ES2371192A1 - Pre-treatment and water conditioning filter of pressure-closed granular body type with cooling washing machines (Machine-translation by Google Translate, not legally binding) - Google Patents

Abstract

Pre-treatment filter and water conditioning of granular bed type closed under pressure with countercurrent washing 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, treatment of wastewater and treatment of reuse or regeneration of wastewater, to which have been incorporated means of injection of compressed air at the same operating pressure of the filter during the service cycle or filtering thereof, as well as a means of extraction-simultaneous evacuation of said injected air, by the upper part of the filter to the exterior. The air injected into the filter passes through the granular bed, breaking and lifting the layers closest to the surface, leaving passage channels 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 filtration under pressure with the filter unit described here, as well as the raw water pre-treatment and conditioning plant incorporating said filter. (Machine-translation by Google Translate, not legally binding)

Description

Pretreatment and conditioning filter water of the closed-bed granular bed type with means of backwash

Technical sector

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

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State of the art

The raw water to be treated in processes of purification, wastewater treatment, treatment of wastewater reuse or regeneration and desalination must meet a series of quality requirements before its entry in the treatment plant, among other reasons to avoid obstructions and reduce the number of washes. In order to comply the required quality standards, usually one or several stages of pre-treatment in said processes

Among the systems of known pretreatment (coagulation / flocculation, decantation, filtration, flotation, addition of different reagents for pH adjustment, disinfection ...), the most widespread by its simplicity, reduced investment and exploitation costs is the filtration through granular beds in closed filters at Pressure. These filters are intended to eliminate most of the decantable and suspended solids contained in fresh water, from sea or brackish and in sewage from the source of collection. Filtration on granular beds is a known and very well known technique. implanted especially in treatment plants Conventional drinking water (river waters, reservoirs, lagoons, freshwater aquifers, etc.), so you can find a extensive bibliography in this regard, among which one can cite of Featured way: "Wastewater engineering. Treatment, pouring and reuse ", Metcalf & Eddy, Third Edition (1998), Ed. McGraw-Hill (chapters 6.8 and 11.3); Y "Water Technical Manual", Degrémot, Fourth Edition (1979), Ed. Grafo, S.A. (chapters 3 and 4).

Currently filter batteries are used in one or two stages in series to perform this function. He Filter operation is based on the progressive retention of the mentioned solids on the layer of filter sand. One time that the filter is clogged and therefore loses its ability to follow filtering it is necessary to remove it from the production line (that is, end its service cycle) and wash it countercurrently to remove the material retained therein; normally washed with raw seawater or brine produced in the racks of osmosis and / or air blowing at atmospheric pressure. Once washed the filter, is put back into service to perform a new cycle of filtered out.

A clear disadvantage of this process is that most of the solids retained in the filters are located in the first centimeters of the sand bed, which implies an underutilization of the filtering 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 larger filter surface to provide for high washing frequencies and, therefore, a greater number of filter units and all their auxiliary elements, ultimately a higher investment cost of the plants.
desalination plants

In view of these inconveniences, one of the fundamental objectives of the present invention consists of incorporate an injection and evacuation system of compressed air to the current pressure granular bed filters in order to significantly increase its filtration capacity, measured as kilograms of water retained matter to filter per kilogram of filter bed material, and as a consequence the reduction of number of filtration units needed to achieve the same finish.

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Description of the invention brief description

The present invention relates to a unit of filter of the closed pressure granular bed type, such as commonly used in pre-treatment and water conditioning of seawater desalination processes or brackish, fresh water purification, water treatment Waste and water reuse or regeneration treatment residuals, to which injection means of compressed air at the same filter operating pressure during the service cycle or filtering thereof, as well as some means of simultaneous extraction-evacuation of said air injected from the top of the filter to the outside. How fresh, brackish or marine water, as cited herein invention, it is understood that which has a salt content less than 0.05%, between 0.05% and 3%, and between 3% and 5%, respectively.

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

Since the filter is a closed pressure system, it is necessary to evacuate the air injected into the fake inside background, and that accumulates in the upper chamber after crossing the granular bed, to achieve the continuity of the operation of the filtration phase The extraction of compressed air from the upper chamber is performed by means of evacuation, connected to the housing, which comprise at least one means of aeration located in the highest part of said housing; said medium aeration 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 granular bed filter at pressure should be noted the significant increase in its ability to filtration, and as a consequence the reduction in the number of units of filtering in pre-treatment facilities of water to achieve the same performance as a system constituted by a greater number of filters without the two devices object of the present invention.

