GB2129125A - Method and apparatus for detecting pollutants - Google Patents

Abstract

A method and apparatus for detecting the presence of a pollutant, such as oil, floating on the surface of water. The apparatus comprises means (4) for emitting radiation on to the surface (6) of water and of such a wavelength that it will cause the pollutant to absorb said radiation and fluoresce, a detector (5) for detecting radiation of a different wavelength emitted by said pollutant as a result of said fluorescence, and indicator or warning means (3) operated by the signal produced by said detector as a result of detecting said latter radiation. The apparatus may be mounted on floats (2) and powered by solar power (9). <IMAGE>

Description

SPECIFICATION Method and apparatus for detecting pollutants The present invention relates to a method and apparatus for detecting pollutants and more particularly for the detection of oil and other pullutants such as petrochemicals floating on water.

The pollution of off-shore waters, harbours, estuarys and the like by oil is presently a serious probiem. Such pollution may occur, for example, by the illegal discharge of oil from a ship, or due to an accident or the loss of a ship, or again by reason of accidental leakage or spillage of oil at an oil terminal or oil rig.

Whilst such pollution can be prompty detected on many occasions if a proper visual surveillance is maintained, this surveillance is costly both in terms of man power and equipment such as vessels and aircraft and is also of little use during the hours of darkness or under conditions of low visibility or bad weather. Thus, pollution of large areas of water can remain undetected for a long period with resultant damage to the marine environment and possibly to a coast line or harbour. Also a great increase in the cost of clearing the pollution is then incurred, which could have been largely avoided or minimised if the pollution has been detected earlier and appropriate action taken to deal with it.

It is an object of the present invention to provide an improved method and apparatus for the detection of pollutants, particularly oil, and petrochemicals on water.

According to the invention a pollutant, such as oil, floating on water is detected by illuminating the pollutant with radiation so as to cause the pollutant to fluoresce, then detecting the radiation caused by the fluorescence and employing the result of the detection to provide an indication or warning of the presence of the said pollutant.

More specifically, the invention provides a method of detecting the presence of a pollutant, such as oil, floating on water which consists in illuminating the pollutant with radiation which is absorbed by the pollutant and such that the pollutant then fluoresces, that is to say emits radiation of a different wavelength from that which it absorbs, and detecting the said emitted radiation of a different wavelength so as to produce a signal which is employed to operate a warning or alarm device indicating the presence of the pollution.

The invention also provides apparatus for detecting the presence of a pollutant, such as oil, on the surface of water which comprises means for emitting radiation on to the surface of water and of such a wavelength that will cause the pollutant to absorb said radiation and fluoresce, a detector for detecting radiation of a different wavelength emitted by said pollutant as a result of said fluorescence, and indicator or warning means operated by the signal produced by said detector as a result of detecting said latter radiation.

According to a preferred form of the invention, the apparatus is mounted on or incorporated in a floating structure which can be secured or moored In a location where Tt is desired that it will perform its monitoring function, e.g. in an estuary or harbour or in the vicinity of an oil terminal. Thus any pollutant on the water which is carried by a current, tidal stream or the wind into the vicinity of the apparatus will be detected. Clearly a plurality of such floating structures can be employed so as to provide adequate surveillance of any particular area or stretch of water.

According to a preferred embodiment of the invention the apparatus is powered by solar energy so that it is completely independent of other power supplies.

Preferably the radiation is emitted on to the surface of the water intermittently, for example as a series of pulses, which cuts down the power requirements.

The invention will now be further described, by way of example with reference to the accompanying drawings in which: Figs. 1 A and 1 B are respectively a somewhat diagrammatic side sectional view and a plan view of one embodiment of pollutant detecting apparatus according to the invention.

Fig. 2 is a diagram of the detection and optical system employed in the apparatus.

Fig. 3 is a block diagram showing the basic circuit of the apparatus; and Fig. 4 is a diagram of an alternative detection and optical system.

Referring to Figs. 1 A and 1 B the apparatus is intended for detecting the presence of oil or a petrochemical floating on the surface of water by responding to their fluorescence and basically comprises a framework 1 supported above the water by four floats or buoyancy chambers 2 disposed one at each corner of the framework 1.

The latter carries a casing-3 containing the circuitry of the apparatus and from the lower side of which projects a light source 4 and photodetector 5 angled towards the surface 6 of the water in which the apparatus is floating and such as respectively to irradiate and receive fluorescence radiation from a pollutant floating on the water beneath the apparatus. A weatherproof protective housing 7 is disposed over the structure and its lower portion of skirt 8 is in the form of a grill or grating so to allow water to flow freely beneath the apparatus but prevent debris floating beneath the light source and detector. A series of solar panels 9 are mounted on the housing 7 to provide electrical power to the apparatus. In Fig.

1 B the housing 7 is only indicated by a dashed line for the sake of clarity.

Fig. 2 is a diagram of the detection and optical system. A pulsed ultra-violet light source 4 disposed in a reflector 10 emits light through a UV filter 11 and lens 12 to illuminate an area As on the surface 6 of the water.

It is well-known that oil, some petrochemicals, dies, and certain natural organisms exhibit the phenomenon of fluorescence, which means that when excited by light radiation of certain frequencies, they absorb that radiation, and then re-emit radiation of a different frequency. The change in frequency can indicate not only the presence of the said pollutants, but also their type.

This embodiment utilizes the pulsed UV light source 4, which with the appropriate filters 11 emits a fixed small range of frequencies specifically chosen to cause oils and related pollutants to fluoresce in response, again within a range of frequencies.

