NL2007561C2 - A system and method for predicting, monitoring, preventing and controlling algae in open water. - Google Patents

Abstract

A system for preventing and controlling algae in open water comprises a first unit with: a sound transducer to be positioned in a water to be treated; components for generating an ultra sound frequency connected to said transducer; means for determining at least one of algae species and concentration of algae species in the water to be treated; and a power source for electrically feeding said transducer. The system is characterized in that it further comprises a second unit comprising a database that comprises information regarding algae species, concentrations thereof and corresponding characteristics of ultra sound to be transduced by said transducer for controlling said algae species by means of ultra sound frequencies, said characteristics being chosen from at least one of frequency, power output, amplitude and duration of feeding said transducer; wherein said first unit and said second unit each comprise wireless communication means for communicating with each other. Preferably, the system is characterized in that it comprises at least one of solar cells and wind turbines, for powering a battery as power source. The first unit may be provided on a floating body that is anchored or that is attached to the shore, for example a buoy or a platform.

Description

100.041NLpd A system and method for predicting, monitoring, preventing and controlling algae in open water

The present invention relates to a system for preventing and controlling algae according to the preamble of claim 1.

Such a system and method are known from the art.

According to the state of the art, controlling algae growth 5 with ultra sound is a well-established technology that has existed for many years. It is an environmental-friendly technology which is harmless to fish and plants. The treatment is efficient for relatively small ponds and has also been tried for treating algae in smaller lakes. The biggest problem with presently available 10 systems is a limited coverage ranges. The present state of the art provides a system that can be mounted on a buoy and operated on solar power. However, due to high power consumption, high maintenance on cleaning and less effectiveness, this installation is not suitable for large lakes and open water. Another issue is the lim-15 ited efficiency of treating different algae species, since specific sound values must be used to destroy different algae species. Because of this ineffective method of treating the algae, a longer time is necessary to obtain good results. Therefore, the power consumption becomes still higher and the system becomes less suc-20 cessful, even more so since the algae can get resistant to the standard program.

According to the state of the art, a full range frequencies is emitted by a transducer, irrespective the number and kind of algae present in the water and irrespective the attenuation of 25 said sound frequencies in the water. The known system therefore has the disadvantage that much energy is used for emitting a full range of frequencies.

It has now shown that each kind of algae requires a specific frequency with a specific energy output, amplitude, wave form, 30 burst duration and pauses for destroying same.

The invention aims at providing a system that uses less energy than existing systems but that nevertheless efficiently and ef- 2 fectively destroys algae in open water.

The present invention aims at providing an improved system so as to reduce or neutralize at least one of the aforementioned disadvantages of the known system and method.

5 The present invention at least aims at providing a system and method as mentioned above, that makes it possible to reduce the energy consumed by the system, such that the transmitter can be operated as a stand alone device, without any physical connection to a mains.

10 The invention further aims at providing a method that can be used for destroying a specific algae, without influencing another algae present in the water.

So as to obtain at least one of the aforementioned goals, the invention provides a system as mentioned in claim 1. It has shown 15 that not only the energy consumption issue has been solved by this new device but also the problem of algae becoming resistant for the program. It also provides a solution for a generally known maintenance issue, as the presently available systems are not able to clean the transducer heads of for example a hundred transducers 20 spread over a 5 km lake.

Preferred embodiments are mentioned in the dependent claims.

It is preferred that said components for generating an ultra sound frequency comprise a wave form generator, preferably a sine wave form generator. It has shown that such waveform provides an 25 optimum frequency for destroying algae.

It has further shown, that if the system comprises an amplifier, wherein said waveform is amplified by said amplifier and transmitted to the transducer, the sound waves can be carried over a longer distance.

30 In order to maximize the ultrasonic power transfer and to minimize reflections from the transducer, it is preferred that the waveform is amplified and transmitted to the transducer through an impedance matching circuit which is formed by a capacitor and an insulating transformer. It has also shown, that the sound waves 35 will have less harmonic noise, which improves the efficiency.

