WO2022086457A1

WO2022086457A1 - Industrial filter for reducing turbidity and suspended solids with an effective backwash equipment

Info

Publication number: WO2022086457A1
Application number: PCT/TR2020/050964
Authority: WO
Inventors: Osman Oguz Tameroglu
Original assignee: Antel Aritma Tesisleri Insaat Sanayi Ve Ticaret A.S.
Priority date: 2020-10-20
Filing date: 2020-10-20
Publication date: 2022-04-28

Abstract

The present invention provides a filter apparatus (2) of industrial type for reducing turbidity and suspended solids in a liquid, comprising a filter housing (23), a filter screen (1) of hollow shape concentrically located in said filter housing (23), an inlet (21) for supplying liquid to be filtered on inner surface (14) of the filter screen (1), an outlet (22) carrying filtrated liquid out of the filter housing (23), and a backwash equipment (3) for cleaning the inner surface (14) of the filter screen (1). The filter screen (1) comprises at least two screen layers (11, 11') and a filter layer (13) disposed therebetween, and said filter layer (13) is composed of a non-woven fabric which is made up by polymer or copolymer fibers. Said backwash equipment (3) is rotatably placed into the inner volume of the filter screen (1), and comprising at least a brush (33), plurality of nozzles (31) and a collection pipe (32) in fluid communication with said nozzles (31).

Description

INDUSTRIAL FILTER FOR REDUCING TURBIDITY AND SUSPENDED SOLIDS WITH AN EFFECTIVE BACKWASH EQUIPMENT

Technical Field

The present invention relates to a novel filter apparatus for the separation of very fine particles creating turbidity in water either suspending or forming a cake therein. More particularly, the present invention provides an industrial filter apparatus which carries out a more effective backwashing and effectively reduces turbidity and suspended solids inside an aqueous media. Further, the present invention presents methods for producing such a filter apparatus as well as methods for carrying out filtration.

Background of the Invention

Filtration assemblies are commonly used in different areas such as well water applications, water treatment plants, swimming pools, cooling towers, manufacturing plants and supply of mains water. These filters mostly include a tubular filter screen having a certain mesh size depending on particle size of dirtiness and substances coming through the liquid. Therefore, these filters are expected to clean themselves periodically according to predetermined parameters such as pressure drop through the filter, or otherwise are cleaned manually by labour which is cumbersome and not feasible in the plants of industrial scale.

EP 3044165 Bl discloses a filter screen located in a filter housing, which is provided also with a combined nozzle and brush back-flush device for effectively removing dirtiness accumulated on inner surface of the filter screen.

EP 3110521 Bl discloses another type of an industrial filter for gradually screening of fine and coarse particles in a single system by using different filtration screens concentrically formed in a single filter body.

WO 2018/188934 Al discloses a method for a filter arrangement and a backwashing arrangement. This document is based on the principle of aligning a plurality of nozzles along a straight line such that they all project in the same direction in a back-washing arrangement, allowing for a more efficient backwashing of a folded filter and thereby an efficient backwashing of a compact filter. The mechanical filters of the foregoing types, being suitable for removing dirtiness up to a certain level, are still insufficient for reducing turbidity and very fine particles suspended in the liquid. In order to seek a further solution to carry out a deep filtration and eliminating very fine particles, CA 2792609 provides a process and a backwash filter apparatus equipped with a filter fabric, as the filter material, having an air permeability of 700-1300 1/m³ at pressure differential 200 Pa. There is, however, no information about specific type of the filter material which is important for backwash cleaning capacity of the filter after accumulation of the particles and dirtiness on its surface. Furthermore, the document is silent about how to improve performance of the backwashing in a filter apparatus equipped with a fibrous (i.e. fabric) material.

In a typical filter apparatus carrying out deep filtration or filtration of very fine particles, particles and agglomerates are absorbed/adsorbed through the texture of the filter material, and then backwashing is initiated automatically or manually for cleaning inner surface of the filter material. Thereby, the particles and cake forming agglomerates clogging the very fine pores of said filter material are removed usually with nozzles sucking said agglomerates and discharging the same in order to reduce the pressure drop (AP).