The invention also relates to a pre-treatment and conditioning installation of water comprising at least one filter as described previously, as well as specifically to a desalination plant, more preferably reverse osmosis, comprising said installation of pre-treatment that incorporates one or several filters with the injection-evacuation device of compressed air. Also, the invention discloses the use of said filter for pretreatment and conditioning of water in freshwater purification processes, seawater desalination or brackish, sewage treatment and treatment of wastewater reuse or regeneration, and more specifically refers to the use of said installation of pre-treatment of brackish or marine water in a reverse osmosis desalination plant.

Another object of the present invention consists in a pre-treatment procedure and water conditioning by the filter unit before described, which comprises at least injecting compressed air into the inside the filter at its operating pressure, and simultaneously evacuate said air to the outside during operation of the filter, that is, during the process of water filtration

Detailed description

The main object of the present invention is a water pretreatment and conditioning filter of the type of Pressed granular bed with washing means a countercurrent, which comprises at least:

-

a housing (1) compartmentalized in two chambers closed to Pressure,

-

a upper chamber (2) that contains the granular bed inside filter (4), provided with at least input or feed means of the water to be filtered (3),

-

a lower chamber (5) as a false bottom of the filter, equipped with less means of exit (6) of filtered and conditioned water, Y

-

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

characterized in that the filter comprises also:

-

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

-

media of evacuation (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 a pipe (14) and aeration means (15).

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Preferably, the pretreatment and water conditioning using the filter described is included within freshwater purification processes, desalination of seawater or brackish water, sewage treatment and treatment of reuse or regeneration of wastewater.

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For a better understanding of the filter here described, an illustrative scheme of the same, without said figure having a limiting nature of the invention.

Compressed air is injected into the chamber bottom (5) corresponding to the false bottom of the shape filter similar to how atmospheric blowing air is injected in the phase backwash However, there are clear differences. between both processes of air injection: on the one hand, the air of washing is injected into the filter unit when it It is stopped or out of service and at atmospheric pressure, while that compressed air is injected into the present invention during the operation or service of the filter and at the same pressure of its work, which is never at atmospheric pressure, but greater. In short, the backwash of the filter can be perform only and exclusively at stop, that is, when it has stopped and removed from the filtration line due to its clogging On the contrary, the injection devices (10) and evacuation (12) of compressed air of the present invention they work simultaneously and during the filter duty cycle, that is, during the water filtration process, since It starts until it ends. This function is not possible in the case of the washing system (9), since no known device of backwash blown is designed and enabled for inject air at the pressure at which filters commonly work granular bed (a pressure considerably greater than the required for backwashing), and in it reside the beneficial effects achieved with respect to the conditioning of water to be filtered in a desalination process.

Compressed air is injected into the filter by its false bottom (5) at the same pressure as that of the water that is being filtered, that is, at the set working pressure inside the filter. As at the same pressure the air has a density lower than that of water, it will rise in the form of bubbles to the upper chamber (2) through one or more nozzles (8) distributors located on the bed support plate (7) granular, going through said granular bed (4) and lifting and breaking the layers closest to the bed surface, leaving passage channels for the filtration process to continue. Further, in this way, when lifting the mantle of solids deposited in the first superficial layers, the penetration of the smaller particles in the bed, which will be retained to greater depth, thereby increasing the retention capacity of Matter in the filter. Also in this way the differential pressure between feed water inlet to be filtered and water outlet filtered in the filter, which measures the degree of clogging or clogging of the same, will gradually decrease well with the injection continuous air or staggered with each injection pulse of air, thus extending the time between the pressure initial and final service differential, before the stop of the filter to proceed to its washing. This phenomenon can be seen. represented in the attached Figures 3 and 4 where the evolution of filtered water flow and solids load retained by the filter (Figure 3), and the differential pressure of the same depending on the service time or filtration phase (Figure 4).

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

Preferably, the granular filter bed (4) It consists of a material selected within the composite group by sand, gravel, anthracite, activated carbon, garnet, rock fragmented, porous rock, pumice, ceramic fragments, plastic fragments, metal fragments, basalt and any combination thereof. In turn, the filter housing (2) can be constructed with any material commonly used, be it steel, plastic materials or other.

The compressed air injection-evacuation system described here works and allows to achieve the abovementioned improvements 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 bar, and more preferably it is 6
pubs.

In a preferred embodiment, the injection of compressed air at the same filter operating pressure during the entire service cycle it is carried out at flow continuous. In another embodiment, the injection is pulsating, that is to say regular or irregular time intervals. Every pulse of compressed air injection preferably have 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 the Pulsed air injection is used, the air pulses are more short and spaced in time at the beginning of the period of operation of the filter that at the end of said period, in which the pulses have a longer duration and are less spaced between yes.

