Method for increasing the concentration of pathogens in a water sample, method for analysing a water sample, and device for the concentration of pathogens in water

Abstract

A method for increasing the concentration of pathogens in a water sample, wherein the method comprises: providing a water sample in a concentration deposit; performing concentration steps comprising: filtering water from the concentration deposit, the filtering step comprising circulating water from the concentration deposit through a tangential flow filter to obtain a permeate of filtered water and a retentate of concentrated water and circulating the retentate back to the concentration deposit and the permeate to a filtered water deposit; backflushing the tangential flow filter by circulating filtered water from the filtered water deposit through the tangential flow filter in a backflushing direction to remove pathogens from the tangential flow filter; and recovering the water from the concentration deposit as a concentrated water sample.

Description

[0001] METHOD FOR INCREASING THE CONCENTRATION OF PATHOGENS IN A WATER SAMPLE, METHOD FOR ANALYSING A WATER SAMPLE, AND DEVICE FOR THE CONCENTRATION OF PATHOGENS IN WATER

[0002] The present application claims the benefit and priority of EP2483298.7 filed on November 29, 2024.

[0003] The present disclosure relates to a method for increasing the concentration of pathogens in a water sample, a method for analysing pathogens in a water sample and a device for the concentration of pathogens in water.

[0004] BACKGROUND

[0005] Water is an essential resource for many aspects of the world. Waterborne pathogen microorganisms are recognized as tangible threats to public health. In addition, pathogen contamination in water poses a serious risk in those water resources. Pathogens are present in wastewater, potable water, treated or untreated recreational water, saline water, groundwater, rivers, lakes, coastal environments, estuaries, etc. Pathogens can also be found in water sources from facilities such as wastewater treatment plants and refrigeration towers.

[0006] To address pathogen contamination, water from different facilities is analysed overtime to check its quality, by extracting water samples from a water source of a facility. Monitoring the levels of a certain indicator organism (the indicator organism being a pathogen such as faecal coliforms, Escherichia coli spp, Legionella spp, Clostridium spp, Salmonella spp, Listeria spp, Campylobacter spp, Pseudomonas aeruginosa, etc.) is a common approach for quantifying the potential pathogen loads in ambient water bodies.

[0007] Pathogens in water can be analysed, detected, and quantified by several methods, which include cell cultures, polymerase chain reaction (PCR) techniques and the use of biosensors. The quality criteria for water ranges from between 1 and 106colonyforming units per millilitre (CFU / mL), depending on the type of water (freshwater, wastewater, etc.) and the type of pathogen or indicator organism to be analysed.

[0008] Biosensors are analytical devices used for the detection of a chemical and / or biological substance. Biosensors can be used to analyse the presence and concentration of a pathogen in a water sample. Biosensors have the advantage of providing results much faster than other methods, and some biosensors may be portable, so they can be used at the water source where the water sample has been collected without the need of taking the sample to a lab. However, methods of determination of pathogens based on biosensors usually present a limit of detection (LOD) of around 1000 CFU / mL, while the concentration of pathogens in water samples is usually lower than the limit of detection of the biosensor. Therefore, the use of biosensors for monitoring the presence and the concentration of pathogens in facilities is still limited, and currently biosensors may not be useful for an early detection of pathogens when their concentration in the water sample is still low.

[0009] Water samples are usually transported to a laboratory to be analysed. Microbiological techniques, such as cell culture and PCR techniques, are processes that allow detection and quantification of microorganisms in water samples even in a low concentration, although these microbiological techniques sometimes require a concentration step to increase the concentration of pathogens in the water samples and to reduce the technique limit of quantification (LOQ). These techniques are also very sensitive and require an extensive period of time in order to perform the analysis. This is a slow process that implies that the overall process of analysing the water sample takes at least 24 to 48 hours. Therefore, these techniques do not allow fast detection of pathogens when their concentration is still low. Furthermore, they are not portable, and therefore are not suitable to be performed in-situ at the water source where the water sample has been collected. This implies an uncertainty in the quality of the water source from which the water sample was taken during the long waiting period until the analysis has been completed. This implies that the water source where the water sample has been obtained is running for an extended period without knowing its pathogen concentration and therefore without knowing the adequateness of the water for other living organisms.

[0010] Another problem with these pathogen analysing methods is that the water sample has to be transported from the water source, such as a facility, to a laboratory in order to be analysed. This task can be cumbersome, and also consumes a relevant amount of time.