It is usually cumbersome to remove those particles and agglomerates adhered on the filter material because of the very fine pores intrinsically possessed by said filter material such as fabrics. The nozzles carrying out suction during backwashing are usually inadequate to remove dirtiness deeply penetrated through the filter material, and this causes incomplete backwashing and/or longer periods of backwashing process. Furthermore, even if a filter material of smaller pore size is used, turbidity (NTU) and total suspended solids (TSS) are not easy to reduce from water.

Therefore, there is a long felt need to provide an industrial filter with specific filter material which greatly reduces turbidity (NTU) and total suspended solids (TSS) while being durable against high pressure and easy to clean during backwashing. It is also desirable to provide a filter material for a filter screen which is cost effective and advantageous in that not causing a critical amount of pressure drop (AP). Further, it is important to remove very fine particles and agglomerates, either penetrating or adhering to the filter material, in a more effective way. Major problem with these type of filters is that conventional backwashing equipment employing nozzles may not be adequate to remove dirtiness accumulated in or on the filter material withing a short while.

The foregoing objectives of the present invention are currently achieved with a filter apparatus as defined in the appended claims. Brief Description of the Invention

The present invention provides a filter apparatus (2) of industrial type for reducing turbidity and suspended solids in a liquid, comprising a filter housing (23), a filter screen (1) of hollow shape concentrically located in said filter housing (23), an inlet (21) for supplying liquid to be filtered on inner surface (14) of the filter screen (1), an outlet (22) carrying filtrated liquid out of the filter housing (23), and a backwash equipment(3) for cleaning the inner surface (14) ofthe filter screen (1). The filter screen (1) comprises at least two screen layers (11, 11’) and a filter layer (13) disposed therebetween. Said filter layer (13) is composed of a non-woven fabric which is made up by polymer or copolymer fibers. Said backwash equipment (3 ) is rotatably placed into the inner volume ofthe filter screen (1), and comprising at least a brush (33), plurality of nozzles (31) and a collection pipe (32) in fluid communication with said nozzles (31).

The filter layer (13) is preferably made of a non-woven fabric having a density value between 200 and 1500 g/m², and said non-woven fabric has a structure which is needle punched and surface modified with calendering before being disposed into the filter screen (1).

Density of the non-woven fabric is more preferably at least 500 g/m², and most preferably is from 500 g/m² to 1500 g/m².

Calendering of the filter material is quite important as it reduces pore sizes, thereby reducing permeability of the material for increasing filtration efficiency. More importantly, surface modification with calendering flattens the surface such that it can be more easily and quickly cleaned with the backwash equipment (3). The calendering as mentioned herein can be carried out at a roller pressure of 2 to 1000 kPa, but best results were obtained at a roller pressure between 100 kPa and 1000 kPa. The calendering is preferably carried out with heattentering at a temperature between 100 °C and 250 °C. Preferably, both sides of the filter layer (13) is treated with calendering which advantageously improve filtration of very fine particles.

In a further embodiment, the filter layer (13) is also coated with a reinforcing polymer for improving agility and endurance thereof. The fibers of the non-woven fabric in the filter material are made of polyester or polypropylene. The polyester is preferably ethylene polyester (PET) or PCDT polyester. Polyester and derivatives thereof are preferred.

The filter layer (13) can be divided into two separate layers (13, 13’). For example, if the density of the non-woven fabric is determined as 1000 g/m², it can be divided into two layers with SOO- SOO g/m² density values. In these preferred embodiments, the filter screen (1) may further comprise at least one support layer (12, 12’, 12”) forming a mesh for supporting filter material of the filter layer (13). In the case of separate filter layers (13, 13’), for instance, each of said filter layer can be entrapped between two support layers (12, 12’, 12"). Preferably, the support layer (12, 12’, 12”) comprises holes having dimensions less than those of the screen layers (11, 11’). The filter screen (1) can be embodied with at least one further filter layer (13’) provided with activated carbon and/or sand.