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

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Preferably, the injection means They comprise at least:

-

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

-

a tubing (21) that connects the compressed air equipment valve with the injection socket of the false bottom of the filter.

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Preferably, the automatic valve of Injection is an electrovalve.

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

The injection and evacuation devices of compressed air described here, either in continuous or pulsating flow, can be used without restrictions on any type of filter a granular bed pressure, not only regardless of pressure of design or work of the same, but also of its disposition, already be it vertical, horizontal or other, or of its geometry, being able to have the filter housing a cylindrical, parallelepipedic shape, conical, spherical or another way different to those stated, although preferably the filter is cylindrical and horizontal. A filter like the one claimed here, which incorporates the injection devices (10) and evacuation (12) of compressed air, can also be used in any set or battery of series or parallel filters, and regardless of the granulometry of the bed (4), the length and The diameter of the filter. Preferably, the granulometry of the bed can be comprised 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 between 1 and 25 meters, being more preferably 14 meters

It constitutes another object of the present invention a process of pretreatment and conditioning of water by pressure filtration with the filter unit described here, which comprises the means of simultaneous injection (10) and evacuation (12) of compressed air, characterized in that it comprises at least following stages:

(to)

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

(b)

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

and characterized in that the compressed air is inject and evacuate simultaneously during operation of the filter, that is, during the water filtration cycle. Saying water pretreatment and conditioning process takes to preferably carried out within purification processes of fresh water, desalination of sea or brackish water, treatment of wastewater, or reuse or regeneration treatments of wastewater, among others.

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Preferably, the operating pressure of the filter and, consequently, of compressed air injection, It is between 2 and 8 bars, including both limits, and more preferably it is 6 bars.

In a preferred embodiment, the compressed air it is injected into the false bottom (5) continuously in step (a). In another embodiment, the air is injected in a pulsating manner, it is that is, by injection pulses at regular time intervals or irregular. Each pulse of compressed air injection have preferably 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 interval of time between pulses) is preferably between 1 and 60 minutes, being more preferably 30 minutes. In a preferred embodiment in which air injection is employed pulsating, the air pulses are shorter and spaced apart in the time at the beginning of the filter's operating period than at end of that period, in which the pulses have longer duration and They are less spaced apart. In addition, air injection by pulses it is carried out more preferably in a manner automatic using the pulse programming device air.

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

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

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

Among the most relevant advantages of both present filter, comprising injection devices (10) and evacuation (12) of compressed air at the filtrate pressure, such as of the pre-treatment procedure and conditioning of water that is carried out by said filter, It is worth mentioning:

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

- Reduction of the number of units needed for the same filtration capacity as a conventional system, and reduction of all auxiliary filter elements inherent in filtration process such as foundations and support benches of filters, distribution pipes, brackets, valves feeding and filtering, water inlet and outlet valves backwash, blow air inlet valves and valve venting, solenoid valves associated with pneumatic actuators, electric actuators, force and control wiring, and the part corresponding mechanical and electrical assembly assembly.

- Significant reduction in the frequency of washing and, as a direct consequence, lower water consumption of backwash In addition, in cases where the backwash is performed with raw feed water (most plants desalination plants use raw water for backwashing), they are reduced the raw water design flow needs of the pre-treatment which implies a reduction of 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 pumps backwash by reducing the total water consumption of said backwash

- Higher concentration of solids in the filter wash 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 the decrease in reagent consumption of coagulation and flocculation necessary to obtain the same final dryness of treated sludge.

- Feasibility and simplicity in the application of the present invention for all current pre- systems treatment using granular bed filtration at a low cost.

- Maintenance cost reduction, by decrease the number of equipment and associated elements.

- Last but not least, natural oxidation and inherent to the air injection process ion tablet contained in raw and potentially water Harmful to the reverse osmosis process such as Fe + 2 and the Mn + 2, reducing or eliminating the dosage of products oxidizers traditionally used in the pre-treatment such as sodium hypochlorite, the Chlorine dioxide, potassium permanganate or sodium bisulfite. The oxidized forms Fe 2 O 3 and MnO 2 would be retained in the filter bed, avoiding irreversible damage to the desalination device.

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Description of the figures

Figure 1 illustrates an embodiment of the filter object of the present application, without being limiting of the same.

