WO2010139371A1 - Method for treating water and system therefor - Google Patents

Method for treating water and system therefor Download PDF

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Publication number
WO2010139371A1
WO2010139371A1 PCT/EP2009/056983 EP2009056983W WO2010139371A1 WO 2010139371 A1 WO2010139371 A1 WO 2010139371A1 EP 2009056983 W EP2009056983 W EP 2009056983W WO 2010139371 A1 WO2010139371 A1 WO 2010139371A1
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WO
WIPO (PCT)
Prior art keywords
water
treated
evaporation cell
series
output
Prior art date
Application number
PCT/EP2009/056983
Other languages
French (fr)
Inventor
Roland De Vicq
Original Assignee
Roland De Vicq
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Roland De Vicq filed Critical Roland De Vicq
Priority to PCT/EP2009/056983 priority Critical patent/WO2010139371A1/en
Publication of WO2010139371A1 publication Critical patent/WO2010139371A1/en

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Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D1/00Evaporating
    • B01D1/0011Heating features
    • B01D1/0029Use of radiation
    • B01D1/0035Solar energy
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D1/00Evaporating
    • B01D1/26Multiple-effect evaporating
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D5/00Condensation of vapours; Recovering volatile solvents by condensation
    • B01D5/0033Other features
    • B01D5/0036Multiple-effect condensation; Fractional condensation
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B01PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01DSEPARATION
    • B01D5/00Condensation of vapours; Recovering volatile solvents by condensation
    • B01D5/0057Condensation of vapours; Recovering volatile solvents by condensation in combination with other processes
    • B01D5/006Condensation of vapours; Recovering volatile solvents by condensation in combination with other processes with evaporation or distillation
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00Treatment of water, waste water, or sewage
    • C02F1/02Treatment of water, waste water, or sewage by heating
    • C02F1/04Treatment of water, waste water, or sewage by heating by distillation or evaporation
    • C02F1/14Treatment of water, waste water, or sewage by heating by distillation or evaporation using solar energy
    • CCHEMISTRY; METALLURGY
    • C02TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02FTREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2103/00Nature of the water, waste water, sewage or sludge to be treated
    • C02F2103/08Seawater, e.g. for desalination
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02ATECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A20/00Water conservation; Efficient water supply; Efficient water use
    • Y02A20/124Water desalination
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02ATECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A20/00Water conservation; Efficient water supply; Efficient water use
    • Y02A20/124Water desalination
    • Y02A20/138Water desalination using renewable energy
    • Y02A20/142Solar thermal; Photovoltaics
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02ATECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A20/00Water conservation; Efficient water supply; Efficient water use
    • Y02A20/20Controlling water pollution; Waste water treatment
    • Y02A20/208Off-grid powered water treatment
    • Y02A20/212Solar-powered wastewater sewage treatment, e.g. spray evaporation