The light source 4 is arranged above the body of the water in such a way as to enable light caused by fluorescence to be received by the photocell 5 through lens 1 3. The photocell 5 is protected by light filters 14 which specifically stop reflected light reaching the cell and only allow light of a given (fluoresced) frequency to be passed. The output of the light detector is employed to give a warning or alarm when pollutants are detected as will be described.

Fig. 3 is a block diagram of the basic circuit of the apparatus. Photo-cells form a solar panel 20 from which electrical power is obtained for the power supplies 21. A timer 22 controls a pulse generator 23 which pulses the UV lamp 4 through the trigger 24 so that the lamp 4 emits flashes of light producing the desired wavelength of radiation on the surface of the water. The trigger 24 also energises a navigational warning lamp 25 mounted on the housing to indicate the presence of the apparatus in the water. The pulse generator 23 feeds one input of an AND gate 26 also fed by the light detector 5 (two being shown here) through an amplifier/comparator circuit 27.The pulse signal output from the AND gate which is obtained when the light detector(s) respond to the fluorescence radiation of polluting oil or a related pollutant is fed through a counter 28 whose output can operate an alarm 29. The latter in turn can trigger a transmitter 30 to transmit a warning signal denoting the presence of the pollution to a remote point. Instead of a radio transmitter, a cable connection or land line may be used. Optical cleaning means 31 for automatically cleaning the lens systems may be provided, controlled from the tube 22.

More specifically and if desired the light detector 5 may be connected to a range of electronic instruments which asses any signal emanating from the detector and which can include: a) an integrating system to add the pulses from the cell, and then to activate an alarm if a given level is exceeded, and/or b) a delaying system, which causes the pulses to be ignored if less than a given length of time, and/or c) a screening system, which causes only strong pulses to be read, and/or d) a system to increase the rate at which the light source operates, when a suspected pollutant has been detected, so as to obtain confirmation and/or continuation of the initial pulse, and/or e) an electronic alarm system connected either by wires or by radio to a control centre.

Fig. 4 shows an alternative detecting and optical system in which the light source 4 and detector 5 together with their associated filters and lenses are respectively housed at the upper end of two inclined tubes 41,42 each of which contains a circular apertured plate 43 intermediate along its length. The lower end of each tube is directed on to the area of water under surveillance. Each tube may, for example, be at least 1 metre in length and between 2-5 cm in diameter and the holes in the plates 43 may be only a millimetre or so in diameter. This arrangement provides good protection for the optical systems, light source and detector against atmospheric pollution and thus overcomes the problem of cleaning these components, as is otherwise necessary.

It will thus be seen that the method and apparatus of the invention enables a pollutant such as oil on the surface of water to be detected without the need for human surveillance and which can operate successfully even during the hours of darkness or in poor visibility.

Clearly many modifications may be made to the embodiments described. Thus numerous variations may be made in the form of the floating structure. It could for example be constructed as a glass fibre pod which both houses the apparatus and provides the necessary buoyancy, whilst allowing the free flow of water into the radiated area in which detection of oil was effected.

Moreover, a plurality of radiation detectors may be associated with one light source.

Claims (14)

1. A method of detecting a pollutant, such as oil, floating on water wherein the pollutant is detected by illuminating the pollutant with radiation so as to cause the pollutant to fluoresce, then detecting the radiation caused by the fluorescence and employing the result of the detection to provide an indication or warning of the presence of the said pollutant.

2. A method of detecting the presence of a pollutant, such as oil, floating on water which consists in illuminating the pollutant with radiation which is absorbed by the pollutant and such that the pollutant then fluoresces, that is to say emits radiation of a different wavelength from that which it absorbs, and detecting the said emitted radiation of a different wavelength so as to produce a signal which is employed to operate a warning or alarm device indicating the presence of the pollution.

3. A method as claimed in claim 1 or 2, wherein the radiation is emitted intermittently, for example as a series of pulses.

4. Apparatus for detecting the presence of a pollutant, such as oil, on the surface of water which comprises means for emitting radiation on to the surface of water and of such a wavelength that it will cause the pollutant to absorb said radiation and fluoresce, a detector for detecting radiation of a different wavelength emitted by said pollutant as a result of said fluorescence, and indicator or warning means operated by the signal produced by said detector as a result of detecting said latter radiation.

5. Apparatus as claimed in claim 4, wherein the apparatus is mounted on or incorporated in a floating structure which can be secured or moored in a location where is it desired that it will perform its monitoring function.

6. Apparatus as claimed in claim 5, comprising a plurality of such floating structures which are employed so as to provide adequate surveillance of any particular area or stretch of water.

7. Apparatus as claimed in claim 4, 5 or 6, wherein said apparatus is powered by solar energy so that it is completely independent of other power supplies.

8. Apparatus as claimed in claim 4, 5, 6 or 7, wherein the radiation is emitted on to the surface of the water intermittently, for example as a series of pulses.

9. Apparatus as claimed in claim 8, including a pulsed ultra violet light source.

10. Apparatus as claimed in any of claims 4 to 9, including a light source and a detector which are respectively housed at the upper ends of two inclined tubes directed on to the area under surveillance.

11. Apparatus as claimed in any of claims 4 to 10, including an integrating system to add pulses from the detector and then to activate an alarm if a given level is exceeded.

12. Apparatus as claimed in claim 11, including a delaying system, which causes the pulses to be ignored if less than a given length of time.

13. Apparatus as claimed in any of claims 4 to 12, including an electronic alarm system connected either by wires or by radio to a control centre.

14. A method of detecting pollutants substantially as hereinbefore described with reference to the accompanying drawings.

1 5. Apparatus for detecting pollutants substantially as hereinbefore described with reference to the accompanying drawings.