To be able to function as a stand alone system, the system preferably comprises at least one of solar cells and wind tur 3 bines, for powering a battery as an energy source. As a consequence, the system does not need any mains power, which makes the system suitable for installation far away from shore.

It is especially preferred if the system comprises a sensor 5 for determining presence of algae in the water and sensors for determining further water characteristics, chosen from at least one of temperature, turbidity, transparency, chlorophyll presence and colour intensity. Such information can be used to predict an algae bloom, based on previous measuring results. When an algae bloom is 10 expected, the ultra sound treatment can be intensified so as to control the presence of the algae before said blooming takes place .

It is preferred that the second unit is provided in a control room, for example ashore or on a boat, separate from a plurality 15 of said first units. For then, maintenance to or updating said database is performed with ease, whereas a plurality of first units together control said algae. In such cases it is preferred that said first units have a wireless connection with said second unit. A wireless connection has the advantage of easy and quick access. 20 Especially, the first unit of the system can send the data, obtained by the sensors, to the second data, after which the second unit may send a control program to said first units. Also, the second unit may provide each of said first units with a unique program.

25 Based on information stored in a database, the second unit may determine a preferred program the first unit should perform. Such database may contain information as mentioned in claim 8.

Regarding the present invention, some further technical information is given hereafter.

30 Low intensity ultrasound affects the algae gas vesicles and plasmalemma (the inner cell wall of the algal cell) cell linings. The blue-green Algae (cyanobacteria) have gas vesicles that are broken by the vibration resonance from the sound waves. Green algae do not have such vesicles, but their contractual vacuoles, 35 connected with the function of the plasmalemma, are damaged. This prevents the algae from obtaining fluids and nutrients, and from controlling their internal pressure. Without these functions, sin- 4 gle celled algae die.

There are a variety of ultra sound based systems for controlling algae. The systems consist of a control box programmed to generate multiple (ultrasonic) frequencies, and an ultra sonic 5 transmitter for transmitting the ultrasonic sound waves. The control box may be placed on shore or on a floating buoy or the like, and is powered from the mains or through solar cells. The transducer, which is placed into the water, is connected via a cable to the control box.

10 The working range is not only limited by the ultra sound pow er emitted from the transmitter but also by the frequency, the wave form and the transducer specifications, as well as by the quality of the water, turbulence, topography, plants, etc. A 20 W unit can typically have an operating range of 100 to 200 meters.

15 So as to ascertain that all algae are destroyed by means of the ultrasonic sound waves, a frequency range is emitted such that all algae that may be present in the water are destroyed. Typically, the complete ultrasonic frequency range applied is from 16 to 150 kHz. As a consequence, the power consumption of the known sys-20 terns is very high.

A further complicating factor, especially in lakes and bigger ponds, is that the presence of different algae species is in a state of constant change. Seasonal variations are common. As a precautionary measure, so as to ensure that all algae are de-25 stroyed, the complete frequency range of 16 to 150 kHz is emitted.

The invention will now be explained by means of the following Example and the Figures.

The drawing shows in fig. 1 a system according to the present invention that comprises a unit to be positioned in the water and 30 a second unit that may be provided at a distance from said first unit.

Figure 2 shows an example of a flow scheme of the present invention .

In the figures, the same or analogous features have been 35 identified by the same reference numerals. However, the features and parts that are not strictly necessary for understanding the invention have been omitted from the figures and description, so 5 as to improve the simplicity and clarity thereof.

Fig. 1 shows a schematic view of the system according to the present invention for treating a water body. The drawing shows two first units 2, 2' that are to be positioned in the water (not 5 shown) to be treated. Each unit 2, 2' consists of a floating body 3, 3', that has sufficient buoyancy to keep each unit 2, 2' floating on the water. Mooring lines 4, 5, 4', 5' keep the units at a predetermined position in the water body. So as to keep the mooring lines at a distance from the floating bodies 3, 3', additional 10 floating bodies 6 may be provided on the mooring lines. Sensors 12, 12' are positioned in the water. These sensors may be comprised of temperature sensors, algae sensors, and the like.

