"Device and method to detect water contamination".

The present patent application for industrial invention relates to a device and a method to detect water contamination, in particular the contamination caused by the presence of non-conductive liquids, such as hydrocarbons, floating on conductive liquids, such as fresh water or saltwater.

US6194433 and US7183778 disclose sensors used to detect hydrocarbons. These sensors are especially used in the geological sector to examine the soil when searching for hydrocarbons. For this reason the sensors are designed in such manner to measure the resistivity of materials. However these sensors are very complex and very expensive because they have to measure resistivity.

Sensors of inexpensive type, which are not adapted to measure resistivity, are known on the market to detect the presence of hydrocarbons. This type of sensors comprises a dielectric layer, generally a Carbon-Black polymer, disposed between two conductive electrodes. The dielectric layer between the two electrodes reacts to the presence of hydrocarbons, absorbing the fluid and increasing its resistivity. Therefore a low resistance between the electrodes indicates the absence of hydrocarbons, whereas the increase of the resistivity detected between the electrodes indicates the presence of hydrocarbons. However such a type of sensor is not suitable for application in water, such as saltwater, to detect the contamination caused by hydrocarbons. Moreover, such a sensor provides no information on the quantity of the hydrocarbons that have been detected.

HOVIG DENKILKIAN ET AL: "Wireless Sensor for Continuous Real-Time Oil Spill Thickness and Location Measurement", IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT, IEEE SERVICE CENTER, PISCATAWAY, NJ, US, discloses a sensor used to detect, process and send information on oil spills (location and thickness).

KOULAKEZIAN ET AL: "Wireless Sensor node for real-time thickness measurement and localization of oil spills", ADVANCED INTELLIGENT MECHATRONICS, 2008, AIM 2008; IEEE/ASME INTERNATIONAL CONFERENCE ON, IEEE, PISCATAWAY, NJ, USA, discloses a wireless sensor used to detect the thickness and location of oil spills in real time. In particular, two detection methods of oil spills are described, which are based on the different electrical conductivity properties of oil and water.

STERNBERGER W AT AL: "Remote Sonar Sensing of At-Sea Oil Layer

Thicknesses", OCEANS 81, IEEE, PISCATAWAY, NJ, USA, discloses techniques used to process sonar signals to measure the thickness of an oil layer in a dynamic oil spill setting.

US4044606 discloses equipment and processes used to measure with ultrasounds the thickness of a layer, for example an oil layer, disposed between two different substances, such as water and air.

EP1589325 discloses apparatuses and methods for monitoring water consumption by using a filter that comprises a microprocessor sensor adapted to detect and monitor the variations in the level of filtered or non-filtered water in a container of filtered water.

US5532679 discloses an oil spill detection system to detect the presence of oil in harbors, bays, gulfs, canals, rivers, environmental sensitive coastal waters, recreational beach areas, shipping lanes, lakes and waters.

The purpose of the present invention is to eliminate the drawbacks of the prior art by devising a device used to detect water contamination that is efficient, efficacious, reliable, versatile, practical, inexpensive and simple to install and use.

These purposes are achieved according to the invention, with the characteristics claimed in the independent claim 1. Advantageous embodiments of the invention appear from the dependent claims.

A device has been devised to detect the presence of floating non- conductive liquids, typically the presence of hydrocarbons at sea, said device using the different electrical conductivity (the inverse of such unit being resistivity) between the water (fresh water or saltwater) and the non-conductive fluid floating on its surface. The physical principles on which the device of the invention is based are related to the different electrical conductivity of fluids. The purpose of the device is to detect the passage of current through the fluid, and not to measure the resistivity value of the fluid.

In particular, fresh water and saltwater behave like a good conductor for the passage of current. If the electrodes attached to a battery are immersed in water, even at very low voltages of the battery, a passage of current between the two electrodes is detected. Instead, if the two electrodes are immersed in a hydrocarbon (oil, gas, etc.), given the fact that the hydrocarbon behaves like an insulating material, no passage of current is detected (unless the voltage of the battery is increased to inimaginable values of thousands of Volts).

