The present invention relates to an apparatus for the disinfection of liquids, especially water, comprising a UV-source for irradiating the liquid, a photocell which reacts on UV-rays from the UV- source, together with a chamber through which the liquid is led and where it is irradiated.

Disinfection by means of UV-irradiation has been used for 20-30 years abroad. In Norway UV- absorption got its breakthrough in the middle of the seventies, and is now mandatory on board all

Norwegian ships above a certain size, and is also employed in many waterworks instead of or as a supplement for disinfection by chlorination.

If the water which is to be disinfected is heavily particle-containing, for example includes larger amounts of humus particles, it ought to be filtered before it is passed through the irradiation. chamber.

In order that the UV-light shall kill at least 99% of pathogenic bacteria, spores and fungus present, these must be exposed to a radiation dose

2 of at least 8,000 nWs/cm . In order to have a certain safety margin, there is required from the side of the Norwegian authorities, represented by SIFF, that is to say the States Institute for Public Health, a

2 radiation dose of at least 16,000 μ\- ^~ s/c .

The radiation dose D is dependent upon the radiation intensity I and the irradiation time t:

D = I x t. The radiation intensity is dependent upon the effect of the UV-source (which decreases with its period of operation) , the distance between the UV- source and the photocell and the purity of the liquid, and the irradiation time depends upon the retention period of the liquid in the irradiation chamber.

In known apparatus for the disinfection of

liquids the radiation intensity which is received by the UV-photocell is converted to electrical pulses which are transferred to a meter where the intensity can be measured. However, no measurement is effected of the rate of flow of the liquid or its retention time in the irradiation chamber, and it is there¬ fore not possible to know what dose the microorga¬ nisms are exposed to at any time. This is a serious disadvantage with known apparatus, since as mentioned above the radiation dose is also dependent upon the irradiation time, which is determined by the re¬ tention time of the liquid in the chamber, and is decisive for the effect of the irradiation.

There is thus a need for an apparatus which makes possible the determination of the radiation dose at any time, and the object of the present invention is to produce such an apparatus.

This is achieved according to the invention by means of an apparatus which is characterised in that there is coupled ^' to the irradiation chamber a flow meter which is adapted to emit electrical pulses which cooperate with electrical pulses from the UV- photocell.

Conveniently the cooperating electrical pulses from the flow water and the photocell are indicated as radiation dose on a meter, where they are prefer-

2 ably shown in^ s/c (ultrarad) . Thereby it is possible to read off the momentary radiation dose directly on the meter. According to a convenient embodiment the flow meter is adapted via an alarm device to close off or choke a valve on not attaining a predetermined dose.

In this connection it can be mentioned that it is required from the Norwegian authorities side that the alarm shall be released and thereby a valve closed if the minimum dose of 16,000 uWs/c 2 is not reached. However, an alarm can also be released by a

dose which lies above the minimum dose, if this should be required.

With particular particle-containing, for example humus-containing water, it is usual to arrange a filter upstream from the irradiation chamber.

The invention will be further explained in the following description having regard to the accompanying drawing which shows a block diagram of the apparatus according to the invention. Water or another fluid is led into a cylindrical irradiation chamber 10 through an in¬ let 11 in the direction shown by the arrow. The water is led out of the chamber through an outlet 12. Inside the chamber, along the axis, there is arranged a UV-light tube 13 which is surrounded by a quartz tube 14, which has good permeability to UV-light (in contrast to conventional glass) . The quartz tube 14 is arranged to protect the UV-light tube 13. Rays from the light tube 13 strike a UV- sensitive photocell 15 and are converted to electrical pulses. For recording of the operative time of the light tube 13 there is arranged a time counter 17, since as mentioned the intensity of the tube decreases with its operative time, and it is therefore necessary to effect a replacement of the light tube after a certain number of operative hours, usually about 9,000 hours.

To the outlet of the irradiation chamber 10 there is connected a flow meter 18 which produces in a manner known per se electrical pulses dependent up¬ on the speed of flow of the liquid. The pulses from the flow meter are caused to cooperate with the pulses from the UV-photocell 15 and are fed to a meter IB, where they are indicated as a radiation dose, directly in i s/c 2. If a predetermined radiation dose is not reached, a signal is emitted from the

OM?I - -

meter 16 which releases an alarm in an alarm device 19 which acts to close or throttle a valve 20. If the transmission of UV-rays through the liquid is reduced, for example as a consequence of poorer water quality with an increased need for irradiation time as a consequence of this, there will thus be effected choking or closing of the valve, until satisfactory conditions are reestablished.