The backwash equipment (3) comprises a plurality of nozzles (31) and at least one brush (33) disposed in close proximity to the inner surface (14) of the filter screen (1). The collecting pipe (32) is connected to a discharge valve (26) such that a negative pressure is created in opening ends of the nozzles (31) for sucking dirtiness accumulated on said inner surface (14). The filter apparatus (2) may also comprise an actuation unit (25) driven by a motor (24) for rotatably moving the collecting pipe (32) and nozzles (31). Preferably the collecting pipe (32) is configured to have a helical movement along the inner surface (14) of the filter screen (1).

The filter apparatus (2) according to the present invention is advantageously configured to activate the backwash equipment (3) at a pressure drop level of adjustable values of AP such as AP 0.8 bar, more preferably AP<0.4 bar. A control unit (not shown) detecting the fluid pressure at the inlet (21) and at the outlet (22), and determining the pressure drop (AP) can be provided to actuate the backwash equipment (3). This can be, for instance, by actuation of the motor (24) for rotating the collecting pipe (32) and opening of the discharge valve (26).

In another aspect, the present invention provides a method for filtrating a liquid containing fine particles comprising the steps of: providing a filter apparatus (2) as explained above, supplying the liquid to be filtered through the inlet (21) of the filter apparatus (2) and filtrating the liquid through the filter screen (1) followed by discharging the filtrated liquid through the outlet (22), measuring the pressure difference between inlet (21) and outlet (22) of the filter apparatus (2), and activating the backwash equipment (3) once the pressure difference reaches to a predetermined value.

In another aspect, the present invention provides a method for producing a filter apparatus (2) as defined above, comprising the steps of: providing a filter housing (23) having an inlet (21) and outlet (22), providing a filter screen (1) and a backwash equipment (3) for cleaning the inner surface (14) of the filter screen (1), wherein;

- the filter screen (1) comprises at leasttwo screen layers (11, 11’) and a filter layer (13) disposed therebetween, and said filter layer (13) is composed of a nonwoven fabric which is made up by polymer or copolymer fibers, and

- said backwash equipment (3) is rotatably placed into the inner volume of the filter screen (1), and comprising at least a brush (33), plurality of nozzles (31) and a collection pipe (32) in fluid communication with said nozzles (31), mounting said filter screen (1) concentrically into the filter housing (23).

Still in a further aspect, the present invention provides a novel use of the filter apparatus (2) according to the present invention in treatment of a liquid in a drinking water treatment plant, biomass energy plant, mineral water bottling plant, tire production plant, metal pipe and profile production plant, well water filtration, and tap water filtration. The liquid to be filtered can be a washing, cooling or even drinking water used in these applications. Domestic use is possible by the use of the filter apparatus (2) in conventional buildings for improving quality of the tap water.

Brief Description of the Figures

Figure 1 is a general view of a structure of the filter apparatus (2) comprising a filter screen (1) and a backwash equipment (3) according to the present invention.

Figure 2 provides a detailed view of the filter screen (1) and filter apparatus (2) according to the present invention.

Figures 3 a and 3b show cross-sectional view (Section A- A) of a nozzle (31) according to a preferred embodiment of the present invention.

Detailed Description of the Invention

Industrial filters designed for filtration of fine particles and reducing the level of turbidity (NTU) and total suspended solids (TSS) generally employ a filter screen comprising a filter material with very small pore size. As shown in Fig. 1, a filter apparatus (2) of this type typically comprises an inlet (21) and outlet (22), a filter housing (23) accommodating the filter screen (1) and backwash equipment (3). The filter apparatus (2) may further comprise a motor (24) and an actuation unit (25) for driving of the backwash equipment (3).

It has been observed that the performance of the filter apparatus (2) designed for filtration of very fine particles might be seriously affected by the filter material, especially the type of said filter material as well as density and surface characteristics thereof. In more detail, the material, permeability and surface characteristics of the filter structure are noted to be determining the quality of the water, pressure drop (AP) profile during filtration, and more importantly cleaning performance of the backwash equipment Moreover, a filter material like a fabric, unlike the metal screens, carries out deep filtration and entraps very fine particles which can be hard to reverse in the backwashing cycle.

Therefore, there has been a continuous need for the development of new filter screens which can be easily cleaned in a way such that pressure drop (AP) is eliminated within a short course of backwashing while the filter screen, under normal filtration operation, eliminates particles and agglomerates as much as possible. During experiments, it is noted that, even tap water provided in drinking quality contains very high amount of suspended solids mostly invisible to the consumer which may cause serious health risks to the public. It is therefore important to provide a filter structure in industrial scale for better treatment of water in various areas of the industry.