[0011] The methods and the system of the present disclosure address this problem by presenting a method and a system that allows detecting the presence of pathogens in a water sample quickly, and even in low concentrations. SUMMARY

[0012] In a first aspect of the present disclosure, a method for increasing the concentration of pathogens in a water sample is provided. The method comprises providing water containing pathogens in a concentration deposit. The method comprises performing concentration steps. The concentration steps comprise filtering the water from the concentration deposit. The filtering step comprises circulating the water from the concentration deposit through a tangential flow filter to obtain a permeate of filtered water and a retentate of concentrated water. The filtering step also comprises circulating the retentate back to the concentration deposit and the permeate to a filtered water deposit. The concentration steps comprise backflushing the tangential flow filter by circulating filtered water from the filtered water deposit through the tangential flow filter in a backflushing direction to dislodge pathogens from the tangential flow filter. The method also comprises recovering the water from the concentration deposit as a concentrated water sample which is adequate to be analysed.

[0013] The terms "permeate", “filtered water” and their derivatives are to be understood as the part of the fluid that has passed through the membrane of the tangential flow filter, which comprises filtered water, without pathogens or with a lower concentration of pathogens with respect to the initial water sample. The terms "retentate", “concentrated water” and its derivatives are to be understood as the part of the fluid that did not permeate the membrane of the filter, and that comprises a higher concentration of pathogens or other microorganisms than initial water provided to the concentration deposit.

[0014] The method of the present disclosure allows obtaining a highly concentrated water sample, that is, a sample with a higher concentration of a particular microorganism, such as a pathogen, than the water sample collected in the water source or facility. The method of the present disclosure allows the concentration of the water sample in at least one or two orders of magnitude, in a period of time of less than one and a half hours. For example, it allows the concentration of a water sample having a volume of 3 litres into a highly concentrated water sample having a volume of less than 50 millilitres, for example 30 millilitres, with a much higher concentration of pathogens. By virtue of the higher concentration, the analysis can be performed with a biosensor. This means that the water sample can be analysed in-situ at the water source or facility where the sample has been taken, which results in a quick analysis, detection, and quantification of the water sample. It does not require transportation into a laboratory to perform the analysis. An analysis of the quality of the water in-situ can be performed in less than 30 minutes. By having an analysis that is quick, it is possible to know the adequateness of the water from a water source in a brief period of time. Earlier detection of pathogens in water also enables modifying parameters in the water source or facility where the sample has been taken to enhance the quality of the water.

[0015] In addition, the highly concentrated water sample can be also transported to a laboratory to be analysed therein by using a cell culture technique, a PCR technique, a biosensor, or any other technique. By virtue of the higher concentration, the quality of the analysis may be improved in all cases.

[0016] Some Standards on the quality of water require performing a specific analysis. For example, some standards require performing a Polymerase Chain Reaction (qPCR), which is a method that is time-consuming and has to be performed in a laboratory. However, since methods according to the present disclosure allow the determination of the quality of the water sample quickly, if the analysis results show that the water sample has an inadequate quantity of pathogens, the parameters of the water source can immediately be modified in order to obtain a more adequate water, without having to wait 48 hours for the qPCR or other Standards analysis to be performed. For example, the treatment of a wastewater treatment plant can be modified. If the analysis results show that the water sample has an adequate quality of pathogens, the water from the water source can be safely used, e.g. for agriculture, recreational, and / or drinking purposes, while an analysis according to the Standards like regulation (Ell) 2020 / 741 of the European Parliament and of the Council of 25 May 2020 on minimum requirements for water reuse is performed.

[0017] The filtering step is continued during a prolonged period of time to concentrate the water in the concentration deposit. In an example, the filtering step is performed until at least one backflushing condition occur, such as when a predetermined maximum time lapses. Clogging of the tangential flow filter can be detected, for example, by detecting if the volume inside the concentration deposit is below a determined value.

[0018] By virtue of the backflushing, the method generates less clogging of the tangential flow filter, thus easing the maintenance of a device where the method could be performed.

[0019] In an example, performing concentration steps comprises a purging step. The purging step is performed to purge water from tubes through which fluid is conducted during both the filtering step and the backflushing step. The purging step comprises purging the tangential flow filter. During the purging step, water present in the tangential flow filter, common tubes and pump is returned back to the concentration deposit. In an example, the purge step also comprises forcing air towards the tangential flow filter.