Definitions

  • the present invention relates to a method for treating water, as described in the preamble of the first claim.
  • the present invention also relates to a system for treating water according to such a method, comprising an input for guiding water into the system, a first and a second output for guiding water out of the system, a series of at least one evaporation cell with a condenser and a pre- heater for pre-heating the water to be treated before entering the series of at least one evaporation cell, interconnected to each other and provided such as to perform the method according to the invention.
  • a method is for example known from
  • US4,292,136 in which a method for treating, more specifically desalinising, water is described wherein water to be treated is guided through a first channel from an input towards a first output through an evaporation cell.
  • the evaporation cell is in the form of a solar greenhouse in which the water to be treated is heated and evaporated by the solar energy captured by the solar greenhouse and is led to a condenser where the evaporated, desalinised, water condenses and is collected.
  • the condensing pipe is submersed in a second channel filled with water.
  • the evaporated water condenses on and in the submersed pipe.
  • the pipe leads to a second output which is connected to a tank in which the condensed water is collected.
  • the water is pre-heated before the water to be treated enters the series of at least one evaporation cell.
  • the inventor has found that the yield of treated water by condensing the water onto a condenser increases by increasing the difference in temperature between the condenser and the inside of the evaporation cell, called ⁇ T. According to
  • the inventor has surprisingly found that by increasing the temperature of the water before evaporating it by heating it under influence of solar energy, ⁇ T also increases.
  • the condenser is provided in the evaporation cell and therefore is also heated by the evaporated and heated water condensing on the condenser, the inventor has surprisingly found that a sufficient yield of condensed water is nevertheless obtained without having to cool the condenser. Therefore, since it has been found that the condenser does no longer need to be cooled, construction of a system with which the method according to the present invention can be performed becomes easier compared to the system of US4,292,136.
  • the inventor has found that good results can be obtained with a difference in temperature between the condenser and the inside of the evaporation cell, ⁇ T, of at least 10 0 C, preferably at least 15°C, more preferably at least 20 0 C, more preferably at least 25 0 C.
  • the water to be treated is pre-heated until a temperature of at least 30 0 C, more preferably of at least 40 0 C, most preferably of at least 50°C is reached.
  • a temperature of at least 30 0 C, more preferably of at least 40 0 C, most preferably of at least 50°C is reached.
  • the water to be treated is guided from the input into a basin where it is pre-heated by means of solar energy after which the water to be treated is guided towards the series of at least one evaporation cell. Since such a basin creates a capacity for holding water between the input and before the series of at least one evaporation cell, the length of stay between the input and the series of at least one evaporation cell is increased, leading to an increase in temperature during day-time, due to the solar radiation. Moreover, such basins will often have an increased surface area with respect to channelling leading from the input towards the series of at least one evaporation cell, resulting in an increased capture of solar energy with respect to the channelling and therefore resulting in a further increased temperature.
  • the surface area of the basin is large with respect to the depth of the basin.
  • the inventor has found that the heating of the water contained in the basin under influence of solar radiation is further increased.
  • such a basin creates a buffer between the input and the evaporation cells allowing a more steady and/or continuous flow of the water to be treated through the series of the at least one evaporation cell.
  • the basin has a depth of between
  • the surface area of the basin is 500m 2 - 3000m 2 , more preferably 2000m 2 .
  • the volume of the basin is at least 1000m 3 , preferably at least 1500m 3 most preferably 2000m 3 .
  • the surface area of the basin is 2000m 2 and the depth is 1 m, the total volume retained being 2000m 3 .
  • heat of treated water leaving the series of at least one evaporation cell is transferred to the water to be treated contained in the basin before reaching the first output.
  • the heat of the treated water is not lost after the treated water has reached the first output but instead is used to further increase the heat of the water to be treated contained in the basin.
  • the treated water is outputted by the first output into a natural water reservoir such as for example, the sea, a river, a lake, etc.
  • a natural water reservoir such as for example, the sea, a river, a lake, etc.
  • the evaporation cell is a solar greenhouse through which the water to be treated is guided through an open channel.
  • the solar greenhouse is used to transform energy from solar radiation into heat which is transferred to the water which is flowing through open channels.
  • open channels has been found to be surprisingly efficient for transferring the heat transformed from the solar radiation into heated water which can evaporate more easily.
  • the channel comprises a main channel guiding the water along a flowing direction towards the first output and at least one side channel receiving part of the water to be treated from the main channel and crossing the main channel along a direction transverse to the flowing direction.
  • the main channel has a depth between 10 cm and 100 cm, preferably between 10 cm and 50 cm.
  • the side channel has a depth between 0.1 cm and 10 cm, preferably between 0.1 cm and 5 cm.
  • the evaporation cell comprises at least one ventilator for creating circulation of air in the evaporation cell. The use of a ventilator has been found to increase the circulation of the evaporated water in the evaporation cell, increasing the rate of condensation on the condenser and therefore increasing the yield of condensed water obtained by the method.
  • the invention also relates to a system for treating water according to the method of the invention, comprising an input for guiding water into the system, a first and a second output for guiding water out of the system, a series of at least one evaporation cell with a condenser and a pre- heater for pre-heating the water to be treated before entering the series of at least one evaporation cell, interconnected to each other and provided such as to perform the method according to the invention.
  • Figure 1 shows an overview of an embodiment of the system for treating water according to the method according to the current invention.
  • Figure 2a shows a detail of the working of an embodiment of an evaporation cell according to the current invention.
  • Figure 2b shows a detail of a preferred embodiment of the construction of the evaporation cell according to figure 2b.
  • Figure 3 shows a side view of the system shown in figure 1.
  • Figure 4 shows a detail of a V-shaped condenser used in the evaporation cell shown in figure 2b.
  • Figure 5a shows a detail of a side-view of a valve used in embodiments of the system shown in figure 1.
  • Figure 5b shows a front view of a different valve used in embodiments of the system shown in figure 1.
  • Figure 6 shows an evaporation improver which can be used in the system according to the invention.
  • Figure 1 shows an embodiment of the system 1 according to the present invention for treating water according to the method according to the present invention and illustrates that method.
  • Water to be treated is guided from a water source into the system 1 by an input 3 and outputted by outputs 5 and 6.
  • Treating water can be for example desalinising water.
  • the input 3 of the system 1 is connected to, for example, the sea 2 or any other salt water source known to the person skilled in the art, such as for example a salt lake, a salt river, etc.
  • salt water is inputted through input 3 and treated, in this case desalinised, water is outputted at the second output 6.
  • the remaining water, which is more salt than the desalinised water and is often called brine is outputted at the first output 5. This situation is for example shown in figure 1.
  • the inventor has found that water collected at the second output 6 is significantly purer as the water to be treated entering at the first input 3.
  • the inventor has therefore found that the method according to the current invention is also useful to purify water.
  • the input 3 of the system 1 can therefore also be connected to a source of freshwater or brackish water to treat, i.e. purify, the water by subjecting it to the method according to the invention.
  • the input 3 can also be connected to for example a lake, a river, a sea, etc. or any other depository containing freshwater, brackish water or even salt water.
  • the input 3 can be any input 3 known to the person skilled in the art and preferably is adapted to the type of water source to which the input 3 is connected.
  • the input 3 may for example be a channel leading water from the water source such as a river, a lake, the sea, etc. into the system 1 according to the invention.
  • the input 3 When the water source is subjected to tidings such as the sea 20 and certain rivers, the input 3 preferably is adapted to the working of the tidings. Preferably such an input 3 is adapted to only let water to be treated in at the end of the high tide. Preferably, the input 3 thereto is provided at a certain level such that only during a certain period during high water enters the input 3.
  • the input 3 is provided with a valve, not shown, allowing water to be treated from the water source to enter the system 1 but at least limiting and preferably avoiding water to leave the system 1 through input 3.
  • the dimensions and shape of the input 3 can be chosen by the person skilled in the art depending on the system 1 in which the input is used and the input 3 can for example be a channel having a width of 5 meter and a depth of 0.5m.
  • the system 1 shown in figure 1 comprises only one input 3, the system 1 may also comprise more than one input 3, such as for example 2, 3, 4, 5, 6, 7, 8, 9, 10, 1 1 , 12, 13, 14, 15, etc. respectively originating from a single water source or originating from different water sources.
  • the first output 5 preferably is provided to output water from the system 1 into the source of the water entering the system 1 at the input 3, such as for example the sea, a river, a lake, etc. This is however not critical for the invention and the first output 5 can also be provided to output water in, for example a different repository.
  • the first output 5 can for example be provided to output brine into a facility which is provided to output salt from the brine inputted into the facility.
  • the system 1 may also comprise more than one output 5, such as for example 2, 3, 4, 5, 6, 7, 8, 9, 10, 1 1 , 12, 13, 14, 15, etc. respectively outputting water into one single or several repositories.
  • the dimensions and shape of the first output 5 can be chosen by the person skilled in the art depending on the system 1 in which the first output 5 is used and the first output 5 can for example be a channel having a width of 5 meter and a depth of 0.5m.
  • the system 1 further comprises a series of evaporation cells 10 between the input 3 and the first output 5.