As a solution to the above mentioned long-felt demand, the present invention provides a high performance filter screen (1), a backwash equipment (3) and a filter apparatus (2) comprising the same which is capable of carrying out deep filtration and advantageous in terms of operation. For this purpose, the filter apparatus (2) according to the present invention comprises a filter material and a backwash equipment (3) equipped with at least one brush (33).

As shown in Fig. 2, the filter screen (1) used in the filter apparatus (2) comprises various layers depending on specific needs of the application area. "Detail A” shows details of said layers comprising atleastone filter layer (13) disposed inbetween two screen layers (11, 11’). The filter layer (13, 13’) is composed of a non-woven fabric, as explained in greater detail hereinbelow.

In the context of the present invention, the term "non-woven fabric” refers to a fibrous material which is not knitted as conventionally known, and is made of a polymer or copolymer, for instance, polypropylene (PP) or polyester. More preferably, the filter material is made of polyester which is found to be advantageous as it is cost effective, having good absorption/adsorption properties, being durable and capable of being easily cleaned in backwashing. The polyester material is preferably composed of staple fibers. Said polyester can be of the type, for instance, ethylene polyester (PET) or PCDT polyester.

It has been found that the density of the non-woven fabric plays an important role in determining permeability of the filter which in turn affects the level of turbidity and total suspended solids as well as the pressure profile throughout the filter apparatus. It also affects performance of the filter in removing very fine particles. The inventor has also found out that the density of the non-woven filter material may advantageously be adjusted to a value between 200 and 1500g/m². Notably, a density value of at least 500 g/m²has provided advantageous results such that turbidity and total suspended solids in water are substantially eliminated with a deep filtration while pressure drop (AP) of the filter apparatus is kept at optimum. Additionally, this effect is observed up until 1500 g/m² with excellent results in filtration. However, a lower density value of 200-400 g/cm² was useful and advantageous for treatment of water with lower amount of fine particles such as mains water, and it can be easily cleaned with conventional backwash equipment.

The non-woven fabric is needle punched for improving permeability of the filter material. This specific form of the fabric helps the liquid to pass through the filter material without causing a higher pressure drop. However, the pore size is reduced as explained below.

The non-woven fabric as the filter material serves for collection of small and big size particles and agglomerates on its surface. A certain fraction of said particles and agglomerates penetrate through the pores in texture of the filter material. It is important to revert them with negative pressure during backwashing procedure for regeneration of the filter and eliminate the pressure drop (AP). Very fine particles, however, are prone to remain in texture of the filter material even if a strong negative pressure is applied through the fabric surface. This problem shortens the service life of the filter material which in turn lowers the filter performance and necessitate replacement of the filter screen. In order to solve this problem, the inventor made trials with different surface characteristics and noted that a calendering treatment of the non-woven fabric ensures better cleaning properties in backwashing. Said pre-treatment before usage of the nonwoven fabric as a filter material limits deep penetration of the very fine particles and increases filter performance as explained above.

Calendering can be applied to one or both sides of the flattened filter layer (13). Preferably, both sides of the filter layer (13) is treated with calendering which advantageously improve filtration of very fine particles. In a further embodiment, the filter layer (13) is also coated with a reinforcing polymer for improving agility and endurance thereof. Coating is preferably applied prior to calendering. Reinforcing polymer is applied to the surface of the filter layer (13) as a hot melt at a high temperature (ca. 400 °C). Said polymer may, for instance, be selected from the group consisting of PE, PP and PVC. It was observed that coating of only one surface of the filter layer (13) is generally sufficient even at high pressure values inside the filter apparatus (2).

The calendering process is carried out at a roller pressure of 2 to 1000 kPa, which is more preferably between 100 kPa and 1000 kPa. The calendering process is preferably carried out along with finishing heat tentering at a temperature between 100 °C and 250 °C. The calendering process changes density and stiffness besides the surface characteristics. Therefore, the density value wherever it appears along with calendering is indeed the density of the raw non-woven fabric before treatment with rollers of the calendering step.