[0020] In an example, the water from the concentration deposit is circulated to the tangential flow filter during the filtering step through a pump, and the filtered water is circulated during the backflush step through same pump, by circulating the filtered water through a conduit bypassing the tangential flow filter, entering the tangential flow filter through the permeate outlet of the tangential flow filter. Therefore, during the filtering step, the purging step and the backflushing step, the water is pumped by the same peristaltic pump. By virtue of using a single peristaltic pump, the method is simplified, and it is more cost-effective as less pumps are needed to circulate the water. The use of a single pump also implies that the volume of the device in which the method is applied can be reduced. As the same pump is used during both the filtering step and the backflushing step, during the purge step the pump is purged.

[0021] In an alternative example, during the backflush step the filtered water is circulated from the filtered water deposit to the tangential flow filter. Filtered water enters the tangential flow filter through the permeate outlet of the tangential flow filter without circulating through a conduit bypassing the tangential flow filter. This alternative example would require one pump for the filtering step and one pump for the backflushing step. As in this alternative example two different pumps are used, the purging step may be avoided.

[0022] In a second aspect of the present disclosure, a method for analysing samples in water is provided. The method of the second aspect comprises concentrating pathogens in water using the method of the first aspect and analysing the recovered water with a biosensor. By virtue of concentrating pathogens in water using the method of the first aspect, the overall method of analysing samples in water can be performed in less than two hours. This time period is an improvement over the prior art, where the overall method could take 24 to 48 hours. The biosensor may be placed in the same device in which the method of the first aspect is performed, which further reduces the time in which the analysis is performed.

[0023] In a third aspect of the present disclosure, a device for the concentration of pathogens in water is provided. The device according to the third aspect of the disclosure allows increasing the concentration of pathogens in a water sample. The device according to the third aspect comprises: a concentration deposit; a filtered water deposit; a tangential flow filter; a filter inlet tube connecting an outlet of the concentration deposit with the feed inlet of the tangential flow filter; a first filter outlet tube connecting the permeate outlet of the tangential flow filter with the filtered water deposit; a second filter outlet tube connecting the retentate outlet of the tangential flow filter with the concentration deposit.

[0024] The device can comprise valves to regulate and / or impede the flow of water through the tubes. These valves have at least two positions, and can be two-way valves, three- way valves or valves having more than three ways. In an example, the device comprises a proportional valve placed in the first filter outlet tube configured to regulate the pressure of the first filter outlet tube to a predetermined pressure.

[0025] In an example, the device comprises a tangential flow filter bypass tube connecting the filter inlet tube with the second filter outlet tube, and a backflush tube connecting the filtered water deposit with the filter inlet tube.

[0026] In an example, the device comprises a peristaltic pump configured to pump the water through the filter inlet tube, the first filter outlet tube, the second filter outlet tube, the tangential flow filter bypass tube and through the backflush tube.

[0027] In an example, the device is a portable device. That is, the device can easily be installed in facilities such as wastewater treatment plants. In an example, the concentration deposit has a volume of less than 3 litres, preferably a volume of less than 2.5 litres, preferably a volume of less than 2 litres. The device also allows increasing the concentration of the pathogens in the same facility the water sample has been collected.

[0028] BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Non-limiting examples of the present disclosure will be described in the following, with reference to the appended drawings, in which: Figure 1A illustrates a flow chart of a method according to the first aspect of the disclosure.

[0030] Figure 1B illustrates a flow chart of a method according to the first aspect of the disclosure.

[0031] Figure 1C illustrates a flow chart of a method according to the first aspect of the disclosure.

[0032] Figure 2 illustrates a schematic representation of an example of a device according to the third aspect of the disclosure.

[0033] Figures 3A, 3B and 3C illustrate an example of the flow of fluid during a filtering step, a purging step, and a backflushing step in the device according to Figure 2.

[0034] Figure 4 illustrates a schematic representation of an example of a device according to the third aspect of the disclosure.

[0035] Figure 5 illustrates a schematic representation of an example of a device according to the third aspect of the disclosure.

[0036] Figure 6 illustrates a flow chart of a method according to the first aspect of the disclosure.

[0037] Figures 7A-7E illustrate an example of the flow of fluid during steps of the method of Figure 6 in the device according to Figure 5.

[0038] Figure 8 illustrates a flow chart of a method according to the second aspect of the disclosure.