Since the equipment in the units consume power, the units as shown in Fig. 1 are provided with solar cells 7. As a matter of 15 fact, the units 2, 2' comprise batteries that are fed by said solar cells 7, as well.

Ultra sound is sent by transducers 8, 8', 9. The transducers are controlled by components provided in said unit 3, 3'. The transducers 8, 8' have a limited coverage, i.e. they each cover an 20 area of about 180°. Since two transducers 8, 8' have been provided at opposite sides of the unit 2, a total area of 360° around the unit 2 is covered. Unit 2' has a single transducer 9, which has coverage of 360°. I.e., in this case a single transducer is sufficient to cover an area of 360° around the unit 2'.

25 In the embodiment shown in Fig. 1, each unit comprises weath er sensors 13, 13' as well, for measuring air temperature, measuring the amount of sunshine, rain or the like, wind speed and direction. Of course, if more than one unit is provided in a water body, only one unit (or a few units) may be provided with weather 30 sensors 13, 13'.

Each unit 2, 2' is provided with wireless communication means, comprising an antenna 10, 10'. These communication means are in contact with a separately provided second unit 11 comprising a database containing information regarding algae species and 35 corresponding characteristics for controlling said algae dependent on, for example, concentration thereof in the water, temperature of the water, and required frequency, power output, amplitude, du- 6 ration of feeding the transducer, and the like.

According to the present invention, a plurality of units 2 may be provided that each may be brought and/or kept in contact with said second unit 11.

5 The flow scheme of Fig. 2 is a preferred example of the pre sent invention. The parts identified in the scheme are hereby incorporated in the description. It is to be understood that amendments may be made, for example, only one amplifier may be provided instead of three. In that case, only one transducer may be provid-10 ed. Furthermore, an embodiment comprising no weather station measuring air temperature and amount of sunshine, among others, may be omitted.

The system according to the present invention may preferably consist of a (web-based) management SW-program, running on a PC, 15 and one or several satellite unit(s) (for example buoys or platforms, floating in the water to be treated). The satellite units are located at selected points in the lake and can be individually accessed through the management system via a GPRS or similar connection. The management system can perform read-outs of sensor da-20 ta and status information. It can also program new ultra sound operational parameters into the satellite units. The read sensor data is collected in a database. The data collected provides input to a biological algorithm, which is used to predict the development of algae in the lake. The algorithm is also used to control 25 the growth of algae by outputting the optimal parameters for the ultra sound acoustic system onboard the satellite unit(s).

Hence, the system may be embodied as follows: A buoy will collect data from different sources, for example, at least one of the following but not limited thereto: 30 - Water sensors (chlorophyll, pH, TSS etc.) - Weather sensors (temperature etc.) - Satellite pictures - Transducer readings

This data will be send to a database, this database can be 35 within the buoy itself or on another place, like a pc. After receiving the data, a computer will provide a treatment plan. The treatment plan may comprise at least one of the following actions: 7 determine a frequency(-cies) the ultrasound devices will emit.

determine the power output the ultrasound devices will use.

5 - determine the duration for the program.

determine which transducers are used on the buoy (transducer on/off).

determine in which order the units will emit the frequency (-cies).

10 - determine which pauses/silent phases are used.

The system will send this information to the buoy and after a set time period, the buoy will provide feedback with the data from above mentioned sources to the database again. This allows the Database to provide a different treatment plan, if necessary.

15 By making a unit like this, three problems will be solved:

Maintenance: by adding a GSM module and Wiper or self cleaning transducer.

Effectiveness: The units become more effective by the flexible programs and resistance against ultrasound is 20 solved.

Energy consumption: Because of the treatment plan and monitoring which will create a special program, the energy consumption of the device will be low.

The satellite units are also equipped with a GPS-receiver or 25 the like in order to provide the management system with positional information. The management system may make use of a map service for visualising the position of each satellite unit to an operator. The satellite units are self supporting of power. The power is generated from solar panels and/or a windmill generator.