Thus, a sectional view of a conventional horizontal cylindrical filter pre-treatment and water conditioning of the type closed pressure granular bed comprising the means of injection and evacuation of compressed air at the pressure of filtration according to the invention. This view shows the following elements:

(one)

External compartmentalized housing or enclosure filter

(2)

Upper chamber

(3)

Raw water inlet means (tubing) a filter

(3.1)

Raw water pipe to filter

(3.2)

Raw Water Inlet Valve

(4)

Granular filter bed

(5)

False bottom (or lower chamber)

(6)

Water outlet means (tubing) filtered

(6.1)

Filtered water pipe

(6.2)

Filtered water outlet valve

(7)

Support plate / bed support granular

(7.1)

Bed support filter

(8)

Distribution nozzle or crepe

(9)

Means for backwashing of filter

(9.1)

Water inlet valve

(9.2)

Wash 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 blow air distribution pipe. This tubing is located between the plane of the support plate (7) and the plane formed by the ends of the nozzle tails (8)

(eleven')

Compressed air injection socket (tubing), in the case of filters with distribution / distribution pipe (23) blow air for cleaning the filter. The compressed air is injected into the circular crown that exists between the tubing of outlet (6) and said delivery tube (23)

(12)

Means for evacuating compressed air injected

(13)

Outlet of compressed air

(14)

Tubing

(fifteen)

Aeration medium, for example a suction cup automatic compressed air outlet

(16)

Compressed air equipment

(17)

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

(18)

Pressure gauge with pressure control valve compressed air

(19)

Rotameter for compressed air flow measurement 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)

Blow air distribution pipe for the filter cleaning, optional for cylindrical length filters less than 12 meters

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

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(one)

External compartmentalized housing or enclosure Filter, transparent PCV DN 160 and PN6

(2)

Upper filter chamber

(3)

Raw water inlet means (tubing) a filter

(4)

0.45 silica sand filter granular bed mm effective size, 1.6 uniformity coefficient and 1 meter of bed height This is the same type of granular medium and height of bed than that corresponding to a real-scale filter currently working.

(5)

False bottom (or lower chamber)

(6)

Water outlet means (tubing) filtered

(6.1)

Filtered water pipe

(7)

Support plate / bed support granular

(8)

Distribution nozzle or crepe; the surface of nozzle influence follows the ratio of a scale filter real, that is, 50 nozzles / m2

(9.1)

Water inlet valve filter

(10)

Compressed air injection means

(eleven)

Air injection socket (tubing) compressed

(fifteen)

Aeration means of the automatic suction cup type 1 '' compressed air outlet

(16)

Compressed air equipment

(17)

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

(18)

1 '' pressure reducing valve, for regulating the compressed air inlet pressure, with a regulation range of 0-8 bars

(19)

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

(twenty)

Compressed air pulse programmer

(22)

Filter drain valve

(24)

Rotameter for the measurement of raw water flow a filter, with a measuring range between 0-500 1 hour

(25)

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

(26)

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

(27)

Pressure gauge for water pressure measurement filtered, with a measurement range of 0-6 pubs

(28)

Water pressure regulating valve filtered, with a range of 0-4 bars

(29)

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

(30)

Differential pressure gauge to measure loss of load in the bed, with a measurement range of 0-2 pubs

(31)

Select wash and blow valve for each one of the columns

(32)

Blow air inlet

(33)

Filter wash water inlet

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

The line represented by \ blacksquare 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 \ ding {53} is called the theoretical curve of continuous compressed air injection, or q_ {ic} as a function of time (q_ {ic} (T)), or m_ {ic} as a function of time ( m_ {ic} (T)). Thickest line 100 represents the theoretical curve with pulsed compressed air injection, or q_ {ip} as a function of time (q_ {ip} (T)), or m_ {ip} as a function of time (m_ {ip} (T)). T 0 corresponds to the start time of filtration, T f the end time of the filtration cycle without air injection, and T fi the final time of the filtration cycle with air injection.

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

one

where 10 represents the volume with continuous air injection, 2 represents the volume with pulsed air injection, and 3 It represents the volume without air injection.

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In turn, Figure 4 shows the evolution of the differential pressure ΔP (in bars) as a function of the service time T of the filter, where the line represented by muestrasquare shows the real curve of the filter without air injection. The line represented by \ ding {53} shows the theoretical curve of continuous compressed air injection. Thickest line 100 represents the theoretical curve with pulsed compressed air injection. T 0 corresponds to the initial time of the beginning of filtration, T f to the final time of the filtration cycle without air injection, and T f the final time of the filtration cycle with air injection.