[0039] DETAILED DESCRIPTION OF EXAMPLES

[0040] Figures 1A and 1 B illustrate a method 1000a for increasing the concentration of pathogens in a water sample, such as a water sample from a wastewater treatment plant. The method comprises providing at 101 water containing pathogens in a concentration deposit and performing concentration steps 100a. The concentration steps 100a, comprise filtering at 102 the water from the concentration deposit, by circulating the water from the concentration deposit through a tangential flow filter to perform a tangential flow filtration and then backflushing at 104 the tangential flow filter. Figure 1C illustrate a preferred example in which the concentration steps 100b comprise a purging step 103.

[0041] Figure 2 illustrates an example of a device 200 suitable for performing methods according to the disclosure. Essentially, the device 200 comprises a tangential flow filter 500 that performs a tangential flow filtration during the filtering step 102. The tangential flow filter 500 comprises a feed inlet 501 , a retentate outlet 502, a permeate outlet 503, and a membrane 510. The membrane 510 defines a feed chamber 511 of the filter and a permeate chamber 513 of the filter. The feed inlet 501 and the retentate outlet 502 are placed in the feed chamber 511 while the permeate outlet 503 is placed in the permeate chamber 513.

[0042] Tangential flow filters are preferred because they use tangential flow filtration or crossflow filtration. Thus, the feed flow travel tangentially across the surface of the filter, rather than into the filter, and therefore the filter cake (which can clog the filter) is substantially washed away during the filtration process, reducing the accumulation of solids, particles and pathogens in the filter and increasing the length of time that a filter unit can be operational. A principal advantage of this is that it can be a mostly continuous process, unlike batch-wise dead-end filtration. The main driving force of crossflow filtration process is transmembrane pressure. Examples of tangential flow filters include tangential flow filters with flat plate membranes, hollow fibre membranes, spiral wound modules, or disc membranes, as well as tangential flow filters made of polymeric or organic materials.

[0043] In an example, the membrane is a disc membrane. The size of the pores of the membrane 510 is in accordance with the size of the pathogen to be concentrated. The pathogens to be concentrated can comprise at least one of faecal coliforms, Escherichia coli spp, Legionella spp, Clostridium spp, Salmonella spp, Listeria spp, Campylobacter spp, Pseudomonas aeruginosa, etc, preferably Escherichia coli spp. In an example, the size of the pores of the membrane is of at least 1 pm. In an example, the tangential flow filter 500 comprises a 0,14 pm membrane 510, to concentrate pathogens such as Escherichia coli spp. The tangential flow filter may have any other membrane size adapted to another pathogen. A higher pore size could increase the efficiency of the device. In a tangential flow filter, a feed passes through the membrane 510 of the filter 500 tangentially at positive pressure relative to the permeate chamber 513. In this example, the feed is water from the concentration deposit 201 . A pressure higher in the feed chamber 511 than in the permeate chamber 513 improves the filtration. A proportion of the material which is smaller than the membrane pore size passes through the membrane as permeate or filtrate, while everything else (which include particles and the pathogens) is retained on the feed chamber 511 as retentate. The permeate is circulated from the permeate outlet 503 to a filtered water deposit 203, where is collected. The retentate is circulated through the retentate outlet 502 of the tangential flow filter 500 back to the concentration deposit 201 . As a volume of water with a low concentration of pathogens has permeated the membrane 510 of the filter, the retentate obtained at the filtering step 102 comprises water with a higher concentration of pathogens.

[0044] The method 1000a, 1000b of Figures 1 B, 1C comprises a backflushing step 104 to clean the tangential flow filter 500. The backflushing step 104 allows dislodging solids, particles and pathogens clogging the membrane towards the concentration deposit 201 , also increasing the concentration of pathogens in this deposit 201. Solids and pathogens are dislodged, for example, by pumping a flow of water through the filter membrane and conduits in a different direction than the direction of the flow during the filtering step 102.

[0045] The method 1000a, 1000b seeks to recover water with a high concentration of pathogens, contrary to known systems that aim to obtain filtered, pathogen-free water for recreational, domestic, or agricultural uses. Therefore, the filtered water resultant from the filtering step 102 can be considered as a byproduct. As filtered water from the filtered water deposit 203, which can be considered a byproduct of the method 1000a, 1000b, is used during the backflush, the method 1000a, 1000b avoids the need for an external water input to perform the backflushing. The method 1000a, 1000b is then sustainable as less water is used, and its economic cost is reduced. Thus, a device able to perform the method does not require an additional deposit to store clean water for performing the backflushing step 104, and the size of the device and the maintenance needed is also reduced. This improves the portability of the device 200.