The idea of the device according to the present invention is to detect the passage of current between two electrodes immersed in the fluid to determine the presence of non-conductive fluids floating on the water surface (in particular saltwater).

Further characteristics of the invention will appear clear from the detailed description below, which refers to merely illustrative, not limiting, embodiments, illustrated in the attached drawings, wherein:

Fig. 1 is a diagrammatic view of a device used to detect water contamination according to the invention, in case of non-contamination;

Fig. 1A is an enlarged view of the device of Fig. 1;

Fig. 2 is the same view as Fig. 1, except for it shows the device of the invention in case of contamination; Fig. 3 is the same view as Fig. 1, except for it shows a different version of the device of the invention in case of non-contamination;

Fig. 4 is the same view as Fig. 3, except for it shows the different version of the device of the invention in case of contamination;

Fig. 5 is a block diagram that shows the operation of the device of the invention; and

Fig. 6 is a partially sectional diagrammatic view of the device of the invention, comprising a buoy.

With reference to the figures, the device used to detect water contamination is disclosed, which is generally indicated with reference numeral (100).

Referring now to Fig. 1 , the device (100) comprises a body (101) adapted to be connected to a support in such manner that the body (101) is out of the liquid (L) in which contamination is to be detected. The liquid (L) must be a conductive liquid, such as for instance fresh water or saltwater.

The support can be a floating buoy (in such a case the support can be integrated in the device (100)) or a pre-existing fixed support disposed in the liquid (L), such as for example an oil platform or a harbor dock (in such a case the support is not integrated in the device).

The body ( 01) of the device has a lower surface (102) from which a first column (103) and a second column (103') protrude in lower position, being suitable to be partially immersed in the water (L).

The lower surface (102) of the body (101) is disposed at a certain distance from the free surface (Lo) of the water, i.e. the separation line between the liquid (L) and the air, in such manner to ensure that the free surface (Lo) does not reach the lower surface (102) of the body (101).

A plurality of conductive electrodes (1-7) is disposed in the first column (103), being mutually spaced along a vertical axis so that at least some conductive electrodes are situated under the free surface (Lo) of the water. With reference to Fig. 1A, the conductive electrodes (1- 7) are numbered in increasing order from up downwards and are disposed in a predefined position, using the lower surface (102) of the device body as reference. In view of the above each conductive electrode (1-7) is disposed in a known position (D1 - D7) with respect to the lower surface (102) of the body (101). The positions (D1-D7) of the electrodes are stored in a control unit (U) (see Fig. 5) of the device (100).

For illustrative purposes only Fig. 1 shows seven conductive electrodes highlighted in black, wherein the first three electrodes (1-3) are above the free surface (Lo) of the water and the other four electrodes (4 -7) are under the free surface (Lo) of the water.

Preferably each conductive electrode (1-7) has a low thickness, approximately 1-2 mm. In spite of being insulated, the electrodes are very close to each other, for example at a distance of approximately 1-3 mm. This guarantees a higher accuracy during detection, as illustrated below.

At least one conductive electrode is disposed in the second column (103') and electrically coupled with the conductive electrodes (1-7) of the first column (103).

With reference to Fig. 5, a voltage generator (V) generates a potential difference between each electrode (1-7) of the first column and at least one electrode of the second column. For illustrative purposes, the voltage generator (V) generates a potential difference of approximately 1 Volt.

A current detector (A), such as for example an amperometer, measures the current between each electrode (1-7) of the first column and said at least one electrode of the second column.

According to a preferred embodiment only one voltage generator (V) is provided to power the pairs of electrodes in cascade and only one current detector (A) is provided to measure the current in each pair of electrodes. In such a case the electronics of the device addresses the pairs of electrodes, allowing for cyclically reading the pairs of electrodes with only one current detector (A).