30 The ultra sound acoustic system on-board the satellite unit, is the core component of the algae control system. Ultrasound, defined as mechanical vibrations of the medium in frequencies above 20 kHz, is widely used as a carrier of measurement information. Ultrasound is also used as a means of energy transfer to achieve a 35 desired physical influence on an object. According to the present invention, use is made of both of these properties of ultrasound.

According to the present invention, ultrasonic vibrations, 8 propagating in water, are used as a means of transferring mechanical energy. When these vibrations encounter an object in their path of propagation, they have a physical effect on this object forcing it to vibrate at the same frequency. When the frequency of 5 the ultrasonic waves matches the natural frequency of vibration of the object, resonance occurs. Resonance can alter the mechanical properties (composition, structure) or even be totally destructive to the object. Ultrasonic vibrations in a pure water environment have a very useful property. They propagate with very small energy 10 losses, i.e. ultrasonic vibrations (waves) have a low attenuation in pure water.

Ultrasonic waves (vibrations) reflect from mediums or objects which have different acoustic impedances with regard to water. The reflection is greater when the difference between acoustic imped-15 ances of water and the object is bigger. In the present case, the acoustic impedance of the object of interest, blue algae for instance, and water is similar, but the algae cell has a gas vesicle. The acoustic impedance of the gas vesicle is about 104 times different from the surrounding structure. By tuning the frequency 20 of ultrasonic vibrations in line with transversal dimensions of the gas vesicle, resonance vibrations of the gas bubble (and simultaneously of the membrane walls which surround the gas) occurs. The resonance is capable of rupturing the gas vesicle. Therefore, by rupturing the gas vesicle, algae cells become ineffective and 25 die. According to several researches and monitoring of lakes and (waste) water treatment plants, algae live optimally when the water is stagnant. For example, a rising and falling water surface as in tides causes oscillation to the blue-green algae cells, which stresses them causing lower concentrations and cell death.

30 To generate ultrasonic vibrations, piëzo electric transducers are used most frequently. They are able to transform electrical energy into mechanical energy and vice versa. In practice, out of the entire group of piëzo electric transducers, piëzo ceramic transducers are most commonly used. These transducers are manufac-35 tured using special artificial ceramic materials which have piëzo electric properties. Some of the transducer surfaces are covered with electrodes. Such transducers, depending on application and 9 type of required vibrations, can be produced with different shapes and electrodes.

For operation in a water environment, transducers with longitudinal and flexural vibrations are most suitable, due to their 5 acoustic impedance being close to the acoustic impedance of water. Practically applied matching layers improve the transfer of energy even more. Depending on the transversal measurements and the shape of the transducer, the transmission and reception of acoustic energy will not be identical in all sectors of the environment 10 (transducers have different radiation patterns). Required radiation patterns are obtained by modifying the physical parameters and the technical design of the transducer. It should be noted, that when the frequency of ultrasonic vibrations is increased, the wavelength of the ultrasonic waves becomes shorter. Because of 15 these shorter wavelengths, transversal measurements of the transducer also become smaller while retaining the same radiation pattern .

It should also be noted that bare piëzo ceramic transducers cannot be used for operation in water. They have to be protected 20 by metal, rubber or plastic encasements. When such transducers operate in water with ultrasonic vibrations having relatively small amplitudes, they gradually become covered by various undesired materials (biofilm and other components), which decreases their effectiveness. Therefore, the transducers should be cleaned by peri-25 odically transmitting high-power electrical signals, which produces cavitation. Cavitation is the process in which high power, low frequency ultrasound causes the growth and implosion of gas bubbles within the water. Implosion of gas bubbles induces a local high temperature (5000 K), high pressure and micro-jets. Besides 30 that, water molecules are split into hydrogen free radicals, that can break down cell walls and some other molecules. When emitting these periodically, biofilm is being killed and degraded.