[0046] The method 1000a, 1000b also comprises a recovering step 105. The recovering step 105 is performed after the filtering step 102. During the recovering step 105, the water from the concentration deposit 201 is recovered. Therefore, the water that has been recovered, which has a higher concentration of pathogens than the water sample initially provided to the concentration deposit during the providing step 101 , can be analysed, for example by using a biosensor.

[0047] The backflushing step 104 is advantageously performed before the recovering step 105. By performing the steps in this order, solids, particles and pathogens that were stuck in the tangential flow filter 500 are sent back to the concentration deposit 201 before the recovering step 105, and the water recovered during the recovering step 105 has a higher concentration of pathogens than if the backflushing step 104 was performed after the recovering step 105.

[0048] In an example, during the filtering step 102 and during the backflushing step 104 the water is pumped by a peristaltic pump. In an example, the same peristaltic pump is used for the filtering step 102 and for the backflushing step 104.

[0049] In a preferred example, the method 1000b also comprises a purging step 103 to purge the tangential flow filter so that water from the tangential flow filter is returned back from the tangential flow filter to the concentration deposit 201. The purging step 103 also comprises purging the tubes common to the filtering step 102 and the backflushing step 104 and purging the pump. The purge ensures that the water used during the backflushing step 104 does not comprise pathogens, or concentrated water,

[0050] In an example, the steps of the method 1000a, 1000b are controlled by a controller. That is, the controller is configured to perform the method of the first aspect. Therefore, the method 1000a, 1000b can be automated.

[0051] Figure 2 shows a device 200 configured to perform any of the methods 1000a, 1000b disclosed in Figures 1A, 1 B and 1C. The device 200 comprises a concentration deposit 201 , a filtered water deposit 203, and a tangential flow filter 500. The device 200 comprises a filter inlet tube 451 connecting an outlet of the concentration deposit 201 with a feed inlet 501 of the tangential flow filter 500. The filter inlet tube 451 allows conducting water from the concentration deposit 201 to the tangential flow filter 500. The device 200 also comprises a first filter outlet tube 452 connecting the retentate outlet 502 of the tangential flow filter 500 with the concentration deposit 201 , and a second filter outlet tube 453 connecting the permeate outlet 503 of the tangential flow filter 500 with the filtered water deposit 203. The device 200 disclosed comprises only two deposits 201 , 203, and therefore the device has reduced dimensions. The reduced size of the device eases its portability. The concentration deposit 201 may have a volume of less than 3 litres, preferably a volume of less than 2.5 litres. The filtered water deposit 203 has a volume of less than 3 litres, preferably a volume of less than 2.5 litres, preferably a volume lesser than the volume of the concentration deposit.

[0052] Figure 3A illustrates the general flow of water in the device 200 of Figure 2 during the filtering step 102. After the step of providing at 101 water containing pathogens in the concentration deposit 201 , the filtering step 102 is initialized. During the filtering step 102, water from the concentration deposit 201 is circulated through the filter inlet tube 451 to the feed inlet 501 of the filter 500. The water is filtered by the tangential flow filter 500. Most of the pathogens do not permeate the membrane 510 and are circulated back to the concentration deposit 201 through the first filter outlet tube 452. The permeate, which is the part of the fluid that passed through the membrane 510 of the tangential flow filter, is circulated through the second filter outlet tube 453 into the filtered water deposit 203. By virtue of the filtering step 102, the concentration of pathogens in the water from the concentration deposit 201 is increased.

[0053] Figure 3B illustrates the general flow of water in the device 200 of Figure 2 during the purging step 103. After the filtering step 102, some residual water containing pathogens may be present in the tubes in which water was circulated during the filtering step 102, such as the filter inlet tube 451 and the first filter outlet tube 452. During the purging step 103, the water is circulated in a direction which is opposite to the direction of the flow of water during the filtering step 102. That is, the purging step 103 comprises circulating air tangentially at the tangential flow filter 500, from the retentate outlet 502 to the feed inlet 501. Due to the circulation of air, the water is also circulated tangentially at the tangential flow filter 500. In the purging step 103, the liquid present in the tubes, the tangential flow filter or in a pump placed in the filter inlet tube 451 are returned back to the concentration deposit 201. Solids at the tubes are returned back to the concentration deposit. The purging step 103 allows recovering of the water while removing the liquid in the tubes before the backflushing step 104. The purging step 103 can be improved by conducting air towards the tangential flow filter. The air may be introduced to the device 200 through an air entrance placed in the filtered water deposit 203 and circulated through the tangential flow filter 500 to the concentration deposit 201 improving the circulation of the residual water towards the concentration deposit 201. The air may be removed from the device through the first filter outlet tube 452 during the recovering step 105.