Turning back to Fig. 2, the screen layers (11, 11’) of the filter screen (1) can be determined depending on chemical and physical properties of the fluids to be filtered. The material of said screen layers (11, 11’) can be selected from carbon steel, all types of stainless steel, duplex, super duplex, bronze, GRP, or polymer structures.

In preferred embodiments, the filter screen (1) according to the present invention may further comprise one or more support layer (12, 12’) in the form of a mesh for supporting filter material of the filter layer (13). The support layer (12, 12’) is preferably provided with a thickness less than that ofthe screen layers (11, 11’). Likewise, the size ofthe holes on the support layer (12, 12’) is less than the size of the holes on the screen layers (11, 11’). This embodiment facilitates the filter material in the filter layer (13) to withstand against high pressure ofthe fluid passing through the filter equipment

In further embodiments, the filter screen (1) according to the present invention further comprises at least one further filter layer (13’) which can be made of the same or a different material than the filter layer (13) explained above. If the filter layers (13, 13’) are made of the same material, i.e. non-woven fabric, the desired density of the material can be divided and apportioned to these two layers. For instance, instead of using a single filter layer (13) with a density of 1000 g/cm², two filter layers (13, 13’) with 500 - 500 g/cm² density values can be used in the filter screen (1). Both layers (13, 13’) can be separated by a support layer (12"). This embodiment is advantageous particularly if the liquid to be filtered contains very fine particles easily penetrating through the filter material which can hardly be removed in backwashing. Deep penetration of very fine particles is thereby interrupted inbetween the both layers (13, 13’). It is also advantageous to divide a thick filter material into two thinner layers with support layers (12, 12’, 12”) as they may then be more rigidly withstand against high pressure of the fluid inside the filter. Therefore, the second filter layer (13’) may preferably be supported by an additional support layer (12’, 12”).

In another embodiment, the second filter layer (13’) can be provided with a different material such as activated carbon and/or sand. The combined effect with nonwoven fabric makes this embodiment unique in terms of the filtration performance for effectively reducing of turbidity and suspended solids. In a preferred embodiment, the second filter layer (13’) is provided with activated carbon. In another embodiment, the second filter layer (13’) is provided with sand, such as a sand pack. In a further embodiment, the second filter layer (13’) is provided with activated carbon and sand either as a mixture or separate layers.

Turning back to Fig. 1, the filter screen (1) as explained above is placed into a filter apparatus (2) having an inlet (21) and outlet (22). The liquid to be filtered enters into the filter apparatus (2) through the inlet (21) and then passes through the filter material(s) of the filter layer(s) (13, 13’) whereby the liquid is treated with deep filtration in order to reduce turbidity and leaving suspended solids/agglomerates on the filter material. Depending on the predetermined pressure drop (AP) as measured between the inlet (21) and outlet (22), backwash equipment (3) is activated with an actuation unit (25) driven by a motor (24).

The backwash equipment (3) comprises at least one brush (33) and a plurality of nozzles (31) in fluid communication with a collecting pipe (32) which in turn is connected to a discharge valve (26), preferably on the bottom side of the filter apparatus (2). In the backwashing cycle, a negative pressure is applied on the nozzles (31) such that the dirtiness accumulated on the filter layer (13) is eradicated with vacuum and is discharged by means of the collecting pipe (32) and the discharge valve (26). It has been noted that nozzles per se wouldn’t be sufficiently effective for removing dirtiness accumulated on the filter material. This is because the filter material made of nonwoven fabric carries out deep filtration and dirtiness accumulates not only on the surface but also through the texture of the filter material. The dirtiness can be versatile depending on the source of water which may contain fine particles as well as much larger agglomerates, and this requires a more versatile cleaning of the filter surface. The brush(es) (33) on the backwash equipment (3) in addition to the nozzles (31) can therefore meet this requirement and remove majority of the dirtiness on the filter material so that the nozzles (31) would be more effective in suction of the deeply penetrated dirtiness in cross-sectional area of the filter material. In an advantageous embodiment, the nozzles (31) as used in the backwash equipment (3) has a specific structure as shown in Figures 3a and 3b. Accordingly, the nozzles (31) having a tubular body have a sucking end portion (312) and a narrowing portion (311) which has a cross-sectional area smaller than that of said sucking end portion (312). With this specific arrangement, the negative pressure at the sucking end portion (312) increases which eventually causes a stronger suction capability and better cleaning performance over the filter material. This also ensures less amount of drainage liquid to be discharged from the filter apparatus (2).

