Method and device for carrying out the protected detection of the pollution of water

The method according to the invention consists in providing two containers fed by the water source whose pollution is desired to be measured, each of the containers containing fish and being equipped with a detector able detect any abnormal behaviour of the fish, alternate the lighting and obscurity periods for said two containers, carry out the detection of the behaviour of the fish in the two containers and trigger an alarm signal when the detection shows an abnormal behaviour of the fish.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention concerns a method and device allowing the protected detection of the pollution of water.

2. Description of the Prior Art

Generally speaking, it is known that so as to detect pollution thresholds, the fish, usually trout, are placed in a container inside which the water is to be controlled circulates, and parameters representing the behaviour of the fish are detected. An alarm signal is transmitted when the detected parameters show an abnormal behaviour of the fish, said alarm likely to be generated by a pollution threshold being exceeded.

Thus, in particular in the French patent No. 98 01387 filed in the name of the applicant, a method is being proposed consisting of:generating in the water of the container a series of ultrasonic wave trains spaced from one another by periods of silence,detecting during the periods of silence the echoes generated by each of said trains,carrying out the temporal analysis of said echoes and memorising the results of theses analyses,comparing the results of the time analyses of the echoes resulting from each wave train with reference values and/or with the results of the time analysis of the echoes resulting from the preceding wave train,determining the degree of pollution of the water according to the results of said comparison.

This method is based on the fact that the form and the layout of the echoes (variation in the process of time of analysis of the signal) depend on the position of the various obstacles and that consequently, by comparing the form of various echoes detected during two successive silent periods, it is possible to determine a modification of the movement of the fish. In the case of no movement occurring, the echoes shall always be identical and there shall be no difference between two successive echoes. On the other hand, when the fish move, the difference between two echoes is proportional to the amount of movement. An alarm could be triggered below or above an adjustable threshold between two echoes.

This solution proves to have a significant drawback owing to the fact that like most animals, trout are subject to going to sleep. Consequently, during periods of sleep, usually at night, the behaviour of the trout is closely related to abnormal behaviour giving rise to the transmission of the alarm signal. As a result, false signals are triggered, thus rendering this method unusable during the periods when the trout are likely to sleep.

OBJECT OF THE INVENTION

Thus, the aim of the invention is more specifically to eliminate these drawbacks.

To this effect, this aim is based on the fact that it is possible to artificially provoke periods of sleep for the fish by placing the containers under artificial lighting and by alternating lighting periods and periods of obscurity.

SUMMARY OF THE INVENTION

Consequently, the method according to the invention consists of:providing two containers fed by the water source whose pollution is desired to be measured, each of said two containers containing fish and being equipped with means able to detect an abnormal behaviour of said fish,Alternating lighting and obscurity periods of the two containers so that when one of the two containers is lit up, the other one is in obscurity or vice versa,Carrying out detection of the behaviour of the fish in the two containers, andTriggering an alarm signal when said detection shows an abnormal behaviour of the fish depending on whether the container is lit up or not.

By means of this arrangement, it is possible to continuously carry out the detection of the pollution without said detection being disturbed by the sleep periods of the fish which exclusively occur during the periods when the containers are in obscurity.

Of course, the information resulting from the detection carried out during the periods of obscurity of the containers could be used to validate the behaviour anomalies picked up during the lighting phases. This process could particularly concern a transitory period including the changing of the containers from a lit up period to a period of obscurity. Indeed, the behaviour of the fish during these changes discloses the health of the fish.

DESCRITPTION OF THE PREFFERED EMBODIMENTS

In this example, the installation consists of two containers B1-B2partially filled with water and fed by a common water source for which it is desired to monitor the level of pollution.

These two containers B1-B2are placed in two cells C1-C2sealed from the light and each having means E1-E2able to be controlled by means of a processor22so as to provoke an alternation of periods of light and obscurity, the period of lighting of one of the containers B1corresponding to the obscurity period of the other container B2and conversely. The lighting periods can overlap so as to take account of awakening and sleep period of the fish. By means of this arrangement, it can be ensured that the fish in one of the two containers are awake whilst the fish in the other container are asleep, are waking up and even going to sleep.

Each of said containers B1-B2can be equipped as shown on FIG.2and be divided into three chambers3,4,5by two vertical partitions6,7, namely:a water intake chamber and possibly cooling chamber3,a main chamber4in which the fish are placed,an evacuation chamber5provided with an excess circuit6′.

The intake chamber3and the evacuation chamber can be common for the containers B1-B2with the main chamber4.