[0054] Figure 3C illustrates the general flow of water in the device 200 of Figure 2 during the backflushing step 104. During the backflushing step 104, filtered water from the filtered water deposit 203 is circulated through the tangential flow filter 500 in a backflushing direction to dislodge solids, particles and pathogens from the membrane 510. The backflushing direction is defined by the direction from a permeate outlet 503 of the tangential flow filter 500 to a retentate outlet 502 of the tangential flow filter so that solids, particles and pathogens are dislodged from the tangential flow filter and circulated towards the concentration deposit. Thus, during the backflushing step 104 the filtered water from the filtered water deposit is circulated from the permeate outlet 503 to the retentate outlet 502. Solids, particles and pathogens that may have been stuck in the side of membrane 510 corresponding to the feed chamber 511 are pushed by the water that is circulated through the membrane of the tangential flow filter 500 in the backflushing direction, and are circulated through the first outlet tube 452 back into the concentration deposit 201. That is, during the backflushing step 104, the elements at the interface of the membrane (that is, at the surface of the membrane), which have not been removed from the filter during the purging step, are removed from the tangential flow filter 500 and circulated to the concentration deposit 201. These elements removed during backflush are mostly pathogens, as most of the solids and particles have been removed during the purging step 103. Due to the reception of pathogens from the membrane, the concentration of pathogens at the concentration deposit may be increased regardless of the type of water used during the backflushing step 104. Therefore, the tangential flow filter 500 is cleaned. This allows a new filtering step 102 to be performed. The water from the concentration deposit 201 used during the new filtering step 102 has a concentration higher than the concentration of the water at the concentration deposit during the previous filtering step 102. In addition, as water from the filtered water deposit 203 is used during the backflushing step 104, the device 200 does not require additional deposits and the size of the device is small. The smaller size of the device improves its portability.

[0055] The device 200 may comprise valves to regulate and / or impede the flow of water through the tubes, such as described in accordance with the example of Figures 5 and 6. These valves can be two-way valves or three-way valves, so that the flow of the fluid is directed in a desired direction, or proportional valves. Three-way valves can have more than one position, to allow the pass of the fluid in two different directions. The circulation of the flow of water during the filtering step 102, the purging step 103 and the backflushing step 104 may be obtained by one or more pumps to pump the flow of water through the tubes. That is, the device may comprise a pump configured to pump water from the concentration deposit through the filter inlet tube 451 to the feed inlet 501 of the filter 500. The device may comprise a pump configured to pump liquid back to the concentration deposit 201. The device may comprise a pump configured to pump filtered water from the filtered water deposit 203 through the tangential flow filter in a backflushing direction to remove pathogens from the tangential flow filter, wherein the backflushing direction is defined by the direction from the permeate outlet 503 of the tangential flow filter to the retentate outlet 502 of the tangential flow filter so that solids, particles and pathogens are dislodged from the tangential flow filter and circulated towards the concentration deposit. In an example, the device 200 may comprise a single pump configured to pump water as explained herein, such as described in Figure 5, or may comprise different pumps. In another example, the device 200 may comprise a pump placed at the filter inlet tube 451 to pump water during the filtering step 102 and purging step 103 and a pump placed at the second filter outlet tube 453 to pump water during the backflushing step 104. The pumps may be a peristaltic pump, a piston pump, a lobe pump or a turbopump.

[0056] Figure 4 discloses a second example of a device 200 for the concentration of pathogens in water. The device 200 comprises a concentration deposit 201 , a filtered water deposit 203, a tangential flow filter 500, a filter inlet tube 451 , a first filter outlet tube 452, and a second filter outlet tube 453 such as the device 200 described according to Figure 2. Analogous elements with the elements described in Figures 2, 3A, 3B, 3C have been represented with the same reference signs.