The inventor has tested the filter apparatus of the present invention in various tests as shown in the following examples which, however, shouldn’t be construed as limiting the invention in anyway.

Examples

Filter screens used in the test sites were prepared with filter material of the following types:

Type 1 - Technical data sheet

• Needle punched

• Composition: 100% Polyester staple fiber

• Fibre length 60 mm

• Fiber dTex: 3,3 dtex / 6,7 dtex (50/50)

• Weight per square meter (density): 1000 g/m² [± 10%]

• Thickness 4,00 mm [± 10%] Wide 160 cm

• Finishing: Heat tentering with calendering at 300 kPA

Type 2 - Technical data sheet

• Needle punched.

• Composition: 100% Polyester staple fiber

• Fibre length 60 mm

• Fiber dTex: 3,3 dtex / 6,7 dtex (50/50)

• Weight per square meter (density): 1500 g/m² [± 10%]

• Thickness 6,00 mm [±10%] Wide 160 cm

• Finishing: Heat tentering with calendering at 300 kPA

Example 1. Filtration Tests in Drinking Water Treatment Plant

Two filter apparatus prepared with Type-1 and Type-2 filter materials were skid mounted in a water treatment plant supplying mains water to the city whereby dam water is processed with aeration - agitation - settling - sand filtration - final disinfection. The dirty water used for backwashing of the sands was treated with the filters prepared for the tests. Effluent of the sand backwashing process was connected to the inlet of the filter apparatus. Water to be filtered was fed to the filter apparatus with a flow rate of 4 m³/h. Samples were taken at the inlet, outlet and drainage line of the filter apparatus. Turbidity (NTU) and Total Suspended Solids (TSS) were measured at various differential pressure (pressure drop) values (AP) as shown in Tables 1-4.

Table 1

Table 2

* Measurement tools indicate ''overrange" when TSS is over 750 mg/l and Turbidity is over 1000 NTU.

Table 3

Table 4

The difference in turbidity between the inlet and outlet water was notable and visible. It was observed that efficiency of the filter is increased if filtration is carried out at low levels of AP. Notably, efficiency of the filter type-1 (density = 500 g/m²) was better if AP is below 0.8 bar. Likewise, efficiency of the filter type-2 (density = 1000 g/m²) was better if AP is below 0.8 bar and particularly 0.4 bar.

Example 2. Filtration Tests in Biomass Energy Plant

A filter apparatus prepared with Type-1 filter material was skid mounted in a Biomass Energy generating plant using of well water whereby said well water is normally treated with Turbidex - softening and further treatment steps. The filter apparatus was connected to treat raw well water.

The filter apparatus has been designed to work at 100 m³/h and 5 bar. Samples were taken at the inlet, outlet and drainage line of the filter apparatus. Turbidity (NTU) and Total Suspended Solids (TSS) were measured at various times of the operation as shown in Table 5.

Table 5

Example 3. Filtration Tests in Mineral Water Bottling Plant

A filter apparatus prepared with Type-1 filter material was skid mounted in a mineral water bottling plant. The filter apparatus was mounted to treat mineral water.

The filter apparatus has been designed to work at 7 m³/h. Samples were taken at the inlet, outlet and drainage line of the filter apparatus. Turbidity (NTU) and Total Suspended Solids (TSS) were measured at various times of the operation as shown in Table 6, and surprisingly, mineral water which normally appeared very clear at first sight gave veiy dirty liquid in the drainage line connected to the backwash equipment Table 6

Underrange (<1 ppm] Overrange (>1000 NTU]

Example 4. Filtration Tests in Tire Production Plant

A filter apparatus prepared with Type-1 filter material was skid mounted to the cooling water of the extruder line of a tire company. The filter apparatus has been designed to work at 7 m³/h. Samples were taken at the inlet, outlet and drainage line of the filter apparatus. Turbidity [NTU] and Total Suspended Solids [TSS] were measured at various times of the operation as shown in Table 7.