  • the system 1 guides the water to be treated through the series of evaporation cells 10 where the water to be treated is heated under the influence of solar energy and at least partly evaporated under influence of the heat.
  • the evaporated water condenses on a condenser 18 which guides the condensed water to a second output 6. Since substantially only water evaporates, substantially only water condenses on the condenser 18 and the condensed water, originating from the water to be treated, is desalinised, purified, etc.
  • figure 1 shows a series of ten evaporation cells 10, this is not critical for the invention and the system 1 can also comprise more or less than ten evaporation cells 10, such as for example 1 , 2, 3, 4, 5, 6,
  • the inventor has found that by increasing the number of evaporation cells 10, the temperature of the water which is guided through the series of at least one evaporation cell 10 is consecutively raised in each evaporation cell 10 of the series of at least one evaporation cell 10 such that in every consecutive evaporation cell 10, the yield of the condensed water obtained by the method in each evaporation cell 10 is consecutively increased.
  • the number of the evaporation cells 10 in the series of evaporation cells 10 can be determined by the person skilled in the art depending on the desired yield of water at the second output 6, the available place for providing the evaporation cells 10, the degree of desalinisation desired, purification, etc.
  • the evaporation cells 10 of the series of evaporation cells 10 are interconnected by channels 19.
  • the channels 19 are provided to transfer the water contained in them without a substantial loss in temperature from one evaporation cell 10 to another.
  • the evaporation cells 10 are for example located in proximity to each other such as to limit the distance bridged by the channels 19.
  • the channels 19 may for example alternatively or in combination with their relative proximity to each other be thermally isolated to limit the transfer of any heat from the channels 19 to the surrounding environment.
  • the channels 19 are preferably provided buried under ground, but can also be open to air.
  • FIG. 2a The working of a preferred embodiment of an evaporation cell 10 according to the invention is shown in figure 2a.
  • a preferred construction is for example shown in figure 2b.
  • the evaporation cell 10 shown in figure 2b has the form of a solar greenhouse 20.
  • the solar greenhouse 20 comprises at least one transparent wall 21 , made from for example glass, plastic, such as for example plexiglass, etc.
  • the solar greenhouse 20 preferably is substantially made from transparent walls 21 and for example is substantially made in the shape of a triangular prism with the parallel faces being substantially perpendicular to the ground and roof walls 22 extending under an angle with the ground, as shown in figure 2a and 2b.
  • the parallel faces and/or the roof walls 22 preferably are transparent walls 21.
  • the greenhouse 20 is substantially closed such that heat and/or water evaporated under influence of heat can not substantially leave the evaporation cell 20, avoiding that any evaporated water and/or heat may leave the evaporation cell 20.
  • the solar greenhouse 20 preferably is oriented with respect to the magnetic and/or geographic north pole such that maximal solar energy can be captured by the solar greenhouse 20.
  • at least one of the transparent walls 21 is directed to the geographic south.
  • this is not critical to the invention and the solar greenhouse 20 may also be directed along any other direction.
  • the dimensions and the shape of the solar greenhouse 20 may be chosen by the person skilled in the art but are preferably adapted to their specific application in the system 1 according to the invention.
  • a typical solar greenhouse for example is in the form of a triangular prism, covers a surface of 5m by 20 m and has a height of about 1.5m, leading to a preferred volume of the solar greenhouse of about 75m 3 .
  • the condenser 18 preferably comprises the transparent walls 21 , the evaporated water condensing on the transparent walls 21.
  • the transparent roof walls 22 also are condensers 18.
  • the inventor has found that in such an embodiment the condensed water can flow down along the roof walls 22 and can be collected at the bottom of the roof walls 22 by a collector 15.
  • the collector 15 then preferably guides the condensed water towards the second output 6.
  • the evaporation cell 10 also comprises an additional condenser 18 in the form of a condensing surface 16 collecting water towards the second output 6.
  • the condensing surface 16, as mounted in the evaporation cell 20 is shown in figure 2b and preferably is V- shaped such that water condensing on the inside of the V-shaped surface is collected at the bottom of the V-shape and can be guided away from the V- shaped condenser 16, for example by a tube attached to a lower region of the V-shaped condenser 16.
  • the V-shaped condenser also comprises a rim at the outside of the V-shaped condenser for collecting any water condensed on the outside surface of the V-shaped condenser 16 and guiding the condensed water away from the V-shaped condenser 16, for example by a tube attached to a lower region of the V-shaped condenser 16.
  • the V-shaped condenser 16 is provided to guide the condensed water towards the collector 15.
  • the V-shaped condenser 16 is provided near the top of the solar greenhouse 20, more preferably, in case the solar greenhouse 20 is in the shape of a triangular prism, in the region where the roof walls 22 meet.
  • the V-shaped condenser preferably is made substantially from plastic, more preferably from plexiglass.
  • any other material deemed appropriate by the person skilled in the art is also possible such as for example, metal, etc.
  • the V-shaped condenser 18 is filled with rachit rings, not shown, for increasing the surface of the V-shaped condenser 18 to further increase the yield of evaporated water condensing on the V-shaped condenser 18.
  • V-shaped condenser can be determined by the person skilled in the art but preferably the V-shaped condenser offers an additional 75m 2 of condensing surface on which evaporated water can condense per about 75m 3 , the preferred volume of a solar greenhouse according to the invention as described above.
  • the V-shaped condenser substantially runs along the length of the region where the roof walls 22 meet, as shown partly in figure 2b.
  • At least one ventilator 17 is provided in the evaporation cell 10, more preferably the solar greenhouse 20, for circulating the evaporated water inside the evaporation cell 10 such that an increased yield of condensation is obtained.
  • the shape and dimensions of the ventilator 17 can be determined by the person skilled in the art depending on the application in which the ventilator 17 is being used. But in the preferred solar greenhouses 20 the ventilator 17 has a diameter of substantially 1 m.
  • the ventilator 17 is driven by a windmill 24 such that when the windmill 24 is driven by wind naturally occurring in the vicinity of the system 1 , on its turn drives the ventilator 17 in the evaporation cell 10.
  • the collector 15 preferably is provided in the form of a channel running along the bottom of the transparent walls 21 which also act as condensers 18.
  • the transparent wall 21 and collector 15 are provided such that the water flows down from the transparent walls 21 into the collector 15, as for example shown in figure 2b.
  • one collector 15 is provided for each transparent wall 21 such that for example in the solar greenhouse shown in figure 2b, preferably two collectors 15 are provided, one for each for each transparent wall 21 , here the roof walls 22, of which only one collector 15 has been shown.
  • the collector 15 preferably is provided to limit the amount of condensed water to evaporate again.
  • the condenser 18 thereto preferably comprises a shader 35 for limiting the amount of solar radiation to reach the water contained in the collector 15 by creating a shade at the location at which the water is guided through the collector 15.
  • the shader 35 is in the form of a reflector or mirror for reflecting away the solar radiation.
  • the collector 15 is substantially directly connected to the second output 6.
  • the second outputs 6 are in the form of channels leading part of the water contained in the collector 15 away from the collector 15.
  • the second outputs 6 shown in figure 2a are provided such as to lead water contained in the collector 15 towards agricultural fields 23 adjacent to the solar greenhouses 20.
  • the agricultural fields 23 preferably are located in between the solar greenhouses 20 as shown in figure 2a such as to limit the travelling distance of the water from the collector 15 to its place of use.
  • the water contained in the collector 15 is led to the agricultural fields 23 to irrigate an irrigation zone 14 on the agricultural fields.
  • a combination of the series of at least one evaporation cell 10 with agricultural fields 23, such as for example discussed above and shown in figure 1 and 2a, which are irrigated by the water treated by the series of at least one evaporation cell 10 offers the advantage that next to the creation of treated water which can for example be used for human and/or animal consumption, the irrigation of the agricultural fields 23 improve the yield of the agricultural fields 23.
  • This combination even makes it possible to make agriculture possible in dry regions, especially when the agricultural fields 23 are nevertheless relatively close to water which however needs to be treated before it can be used for agricultural purposes, such as for example agricultural fields 23 close to salt water sources such as the sea or agricultural fields 23 which are close to polluted water of for example rivers, lakes, etc.
  • Regions in which such a method and/or system 1 can be used are for example, but not limited to, Southern desert of Morocco, Western Sahara, Western Africa, Middle-East, more preferably Oman, Central America, India, West Australia, etc.
  • the agricultural fields 23 may for example be used to grow Phramites australis, halophytes, which are more tolerant to salt environments, such as for example Artiplex, Salicornia europea, Limonium vulgare, Suaeda maritima, Beta maritima, etc.
  • the system 1 shown for example in figure 2a and 2b for example comprise a multitude of second outputs 6. This is however not critical for the invention and the system 1 may also comprise a single second output 6.
  • the shape and dimensions of the second output 6 can be adapted to their specific application in the system 1 and are not critical for the invention.
  • the greenhouse 20 covers a channel
  • the channel 11 preferably is an open channel 11 allowing the heated water to easily evaporate and condense onto the condenser 18.
  • the open channel 11 preferably comprises a main channel 12 and at least one side channel 13.
  • the main channel 12 guides water along a flowing direction from an inlet 25 of the evaporation cell 10 towards an outlet 26 of the evaporation cell 10.
  • the side channels 13 are provided to receive part of the water to be treated flowing through the main channel 12.
  • the side channels 13 cross the main channel 12 along a direction traversing the flowing direction.
  • the main channel 12 and the side channel 13 can have any shape and form deemed appropriate by the person skilled in the art but preferably are rectangularly shaped.
  • the main channel preferably has a depth between 10 cm and 100 cm, preferably between 10 cm and 50 cm and has a width of approximately 100cm.
