ES2371192B1 - WATER PRE-TREATMENT AND CONDITIONING FILTER OF PRESSURE GRANULAR MILK TYPE CLOSED - Google Patents

Abstract

Pretreatment and conditioning water filter of the type of granular bed closed under pressure with backwashing means. # The present invention relates to a filter of the type of granular bed closed under pressure, such as those commonly used in the pre-treatment of water within processes of purification, desalination, wastewater treatment and treatment of reuse or regeneration of wastewater, to which compressed air injection means have been incorporated at the same filter operating pressure during the service or filtering cycle thereof, as well as means of simultaneous extraction-evacuation of said injected air, from the top of the filter to the outside. The air injected into the filter crosses the granular bed, breaking and lifting the layers closest to the surface, leaving passageways in the bed that favor and enhance the penetration of smaller particles in lower layers. Another object of the present invention is a process of pre-treatment and conditioning of water by pressure filtration with the filter unit described herein, as well as the pre-treatment and conditioning plant of raw water incorporating said filter.

Description

Pretreatment and conditioning water filter of the granular bed type closed under pressure with countercurrent washing means.

Technical sector

The present invention pertains to the field of water treatment, whether in freshwater purification processes, wastewater treatment, reuse or wastewater regeneration treatment, and desalination of brackish or marine water, especially in osmosis desalination plants conversely, and more specifically it relates to the pre-treatment and conditioning stage to which said water source is subjected before desalination, disinfection and / or purification. Among the wide variety of known pre-treatment systems, the invention is applicable to all pressure filtration devices on granular beds, such as sand, gravel, anthracite, activated carbon, garnet, porous rock, pumice stone, basalt. or any combination thereof, regardless of the design or work pressure (operation) of the device.

State of the art

The raw water to be treated in processes of purification, wastewater treatment, wastewater reuse or regeneration treatment and desalination must meet a series of quality requirements before entering the treatment plant, among other reasons to avoid obstructions and reduce the number of washes. In order to meet the required quality standards, one or more stages of pre-treatment are generally included in these processes.

Among the known pre-treatment systems (coagulation / fl oculation, decantation, fi ltration, fl otation, addition of different reagents for pH adjustment, disinfection ...), the most widespread due to its simplicity, reduced investment and exploitation costs is filtration through granular beds in closed pressure filters. These filters are intended to eliminate most of the decantable and suspended solids contained in freshwater, seawater

or brackish and in sewage from the source of collection. Filtration on granular beds is a well-known and well-implemented technique especially in conventional drinking water treatment plants (river waters, reservoirs, lagoons, freshwater aquifers, etc.), so an extensive bibliography can be found in this regard. , among which we can mention in an outstanding way: “Wastewater engineering. Treatment, discharge and reuse ”, Metcalf & Eddy, Third Edition (1998), Ed. McGraw-Hill (chapters 6.8 and 11.3); and “Water Technical Manual”, Degrémot, Fourth Edition (1979), Ed. Grafo, S.A. (chapters 3 and 4).

Currently, fi lter batteries are used in one or two stages in series to perform this function. The operation of the fi lters is based on the progressive retention of the mentioned solids on the fi lting sand layer. Once the fi lter becomes clogged and therefore loses its ability to continue filtering, it is necessary to remove it from the production line (that is, it ends its service cycle) and wash it countercurrently to remove the retained material in it; normally washed with raw sea water or with the brine produced in the osmosis and / or air blown racks at atmospheric pressure. Once the fi lter is washed, it is put back into service to perform a new fi ltering cycle.

A clear disadvantage of this process is that most of the solids retained in the fi lters are located in the first centimeters of the sand bed, which implies an underutilization of the fi ltrant capacity of the total bed volume and, as a consequence, a rapid clogging which translates into short periods of service or high washing frequencies, increased consumption of backwash and displacement water, water that must be pumped with the consequent energy expenditure. Another drawback of the conventional process is the need to have a higher fi ltering surface to provide for high washing frequencies and, therefore, a greater number of filter units and all their auxiliary elements, in de fi nition a higher investment cost of desalination plants. .

In view of these drawbacks, one of the fundamental objectives of the present invention is to incorporate an injection and evacuation system of compressed air into the current filters of granular bed under pressure in order to significantly increase its fi ltration capacity, measured as kilograms of water retained matter to filter per kilogram of fi lter bed material, and as a consequence the reduction in the number of fi ltration units necessary to achieve the same end.

Description of the invention

brief description

The present invention relates to a fi lter unit of the type of granular bed closed under pressure, such as those commonly used in the pre-treatment and conditioning of water of seawater desalination processes

or brackish, fresh water purification, wastewater treatment and wastewater reuse or regeneration treatment, to which compressed air injection means have been incorporated at the same operating pressure of the fi lter during the fi ltered duty cycle. same, as well as means of simultaneous extraction and evacuation of said air injected from the top of the fi lter to the outside. As fresh, brackish or marine water, as cited in the present invention, is understood to be that which has a salt content of less than 0.05%, between 0.05% and 3%, and between 3% and 5%, respectively.