Table 7

* Overrange (>750 ppm )

** In this application, high amount of dirt particles (rubber raw materials) come continuously to the cooling water reservoir. The goal is to stop addition ofclean water for dilution and controlling TSS concentration by only applying filtration to keep TSS at desired level. The need for adding clean water after the fourth sampling was eliminated and 10 m³ of water per day was saved by virtue of the filtration system.

Example 5. Filtration Tests in Pipe & Profile Industry

A filter apparatus prepared with Type-1 filter material was skid mounted in a cleaning water supply system used for washing of pipes and metal profiles produced in a metal factory. The production plant was comprising a process having sections of: product washing - drum filter - FeCh dosing in water tank - settling tank - water tank.

The dirty water accumulated in the water tank was treated with the filter prepared for the tests. Water to be filtered was fed to the filter apparatus with a flow rate of 2 m³/h. Samples were taken at the inlet and outlet of the filter apparatus. Turbidity (NTU) and Total Suspended Solids (TSS) were measured as shown in Table 8.

Table 8

Example 6. Filtration Tests in Mains Water

Three filter apparatus prepared with Type-1 filter material were skid mounted in mains water supply line of different domestic buildings in three different locations for improving quality of the tap water. Filtration was continuously monitored by taking samples at the inlet and outlet of the filter apparatus. Turbidity (NTU) and Total Suspended Solids (TSS) were measured as shown in Table 9. Table 9

* Underrange (<1 ppm)

Example 7. Filtration Tests in Well Water

A filter apparatus prepared with Type-1 filter material was skid mounted to a water pipeline of a well at a flow rate of 20-25 m³/h. Turbidity (NTU) and Total Suspended Solids (TSS) were measured as shown in Table 10.

Table 10

In all experiments, it was noted that the filter material was easily cleaned with backwash equipment of the filter apparatus within a short period in order and AP was brought to the desired level (<0.1 bar). The filters provided highest efficiency when AP<0.8 bar, and more particularly when AP<0.4 bar.

Claims

1. A filter apparatus (2) of industrial type for reducing turbidity and suspended solids in a liquid, comprising a filter housing (23), a filter screen (1) of hollow shape concentrically located in said filter housing (23), an inlet (21) for supplying liquid to be filtered on inner surface (14) of the filter screen (1), an outlet (22) carrying filtrated liquid out of the filter housing (23), and a backwash equipment (3) for cleaning the inner surface (14) of the filter screen (1), characterized in that; the filter screen (1) comprises atleasttwo screen layers (11, 11’) and a filter layer (13) disposed therebetween, said filter layer (13) is composed of a non-woven fabric which is made up by polymer or copolymer fibers, and said backwash equipment (3) is rotatably placed into the inner volume of the filter screen (1), and comprising at least a brush (33), at least one nozzle (31) and a collection pipe (32) in fluid communication with said nozzles (31).

2. A filter apparatus (2) according to claim 1 wherein, the filter layer (13) made of a nonwoven fabric has a density value between 200 and 1500 g/m².

3. A filter apparatus (2) according to claim 1 wherein said non-woven fabric has a structure which is needle punched and surface modified with calendering before being disposed into the filter screen (1).

4. A filter apparatus (2) according to claim 2 wherein density of the non-woven fabric is at least 500 g/m².

5. A filter apparatus (2) according to claim 4 wherein density of the non-woven fabric is from 500 g/m² to 1500 g/m².

6. A filter apparatus (2) according to claim 3 wherein the calendering is carried out at a roller pressure of 2 to 1000 kPa.

7. A filter apparatus (2) according to claim 6 wherein the calendering is carried out at a roller pressure between 100 kPa and 1000 kPa.

8. A filter apparatus (2) according to claim 3 wherein the calendering is carried out with heat tentering at a temperature between 100 °C and 250 °C.

9. A filter apparatus (2) according to claim 1 wherein fibers of the non-woven fabric are made of polyester or polypropylene.