  • the side channel preferably has a depth between 0.1 cm and 10 cm, preferably between 0.1 cm and 5 cm and has a width of approximately 30cm.
  • the channel 1 1 more preferably the bottom and/or sidewalls of the main channel 12 and/or the side channel 13, are dark, preferably substantially black, by for example lining them with a dark, preferably substantially black, material such as for example paint, plastic, etc. It has been found that such dark sidewalls and/or bottom increases the transfer of heat to the water to be treated contained in the channel 1 1.
  • the channels 11 comprise an evaporation improver 36, shown in figure 6, comprising a metal plate 37 provided to be located beneath the water surface contained in the channels 11.
  • a metal plate can transfer any captured heat to the water being contact with it such that the water contacting the evaporation improver can be more efficiently heated.
  • the metal plate of the evaporation improver is dark, preferably black, and/or non-reflective to increase the efficiency of the heating of the plate by solar energy.
  • the metal plate is mounted to floating elements 38, 39 such that it is located substantially beneath the water surface.
  • the floating element 38, 39 preferably comprises elongated elements which are provided be mounted along the length of the metal plate 37 along opposing edges of the metal plate 37 such that when put into the water contained in the channel, the metal plate 37 is substantially submersed in the water.
  • the floating capacity of the floating element 38, 39 is adapted to allow the evaporation improver to float in the water of the channels 1 1.
  • Such a floating element is for example shown in figure 6.
  • the metal plate 37 when floating the metal plate 37 is provided near the water surface, preferably between 0.5 cm and 5cm and more preferably between 0.5 and 1 cm. Such a positioning of the metal plate 37 has been found to increase heating of the metal plate 37 and therefore the heating of any water on top of the metal plate to increase the evaporation of the water contained in the channels 11.
  • the metal of the metal plate 37 is adapted to being submersed into salt water, such as for example by coating the metal plate, preferably by coating the metal plate 37 with a dark-colored coating.
  • the metal plate can for example be made of carbonsteel.
  • the water is further pre-heated before entering the series of at least one evaporation cell, preferably until a temperature of at least 30 0 C, more preferably of at least 40 0 C, most preferably of at least 50°C is reached.
  • the water to be treated is preferably guided from the input 3 into a basin 4 where it is pre-heated by means of solar energy after which the water to be treated is guided towards the series of at least one evaporation cells 10.
  • a basin 4 is for example shown in figure 1.
  • the water is pre-heated by a solar water heater in
  • the surface area of the basin 4 is large with respect to the depth of the basin 4. More preferably, the basin 4 has a depth of between 0.1 cm and 1 m. Preferably, the surface area of the basin 4 is 500m 2 - 3000m 2 , more preferably 20000m 2 . Preferably, the volume of the basin 4 is at least 1000m 3 , preferably at least 2000m 3 . Preferably, the basin 4 has a surface area per evaporation cell 10 of more than or equal to 50 - 100 m 2 and a volume of more than or equal to 50m 3 - 100m 3 .
  • heat of treated water leaving the series of at least one evaporation cell 10 is transferred to the water to be treated contained in the basin 4 before reaching the first output 5.
  • Figure 1 shows that this is done by guiding the water through the water contained in the basin 4 through a heat conductive pipe 34 allowing the heat of the water contained in the heat conductive pipe 34 and flowing towards the first output 5 to be transferred to the water contained in the basin 4 and contributing to the pre-heating of the water contained in the basin 4.
  • the input 3, the basin 4, the series of at least one evaporation cell 10 and the first output 5 are interconnected by channels 7, 8, 9.
  • the channels 7, 8, 9 are provided to transfer the water contained in them without a substantial loss in temperature from one of the input 3, the basin 4, the series of at least one evaporation cell 10 and the output 5 to another of the input 3, the basin 4, the series of at least one evaporation cell 10 and the first output 5.
  • the input 3, the basin 4, the series of at least one evaporation cell 10 and the first output 5 are for example located in proximity to each other such as to limit the distance bridged by the channels 7, 8, 9.
  • the channels 7, 8, 9 may for example alternatively or in combination with their relative proximity to each other be substantially thermally isolated to limit the transfer of any heat from any one of the channels 7, 8, 9 to the surrounding environment.
  • the channels 7, 8, 9 are preferably provided buried under ground, but can also be open to air. However, depending on the cooling of the water leaving the series of at least one evaporation cell 10 guided towards the first output 5 needed, the channel 9 guiding water from the series of at least one evaporation cell 10 towards the first output 6 may not be thermally isolated and may even be provided to transfer as much heat as possible to the surrounding environment such as, when for example buried, the surrounding ground.
  • Such a construction may for example be provided in combination with or replacing the heat conductive pipe 34 allowing the heat of treated water leaving the series of at least one evaporation cell 10 to be transferred to the water to be treated contained in the basin 4 before reaching the first output 5.
  • Such a provision may be supplemented with or may be replaced with a cooling cell for cooling the water leaving the series of at least one evaporation cell 10.
  • the system 1 is constructed such that water runs through the series of at least one evaporation cell 10 with a velocity which on one hand is fast enough to avoid deposition of any material part of the water to be treated, such as for example salt when treating salt water, due to the evaporation of part of the water in the series of at least one evaporation cell 10 but on the other hand is slow enough to allow the water to be treated to evaporate with a sufficient yield to obtain the desired amount of condensed and treated water at the second output 6.
  • a velocity which on one hand is fast enough to avoid deposition of any material part of the water to be treated, such as for example salt when treating salt water, due to the evaporation of part of the water in the series of at least one evaporation cell 10 but on the other hand is slow enough to allow the water to be treated to evaporate with a sufficient yield to obtain the desired amount of condensed and treated water at the second output 6.
  • the inventor has found that with a velocity of the water running through the series of at least one evaporation cell 10 of less than 0.1 m/s, more specifically a velocity of the water running through the main channel 12 of less than or equal to 0.1 m/s and a velocity of the water running through the side channel 13 of less than 0.01 m/s, satisfying results are obtained.
  • the in- and outlet 25, 26 of the series of at least one evaporation cell 10 are provided with regulating means for regulating the flow of water to be treated through the series of at least one evaporation cell 10.
  • the regulating means are for example shown in figure 5b and preferably comprise a float 27 at the inlet 25 and a first valve 28 at the output 26 coupled to the float 27 for regulating the throughput of water to be treated through the series of at least one evaporation cell 10.
  • the first valve 28 is coupled to the float 27 such that when the float 27 rises due to an increased amount of water to be treated entering the inlet 25, the first valve 28 lets an increased amount of water through the outlet 26.
  • Such a configuration allows that the flow of water to be treated through the series of at least on evaporation cell 10 is regulated according to the amount of water present at the inlet 25 such that when the amount of water at the inlet 25 increases the throughput of water through the series of at least one evaporation cell 10 is increased, decreasing the risk that the series of at least one evaporation cell 10 are provided with to much water and for example flood.
  • the first valve 28 will let a decreased amount of water through the output 26 such that the water to be treated will for example stay for a prolonged period in the series of at least one evaporation cell 10 such that the yield of condensed water obtained at the second output is at least partly compensated.
  • the float 27 and the first valve 28 shown in figure 5b are coupled to each other by means of pulleys 29 and a weight 30 in between them.
  • the float 27 is for example made of HDPE and has a weight of
  • the weight 30 for example has a weight of ⁇ 60kg and the first valve 28 for example is a substantially non-floating plate of ⁇ 60kg for closing at least part of the inlet 25 when lowered into the channel, more preferably closing a substantial part of the inlet 25.
  • the first valve 28 is operated solely by the floating of the float 27 and that no additional energy is necessary to operate the regulating means.
  • the first output 5 is provided with a non-return valve 31 , especially during flood if the first output 5 is connected to a water source which is subjected to tides.
  • the non-return valve 31 is coupled to a second valve 32 which is adapted to closing the inlet 25 of the series of at least one evaporation cell 10 such that the second valve 32 closes the inlet 25 when the non-return valve 31 closes the first output 5 to intermediately stop any new water to be treated to enter the series of at least one evaporation cell 10 while there is a risk of water entering the first output 5.
  • a preferred embodiment of the non-return valve 31 and the second valve 32 is shown in figure 5a.
  • the non-return valve 31 is a float which closes the first output 5 when the level of the water at the first output 5 rises.
  • the second valve 32 is a plate closing the inlet 25 to the series of at least one evaporation cell 10 when the non-return valve 31 closes the first output 5.
  • the non-return valve 31 and the second valve 32 thereto are connected to each other by means of a pulley 33.
  • some electronic sensors are provided to measure the water level and/or throughput of the water.
  • the required energy can be provided by solar energy.
  • each covering 100m 2 are provided next to each other as shown in figure 1 with next to each solar greenhouse agricultural fields irrigated by water treated by the system 1.
  • the total agricultural field irrigated by the system 1 in the example is 7500m 2 .
  • the total surface covered by the solar greenhouses 20 is 1000m 2 .
  • the open channels 1 1 under the greenhouses 20 have a surface of more than or equal to 750m 2 and in other words each solar greenhouse covers a surface of more than or equal to 75m 2 of channelling 1 1 under it.
  • a flow of 50 - 100m 3 / hour of salt water is ran through the channels resulting in a yield of about 100m 3 of condensed water a day or an average of 10m 3 / hour, assuming that the method can be performed 10 hours a day.
  • One cell approximately produces about 5 - 10 m 3 /day condensed water.
  • the time between water entering for treatment according to the method according to the present invention and the water leaing the first output 5 is at least 24 hours but preferably about 3 days.
  • the water quality obtained has a pH 6 - 9, a BOD ⁇ 50, a TSS ⁇ 50, a turbidity of ⁇ 5 NTU and a conductivity of « 500 ⁇ S.