[0057] The device 200 comprises a peristaltic pump 60 to pump the water through the tubes in which the concentration steps 100a, 100b are performed. That is, in the example of Figure 4, the device 200 comprises a single pump to perform the concentration steps 100a, 100b. The peristaltic pump 60 is configured to pump the water though the tangential flow filter 500, the filter inlet tube 451 , the first filter outlet tube 452 and the second filter outlet tube 453 in order to circulate water during the filtering step 102 and the backflushing step 104. In other examples, the pump may be a piston pump, a lobe pump or a turbopump. The pump 60 is placed on the filter inlet tube 451 . The placement of the pump 60 defines a pump feed tube portion 4511 of the filter inlet tube 451 and a filter feed tube portion 4512 of the filter inlet tube 451 , wherein the pump feed tube portion 4511 connects an outlet of the concentration deposit 201 with a feed inlet 601 of the peristaltic pump 60, and wherein the filter feed tube portion 4512 connects an outlet 602 of the peristaltic pump 60 and the feed inlet 501 of tangential flow filter 500. In an example, the pump 60 is a flow rate peristaltic pump, configured to pump water at variable rate pumps and speeds. In an example, the pump is controlled by a controller 9.

[0058] The device 200 comprises a proportional valve 75 placed in the first filter outlet tube 452. The proportional valve 75 is configured to regulate the pressure of the feed chamber 511 to a predetermined pressure. This regulation is performed by regulating the proportion of aperture of the valve, and therefore of the first filter outlet tube 452, which is fluidically connected to the feed chamber 511 , based on the pressure value determined by a pressure probe 811. Thus, the flow of water circulating through the first filter outlet tube 452 is regulated. In an example, the predetermined pressure value in the chamber is of 0.75 bar, and the proportional valve is opened at 60-70% of its maximum opened position before starting the method. Based on the pressure value determined by the pressure probe 811 , the proportion of aperture of the proportional valve 75 is regulated to maintain the predetermined pressure value of the feed chamber 511 at 0.75 bar. By regulating the pressure of the feed chamber 511 , the proportional valve 75 improves the pressure differential between the feed chamber 511 and the permeate chamber 513 of the filter, and therefore improves the filtration of the flow.

[0059] The device 200 comprises a backflush tube 435 connecting the filtered water deposit 203 with the filter inlet tube 451. In the example shown, the backflush tube 435 connects the pump feed tube portion 4511 of the filter inlet tube 451 with the filtered water deposit 203. The backflush tube 435 allows water from the filtered water deposit 203 to be circulated to the tangential flow filter 500 by using the peristaltic pump 60 used during the filtering step 102.

[0060] The device 200 also comprises a tangential flow filter bypass tube 455 connecting the filter inlet tube 451 with the second filter outlet tube 453. In the example shown, the flow filter bypass tube 455 connects the filter feed tube portion 4512 of the filter inlet tube 451 with the second filter outlet tube 453. As stated before, during the backflushing step 104 water is circulated through the tangential flow filter in a backflushing direction to dislodge pathogens that may have been stuck in the membrane 510 by its feed chamber 511 side during the filtering step 102. To dislodge the pathogens, water has to be circulated from the permeate outlet 503 to the retentate outlet 502. If water were circulated through the feed inlet 501 , it would not dislodge the pathogens that clog the membrane by its feed chamber 511 side. The tangential flow filter bypass tube 455 allows bypassing water from the filter inlet tube 451 to the second filter outlet tube 453 and circulating the water in the backflushing direction. Without the flow filter bypass tube 455, the device would require an additional peristaltic pump to pump the water from the filtered water deposit 203 through the first filter outlet tube 452 and to the permeate outlet 502.

[0061] The bypass tube 455 allows the circulation of water from the filtered water deposit 203 into the permeate outlet 503 of the tangential flow filter 500 during the backflushing step 104 by using the same peristaltic pump 60 used to pump water during the filtering step 102. The same peristaltic pump 60 configured to pump the water through the tangential flow filter 500, the filter inlet tube 451 , the first filter outlet tube 452 and the second filter outlet tube 453, is also configured to pump the water through the flow filter bypass tube 455 and the backflush tube 435, allowing the water to be circulated in the concentration steps 100a, 100b by a single peristaltic pump 60. By only having one peristaltic pump 60 to pump the water during the concentration steps 100a, 100b, the size of the device 200 is reduced, increasing its portability.