The injection of compressed air into the fi lter, which can be continuous or pulsating, is carried out in the lower part of a plate on which the fi ltering granular bed is held and separating said bed and the upper chamber where it is housed in a false bottom (lower chamber), similar to the injection of atmospheric blowing air in the washing phase when the fi lter is out of service. The plate is provided with at least one nozzle or crepe that allows the distribution of water and air, such as those that allow backwashing in this type of pressure filters with false bottoms.

Since the fi lter is a closed pressure system, it is necessary to evacuate the air injected into the false bottom from its interior, and which accumulates in the upper chamber after crossing the granular bed, in order to achieve the continuity of the fi ltration phase. The extraction of compressed air from the upper chamber is carried out by means of evacuation means, connected to the housing, which comprise at least one aeration means located in the highest part of said housing; said aeration means may preferably be a suction cup, and more preferably a trifunctional suction cup.

Among the main advantages derived from the incorporation of both media to a pressurized granular bed fi lter, the significant increase in their fi ltration capacity, and consequently the reduction in the number of units filtered in the water pre-treatment facilities, should be highlighted. to achieve the same performance as a system consisting of a greater number of filters without the two devices object of the present invention.

The invention also refers to a pre-treatment and water conditioning installation comprising at least one filter as described above, as well as specifically to a desalination plant, more preferably reverse osmosis, comprising said pre-treatment installation which It incorporates one or several filters with the injection-evacuation device of compressed air. Likewise, the invention discloses the use of said fi lter for the pretreatment and conditioning of water in freshwater purification processes, seawater desalination

or brackish, wastewater treatment and wastewater reuse or regeneration treatment, and more specifically refers to the use of said brackish or marine water pre-treatment facility in a reverse osmosis desalination plant.

Another object of the present invention is a process of pre-treatment and conditioning of water by means of the fi lter unit described above, which comprises at least injecting compressed air inside the fi lter at the operating pressure thereof, and simultaneously evacuating said outside air during fi lter operation, that is, during the water fi ltration process.

Detailed description

The main object of the present invention is a pretreatment and conditioning water filter of the type of granular bed closed under pressure with countercurrent washing means, comprising at least:

-

a housing (1) compartmentalized in two chambers closed by pressure,

-

an upper chamber (2) containing inside the fi ltering granular bed (4), provided with at least means of entry or feeding of the water to be filtered (3),

-

a lower chamber (5) as a false bottom of the fi lter, provided with at least the outlet means (6) of the filtered and conditioned water, and

-

a support plate (7) of the fi ltering granular bed separating both upper and lower chambers, said plate being provided with at least one nozzle or crepe (8) for water and air distribution, which is part of the means (9) of backwashing of the fi lter;

characterized in that the filter further comprises:

-

compressed air injection means (10) at the working pressure of the fi lter and during operation thereof, connected to the false bottom by means of an injection socket (11) located in the housing; Y

-

evacuation means (12) outside said injected air, connected to the upper chamber by means of an evacuation socket (13) located in the highest part of the housing (1), and comprising at least one tubing (14) and aeration means (15).

Preferably, the pretreatment and conditioning of water by means of the described fi lter is encompassed within processes of purification of fresh water, desalination of sea or brackish water, treatment of wastewater and treatment of reuse or regeneration of wastewater.

For a better understanding of the fi lter described herein, an illustrative scheme thereof is presented in Figure 1, without said figure having a limiting character of the invention.

Compressed air is injected into the lower chamber (5) corresponding to the false bottom of the fi lter in a manner similar to how atmospheric blowing air is injected in the backwash phase. However, there are clear differences between both air injection processes: on the one hand, the washing air is injected into the fi lter unit when it is stopped or out of service and at atmospheric pressure, while the compressed air is injected into the present invention during the operation or service of the fi lter and at the same working pressure thereof, which is never at atmospheric pressure, but higher. In short, backflushing of the fi lter can be performed only and exclusively at a standstill, that is, when it has stopped and removed from the fi ltration line due to its clogging. On the contrary, the injection (10) and evacuation (12) devices of compressed air of the present invention operate simultaneously and during the fi lter duty cycle, that is, during the water fi ltering process, from the beginning until it ends. This function is not possible in the case of the washing system (9), since no known blow-up backwash device is designed and enabled to inject air at the pressure commonly used by granular bed fi lters (a pressure considerably greater than that required for backwashing), and therein lie the beneficial effects achieved with respect to the conditioning of the water to be filtered in a desalination process.