Abstract

A method for treating water comprising the steps of guiding water to be treated from an input (3) through a series of at least one evaporation cell (10) towards a first output (5) while evaporating a part of the water in the series of at least one evaporation cell (10) by heating the water using solar energy, condensing at least part of the evaporated water on a condenser (18) provided in the evaporation cell (10) and guiding at least part of the condensed part towards a second output (6), wherein the water is pre-heated before the water to be treated enters the series of at least one evaporation cell (10).

Description

Method for treating water and system therefor
The present invention relates to a method for treating water, as described in the preamble of the first claim.
The present invention also relates to a system for treating water according to such a method, comprising an input for guiding water into the system, a first and a second output for guiding water out of the system, a series of at least one evaporation cell with a condenser and a pre- heater for pre-heating the water to be treated before entering the series of at least one evaporation cell, interconnected to each other and provided such as to perform the method according to the invention. Such a method is for example known from
US4,292,136 in which a method for treating, more specifically desalinising, water is described wherein water to be treated is guided through a first channel from an input towards a first output through an evaporation cell. The evaporation cell is in the form of a solar greenhouse in which the water to be treated is heated and evaporated by the solar energy captured by the solar greenhouse and is led to a condenser where the evaporated, desalinised, water condenses and is collected. However, in order to obtain a sufficient yield of condensed desalinised water, the condensing pipe is submersed in a second channel filled with water. Due to the difference in temperature between the water heated and evaporated by solar energy in the solar greenhouse and the submersed pipe cooled by the water in the second channel, the evaporated water condenses on and in the submersed pipe. The pipe leads to a second output which is connected to a tank in which the condensed water is collected.
However, the requirement that the condenser is constantly cooled by immersing it in water, requires the provision of a second channel, making the construction of a facility in which the method can be performed more difficult. There is thus a need for a method for treating water which is easier to adopt.
This is achieved in the present invention with the technical features of the characterising part of the first claim. Thereto, the water is pre-heated before the water to be treated enters the series of at least one evaporation cell.
Without wanting to be bound by any theory the inventor has found that the yield of treated water by condensing the water onto a condenser increases by increasing the difference in temperature between the condenser and the inside of the evaporation cell, called ΔT. According to
US4,292,136 this increase in temperature is accomplished by decreasing the temperature of the condenser by immersing the condenser into streaming water.
However, the inventor has surprisingly found that by increasing the temperature of the water before evaporating it by heating it under influence of solar energy, ΔT also increases. Although the condenser is provided in the evaporation cell and therefore is also heated by the evaporated and heated water condensing on the condenser, the inventor has surprisingly found that a sufficient yield of condensed water is nevertheless obtained without having to cool the condenser. Therefore, since it has been found that the condenser does no longer need to be cooled, construction of a system with which the method according to the present invention can be performed becomes easier compared to the system of US4,292,136.
The inventor has found that good results can be obtained with a difference in temperature between the condenser and the inside of the evaporation cell, ΔT, of at least 10 0C, preferably at least 15°C, more preferably at least 20 0C, more preferably at least 25 0C.
In preferred embodiments of the method for treating water according to the invention, the water to be treated is pre-heated until a temperature of at least 300C, more preferably of at least 400C, most preferably of at least 50°C is reached. Without wanting to be bound by any theory, the inventor believes that when water is heated until such temperatures are reached, the yield of the condensed water obtained according to the method according to the invention is even more increased.
In preferred embodiments of the method for treating water according to the invention, the water to be treated is guided from the input into a basin where it is pre-heated by means of solar energy after which the water to be treated is guided towards the series of at least one evaporation cell. Since such a basin creates a capacity for holding water between the input and before the series of at least one evaporation cell, the length of stay between the input and the series of at least one evaporation cell is increased, leading to an increase in temperature during day-time, due to the solar radiation. Moreover, such basins will often have an increased surface area with respect to channelling leading from the input towards the series of at least one evaporation cell, resulting in an increased capture of solar energy with respect to the channelling and therefore resulting in a further increased temperature.
In preferred embodiments of the method for treating water according to the invention, the surface area of the basin is large with respect to the depth of the basin. When the surface area is large with respect to the depth of the basin, the inventor has found that the heating of the water contained in the basin under influence of solar radiation is further increased. Moreover, such a basin creates a buffer between the input and the evaporation cells allowing a more steady and/or continuous flow of the water to be treated through the series of the at least one evaporation cell.
In preferred embodiments of the method for treating water according to the invention, the basin has a depth of between
0.1cm and 1 m.
In preferred embodiments of the method for treating water according to the invention, the surface area of the basin is 500m2 - 3000m2, more preferably 2000m2. In preferred embodiments of the method for treating water according to the invention, the volume of the basin is at least 1000m3, preferably at least 1500m3 most preferably 2000m3. In a more preferred embodiment of the method for treating water according to the invention, the surface area of the basin is 2000m2 and the depth is 1 m, the total volume retained being 2000m3.
In preferred embodiments of the method for treating water according to the invention, heat of treated water leaving the series of at least one evaporation cell is transferred to the water to be treated contained in the basin before reaching the first output. Such a configuration allows that the heat of the treated water is not lost after the treated water has reached the first output but instead is used to further increase the heat of the water to be treated contained in the basin. Moreover, often the treated water is outputted by the first output into a natural water reservoir such as for example, the sea, a river, a lake, etc. In such a case, taking environmental considerations into account, it is often undesirable that heated water is outputted into the reservoir and it is desirable that the water is cooled, in this case by exchanging its heat with water contained in the basin, before outputting it into the natural water reservoir.
In preferred embodiments of the method for treating water according to the invention, the evaporation cell is a solar greenhouse through which the water to be treated is guided through an open channel. Such configurations have shown that the water to be treated can be sufficiently heated using solar energy whereas such constructions are easy to construct and are relatively durable. The solar greenhouse is used to transform energy from solar radiation into heat which is transferred to the water which is flowing through open channels. The use of open channels has been found to be surprisingly efficient for transferring the heat transformed from the solar radiation into heated water which can evaporate more easily.
In preferred embodiments of the method for treating water according to the invention, the channel comprises a main channel guiding the water along a flowing direction towards the first output and at least one side channel receiving part of the water to be treated from the main channel and crossing the main channel along a direction transverse to the flowing direction. By providing a side channel the total surface area of the channel in the solar greenhouse may be increased by adding side channels to the main channel. The inventor has found that this increased surface area of the channel in the solar greenhouse increases the yield of evaporating water, leading to an increased yield of condensed water collected by the condenser.
In preferred embodiments of the method for treating water according to the invention, the main channel has a depth between 10 cm and 100 cm, preferably between 10 cm and 50 cm.
In preferred embodiments of the method for treating water according to the invention, the side channel has a depth between 0.1 cm and 10 cm, preferably between 0.1 cm and 5 cm. In preferred embodiments of the method for treating water according to the invention, the evaporation cell comprises at least one ventilator for creating circulation of air in the evaporation cell. The use of a ventilator has been found to increase the circulation of the evaporated water in the evaporation cell, increasing the rate of condensation on the condenser and therefore increasing the yield of condensed water obtained by the method.
The invention also relates to a system for treating water according to the method of the invention, comprising an input for guiding water into the system, a first and a second output for guiding water out of the system, a series of at least one evaporation cell with a condenser and a pre- heater for pre-heating the water to be treated before entering the series of at least one evaporation cell, interconnected to each other and provided such as to perform the method according to the invention.
The invention is further elucidated in the appending figures and description of the figures.
Figure 1 shows an overview of an embodiment of the system for treating water according to the method according to the current invention.
Figure 2a shows a detail of the working of an embodiment of an evaporation cell according to the current invention.
Figure 2b shows a detail of a preferred embodiment of the construction of the evaporation cell according to figure 2b. Figure 3 shows a side view of the system shown in figure 1.
Figure 4 shows a detail of a V-shaped condenser used in the evaporation cell shown in figure 2b. Figure 5a shows a detail of a side-view of a valve used in embodiments of the system shown in figure 1.
Figure 5b shows a front view of a different valve used in embodiments of the system shown in figure 1.
Figure 6 shows an evaporation improver which can be used in the system according to the invention.
Figure 1 shows an embodiment of the system 1 according to the present invention for treating water according to the method according to the present invention and illustrates that method. Water to be treated is guided from a water source into the system 1 by an input 3 and outputted by outputs 5 and 6.
Treating water can be for example desalinising water. In such case the input 3 of the system 1 is connected to, for example, the sea 2 or any other salt water source known to the person skilled in the art, such as for example a salt lake, a salt river, etc. In such case salt water is inputted through input 3 and treated, in this case desalinised, water is outputted at the second output 6. The remaining water, which is more salt than the desalinised water and is often called brine, is outputted at the first output 5. This situation is for example shown in figure 1.
The inventor has found that water collected at the second output 6 is significantly purer as the water to be treated entering at the first input 3. The inventor has therefore found that the method according to the current invention is also useful to purify water. The input 3 of the system 1 can therefore also be connected to a source of freshwater or brackish water to treat, i.e. purify, the water by subjecting it to the method according to the invention. In such an embodiment the input 3 can also be connected to for example a lake, a river, a sea, etc. or any other depository containing freshwater, brackish water or even salt water. The input 3 can be any input 3 known to the person skilled in the art and preferably is adapted to the type of water source to which the input 3 is connected. The input 3 may for example be a channel leading water from the water source such as a river, a lake, the sea, etc. into the system 1 according to the invention.
When the water source is subjected to tidings such as the sea 20 and certain rivers, the input 3 preferably is adapted to the working of the tidings. Preferably such an input 3 is adapted to only let water to be treated in at the end of the high tide. Preferably, the input 3 thereto is provided at a certain level such that only during a certain period during high water enters the input 3.