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Execution Example

Below is detailed, by way of example and non-limiting nature of the invention, an embodiment of the filter in question in a pilot installation at scale of water pre-treatment that would correspond to the flow chart shown in Figure 2, in order to improve the understanding of the invention

Currently, it has been designed and built a pilot pre-treatment and conditioning plant of water by filtration, specially designed for installation in a reverse osmosis desalination plant. The pilot plant has a filter A, of granular bed under pressure conventional, and a second filter B, similar to the first but implemented with the means of injection and evacuation of air compressed at the filtration pressure object of the present invention, which allows real-time operation to be compared of each filter under similar working conditions. The two filters or filtration columns are vertical cylindrical filters that they have a transparent PVC casing (1) 160 mm in diameter exterior, PN6, 4 mm thick and 2.1 m long, compartmentalized in two chambers, one upper (2) with dimensions and one lower or of false bottom (5). In both filters, the false bottom (5) or camera lower is separated from the upper chamber by a plate bed support (7). Said plate is provided with nozzles (8) or typical crepes that serve both to retain particles of the bed as distribution of the air and water of backwashing and, in the case of the second filter, also of the compressed air to be injected; for the design and construction of the plant pre-treatment similarity has been sought geometry of the pilot as for the ratio of 50 nozzles / m2 of filter surface, which is normally used in this type of filtration systems. For its part, the granular bed (4) It is 0.45 mm effective silica sand, 1.6 of uniformity coefficient and 1 meter of bed height. This is the same type of granular medium and bed height as the corresponding to a real-scale filter currently in functioning.

Pilot plant filters are equipped with inlet means (3) of raw water to be filtered with valve, provided with a rotameter to measure the flow of inlet water (24) and a pressure gauge (25), as well as outlet means (6), also with regulating valve (28) to control the back pressure of filtered water flow, pressure gauge for measuring said pressure (27) and a rotameter (29) for measuring water flow washing

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

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

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

A pilot plant of pre-treatment like the one described here, which can incorporate more than one filter with injection means and compressed air evacuation, can be located in any plant seawater desalination plant in operation, such as OHL Medio Ambiente INIMA currently has an operating system with conventional filtration as a stage of pretreatment By incorporating the pilot plant to a conventional desalination plant, can be used without problems the same granular bed as used in said plants conventional. Similarly, the dimensions and parameters before exposed for the elements that make up the filter object of the present invention (bed height, number of nozzles, pressure of operation ...) can be adapted without problems to corresponding to the real filters of the desalination plant. The transposition of the elements of the pilot plant to the scale Industrial is simple. All the necessary elements are commercial and do not require manufacturing specifications singular that hinder its acquisition.

As for the specific tests and trials that allows the pilot plant to be carried out at scale, the measure is included and record of the following variables:

?

Filtration flows, water from washing and blowing air.

?

Compressed air flow rates in continuous injection.

?

Compressed air flow rates in pulsating injection.

?

Frequency and duration of pulses

?

Differential pressure between raw water inlet and filtered water outlet.

?

Solids concentration and turbidity in each phase of the complete cycle filter wash-service, in at least three time intervals in each phase.

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Each of the previous magnitudes has always reference to the time scale of the complete cycle of filter wash-service.

The analysis of all this data allows experimentally establish the three key curves shown in the 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 filter service time, for both the reference (or conventional) filtration column A that is the filter that operates in the same conditions as a real pre-treatment plant) as for the column of filtration B that incorporates the means of injection and evacuation of compressed air. These curves are represented for the value parametric injection air flow (continuous air and / or pulsating).

Claims (18)

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

-

a enclosure (1) compartmentalized closed under pressure,

-

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

-

a lower chamber (5) as a false bottom of the filter, equipped with less than filtered water outlet means (6), and

-

a granular bed support plate (7) that separates both cameras, said plate being provided with at least one nozzle of distribution (8) of water and air as part of the washing medium a filter countercurrent (9);

characterized in that the filter further comprises:

-

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

-

media of evacuation (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 a pipe (14) and aeration means (15).

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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 valve injection (17), a pressure reducer with control valve pressure (18), a rotameter for compressed air flow measurement injected (19) and an air pulse programming device (twenty); Y

-

a tubing (21) that connects the compressed air equipment valve with the injection socket of the false bottom of the filter.

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4. 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 filter unit described in any one of claims 1 to 6, characterized in that it comprises at least the following steps:

to)

inject compressed air into the false bottom of the filter at the operating pressure thereof, by means of injection means (10), and

b)

evacuate the air injected into the outside of the filter step 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.

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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. 11. 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 filter described in any one of claims 1 to 6 for pretreatment and water conditioning in water purification processes fresh, desalination of sea or brackish water, water treatment Waste and water reuse or regeneration treatment residual 13. Use according to claim 12 in a installation of pretreatment of brackish water or sea of a plant desalination plant 14. Use according to claim 13, characterized in that the desalination plant is reverse osmosis. 15. 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 filters 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.