Alternatively, one dedicated voltage generator and/or one dedicated current detector can be provided for each pair of electrodes.

Figs. 1 and 2 show an embodiment in which the second column comprises a number of electrodes (1' - 7') equal to the number of electrodes of the first column (103). The electrodes (1'-7') of the second column are disposed like the electrodes (1-7) of the first column. The electrodes (1-7; 1'-7') of the first and the second column are coupled in pairs, meaning that the first electrode (1) of the first column is electrically connected to the first electrode (1 ') of the second column by means of a voltage generator (V) and so on, until the last electrode (7) of the first column, which is electrically connected to the last electrode (7') of the second column.

An ultrasound probe (T, E) is disposed in the lower surface (102) of the body (101) between the two columns (103, 103'). The ultrasound probe comprises one ultrasound transmitter (T) and one ultrasound receiver of sensor (E). The transmitter (T) sends an ultrasound signal (S1) that is reflected onto the free surface (Lo) of the liquid generating a reflected ultrasound signal (S2) that is detected by the receiver (E).

With reference to Fig. 5, a control unit (U) detects the time elapsed between transmitting the signal (S1) and receiving the signal (S2) and calculates accordingly the position (Do) of the free surface (Lo) of the liquid with respect to the lower surface (102) of the body (101).

As shown in Fig. 1 , when it is applied to the first three pairs of electrodes (1-1\ 2-2', 3-3'), the current detector (A) does not measure any passage of current because the air acts as a good insulator (for the small voltages used, which are equal to or lower than one Volt). Instead, when it is applied to the remaining four pairs of electrodes (4-4', 5-5', 6-6', 7-7'), the current detector (A) measures a passage of current because the electrodes are immersed in a conductive liquid (L). In particular, the first electrode to detect the passage of current, from up downwards, is electrode (4).

Simultaneously the ultrasound probe (T, E) measures the position (Do) of the free surface (Lo) of the water. Then the control unit (U) compares the position (Do) of the free surface of the water measured by the ultrasound probe (T, E) with the position (D4) of the first electrode (4) that detects the passage of the current.

As shown in Fig. 1 , the position (D4) of the first pair of electrodes (4-4') that detects the passage of current, coincides with the position (Do) of the free surface (Lo) of the water (i.e. Do = D4), indicating the absence of contamination liquid floating on the water.

Fig. 2 shows the situation in which a non-conductive liquid (C), such as hydrocarbons, floats on the water (L); therefore, the free surface (Lo) corresponds to the separation surface between the non-conductive liquid (C) and the air. In this case, the first three pairs of electrodes (1-1 ', 2-2', 3-3') are still in the air and do not detect the passage of current, whereas among the remaining pairs of electrodes, two pairs of electrodes (4-4', 5-5') are immersed in the non- conductive liquid (C) and detect no passage of current and the last two pairs of electrodes (6-6', 7-7') are immersed in the water (L) and detect a passage of current.

Therefore, the first pair of electrodes to detect the passage of current is the pair (6-6'). Therefore the position (D6) of the first pair of electrodes (6-6') that detects a passage of current will not coincide with the position (Do) of the free surface (Lo). In fact, the position (Do) of the free surface coincides with the position (D4) of the pair of electrodes (4-4') that does not detect a passage of current. In view of the above the position (D6) of the first pair of electrodes to detect a passage of current is different from the position (Do) of the free surface detected by the ultrasound probe. In this way the presence of the floating non- conductive liquid (C) is detected. As shown in Fig. 5, when the control unit (U) detects the presence of a floating non-conductive liquid, it sends a control signal to an alarm (200) that informs the presence of a contaminating substance.