According to the present invention, a transducer is proposed which is not only capable of destroying the gas vesicle of the al-35 gae, but which also has a self-cleaning function. To achieve this, a complex-shaped piëzo ceramic transducer is developed for transformation of vibrations.

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The transducer is the most critical component of any ultra sound acoustics system, because it determines the technical and operational characteristics of the ultrasonic system. Therefore, in the present case of a new system and corresponding equipment 5 design, a specialized piëzo ceramic transducer has been developed as well. As mentioned before, a bare piëzo ceramic transducer (without encasement and matching mechanical elements) cannot be used in practical applications. Electro-acoustically active elements (piëzo ceramics) only transform electrical energy into me-10 chanical energy and vice versa. The operation of a transducer is impossible without a transformation of mechanical vibration which matches acoustic elements and matching layers that are essential for transducer operations.

The key characteristics and requirements for piëzo ceramic 15 transducers are: - Operating frequency interval.

- Highly effective electro-acoustic transformation of electrical signals .

- Similarity of acoustic impedances for the transducer and its 20 operating environment.

- Shape of the radiation pattern.

- Sufficient dynamic range.

- Stability of parameters in the transducer.

- Reliability and longevity of the transducer.

25 - Simple construction, simple production technology, low weight and low cost.

The successful development of the transducer means solving an array of problems to meet these requirements. Therefore, according to the present invention, not only the effects of ultrasound on 30 algae cells have been evaluated, but also a specialized, optimal electro-acoustic transducer and optimal and economical electronic components have been developed.

More specifically, preferably 4 transducers are used with a 90° radius, or 3 transducers with a 120° radius or 2 with 180° ra-35 dius or 1 with a 360° radius to cover the complete water surface, or any other configuration that covers 350°.

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The management system for use in the present system will be built as a central server solution with internet connection. Data will be transferred via a GPRS communication link (or the like) from and/or to each satellite unit (for example a buoy). The data 5 may comprise: control parameters for the ultrasound acoustic system, biological parameters such as pH-value, water and air temperature, phosphate, nitrogen levels, etc. The system may also comprise status information like: accumulator power level, sensor failure and other relevant service messages. Furthermore, measured 10 data obtained from the sonar may also be transferred. These may comprise data obtained from the communication between two transducers from the present transducer and a transducer of a different buoy, or it may comprise reflected sound from the present transducer .

15 For example: When the present transducer emits a certain fre quency, with a certain power, this frequency may hit a boat, rock, fish or plant and is reflected back. When the transducer (or a transducer located under this buoy to "measure" this sound) measures the reflected sound (and accordingly identifies said ob-20 ject blocking the sound waves), it can inform the database accordingly, upon which the database will instruct the system to shut of the said transducer.

Also, the data it receives from communication between transducers, for example when Buoy A emits a sound wave with a certain 25 strength, Buoy B can measure the strength again and see the power is less then it should be, which indicates high turbidity and the power should be increased.

This can all in turn be combined with the other parameters to obtain a good image of the situation in and on the lake. In case 30 of divergence from normal operation, any required action can be initiated.

The system may comprise for example four software modules: a communication module, a data base management unit, a data processing module, and a graphical user interface. Each module should 35 meet different requirements. Each module must be able to communicate with the other modules.

The communication between the satellite unit (i.e. the buoy) 12 and the management system will be based on a (wireless) internet connection meeting the GPRS or or any other suitable wireless (for example edge, gsm, hsdpa, 3G, Bluetooth, wifi) connection provided on each satellite unit. The communication protocol used, should be 5 able to simultaneously handle data from a large amount of satellite units in operation. Building the architecture of the database requires design for flexibility, so as to make sure that the different configurations of the satellite units can be connected to the management system.

10 Appropriate algorithms based on biological data of all types of algae that may be present in the water to be treated, will be implemented for calculating desired parameters for the ultrasound acoustics system. The calculation will be based on sensor data and will be calculated by the processing software module.