The compressed air is injected into the fi lter by its false bottom (5) at the same pressure as that of the water being filtered, that is, at the working pressure established inside the fi lter. Since at the same pressure the air has a density lower than that of the water, it will rise in the form of bubbles to the upper chamber (2) through one or several nozzles (8) distributors located on the support plate (7) of the bed granulate, crossing said granular bed (4) and lifting and breaking the layers closest to the bed surface, leaving passage channels for the fi ltration process to continue. In addition, in this way, by lifting the blanket of solids deposited in the first surface layers, penetration of smaller particles in the bed is facilitated, which will be retained in greater depth, thereby increasing the retention capacity of matter in the fi lter. Also in this way the differential pressure between feed water inlet to fi lter and outlet of water fi ltered in the fi lter, which measures the degree of clogging or clogging thereof, will decrease either gradually with continuous air injection or stepwise with each pulse. of air injection, thus managing to lengthen the time between the initial differential pressure and the final pressure, before the fi lter stops to proceed to its washing. This phenomenon can be seen in the attached Figures3 and 4 where the evolution of the flow of filtered water and the solids load retained by the fi lter is shown (Figure 3), and the differential pressure thereof depending on the service time

or fi ltration phase (Figure 4).

The compressed air injected to the false bottom (5) is distributed along the bottom of the nozzles (8), said air forming a mattress that rises homogeneously through all of them towards the granular bed (4). In this way, although the evacuation means (12) can be connected to the fi lter in any part of the highest area of the housing (1), they will preferably be housed towards the middle of the fi lter (and, therefore, also the outlet of evacuation (13)), this being the most favorable hydraulic situation for the evacuation of compressed air.

Preferably, the fi ltering granular bed (4) is composed of a material selected from the group consisting of sand, gravel, anthracite, activated carbon, garnet, fragmented rock, porous rock, pumice stone, ceramic fragments, plastic fragments, metal fragments, basalt and any combination thereof. In turn, the housing

(2) The fi lter can be constructed of any material commonly used, be it steel, plastic materials or other.

The compressed air injection-evacuation system described here works and allows the above-mentioned improvements to be achieved for any design or working pressure of the filter. Preferably, the operating pressure of the filter and injection of the compressed air is between 2 and 8 bars, and more preferably it is 6 bars.

In a preferred embodiment, the injection of compressed air at the same operating pressure of the fi lter during the entire service cycle thereof is carried out at continuous flow. In another embodiment, the injection is pulsating, ie at regular or irregular time intervals. Each compressed air injection pulse preferably has a duration between 1 and 10 seconds, more preferably between 3 and 6 seconds, and more preferably still 3 seconds, while the frequency (or time interval between pulses) is preferably comprised between 1 and 60 minutes, more preferably 30 minutes. In a preferred embodiment in which pulsed air injection is used, the air pulses are shorter and spaced in time at the beginning of the fi lter operating period than at the end of said period, in which the pulses have longer duration and They are less spaced apart.

In another embodiment of the invention, in which the filter includes in its false bottom a blow-off / backwash air distribution pipe (element (23) of Figure 1), the compressed air is injected into the circular crown which it exists between the outlet pipe (6) and said air distribution or distribution tube (23), in this case constituting the injection of compressed air (11 ').

Preferably, the injection means comprise at least:

-

a compressed air equipment (16) comprising an automatic injection valve (17), a pressure reducer with pressure control valve (18), a rotameter (19) for measuring the flow of compressed air injected and a programming device for air pulses (20); Y

-

a tubing (21) that connects the valve of the compressed air equipment with the injection inlet of the false bottom of the fi lter.

Preferably, the automatic injection valve is an electrovalve.

On the other hand, in another preferred embodiment the means of evacuation (12) of the injected air comprise, in addition to a tubing (14) and an aeration means (15), a pipe that conducts the air evacuated from said aeration means to a drainage box More preferably, the aeration means (15) is an air evacuation suction cup, more preferably it is still a trifunctional suction cup. Also preferably, the tubing (14) has a nominal diameter between 1 "and 8", being more preferably 4 ".

The injection and evacuation devices of compressed air described herein, whether in continuous or pulsating fl ow, can be used without restrictions in any type of granular bed pressure filter, not only regardless of the design or working pressure thereof, but also of its arrangement, whether vertical, horizontal or other, or of its geometry, the fi lter housing being able to have a cylindrical, parallelepipedic, conical, spherical or other shape other than those stated, although preferably the fi lter is cylindrical and horizontal. A fi lter like the one claimed here, which incorporates the devices for injection (10) and evacuation (12) of compressed air, can also be used in any series or parallel fi lter set or battery, and independently of the bed granulometry (4) , the length and diameter of the fi lter. Preferably, the bed granulometry may be between 0.1 and 10 millimeters, the diameter of the housing (2) has a maximum value of 6 meters and is more preferably 4 meters, and the length of the housing is comprised between 1 and 25 meters, being more preferably 14 meters.