The thickness (W) of the floating non-conductive liquid (C) is obtained as difference between the position (D6) of the first electrode that detects the passage of current and the position (Do) of the free surface detected by the ultrasound probe, i.e. W = D6 - Do. The smaller the distance between the electrodes of the same column and the thickness of the electrodes is, the more exact the measurement will be. It must be noted that the ultrasound probes (T, E) are preferably low-cost ultrasound probes that have a sensitivity of approximately one millimeter and therefore the sensitivity in the measurement of the thickness (W) of the non-conductive liquid (C) will be of max. one millimeter (and consequently also the dimension of the electrodes and the distance between them must be of approximately one millimeter).

Referring to Figs. 3 and 4, the device (100) operates also if the second column (103') is an entire electrode (130) either totally or partially made of conductive material. In such a case the passage of current only depends on the presence of non-conductive liquid around the separate electrodes (1 - 7) of the first column (103).

By applying a potential difference between the entire electrode (130) of the second column and the electrode 4 or 5 of the first column, in case of non- contaminating substances (Fig. 3), a passage of current is determined because the electrodes 4 and 5 of the first column are immersed in a conductive liquid (L), whereas in the case of contaminating substances (Fig. 4), a passage of current is not determined because the electrodes 4 and 5 of the first column are immersed in a non-conductive liquid (C).

The measurement process of the device (100) comprises the following steps: a) disposition of a first column (103) and a second column (103') at least partially in a conductive liquid (L) and systematic application of a potential difference between pairs of electrodes disposed on said columns (103, 103') in known positions (D1 - D7);

b) determination of the pairs of electrodes used to detect the passage of current;

c) determination of the position (Do) of the free surface of the liquid by means of an ultrasound probe (T, E);

d) discrimination of a non-conductive liquid (C) floating on the conductive liquid (L) by comparing the position (Do) of the free surface of the liquid and the position (D1-D7) of the electrodes between which a passage of current has been detected.

In steps (a) and (b) a potential difference in cascade is applied on all pairs of electrodes, which are observed in order to detect the pairs with a passage of current; the data is momentarily stored in the control unit (U).

Step (c) provides for determining the position (Do) of the free surface (Lo) of the liquid by means of the ultrasound probe.

In step (c) the software processes the results by comparing the position of the first pair of electrodes between which a passage of current is detected and the position (Do) of the free surface (Lo) of the fluid.

This data is sufficient to detect the presence of a floating non-conductive fluid (C) and determine its thickness (W). Evidently, only the combination of the two types of measurement will provide the desired information.

As shown in Fig. 6, given that the device (100) will have to operate at sea, in presence of wave motion, the two columns (103, 103') must be at a distance lower than 0 cm in order to be equally immersed in the fluid.

In order to prevent the electrodes from bumping against fish or other semi- immersed objects, a protection cage (G) may be disposed around the electrodes. The meshes of the protection cage (G) must be large enough to allow for the passage of the non-conductive fluid.

The electrodes must be made of a material that can resist saltwater corrosion, such as for example Activated Titanium. Moreover, the passage of current through the electrodes immersed in the water may prevent microorganisms from being deposited on the electrodes. It may also useful to provide for inversion cycles in the direction of the passage of current between the electrodes in order to avoid the formation of deposits on the electrodes due to electrolysis.

Preferably the support is integrated in the device (100). In this case the support is a buoy (104). The buoy (104) can be provided with a solar panel system (140) in order to power the electronics of the device (100). The device (100) also comprises a radio transmitter (141) for the remote transmission of signals and a GPS (142) for localization (in case the buoy is free to follow sea currents). In such a case the radio transmitter (141) and the GPS (142) can be mounted on the buoy (104) and electrically connected to the control unit (U) of the device.

The device (100) managed by the software will make measurements on the presence of floating non-conductive liquids at regular adjustable time intervals (for example every 15 minutes). If the presence of these liquids is detected, the buoy uses the radio transmitter (141) to send a message and the GPS (142) (in case the buoy is free to follow the sea currents) will allow for detecting the position where the liquid has been detected.

Variations and modifications can be made to the present embodiments of the invention, within the reach of an expert of the field, while still falling within the scope of the invention.