Preferably, the input 3 is provided with a valve, not shown, allowing water to be treated from the water source to enter the system 1 but at least limiting and preferably avoiding water to leave the system 1 through input 3.
The dimensions and shape of the input 3 can be chosen by the person skilled in the art depending on the system 1 in which the input is used and the input 3 can for example be a channel having a width of 5 meter and a depth of 0.5m. Although the system 1 shown in figure 1 comprises only one input 3, the system 1 may also comprise more than one input 3, such as for example 2, 3, 4, 5, 6, 7, 8, 9, 10, 1 1 , 12, 13, 14, 15, etc. respectively originating from a single water source or originating from different water sources. As shown in figure 1 the first output 5 preferably is provided to output water from the system 1 into the source of the water entering the system 1 at the input 3, such as for example the sea, a river, a lake, etc. This is however not critical for the invention and the first output 5 can also be provided to output water in, for example a different repository. The first output 5 can for example be provided to output brine into a facility which is provided to output salt from the brine inputted into the facility.
Although only one first output 5 is shown in figure 1 , the system 1 may also comprise more than one output 5, such as for example 2, 3, 4, 5, 6, 7, 8, 9, 10, 1 1 , 12, 13, 14, 15, etc. respectively outputting water into one single or several repositories.
The dimensions and shape of the first output 5 can be chosen by the person skilled in the art depending on the system 1 in which the first output 5 is used and the first output 5 can for example be a channel having a width of 5 meter and a depth of 0.5m.
As shown in figure 1 , the system 1 further comprises a series of evaporation cells 10 between the input 3 and the first output 5. The system 1 guides the water to be treated through the series of evaporation cells 10 where the water to be treated is heated under the influence of solar energy and at least partly evaporated under influence of the heat. The evaporated water condenses on a condenser 18 which guides the condensed water to a second output 6. Since substantially only water evaporates, substantially only water condenses on the condenser 18 and the condensed water, originating from the water to be treated, is desalinised, purified, etc.
An overview of the series of evaporation cells 10 is shown in figure 1. Although figure 1 shows a series of ten evaporation cells 10, this is not critical for the invention and the system 1 can also comprise more or less than ten evaporation cells 10, such as for example 1 , 2, 3, 4, 5, 6,
7, 8, 9, 1 1 , 12, 13, 14, 15, 16, 17, 18, 19, 20, 21 , 22, 23, 24, 25, 26, etc. The inventor has found that by increasing the number of evaporation cells 10, the temperature of the water which is guided through the series of at least one evaporation cell 10 is consecutively raised in each evaporation cell 10 of the series of at least one evaporation cell 10 such that in every consecutive evaporation cell 10, the yield of the condensed water obtained by the method in each evaporation cell 10 is consecutively increased. The number of the evaporation cells 10 in the series of evaporation cells 10 can be determined by the person skilled in the art depending on the desired yield of water at the second output 6, the available place for providing the evaporation cells 10, the degree of desalinisation desired, purification, etc. of the water at the second output 6, etc. Preferably, the evaporation cells 10 of the series of evaporation cells 10 are interconnected by channels 19. Preferably, the channels 19 are provided to transfer the water contained in them without a substantial loss in temperature from one evaporation cell 10 to another. Thereto, the evaporation cells 10 are for example located in proximity to each other such as to limit the distance bridged by the channels 19. The channels 19 may for example alternatively or in combination with their relative proximity to each other be thermally isolated to limit the transfer of any heat from the channels 19 to the surrounding environment. The channels 19 are preferably provided buried under ground, but can also be open to air.
The working of a preferred embodiment of an evaporation cell 10 according to the invention is shown in figure 2a. A preferred construction is for example shown in figure 2b.
The evaporation cell 10 shown in figure 2b has the form of a solar greenhouse 20. However any other form or type of evaporation cell 10 known to the person skilled in the art may be used. The solar greenhouse 20 comprises at least one transparent wall 21 , made from for example glass, plastic, such as for example plexiglass, etc.
The solar greenhouse 20 preferably is substantially made from transparent walls 21 and for example is substantially made in the shape of a triangular prism with the parallel faces being substantially perpendicular to the ground and roof walls 22 extending under an angle with the ground, as shown in figure 2a and 2b. The parallel faces and/or the roof walls 22 preferably are transparent walls 21. Preferably the greenhouse 20 is substantially closed such that heat and/or water evaporated under influence of heat can not substantially leave the evaporation cell 20, avoiding that any evaporated water and/or heat may leave the evaporation cell 20.
As indicated in figure 1 and figures 2a and 2b, the solar greenhouse 20 preferably is oriented with respect to the magnetic and/or geographic north pole such that maximal solar energy can be captured by the solar greenhouse 20. Thereto, preferably at least one of the transparent walls 21 is directed to the geographic south. However, this is not critical to the invention and the solar greenhouse 20 may also be directed along any other direction.
The dimensions and the shape of the solar greenhouse 20 may be chosen by the person skilled in the art but are preferably adapted to their specific application in the system 1 according to the invention. A typical solar greenhouse for example is in the form of a triangular prism, covers a surface of 5m by 20 m and has a height of about 1.5m, leading to a preferred volume of the solar greenhouse of about 75m3.
As shown in figure 2a, the condenser 18 preferably comprises the transparent walls 21 , the evaporated water condensing on the transparent walls 21. For example, in the specific embodiment of figure 2a and figure 2b, the transparent roof walls 22 also are condensers 18. The inventor has found that in such an embodiment the condensed water can flow down along the roof walls 22 and can be collected at the bottom of the roof walls 22 by a collector 15. The collector 15 then preferably guides the condensed water towards the second output 6.
It has been found that the angle between inclined transparent walls 21 acting as a condenser 18 and a horizontal, often the ground, if chosen adequately, offers an improved flow down of condensed water along the surface of the condenser minimising any hindering fog on the transparent walls 21 limiting any solar energy to enter the solar greenhouse 20. The best results were obtained if the angle was between - degrees, more preferably between - degrees and most preferably 30° or more but preferably about 300C. More preferably, the evaporation cell 10 also comprises an additional condenser 18 in the form of a condensing surface 16 collecting water towards the second output 6. The condensing surface 16, as mounted in the evaporation cell 20 is shown in figure 2b and preferably is V- shaped such that water condensing on the inside of the V-shaped surface is collected at the bottom of the V-shape and can be guided away from the V- shaped condenser 16, for example by a tube attached to a lower region of the V-shaped condenser 16. More preferably, the V-shaped condenser also comprises a rim at the outside of the V-shaped condenser for collecting any water condensed on the outside surface of the V-shaped condenser 16 and guiding the condensed water away from the V-shaped condenser 16, for example by a tube attached to a lower region of the V-shaped condenser 16. Preferably the V-shaped condenser 16 is provided to guide the condensed water towards the collector 15.
Preferably, the V-shaped condenser 16 is provided near the top of the solar greenhouse 20, more preferably, in case the solar greenhouse 20 is in the shape of a triangular prism, in the region where the roof walls 22 meet. The V-shaped condenser preferably is made substantially from plastic, more preferably from plexiglass. However, any other material deemed appropriate by the person skilled in the art is also possible such as for example, metal, etc.
Preferable, the V-shaped condenser 18 is filled with rachit rings, not shown, for increasing the surface of the V-shaped condenser 18 to further increase the yield of evaporated water condensing on the V-shaped condenser 18.
The shape and dimensions of the V-shaped condenser can be determined by the person skilled in the art but preferably the V-shaped condenser offers an additional 75m2 of condensing surface on which evaporated water can condense per about 75m3, the preferred volume of a solar greenhouse according to the invention as described above.
Preferably, the V-shaped condenser substantially runs along the length of the region where the roof walls 22 meet, as shown partly in figure 2b.
More preferably, at least one ventilator 17 is provided in the evaporation cell 10, more preferably the solar greenhouse 20, for circulating the evaporated water inside the evaporation cell 10 such that an increased yield of condensation is obtained. The shape and dimensions of the ventilator 17 can be determined by the person skilled in the art depending on the application in which the ventilator 17 is being used. But in the preferred solar greenhouses 20 the ventilator 17 has a diameter of substantially 1 m. More preferably, the ventilator 17 is driven by a windmill 24 such that when the windmill 24 is driven by wind naturally occurring in the vicinity of the system 1 , on its turn drives the ventilator 17 in the evaporation cell 10.
The collector 15 preferably is provided in the form of a channel running along the bottom of the transparent walls 21 which also act as condensers 18. The transparent wall 21 and collector 15 are provided such that the water flows down from the transparent walls 21 into the collector 15, as for example shown in figure 2b. In such a configuration, preferably one collector 15 is provided for each transparent wall 21 such that for example in the solar greenhouse shown in figure 2b, preferably two collectors 15 are provided, one for each for each transparent wall 21 , here the roof walls 22, of which only one collector 15 has been shown.
The collector 15 preferably is provided to limit the amount of condensed water to evaporate again. The condenser 18 thereto preferably comprises a shader 35 for limiting the amount of solar radiation to reach the water contained in the collector 15 by creating a shade at the location at which the water is guided through the collector 15. Preferably, the shader 35 is in the form of a reflector or mirror for reflecting away the solar radiation.
Preferably, and as shown in figure 2a and figure 2b the collector 15 is substantially directly connected to the second output 6.
As shown in figure 2a and figure 2b, the second outputs 6 are in the form of channels leading part of the water contained in the collector 15 away from the collector 15.
The second outputs 6 shown in figure 2a are provided such as to lead water contained in the collector 15 towards agricultural fields 23 adjacent to the solar greenhouses 20. The agricultural fields 23 preferably are located in between the solar greenhouses 20 as shown in figure 2a such as to limit the travelling distance of the water from the collector 15 to its place of use. Preferably, the water contained in the collector 15 is led to the agricultural fields 23 to irrigate an irrigation zone 14 on the agricultural fields.
A combination of the series of at least one evaporation cell 10 with agricultural fields 23, such as for example discussed above and shown in figure 1 and 2a, which are irrigated by the water treated by the series of at least one evaporation cell 10 offers the advantage that next to the creation of treated water which can for example be used for human and/or animal consumption, the irrigation of the agricultural fields 23 improve the yield of the agricultural fields 23. This combination even makes it possible to make agriculture possible in dry regions, especially when the agricultural fields 23 are nevertheless relatively close to water which however needs to be treated before it can be used for agricultural purposes, such as for example agricultural fields 23 close to salt water sources such as the sea or agricultural fields 23 which are close to polluted water of for example rivers, lakes, etc. Regions in which such a method and/or system 1 can be used are for example, but not limited to, Southern desert of Morocco, Western Sahara, Western Africa, Middle-East, more preferably Oman, Central America, India, West Australia, etc. The agricultural fields 23 may for example be used to grow Phramites australis, halophytes, which are more tolerant to salt environments, such as for example Artiplex, Salicornia europea, Limonium vulgare, Suaeda maritima, Beta maritima, etc.