Feeding of each of the containers B1-B2is carried by a water intake circuit7′ opening into the intake chamber3and successively comprising a manometer8, an adjusting valve9and a venture10intended to ensure oxygenation of the water.

The intake chamber3can contain a heat exchanger11(pipe coil) connected to an air-conditioning device12adjusted so that the water penetrating into the main chamber4via orifices or chicanes, preferably situated in the lower portion of the partition6, is at a constant temperature (for example less than 15° C.) corresponding to the temperature the fish are accustomed to live. This air-conditioning device12can include an automatic control circuit comprising a temperature sensor placed at the outlet of the intake chamber.

The evacuation chamber5communicates with the main chamber4by means of orifices provided in the partition7, the overflow circuit6′ whose outlet is fitted with a strainer13determining the level of water contained in the container B1. This overflow circuit6′ is connected to a draining circuit14which opens into the bottom of the main chamber4by means of a drain valve17.

The water passage orifices made in the partitions6and7are designed so as to stop fish passing through and ensure a flowing free from turbulence or any hydrodynamic phenomenon likely to generate noticeable pressure waves in the main chamber4and of a kind to disturb those made by the fish.

The main chamber4is provided with an ultrasound wave transmitter/receiver unit ER whose transmitting portion E is connected to an ultrasound signal generator controlled by a processor22whose keypad23and screen24are diagrammatically represented. Under the control of the processor22, said generator transmits in the water a series of ultrasonic waves separated from one anther by silent periods. The transmitter/receiver unit also contains a temperature sensor T making it possible, following processing by the circuit21, to inform the processor23of the temperature of the water.

The receiving portion R of the unit ER is connected to a receiving circuit RC, also controlled by the processor22, so as to receive the echo signal received by the receiving portion during the silent periods.

Following processing by the receiving circuit RC, the echo signal is transmitted to an analysis circuit21connected to the processor22.

By means of these arrangements, all the seconds (adjustable values) during a period of one millisecond (adjustable value), an ultrasonic wave train, for example at 40 kilohertz (adjustable value), could be transmitted by the transmitting portion E into the water of the container B1-B2, which is lit up. These waves are reflected by all the obstacles they meet, mainly by the fish and glass walls of the aquarium. The reflected waves (echoes) are detected during the silent period by the receiving portion which delivers an echo signal whose form (time variation of the amplitude of the signal) depends on the position (particularly of the receiving portion/obstacle distance). Said signal, once digitised by the analysis circuit, is stored and processed by the processor.

This processing could include a comparison of the echo signal obtained following the transmission of a wave train with the echo signal generated by a wave train previously transmitted so as to determine the physiological state of the fish, it being understood that:in the case of an absence of movement of the fish, the echoes shall still be identical and the difference between two echo signals shall be nil,in the presence of moving fish, the difference of form of two consecutive echo signals is representative of the movement quantity.

Below or above an adjustable difference threshold between two echoes, the processor could trigger an alarm. As the movement of the fish is dependent on the temperature of the water, the measurement of the movement quantity shall be weighted by the temperature measurement.

The processor could be programmed so as to carry out a digital analysis such as for example the Fourrier Transform of the echo signals, for examining the agitation frequency of the fish and its amplitude, that is parameters indicative of the state or the stress of the fish.

In this example the central chamber4is in addition equipped with at least one piezometric sensor18connected to the analysis circuit21by means of an amplifier19and a filter20.

Following digitisation by the circuit21, the signals delivered by the sensor18, which are representative of both the power and speed of the movements and therefore the alertness of the fish, are analysed by the processor22so as to detect any abnormal change in the behaviour of the fish (acceleration, fibrillation, slowing down, prolonged absence of movements). This information could be used to validate or complete the information deduced from the echo signals originating from the receiving portion R.

Of course, the processor22can be programmed so as to identify the changes in the behaviour of the fish and compare these with a previously memorised typological classification of changes so as to determine the nature of the pollution which has caused these changes and/or orientate chemical researches to the determined polluting agents.

Advantageously, the processor22could transmit an alarm signal S by means of an interface25and/or continuously draw up an audio signal which, when applied to a loud-speaker26or similar element, generates a sound signal whose frequency is proportional to the general agitation of the fish bench present in the chamber4.

This process could possibly be carried out in a non-lit container in which the fish are supposed to be asleep. Similarly, the processor could be programmed so as to identify the changes in the behaviour of the fish with a view to determine the occurrence of any pollution.

Likewise, the processor could be programmed so as to analyse the behaviour of the fish during moving from an illuminated state to a non-illuminated state or vice-versa, so as to be able for example to clearly see the fish which died during the period of sleep.

These arrangements make it possible to obtain a reliable functioning free of false alarms.