Another object of the present invention is a process of pretreatment and conditioning of water by means of pressure filtration with the fi lter unit described herein, comprising the injection (10) and evacuation means

(12) Simultaneous compressed air, characterized in that it comprises at least the following stages:

(to)

inject compressed air into the false bottom (5) of the fi lter at its operating pressure, by means of injection means (10), and

(b)

evacuate outside the fi lter the air injected in step (a) by means of the evacuation means (12) connected to the upper chamber (2),

and characterized in that the compressed air is injected and evacuated simultaneously during the operation of the filter, that is, during the water filtration cycle. Said water pretreatment and conditioning process is preferably carried out within freshwater purification, seawater desalination processes.

or brackish, wastewater treatment, or wastewater reuse or regeneration treatments, among others.

Preferably, the operating pressure of the fi lter and, consequently, of compressed air injection, is comprised between 2 and 8 bars, both limits being included, and more preferably 6 bars.

In a preferred embodiment, the compressed air is injected into the false bottom (5) continuously in step (a). In another embodiment, the air is injected in a pulsed manner, that is, by injection pulses at regular or irregular time intervals. Each compressed air injection pulse preferably has a duration between 1 and 10 seconds, more preferably between 3 and 6 seconds, and being more preferably still 3 seconds, while the frequency (or time interval between pulses) is preferably between 1 and 60 minutes, being more preferably 30 minutes. In a preferred embodiment in which pulsed air injection is used, the air pulses are shorter and spaced in time at the beginning of the fi lter operating period than at the end of said period, in which the pulses have longer duration and They are less spaced apart. In addition, the injection of the air by pulses is carried out more preferably automatically by means of the air pulse programming device.

The present invention also refers to the use of the fi lter described herein, which comprises means of injection (10) and evacuation (12) of compressed air at the operating pressure of the fi lter, for the pre-treatment and conditioning of water in purification processes. of fresh water, desalination of sea or brackish water, wastewater treatment and reuse or regeneration treatment of wastewater. Specifically, it also refers to the use of the fi lter in a brackish or seawater pretreatment facility of a desalination plant; preferably, the desalination plant is reverse osmosis.

Likewise, a pre-treatment and water conditioning installation is contemplated in the present invention, characterized in that it comprises at least one pressure granular bed fi lter as described herein, that is, comprising injection (10) and evacuation means ( 12) of compressed air. If said installation comprises more than one filter, preferably the fi lters or filtering units are connected in series or in parallel.

Another object of the present invention is a desalination plant comprising at least one pre-treatment and conditioning system of brackish or marine water by filtration of granular bed under pressure, characterized in that said pretreatment installation comprises at least one filter as claimed herein. . Preferably, the desalination plant is reverse osmosis.

Among the most relevant advantages of both this fi lter, which comprises injection (10) and evacuation (12) devices of compressed air at the set pressure, as well as the pre-treatment and water conditioning procedure carried out by said fi lter, it is worth mentioning:

-

Significant reduction of investment costs of conventional pre-treatment systems.

-

Reduction of the number of units necessary for the same fi ltration capacity as a conventional system, and reduction of all the auxiliary elements of the fi lter inherent in the fi ltration process such as the foundations and support benches of the fi lters, distribution pipes, supports, valves supply and filtering, backwash water inlet and outlet valves, blow air inlet valves and vent valve, solenoid valves associated with pneumatic actuators, electric actuators, force and control wiring, and the corresponding part of the mechanical assembly and electric set.

-

Significant reduction in the frequency of washing and, as a direct consequence, lower consumption of backwash water. In addition, in cases where the backwash is carried out with raw feed water (most desalination plants use raw water for the backwash), the raw water flow design needs of the pre-treatment are reduced, which implies a reduction in the size and capacity of all the equipment and elements that make up the pre-treatment (immissaries and collection pumps, associated civil works, supply pipes, valves and accessories, etc.).

-

Lower energy consumption of backwash pumps by reducing the total water consumption of said backwash.

-

Higher concentration of solids in filter washing waters, which allows, in accordance with the environmental requirements of sludge extraction and treatment, to reduce the size of the ad hoc treatment plant (lower investment) and decrease the consumption of reagents coagulation and fl oculation necessary to obtain the same final dryness of treated sludge.

-

Feasibility and simplicity in the application of the present invention for all current pre-treatment systems that use fi ltration in granular beds at a low cost.

-

Reduction of maintenance cost, by decreasing the number of equipment and associated elements.

-

Last but not least, the natural oxidation inherent in the process of injecting compressed air of ions contained in raw water and potentially harmful to the reverse osmosis process such as Fe + 2 yelMn + 2, reducing or eliminating the dosage of oxidizing products traditionally used in pre-treatment such as sodium hypochlorite, chlorine dioxide, potassium permanganate or sodium bisulphite. The oxidized forms Fe2O3 and MnO2 would be retained in the filter bed, avoiding irreversible damage to the desalination device.

Description of the fi gures

Figure 1 illustrates an embodiment of the fi lter object of the present application, without being limiting thereof.