15 A Graphical User Interface (GUI) may form part of the manage ment system. The GUI may be helpful both for monitoring and control of the satellite units, presentation of sensor values, managing of the complete system etc. For convenient access to the system from different sites, the GUI may be suitable for web presen-20 tation, making it available for users with internet connection. Data security for protecting data and keeping the web site protected from unauthorized users should also be ensured.

The main tasks of the control unit: Interfacing al-gae/environmental sensors and GPS-receiver, power management con-25 trol, communication with management system via GPRS and control of the ultrasound acoustic system. To perform these tasks, the control unit may preferably consist of a microcontroller, filter circuit for the sensor signals, DC/DC converter, GPRS and GPS modules. The microcontroller will read the sensor values and convert 30 them to physical values and send them in pre-defined time intervals to the management system via the GPRS communication link. The management system will return control parameters (frequency and amplitude) for the ultrasound acoustic system which are based on the sensor values. The microcontroller will update the ultrasound 35 acoustic system with the parameters received. The microcontroller will also provide the management system with power capacity status information and well positioning data as well.

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Advantageously, the control unit is optimized for low power consumption, since the unit is self-supported for power. The control unit also needs to be prepared for remote SW upgrades, controlled by the management system. This will enable correction of 5 failures and expansion of new functionality in a very efficient manner. The SW, which will be downloaded, will be transferred via the GPRS connection. When the reception is completed, without errors, a swap of the SW will automatically take place.

Several sensors are available in the art for monitoring the 10 presence of different algae species (for example YSI 6131 and YSI 6132, by the firm YSI Inc., Yellow Springs, OH, USA). By using in-vivo fluorometry technology, based on the direct measurement of the fluorescence of the chlorophyll in the living algal cells, measurements can be performed in real time. This method detects 15 the fluorescence of a specific pigment in living algal cells and determines relative algal biomass. This methodology is also used to detect the phycobilin pigments found in blue-green algae (a.k.a. cyanobacteria), phycocyanin and phycoerythrin.

The data, provided by the sensor, is useful for tracking tem-20 poral or spatial changes in the distribution of the blue-green algae population, and also to provide an early warning of increasing biomass that can lead to a bloom.

During the last decade, solar panels have become a popular power source for units which are located where no power supply is 25 otherwise available. The amount of energy produced from a solar panel will depend on the area, shading, orientation, and watt-class of the module. The power unit onboard the satellite unit will contain a battery, in order to store the energy produced by the solar panel. The output power from the solar panels will vary 30 a lot, depending on the sun's irradiation. Therefore, a smart controlled power converter has to be integrated between the solar panel and the battery. The power converter must be able to both step-up and step-down the voltage created by the solar panel in order to charge the battery at a constant voltage. Many converters 35 available on the market are only designed for stepping down the voltage, which means that the solar panel energy generated with a voltage below the battery voltage will not be used.

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Commercially available solar cell panels are normally only able to use parts of the spectral energy from the sun. For that reason their efficiencies are rated to be in the range of 15% -20% of incident solar power. The solar cell panel manufacturers 5 operate with efficiency rates based on 1000W of incident solar power radiation in a 25 °C environment. Actual incident power will vary a lot with the location on earth, local variations in the weather, and time of year. The eastern part of Norway, in particular the region embracing Oslo, is taken as an example in calcula-10 tion of a possible power generation from a solar cell panel.

The size of the panel is chosen to be 1.0 m2. In Oslo in July, total incident solar power is on average 5000 Wh/m2 per day. A solar panel with the efficiency of 18% will then be able to produce 900 Wh per day. Actual stored power will be less due to the 15 efficiency in the power converter, an accumulator charger. Total stored power is estimated to be 750 Wh/day. A common capacity in a 12 V car battery is 75 Ah, resulting in an accumulator capacity of 900 W. This may prove sufficient, as some of the power from the solar cell panels at day time, can be used directly to drive the 20 ultrasound transducers. To handle variations in the weather it will possibly be required to use higher capacity batteries or two common batteries.