10. A filter apparatus (2) accordingto claim 9 wherein the polyester is ethylene polyester (PET) or PCDT polyester.

11. A filter apparatus (2) according to claim 1 wherein the filter layer (13) is divided into two separate layers (13, 13’).

12. A filter apparatus (2) according to claim 1 wherein the filter screen (1) further comprises at least one support layer (12, 12’, 12”) forming a mesh for supporting filter material of the filter layer (13).

13. A filter apparatus (2) according to claim 12 wherein the support layer (12, 12’, 12”) comprises holes having dimensions less than those of the screen layers (11, 11’).

14. A filter apparatus (2) according to claim 11 wherein the filter screen (1) further comprises at least one further filter layer (13’) provided with activated carbon and/or sand.

15. A filter apparatus (2) according to claim 1 wherein the collecting pipe (32) is connected to a discharge valve (26) such that a negative pressure is created in opening ends ofthe nozzles (31) for sucking dirtiness accumulated on said inner surface (14).

16. A filter apparatus (2) according to claim 1 wherein the filter apparatus (2) further comprises an actuation unit (25) driven by a motor (24) for rotatably moving the collecting pipe (32) along with nozzles (31) and brush(es) (33).

17. A filter apparatus (2) according to claim 16 wherein the collecting pipe (32) is configured to have a helical movement along the inner surface (14) ofthe filter screen (1).

18. A filter apparatus (2) according to claim 1 wherein the filter apparatus (2) is configured to operate the backwash equipment (3) ata pressure drop level of AP<0.8 bar, more preferably AP<0.4 bar.

19. A filter apparatus (2) according to claim 3 wherein calendering is applied to both sides of the filter layer (13).

20. A filter apparatus (2) according to claim 1 wherein the surface of the filter layer (13) comprises a coating with a reinforcing polymer.

21. A filter apparatus (2) according to claim 20 wherein the reinforcing polymer is selected from the group consisting of PE, PP and PVC.

22. A filter apparatus (2) according to claim 1 wherein the nozzle (31) comprises a sucking end portion (312) and a narrowing portion (311) which has a cross-sectional area smaller than that of said sucking end portion (312).

23. A method for filtrating a liquid containing particles comprising the steps of: providing a filter apparatus (2) according to any of the claims 1-22, supplying the liquid to be filtered through the inlet (21) of the filter apparatus (2) and filtrating the liquid through the filter screen (1) followed by discharging the filtrated liquid through the outlet (22), measuring the pressure difference between inlet (21) and outlet (22) of the filter apparatus (2), and activating the backwash equipment (3) once the pressure drop (AP) reaches to a predetermined value.

24. A method according to claim 23 wherein the pressure drop level is AP<0.8 bar, more preferably AP<0.4 bar.

25. A method for producing a filter apparatus (2) according to any of the claims 1-22, comprising the steps of: providing a filter housing (23) having an inlet (21) and outlet (22), providing a filter screen (1) and a backwash equipment (3) for cleaning the inner surface (14) of the filter screen (1), wherein; the filter screen (1) comprises at least two screen layers (11, 11’) and a filter layer (13) disposed therebetween, and said filter layer (13) is composed of a nonwoven fabric which is made up by polymer or copolymer fibers, and

19 - said backwash equipment (3) is rotatably placed into the inner volume of the filter screen (1), and comprising at least a brush (33), plurality of nozzles (31) and a collection pipe (32) in fluid communication with said nozzles (31), mounting said filter screen (1) and backwash equipment (3) concentrically into the filter housing (23). A method according to claim 25 wherein the filter layer (13) made of a non-woven fabric has a density value between 200 and 1500 g/m². A method according to claim 25 wherein said method further comprises needle punching and modifying surface of the non-woven fabric with calendering before being disposed into the filter screen (1). A method according to claim 27 wherein calendering is applied to both sides of the filter layer (13). A method according to claim 27 wherein the method comprises coating of a reinforcing polymer to at least one surface of the filter layer (13) prior to calendering. Use of the filter apparatus (2) according to any of the claims 1-22 in treatment of a liquid in a drinking water treatment plant, biomass energy plant, mineral water bottling plant, tire production plant, metal pipe and profile production plant, well water supply line or a mains water supply line.

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