Thus, a sectional view of a conventional horizontal cylindrical fi lter for pretreatment and conditioning of the type of closed granular bed under pressure comprising the injection and evacuation means of compressed air at the fi ltration pressure according to the invention is shown. This view shows the following elements:

(one)

Enclosed compartment or external envelope of the fi lter

(2)

Upper chamber

(3)

Raw water inlet means (tubing) to filter

(3.1)

Raw water pipe to filter

(3.2) Raw water inlet valve

(4)

Filtering granular bed

(5)

False bottom (or lower chamber)

(6)

Filtered water outlet means (tubing)

(6.1) Filtered water pipe

(6.2) Filtered water outlet valve

(7)

Support plate / granular bed support

(7.1) Supporting supports for the filter bed

(8)

Distribution nozzle or crepe

(9)

Filter backwash media

(9.1) Washing water inlet valve

(9.2) Washing water outlet valve

(9.3) Blown air inlet valve

(9.4) Blown air outlet valve

(10)

Compressed air injection means

(eleven)

Compressed air injection socket (tubing), in the case of filters without air distribution pipe

of blowing. This pipe is located between the plane of the support plate (7) and the plane formed by the

nozzle tails ends (8)

(eleven')

Compressed air injection socket (tubing), in the case of filters with distribution pipe (23)

tion / distribution of blow air for cleaning the filter. Compressed air is injected into the crown

circular that exists between the outlet pipe (6) and said delivery tube (23)

(12)

Means for evacuating the injected compressed air

(13)

Outlet of compressed air

(14)

Tubing

(fifteen)

Aeration means, for example an automatic compressed air suction cup

(16)

Compressed air equipment

(17)

Automatic injection valve, for example all-nothing compressed air solenoid valve

(18)

Pressure gauge with compressed air pressure control valve

(19)

Rotameter for measuring the flow of compressed air injected

(twenty)

Compressed air pulse programmer

(twenty-one)

connection pipe between the valve of the equipment (16) and the injection socket (11)

(22)

Filter drain valve

(2. 3)

Blower air distribution pipe for filter cleaning, optional for length filters

cylindrical less than 12 meters

Figure 2 shows a flow chart of a pilot pre-treatment and conditioning system of brackish and marine water intended for desalination, designed to incorporate 2 filters of granular bed under pressure: an A filter that works in the same conditions as a conventional real fi lter and a fi lter B similar to that shown in Figure 1 and representing the present invention, that is, similar to fi lter A but which also incorporates injection and evacuation means of compressed air at the fi ltration pressure during operation of the fi lter. The diagram shows the following elements:

(one)

Enclosed compartmental or external envelope of the fi lter, transparent PCV DN 160 and PN6

(2)

Upper fi lter chamber

(3)

Raw water inlet means (tubing) to filter

(4)

Granular bed of 0.45 mm silica sand of effective size, 1.6 of uniformity coefficient and 1 meter of bed height. This is the same type of granular medium and bed height as that corresponding to a real-scale fi lter currently in operation.

(5)

False bottom (or lower chamber)

(6)

Filtered water outlet means (tubing)

(6.1) Filtered water pipe

(7)

Support plate / granular bed support

(8)

Distribution nozzle or crepe; the surface of in fl uence of the nozzle follows the ratio of a full-scale fi lter, that is, 50 nozzles / m2

(9.1) Filter wash water inlet valve

(10)

Compressed air injection means

(eleven)

Compressed air injection socket (tubing)

(fifteen)

Aeration medium of the automatic suction type of compressed air outlet, 1 ”

(16)

Compressed air equipment

(17)

Automatic injection valve of the 1 "all-nothing solenoid valve type, for manual control of compressed air pulses

(18)

1 ”pressure reducing valve, for regulation of compressed air inlet pressure, with a regulation range of 0-8 bar

(19)

Rotameter for measuring the flow of blow / wash air, with a range of 0-1.5 Nm3 / h, and also of compressed air for the filtration column B

(twenty)

Compressed air pulse programmer

(22)

Filter drain valve

(24)

Rotameter for measuring raw water flow to filter, with a measuring range between 0-500 1 / h

(25)

Pressure gauge for measuring raw water pressure to filter, with a measuring range of 0-6 bar

(26)

Valve for sampling, for laboratory measurement of suspended solids, SDI and filtered water turbidity

(27)

Pressure gauge for measuring filtered water pressure, with a measuring range of 0-6 bar

(28)

Filtered water pressure regulating valve, with a range of 0-4 bar

(29)

Rotameter for measuring the filter wash water, with a measuring range of 0-1000 1 / h

(30)

Differential pressure gauge to measure pressure loss in the bed, with a measuring range of 0-2 bar

(31)

Wash and blow selection valve for each of the columns

(32)

Blow air inlet

(33)

Filter wash water inlet

Figure 3 shows the evolution of the flow of filtered water q (measured in m3 / h) and retained solids m (measured in kg / h) as a function of the time T of the filter service cycle.