Several environmental factors will of course make significant changes to the Oslo example. Most other parts of Norway will 25 achieve less power. Closer to the equator, the power will be higher, and other times of the year will result in less power to the northern parts. Making the solar cell panel adaptive directional against the sun will increase the incident power.

The main power consumption of the buoy unit comes from driv-30 ing the ultra sound transducers. Driving a number of transducers to cover 360° of the water around the buoy (for example four transducers each covering about 90°, which is an optimum number of transducers for covering 360° around the buoy; or any other number of transducers that is sufficient for covering said 360° field) 35 with 10 W each constantly, will result in 960 Wh each day. The present invention will reduce the need for ultrasound power from the transducers. The power budget may for that reason be met, in- 15 eluding a safety margin, in a system with aim2 solar panel.

The system according to the present invention provides a proper solution for algae control by means of ultra sound transducers provided on buoys, reducing power consumption such that the 5 system can be applied under continuous operational conditions in different environments. As a matter of fact, it has shown that power output is reduced by about 50% after five months, if no intermittent cleaning of the transducer is performed. The present invention provides the advantage that no such intermittent clean-10 ing is required, which saves a lot of energy consumption by the transducer.

More specifically, the system may be embodied as follows:

The ultrasonic transducer is embedded in an enclosure with the ultrasonic-frequency power driven circuit. The embedded design 15 provides good EMC shielding of high frequency circuit and effective power transmission from the power driven circuit to the ultrasonic transducer. Power loss especially at high frequency due to the capacitance of transducer cable becomes insignificant.

The driven circuit consists of several separated functional 20 structures which are: [1] communication over power line transceiver module, [2] small signal control module, [3] power modulation module, [4] impedance matching module, and 25 [5] transducer feedback control module.

Re [1]: The communication transceiver module uses constant current pulse width modulation to communicate with the power supply unit. The frequency range (20kHz to 100kHz) can be input to the transducer driven circuit by using PC, GSM or a data input peb 30 through the power supply unit.

Re [2]: Instruction or parameter received will be decoded and performed by the small signal control module which uses PIC16 microcontroller as a core.

Re [3]: A full bridge PWM consisting of two P-channel MOSFETs 35 NTGS3455T and two N-channel MOSFETs NTGS4141T is utilized for generating a continuous modified SINE wave of required frequency with specified interval in the power modulation module.

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Re [4]: The waveform is then amplified and transmitted to the transducer through the impedance matching circuit which is formed by a capacitor and an insulating transformer.

Re [5]: The transducer feedback control module provides su-5 pervision of power coupling to transducer for the small signal control module to ensure the function of the whole circuitry.

The power supply unit outputs between 12, 15 or 24Vdc to supply the embedded ultrasonic transducer. Other than power supply function, the unit can monitor the power consumption, receive sta-10 tus and send parameter to from the transducer driven circuit.

Conclusion :

When it comes to lakes or bigger ponds, the methods and technologies known from the art used for the control and destruction 15 of algae are all inadequate. The present invention, however, provides a new and inventive algae treatment system that is effective both from a technical and economical point of view. It is also en-vironmentally-friendly. The algae treatment system will be based on ultra sound technology, one of today's documented environment-20 friendly methods deployed in the treatment of algae. In order to achieve efficient treatment of lakes and bigger ponds, there are in principle four major concerns that had to be solved when using ultra sound. These issues have all been solved by the present invention, and are: 25 - Monitoring of present algae species - Remote configurable ultra sound frequency and power - Power supply - Maintenance

In lakes and bigger ponds the presence of different algae 30 species is in a state of constant change. Seasonal variations are common. Therefore it is important to monitor the presence of the current algae species in order to optimize the treatment, which is possible according to the present invention. The presence of different algae species can be monitored in real time, for example by 35 direct measurement of the fluorescence of the chlorophyll in the living algal cells. The same methodology is used to detect the 17 phycobilin pigments found in blue-green algae (also known as cyanobacteria) , phycocyanin and phycoerythrin.