The system 1 shown for example in figure 2a and 2b for example comprise a multitude of second outputs 6. This is however not critical for the invention and the system 1 may also comprise a single second output 6.
The shape and dimensions of the second output 6 can be adapted to their specific application in the system 1 and are not critical for the invention.
Preferably, the greenhouse 20 covers a channel
1 1 through which the water to be treated is guided through the greenhouse 20. The channel 11 preferably is an open channel 11 allowing the heated water to easily evaporate and condense onto the condenser 18. The open channel 11 preferably comprises a main channel 12 and at least one side channel 13. The main channel 12 guides water along a flowing direction from an inlet 25 of the evaporation cell 10 towards an outlet 26 of the evaporation cell 10. The side channels 13 are provided to receive part of the water to be treated flowing through the main channel 12. The side channels 13 cross the main channel 12 along a direction traversing the flowing direction.
The main channel 12 and the side channel 13 can have any shape and form deemed appropriate by the person skilled in the art but preferably are rectangularly shaped. The main channel preferably has a depth between 10 cm and 100 cm, preferably between 10 cm and 50 cm and has a width of approximately 100cm. The side channel preferably has a depth between 0.1 cm and 10 cm, preferably between 0.1 cm and 5 cm and has a width of approximately 30cm. Preferably, the channel 1 1 , more preferably the bottom and/or sidewalls of the main channel 12 and/or the side channel 13, are dark, preferably substantially black, by for example lining them with a dark, preferably substantially black, material such as for example paint, plastic, etc. It has been found that such dark sidewalls and/or bottom increases the transfer of heat to the water to be treated contained in the channel 1 1.
Preferably, the channels 11 comprise an evaporation improver 36, shown in figure 6, comprising a metal plate 37 provided to be located beneath the water surface contained in the channels 11. Such a metal plate can transfer any captured heat to the water being contact with it such that the water contacting the evaporation improver can be more efficiently heated. Preferably, the metal plate of the evaporation improver is dark, preferably black, and/or non-reflective to increase the efficiency of the heating of the plate by solar energy. Preferably, the metal plate is mounted to floating elements 38, 39 such that it is located substantially beneath the water surface. The floating element 38, 39 preferably comprises elongated elements which are provided be mounted along the length of the metal plate 37 along opposing edges of the metal plate 37 such that when put into the water contained in the channel, the metal plate 37 is substantially submersed in the water. The floating capacity of the floating element 38, 39 is adapted to allow the evaporation improver to float in the water of the channels 1 1. Such a floating element is for example shown in figure 6.
Preferably, when floating the metal plate 37 is provided near the water surface, preferably between 0.5 cm and 5cm and more preferably between 0.5 and 1 cm. Such a positioning of the metal plate 37 has been found to increase heating of the metal plate 37 and therefore the heating of any water on top of the metal plate to increase the evaporation of the water contained in the channels 11. Preferably, the metal of the metal plate 37 is adapted to being submersed into salt water, such as for example by coating the metal plate, preferably by coating the metal plate 37 with a dark-colored coating. When the metal plate is not submersed into salt water, scuh as for example freshwater, the metal plate can for example be made of carbonsteel. The water is further pre-heated before entering the series of at least one evaporation cell, preferably until a temperature of at least 300C, more preferably of at least 400C, most preferably of at least 50°C is reached. Thereto, the water to be treated is preferably guided from the input 3 into a basin 4 where it is pre-heated by means of solar energy after which the water to be treated is guided towards the series of at least one evaporation cells 10. Such a basin 4 is for example shown in figure 1.
According to a different embodiment, the water is pre-heated by a solar water heater in
Preferably, the surface area of the basin 4 is large with respect to the depth of the basin 4. More preferably, the basin 4 has a depth of between 0.1 cm and 1 m. Preferably, the surface area of the basin 4 is 500m2 - 3000m2, more preferably 20000m2. Preferably, the volume of the basin 4 is at least 1000m3, preferably at least 2000m3. Preferably, the basin 4 has a surface area per evaporation cell 10 of more than or equal to 50 - 100 m2 and a volume of more than or equal to 50m3 - 100m3.
Preferably, heat of treated water leaving the series of at least one evaporation cell 10 is transferred to the water to be treated contained in the basin 4 before reaching the first output 5. Figure 1 shows that this is done by guiding the water through the water contained in the basin 4 through a heat conductive pipe 34 allowing the heat of the water contained in the heat conductive pipe 34 and flowing towards the first output 5 to be transferred to the water contained in the basin 4 and contributing to the pre-heating of the water contained in the basin 4. Preferably, the input 3, the basin 4, the series of at least one evaporation cell 10 and the first output 5 are interconnected by channels 7, 8, 9. Preferably, the channels 7, 8, 9 are provided to transfer the water contained in them without a substantial loss in temperature from one of the input 3, the basin 4, the series of at least one evaporation cell 10 and the output 5 to another of the input 3, the basin 4, the series of at least one evaporation cell 10 and the first output 5. Thereto, the input 3, the basin 4, the series of at least one evaporation cell 10 and the first output 5 are for example located in proximity to each other such as to limit the distance bridged by the channels 7, 8, 9. The channels 7, 8, 9 may for example alternatively or in combination with their relative proximity to each other be substantially thermally isolated to limit the transfer of any heat from any one of the channels 7, 8, 9 to the surrounding environment. The channels 7, 8, 9 are preferably provided buried under ground, but can also be open to air. However, depending on the cooling of the water leaving the series of at least one evaporation cell 10 guided towards the first output 5 needed, the channel 9 guiding water from the series of at least one evaporation cell 10 towards the first output 6 may not be thermally isolated and may even be provided to transfer as much heat as possible to the surrounding environment such as, when for example buried, the surrounding ground. Such a construction may for example be provided in combination with or replacing the heat conductive pipe 34 allowing the heat of treated water leaving the series of at least one evaporation cell 10 to be transferred to the water to be treated contained in the basin 4 before reaching the first output 5. Such a provision may be supplemented with or may be replaced with a cooling cell for cooling the water leaving the series of at least one evaporation cell 10.
Preferably, the system 1 is constructed such that water runs through the series of at least one evaporation cell 10 with a velocity which on one hand is fast enough to avoid deposition of any material part of the water to be treated, such as for example salt when treating salt water, due to the evaporation of part of the water in the series of at least one evaporation cell 10 but on the other hand is slow enough to allow the water to be treated to evaporate with a sufficient yield to obtain the desired amount of condensed and treated water at the second output 6. The inventor has found that with a velocity of the water running through the series of at least one evaporation cell 10 of less than 0.1 m/s, more specifically a velocity of the water running through the main channel 12 of less than or equal to 0.1 m/s and a velocity of the water running through the side channel 13 of less than 0.01 m/s, satisfying results are obtained.
Preferably, the in- and outlet 25, 26 of the series of at least one evaporation cell 10 are provided with regulating means for regulating the flow of water to be treated through the series of at least one evaporation cell 10. The regulating means are for example shown in figure 5b and preferably comprise a float 27 at the inlet 25 and a first valve 28 at the output 26 coupled to the float 27 for regulating the throughput of water to be treated through the series of at least one evaporation cell 10. The first valve 28 is coupled to the float 27 such that when the float 27 rises due to an increased amount of water to be treated entering the inlet 25, the first valve 28 lets an increased amount of water through the outlet 26. Such a configuration allows that the flow of water to be treated through the series of at least on evaporation cell 10 is regulated according to the amount of water present at the inlet 25 such that when the amount of water at the inlet 25 increases the throughput of water through the series of at least one evaporation cell 10 is increased, decreasing the risk that the series of at least one evaporation cell 10 are provided with to much water and for example flood. When a decreased amount of water is present at the inlet 25, the first valve 28 will let a decreased amount of water through the output 26 such that the water to be treated will for example stay for a prolonged period in the series of at least one evaporation cell 10 such that the yield of condensed water obtained at the second output is at least partly compensated.
The float 27 and the first valve 28 shown in figure 5b are coupled to each other by means of pulleys 29 and a weight 30 in between them. The float 27 is for example made of HDPE and has a weight of
±80kg, the weight 30 for example has a weight of ±60kg and the first valve 28 for example is a substantially non-floating plate of ±60kg for closing at least part of the inlet 25 when lowered into the channel, more preferably closing a substantial part of the inlet 25. Such a configuration of the float 27 and the first valve 28 has the advantage that the first valve 28 is operated solely by the floating of the float 27 and that no additional energy is necessary to operate the regulating means. To avoid that water enters the system 1 through the first output 5, the first output 5 is provided with a non-return valve 31 , especially during flood if the first output 5 is connected to a water source which is subjected to tides. Preferably, the non-return valve 31 is coupled to a second valve 32 which is adapted to closing the inlet 25 of the series of at least one evaporation cell 10 such that the second valve 32 closes the inlet 25 when the non-return valve 31 closes the first output 5 to intermediately stop any new water to be treated to enter the series of at least one evaporation cell 10 while there is a risk of water entering the first output 5. A preferred embodiment of the non-return valve 31 and the second valve 32 is shown in figure 5a. In this embodiment the non-return valve 31 is a float which closes the first output 5 when the level of the water at the first output 5 rises. The second valve 32 is a plate closing the inlet 25 to the series of at least one evaporation cell 10 when the non-return valve 31 closes the first output 5. Preferably, as shown in figure 5a, the non-return valve 31 and the second valve 32 thereto are connected to each other by means of a pulley 33.
It is noted that the preferred embodiments of the different aspects of the invention all allow that water is treated by the method and/or system 1 according to the invention without having to use any external energy which is not obtained by natural resources surrounding the system 1 , such as for example, wind energy for driving the windmill ventilator 17, solar energy, tidings, etc.
Preferably, some electronic sensors are provided to measure the water level and/or throughput of the water. Although such sensors require electrical energy, the required energy can be provided by solar energy.
In an example embodiment of the system 1 according to the current invention, ten solar greenhouses each covering 100m2 are provided next to each other as shown in figure 1 with next to each solar greenhouse agricultural fields irrigated by water treated by the system 1. The total agricultural field irrigated by the system 1 in the example is 7500m2. The total surface covered by the solar greenhouses 20 is 1000m2. The open channels 1 1 under the greenhouses 20 have a surface of more than or equal to 750m2 and in other words each solar greenhouse covers a surface of more than or equal to 75m2 of channelling 1 1 under it. A flow of 50 - 100m3 / hour of salt water is ran through the channels resulting in a yield of about 100m3 of condensed water a day or an average of 10m3 / hour, assuming that the method can be performed 10 hours a day. One cell approximately produces about 5 - 10 m3/day condensed water. Preferably, the time between water entering for treatment according to the method according to the present invention and the water leaing the first output 5 is at least 24 hours but preferably about 3 days.
The water quality obtained has a pH 6 - 9, a BOD < 50, a TSS < 50, a turbidity of < 5 NTU and a conductivity of « 500 μS.