The line represented by _ is called the actual filter curve without air injection, or q as a function of time (q (T)), or m as a function of time (m (T)). The line represented by X is called the theoretical curve of continuous compressed air injection, or qic as a function of time (qic (T)), or mic as a function of time (mic (T)). Thickest line

It represents the theoretical curve with pulsed compressed air injection, or qip as a function of time (qip (T)), omnip as a function of time (mip (T)). T0 corresponds to the fi ltration start time, Tf to the end time of the fi ltration cycle without air injection, and T fi the final time of the fi ltration cycle with air injection.

-

Volume of filtered water (the same also applies to retained solids):

where

represents the volume with continuous air injection,

rep

sit the volume with pulsating air injection, and

It represents the volume without air injection.

In turn, Figure 4 shows the evolution of the differential pressure ΔP (in bars) as a function of the filter service time T, where the line represented by _ shows the actual curve of the filter without air injection. The line represented by X shows the theoretical curve of continuous compressed air injection. The thickest line represents the theoretical curve with pulsed compressed air injection. T0 corresponds to the initial time of the beginning of fi ltration, Tf to the final time of the fi ltration cycle without air injection, and T fi the final time of the fi ltration cycle with air injection.

Execution Example

An embodiment of the fi lter in question in a pilot pre-treatment scale installation corresponding to the flow chart shown in Figure 2, is detailed below, by way of example and not limitation of the invention. in order to improve the understanding of the invention.

Currently, a pilot pre-treatment and water conditioning pilot plant has been designed and built by filtration, specially designed for installation in a reverse osmosis desalination plant. The pilot plant has a fi lter A, of conventional pressure granular bed, and a second fi lter B, similar to the first but implemented with the injection and evacuation means of compressed air at the fi ltration pressure object of the present invention, which allows to compare in real time the operation of each fi lter under similar working conditions. The two fi lter filters or columns are vertical cylindrical fi lters that have a transparent PVC shell (1) of 160 mm outer diameter, PN6, 4 mm thick and 2.1 m long, compartmentalized into two chambers, one upper ( 2) with dimensions and a lower or false bottom (5). In both fi lters, the false background (5)

The lower chamber is separated from the upper chamber by a support plate (7) of the bed. Said plate is provided with nozzles (8) or typical crepins that serve both to retain the bed particles and distribution of the air and water of backwashing and, in the case of the second fi lter, also of the compressed air to be injected; For the design and construction of the pre-treatment plant, the geometric similarity of the piloting has been sought in terms of the ratio of 50 nozzles / m2 of fi ltering surface, which is normally used in this type of fi ltration systems. On the other hand, the granular bed (4) is made of 0.45 mm silica sand of effective size, 1.6 of uniformity coefficient and 1 bed height meter. This is the same type of granular medium and bed height as that corresponding to a real-scale fi lter currently in operation.

The fi lters of the pilot plant are equipped with inlet means (3) of raw water to be filtered with a valve, equipped with a rotameter for measuring the flow of inlet water (24) and a pressure gauge (25), as well as means outlet (6), also with regulating valve (28) to control the back pressure of the fi ltered water fl ow, pressure gauge for measuring said pressure (27) and a rotameter (29) for measuring the flow of wash water.

Both filters are provided with means for washing with water / air blowing at atmospheric pressure (9). To select one of the two cleaning methods that includes this type of fi lters, washing with water or blowing with air, the plant described includes a selection valve (31).

The fi lter implemented with the means of injection and evacuation of compressed air contains, as injection means (10): a conventional compressed air equipment (16), in addition to the backwash, with a solenoid valve for feeding and cutting of air inlet ( 17) connected to a compressed air pressure reducer (18), an air pulse programmer (20) and a rotameter (19) for air flow measurement, both for the blowing air in the fi lter wash phase and for the measurement of the flow of compressed air injected. Said means (10) are connected to the injector socket of the fi lter (11) by means of a tubing (21). On the other hand, the evacuation means (12) are connected to the upper chamber of the fi lter at its highest part and opposite to the part where the water inlet valves to be filtered are connected, by an evacuation outlet (13) by a pipe (14) not larger than 4 ", said means being constituted by a trifunctional suction cup as aeration means (15).

The pilot plant also has sample collection (26) with a shut-off valve both in the raw water inlet means (3) and in the filtered water outlet means (6), which in this case correspond to the means of wash water outlet. This allows samples to be obtained for the measurement of the solids content and the turbidity of each of the referred currents. The whole assembly is housed and fixed to a stainless steel frame.

A pre-treatment pilot plant such as the one described here, which can incorporate more than one filter with means of injection and evacuation of compressed air, can be located in any seawater desalination plant in operation, such as OHL Environment INIMA currently has a conventional fi ltration system in operation as a pre-treatment stage. By incorporating the pilot plant into a conventional desalination plant, the same granular bed as used in said conventional plants can be used without problems. Similarly, the dimensions and parameters described above for the elements that make up the fi lter object of the present invention (bed height, number of nozzles, operating pressure ...) can be adapted without problems to those corresponding to the actual fi lters of The desalination plant. The transposition of the elements of the pilot plant to the industrial scale is simple. All the necessary elements are commercial and do not require unique manufacturing specifications that hinder their acquisition.