The monitoring results may be used to determine the correct ultra sound parameters, as well as frequency and power. The param-5 eters determined will be configured remotely and forwarded to the ultra sound transmitter, thereby resulting in an optimal treatment of the exact algae species that happens to be currently present.

This new approach will lead to an essential reduction of consumed power, compared to the current state-of-the-art ultra sound 10 transmitters, which have no capability for monitoring and distinguishing between the present algae species, operating as they do on multiple frequencies to generally cover the most common species .

The known methods involving ultra sound, aeration and UV-15 lightning, all require power supply from shore, either via electrical cables or air pipes. These methodologies reduce the coverage range and require costly installations. The system according to the present invention will consume sufficiently low energy, through its selective treatment method of only the algae species 20 present, to enable it to be self-supporting of power. The power required will be generated by solar panels and stored in a battery. At certain locations, power may be obtained by a combination of solar panels and a windmill generator. This will simplify the installation and make the product independent of the distance to 25 shore.

Low system maintenance costs are a key factor for delivering a cost-effective solution over time. One of the disadvantages of current ultra sound based treatment systems is the continuous need for maintenance. When a transducer is placed in water for a longer 30 period, a bio-film, and also other particles, will build up and create a layer that degrades the efficiency of the transducer. In the system according to the present invention, this problem will be solved through the development of a transducer possessing selfcleaning functions and properties. The transducer will be cleaned 35 by using high power ultra sound at low frequencies and at predefined time intervals. This technology is well-proven. It is widely deployed, for instance, for the cleaning of ship hulls.

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However, its use for cleaning ultra sound transducers is novel and has never been proposed for such small devices and surfaces.

It can be concluded that the present invention provides a system that efficiently and selectively destroys precisely the al-5 gae species that happen to be present at any given time. The solution will have low installation and maintenance costs, no power from shore being required, nor any need for manual cleaning of transducers .

The invention is not restricted to the embodiments as de-10 scribed above. The invention is only restricted to the scope of the claims.

The invention also relates to all combinations of measures and features as mentioned independently above.

Claims (8)

A system for preventing and controlling algae in open water, comprising a first unit comprising: - a sound converter for positioning in the water to be treated; components for forming an ultrasound frequency which are coupled to the sound converter; - means for determining at least one of an algae species and a concentration of algae species in the water to be treated; and - a power source for electrically feeding the converter; characterized in that the system further comprises: a second unit comprising a database with information about algae species, concentrations thereof in water and corresponding features of ultrasound to be emitted by the transducer for controlling the algae species using the ultra frequencies, wherein the features are selected from at least one of frequency, power delivery, amplitude, and duration of power to the converter; - wherein the first unit and the second unit each comprise wireless communication means for mutual communication. 2. System as claimed in claim 1, wherein the components for forming the ultrasound frequency comprise a waveform generator, preferably a sine wave wave generator. 3. System as claimed in claim 1 or 2, comprising an amplifier, wherein the waveform is amplified by the amplifier and is transmitted to the converter. 4. System as claimed in claim 3, wherein the waveform is amplified by a impedance equalizing circuit composed of a capacitor and an insulating transformer and transmitted to the transducer. System as claimed in any of the claims 1-4, comprising at least one of solar cells and wind turbines, for supplying a battery as a power source. 6. System as claimed in any of the claims 1-5, comprising a sensor for determining the presence of algae in the water and sensors for determining other water characteristics selected from at least one of temperature, turbidity, transparency and color intensity. 7. System as claimed in claim 1, comprising a plurality of first units, wherein the wireless communication means are adapted for communication with at least one of the other first units or with the second unit. The system of claim 1, wherein the database of the second unit comprises information about at least one of: - algae type, 15. algae type and ultrasound characteristics for controlling that type of algae at that concentration selected from power output, amplitude and duration of feeding the inverter, - water temperature, 20. water turbidity, - pH of the water, - chlorophyll concentration in the water. 9. System as claimed in claim 1, wherein the first unit is provided on a floating body that is anchored or attached to the shore, for example a buoy or a platform.