Claims

1. A method for treating water comprising the steps of guiding water to be treated from an input (3) through a series of at least one evaporation cell (10) towards a first output (5) while evaporating a part of the water in the series of at least one evaporation cell (10) by heating the water using solar energy, condensing at least part of the evaporated water on a condenser (18) provided in the evaporation cell (10) and guiding at least part of the condensed part towards a second output (6), characterized in that the water is pre-heated before the water to be treated enters the series of at least one evaporation cell (10).
2. A method for treating water according to claim 1 , characterized in that the water to be treated is pre-heated until a temperature of at least 300C, more preferably of at least 400C, most preferably of at least 50°C is reached.
3. A method for treating water according to any one of the preceding claims, characterized in that the water to be treated is guided from the input (3) into a basin (4) where it is pre-heated by means of solar energy after which the water to be treated is guided towards the series of at least one evaporation cell (10).
4. A method for treating water according to claim 3, characterized in that the surface area of the basin (4) is large with respect to the depth of the basin (4).
5. A method according to claim 3 or 4, characterized in that the basin (4) has a depth of between 0.1cm and 1 m.
6. A method according to any one of claims 3 - 5, characterized in that the surface area of the basin (4) is 500m2 - 3000m2, more preferably 2000m2.
7. A method according to any one of claims 3 - 6, characterized in that the volume of the basin (4) is at least 1000m3, preferably at least 2000m3.
8. A method according to any one of the preceding claims 3 - 7, characterized in that heat of treated water leaving the series of at least one evaporation cell (10) is transferred to the water to be treated contained in the basin (4) before reaching the first output (5).
9. A method according to any one of the preceding claims, characterized in that the evaporation cell (10) is a solar greenhouse (20) through which the water to be treated is guided through an open channel (1 1 ).
10. A method according to claim 9, characterized in that the open channel (1 1 ) comprises a main channel (12) guiding the water along a flowing direction towards the first output (5) and at least one side channel (13) receiving part of the water to be treated from the main channel (12) and crossing the main channel (12) along a direction transverse to the flowing direction.
1 1. A method according to anyone of claims 9 or 10, characterized in that the main channel (12) has a depth between 10 cm and 100 cm, preferably between 10 cm and 50 cm.
12. A method according to claim 10 or 1 1 , characterized in that the side channel (13) has a depth between 0.1 cm and 10 cm, preferably between 0.1 cm and 5 cm.
13. A method according to any one of the preceding claims, characterized in that the evaporation cell (10) comprises at least one ventilator (17) for creating circulation of air in the evaporation cell (10).
14. A system (1 ) for treating water according to the method of any one of the preceding claims, comprising an input (3) for guiding water into the system (1 ), a first (5) and a second (6) output for guiding water out of the system (1 ), a series of at least one evaporation cell (10) with a condenser (18) and a pre-heater for pre-heating the water to be treated before entering the series of at least one evaporation cell (10), interconnected to each other and provided such as to perform the method according to any one of the preceding claims.
PCT/EP2009/056983 2009-06-05 2009-06-05 Method for treating water and system therefor WO2010139371A1 (en)

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Publication number Priority date Publication date Assignee Title
CN110228850A (en) * 2019-06-03 2019-09-13 中国海洋大学 Application of the halophytes in improving saline and alkaline water body in nitrogen and phosphorus pollutants detergent power

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Publication number Priority date Publication date Assignee Title
US4210121A (en) * 1977-06-15 1980-07-01 Virgil Stark Solar energy collection
US4363703A (en) * 1980-11-06 1982-12-14 Institute Of Gas Technology Thermal gradient humidification-dehumidification desalination system
US4383891A (en) * 1979-08-28 1983-05-17 Spie-Batignolles Device for desalting brackish water, and a conditioning method and device relating to said desalting device

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4210121A (en) * 1977-06-15 1980-07-01 Virgil Stark Solar energy collection
US4383891A (en) * 1979-08-28 1983-05-17 Spie-Batignolles Device for desalting brackish water, and a conditioning method and device relating to said desalting device
US4363703A (en) * 1980-11-06 1982-12-14 Institute Of Gas Technology Thermal gradient humidification-dehumidification desalination system

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110228850A (en) * 2019-06-03 2019-09-13 中国海洋大学 Application of the halophytes in improving saline and alkaline water body in nitrogen and phosphorus pollutants detergent power
CN110228850B (en) * 2019-06-03 2021-01-01 中国海洋大学 Application of halophyte in improving capacity of purifying nitrogen and phosphorus pollutants in saline-alkali water body

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