As for the specific tests and tests that the pilot plant allows to carry out at scale, the measurement and recording of the following variables is included:

•

Filter flows, wash water and blow air.

•

Flows of compressed air in continuous injection.

•

Compressed air flow rates in pulsed injection.

•

Frequency and duration of pulses.

•

Differential pressure between raw water inlet and filtered water outlet.

•

Concentration of solids and turbidity in each phase of the complete service-washing cycle of the fi lter, in at least three time intervals in each phase.

Each of the above quantities always has reference to the time scale of the complete service-wash cycle of the fi lter.

The analysis of all these data allows us to experimentally establish the three key curves shown in Figures 3 and 4, namely, filtered water flow and mass flow retained in the filter (Figure 3) and differential pressure (Figure 4), the three variables as a function of the service time of the fi lter, both for the reference fi ltration column A (or conventional, that is the fi lter operating under the same conditions as a real pre-treatment plant) and for the fi ltration column B that incorporates the means of injection and evacuation of compressed air. These curves are represented for the parametric value of injection air flow (continuous and / or pulsating air).

Claims (19)

1. Pretreatment and water conditioning filter of the granular bed type closed under pressure with backwashing means, comprising at least:

-

a housing (1) compartmentalized closed under pressure,

-

an upper chamber (2) provided with at least means for entering the water to filter (3), which contains the granular bed (4) inside,

-

a lower chamber (5) as a false bottom of the fi lter, provided with at least the outlet means of the filtered water (6), and

-

a plate (7) for supporting the granular bed separating both chambers, said plate being provided with at least one water and air distribution nozzle (8) as part of the filter backwashing means (9);

characterized in that the filter further comprises:

-

compressed air injection means (10) at the working pressure of the fi lter and during operation thereof, connected to the false bottom by means of an injection socket (11) located in the housing; Y

-

evacuation means (12) outside said injected air, connected to the upper chamber by means of an evacuation socket (13) located in the highest part of the housing (1), and comprising at least one tubing (14) and aeration means (15).

2.

Filter according to claim 1, characterized in that the granular bed is composed of a material selected from the group consisting of sand, gravel, anthracite, activated carbon, garnet, fragmented rock, porous rock, pumice stone, ceramic fragments, plastic fragments, metal fragments , basalt and any combination thereof.

3.

Filter according to any one of claims 1 or 2, characterized in that the injection means comprise at least:

-

a compressed air equipment (16) comprising an automatic injection valve (17), a pressure reducing valve with pressure control valve (18), a rotameter for measuring the flow of compressed air injected (19) and a programming device for air pulses (20); Y

-

a tubing (21) that connects the valve of the compressed air equipment with the injection inlet of the false bottom of the fi lter.

Four.

Filter according to any one of claims 1 to 3, characterized in that the aeration means (15) is an air evacuation suction cup.

5. Filter according to claim 4, characterized in that the aeration means (15) is a trifunctional suction cup.

6.

Filter according to any one of claims 1 to 5, characterized in that the arrangement thereof is vertical or horizontal, and the geometry of the housing (2) is selected from cylindrical, parallelepipedic, conical and spherical.

7.

Water pretreatment and conditioning process by pressure filtration with the fi lter unit described in any one of claims 1 to 6, characterized in that it comprises at least the following steps:

a) inject compressed air into the false bottom of the fi lter at the operating pressure thereof, through the injection means (10), and b) evacuate outside the fi lter the air injected in stage a) above by means of evacuation (12) connected to the upper chamber (2), and characterized in that the compressed air is injected and evacuated simultaneously during the operation of the filter.

8.

Process according to claim 7, characterized in that the air is injected in step (a) continuously or by injection pulses at time intervals.

9.

Process according to claim 8, characterized in that the injection of air by pulses is carried out automatically by means of the air pulse programming device (20).

10.

Process according to any one of claims 8 or 9, characterized in that the air is injected by pulses of a duration between 1 and 10 seconds, and the time interval between pulses is between 1 and 60 min.

eleven.

Process according to any one of claims 7 to 10, characterized in that the operating pressure of the filter and injection of compressed air is between 2 and 8 bar, both limits being included.

12.

Use of the fi lter described in any one of claims 1 to 6 for pre-treatment and conditioning of water in freshwater purification processes, desalination of sea or brackish water, wastewater treatment and reuse or regeneration treatment of wastewater .

13.

Use according to claim 12 in a brackish or seawater pretreatment facility of a desalination plant.

14. Use according to claim 13, characterized in that the desalination plant is reverse osmosis.

fifteen.

Water pretreatment and conditioning installation, characterized in that it comprises at least one filter as described in any one of claims 1 to 6.

16. Installation according to claim 15, characterized in that the fi lters are connected in series or in parallel.

17.

