number of filter plates. This has the advantage that, for example, the filter 39 acts as a prefilter and separates the coarse contaminants from the water, a more frequent replacement of the filter auxiliary layer being necessary depending on the degree of contamination, while the filter plates arranged in the container 40 serve as a finished filter and because of the circulation of the water between the container 40 and the collecting containers 42 and 43 not only an optimal disinfection but also an optimal filtration of the water is achieved, all of the advantages of the device shown in FIG. 1 also of course applying to the drinking water treatment.

s io

15

20th

25th

30th

35

40

45

50

55

60

65

V

2 sheets of drawings

Claims (20)

618 147 2nd PATENT CLAIMS 1. A method for sterilizing water by irradiation with ultra-violet light, characterized in that the water to be sterilized is passed through a container at a flow rate of 0.5 to 50 cm / sec and is thereby exposed to the irradiation with ultra-violet light . 2. The method according to claim 1, characterized in that the water to be sterilized is passed through an open container, a practically wave-free water surface being maintained during the flow through the container, and in that the free water surface is irradiated with ultra-violet light. 3. The method according to claim 1 or 2, characterized in that the water is circulated through the container. 4. The method according to any one of the preceding claims, characterized in that the water is additionally passed through a filter. 5. The method according to any one of the preceding claims, characterized in that the water surface is mechanically cleaned of floating solids at predetermined time intervals. 6. The method according to claim 5, characterized in that the cleaning of the water surface is carried out by removing water in the region of the water surface. 7. The method according to any one of the preceding claims, characterized in that the water is discharged from the container through a filter surface. 8. The method according to claim 7, characterized in that the filter surface is exposed to UV radiation on the inlet side. 9. Device for performing the method according to claim 1, characterized by an open-topped container (1, 40) with an inlet chamber (3, 48) for water calming, a drain device and UV lamps (28, 52) arranged in the upper region of the container. . 10. Device according to claim 9, characterized in that, preferably tubular UV lamps (28, 52) are used in a cover (27, 51) for the container opening, which UV lamps run approximately parallel to the free water surface. 11. The device according to claim 9 or 10, characterized in that the UV lamps (28, 52) are arranged close above the free water surface of the container. 12. The device according to claim 9 or 10, characterized in that the UV emitters (28,52) are provided with reflectors. 13. The device according to claim 11, characterized in that the surfaces of the cover (27, 51) facing the UV lamps are designed to be reflective. 14. Device according to one of claims 9 to 13, characterized in that the drain device has a collecting space (21, 50) which is adjacent to the container (1, 40) and is connected to it with a plurality of through openings. 15. The device according to claim 14, characterized in that the passage openings between the container and the collecting space are designed as a filter surface. 16. Device according to one of claims 9 to 15, characterized in that the filter surface is formed by a plurality of vertically extending filter plates (18) which are arranged at a distance and parallel to one another, and that at least some of the UV lamps (28) are so arranged above the free water surface is arranged so that they are located above the gaps between the filter plates and run parallel to them. 17. Device according to one of claims 9 to 16, characterized in that, preferably in the inlet region of the container (1), approximately at the level of the water surface, a drain opening (29) is arranged, which is connected to a drain line (30). 5 18. Device according to claim 17, characterized in that a valve is arranged in the exhaust line (30), the actuator of which is connected to a time switching device. 19. Device according to one of claims 9 to 18, characterized in that a level control is provided which keeps the height of the water surface in the container (1, 40) within predetermined level limits. 20. Device according to one of claims 9 to 19, characterized in that in the feed line (31) for loading 15 container (1) a valve (34) is arranged, the actuator (35) with a level measuring device (33) for determining a lower (36) and an upper level (37) of the water surface is connected, when reaching the lower level (36) the valve (34) opens and when the 20 upper level (37) is reached the valve (34) closes. 21. Device according to one of claims 9 to 20, characterized in that the lower edge of a preferably designed as an overflow weir opening (29) is slightly below the upper level (37) of the water surface.