Desalination plant comprising at least one pretreatment and water conditioning installation by filtration of granular bed under pressure, characterized in that said pretreatment installation comprises at least one filter as described in any one of claims 1 to 6.

18. Desalination plant according to claim 17, characterized in that it is reverse osmosis. SPANISH OFFICE OF THE PATENTS AND BRAND Application no .: 200931184 SPAIN Date of submission of the application: 17.12.2009 Priority Date: REPORT ON THE STATE OF THE TECHNIQUE 51 Int. Cl.: See Additional Sheet RELEVANT DOCUMENTS

Category

Documents cited Claims Affected

X

ES 2026546 T3 (ZIMPRO PASSAVANT INC) 01.05.1992, columns 2-6, figure 1 1-18

TO

US 3817378 A (HYDRO CLEAR CORP) 18.06.1974, figures 1-3, columns 2-7. 1-18

TO

US 4976873 (ZIMPRO PASSAVANT INC) 11.12.1990, figures 1-5, columns 1-6 1-18

TO

US 4627923 A (INT TECTONICS INC) 09.12.1986, figures 1, 6, 10, column 3, 5-6 1-18

TO

WO 2008080214 A1 (OASIS FILTER LTD; MANZ DAVID H) 10.07.2008, pages 3-5. 1-18

Category of the documents cited X: of particular relevance Y: of particular relevance combined with other / s of the same category A: reflects the state of the art O: refers to unwritten disclosure P: published between the priority date and the date of priority submission of the application E: previous document, but published after the date of submission of the application

This report has been prepared • for all claims • for claims no:

Date of realization of the report 30.11.2011

Examiner A. Urrecha Espluga Page 1/4

REPORT OF THE STATE OF THE TECHNIQUE Application number: 200931184 CLASSIFICATION OBJECT OF THE APPLICATION B01D24 / 00 (2006.01) C02F1 / 00 (2006.01) B01D24 / 46 (2006.01) B01D35 / 00 (2006.01) Minimum documentation sought (classification system followed by classification symbols) B01D, C02F Electronic databases consulted during the search (name of the database and, if possible, search terms used) INVENES, EPODOC, WPI, TXTUS. State of the Art Report Page 2/4  WRITTEN OPINION Application number: 200931184 Date of Written Opinion: 30.11.2011 Statement

Novelty (Art. 6.1 LP 11/1986)

Claims Claims 1-18 IF NOT

Inventive activity (Art. 8.1 LP11 / 1986)

Claims Claims 1-18 IF NOT

The application is considered to comply with the industrial application requirement. This requirement was evaluated during the formal and technical examination phase of the application (Article 31.2 Law 11/1986).  Opinion Base.- This opinion has been made on the basis of the patent application as published. State of the Art Report Page 3/4  WRITTEN OPINION Application number: 200931184 1. Documents considered.- The documents belonging to the state of the art taken into consideration for the realization of this opinion are listed below.

Document

Publication or Identification Number publication date

D01

ES 2026546 T3 (ZIMPRO PASSAVANT INC) 01.05.1992

2. Statement motivated according to articles 29.6 and 29.7 of the Regulations for the execution of Law 11/1986, of March 20, on Patents on novelty and inventive activity; quotes and explanations in support of this statement The object of the invention is a pressure granular bed type with countercurrent washing means, characterized in that it comprises means for injecting compressed air at the working pressure of the filter during its operation. The object of the invention is also the process of pretreatment of water in said filter, as well as the use of the filter in the purification of fresh water, desalination of seawater and the treatment of wastewater. Document D01 discloses a filter for the treatment of wastewater, drinking water supply and the like, of the granular bed type with countercurrent washing means, characterized in that it comprises means for generating pulses of a countercurrent fluid (can be gas) and that they pass through the filter bed during its operation. The interval between pulses is 6-30 min and these have a duration of 10-120 s. The filter comprises a housing, an upper chamber with inlet means of the water to be filtered, a lower chamber with a false bottom and outlet means of the filtered water and a granular bed support plate that separates both chambers (columns 2-6, Figure 1). The difference between document D01 and the object of the invention as set out in claims 1 and 7 of the application lies in the working pressure of the filter, atmospheric in the case of D01 and pressure in the application. However, in both cases the filtration process is improved by the application of countercurrent pulses during the operation of the filter. The different technical characteristics between D01 and the object of the invention, as set out in the claims of the application, derive from this working condition. However, the constructive variables for pressure work are within the scope of the usual knowledge of the person skilled in the art. Dependent claims 2-6 and 8-11, which contain constructive details of the filter or operating conditions, as well as claims 12-18, relating to the use of the filter in wastewater treatments or desalination plants, do not contain any characteristic that, in combination with the claims on which they depend, meet the established requirements regarding inventive activity. Therefore, the technical object of claims 1-18 lacks inventive activity (Art. 8.1 LP). State of the Art Report Page 4/4