[0062] The device comprises a three-way valve 73 placed in the filter inlet tube 451 , connecting the filter inlet tube 451 with the backflush tube 435, placed between the peristaltic pump 60 and the concentration deposit 201. The three-way valve 73 controls the circulation of water through the backflush tube 435 into the filter inlet tube 451. The device also comprises a three-way valve 74 placed in the filter inlet tube 451 between the peristaltic pump 60 and the feed inlet 501 of the tangential flow filter 500, which connects the filter inlet tube 451 with the flow filter bypass tube 455. The three-way valve 74 controls the circulation of water through the flow filter bypass tube 455. Both valves 73, 74 change their position before the backflushing 104 step in order to allow the circulation of fluid towards the concentration deposit 201 . Although in Figure 4 the valves 73, 74 have been illustrated as three-way valves, the valves can also be two- way valves comprising two distinct positions to able the circulation of water in two different directions.

[0063] The device 200 also comprises a concentrated water recovery tube 418 to recover the water from the concentration deposit 201 circulating it to an outlet 2005. The device can also comprise a biosensor placed in connection with the outlet 2005. In the example shown, the concentrated water recovery tube 418 is placed fluidically connected to the filter inlet tube 451 and the circulation of water through this tube 418 is controlled by a three-way valve 72. Alternatively, the concentrated water recovery tube 418 can be also connected to an outlet of the concentration deposit instead of being connected to the filter inlet tube 451. The device of the example also comprises a filtered water recovery tube 438 fluidically connected to the filtered water deposit 203 to circulate the water from the filtered water deposit 203 to another outlet 2003. The filtered water deposit 203 can comprise a volume level sensor 803 to check the volume of water in the filtered water deposit 203. The volume level sensor 803 eases the evaluation of when the water from the filtered water deposit 203 can be discharged and later recovered. The filtered water recovery tube 438 can also comprise a filtered outlet valve 77 to enable / disable the flow of water through said filtered water recovery tube 438.

[0064] Optionally, the device also comprises a concentration deposit feed tube 441 connecting the concentration deposit 201 with an inlet 2001 of the device. The concentration deposit feed tube 441 is configured to circulate a water sample from an external source into the concentration deposit 201. The concentration deposit feed tube 441 can be configured to suction water from a water source during the providing water step 101. The device can comprise a supplying pump 61 to pump a water sample from a water source into the concentration deposit 201 through the concentration deposit feed tube 441. The device 200 can also comprise a prefilter to filter solids present in the water sample. The supplying pump 61 improves the supply of the water sample, specially improving the supply of water samples from water sources in which the water conduction is not at pressure, such as wastewater treatment plants. Advantageously, the supplying pump 61 is not configured to pump water through the tangential flow filter 500, the filter inlet tube 451 , the first filter outlet tube 452, the second filter outlet tube 453, the flow filter bypass tube 455 and the backflush tube 435, and only the peristaltic pump 60 pumps water through said tubes.

[0065] Optionally, the device 200 comprises an air entrance 403. This air entrance 403 allows introducing air into the device to improve the purging step and the recovering step.

[0066] The device 200 of Figure 4 also comprises a controller 9 to control the methods 1000a, 1000b by operating the pumps and by opening and closing the valves of the device 200 to allow the circulation of water through the tubes corresponding to each step of the process. That is, the controller is configured to perform the method of the first aspect. By virtue of the controller 9, the method 1000a, 1000b can be automated. By virtue of this automation, the method is faster, requires less manual work to control it, while also eases the control in real time of the pressure on the tangential flow filter, therefore lessening the risk of a malfunction in the tangential flow filter.

[0067] The device 200 also comprises an upper-level sensor 800, a lower-level sensor 801 and an empty level sensor 802 placed on the concentration deposit 201 , and a low- level sensor 803 placed on the filtered water deposit 203, to improve the operation of the device 200. The distance between the empty level sensor 802 and the lower-level sensor 801 is equivalent to the volume of concentrate required for the analysis processes which, depending on the pathogen, it can vary between 15 and 60 millilitres.

[0068] Figure 5 illustrates a third example of a device 200, configured to perform the method 1000a, 1000b and the method 1000c illustrated in Figure 6. The device 200 comprises a cleaning product deposit 204, a cleaning product valve 71 , a supplying pump 61 and a solid filter 504 placed on the concentration deposit feed tube 441 , The device 200 also comprises a concentrated water recovery tube 418 to recover highly-concentrated water to an outlet 2005 of the device, a filtered water recovery tube 438 to recover the filtered water into an outlet 2003 of the device, a discharge pump 63 to pump the water from the filtered water deposit 203 to the outlet 2003, and a filtered outlet valve 77 to able the circulation of water through the filtered water recovery tube 438, and pressure probes 811 , 812. The device can also comprise a dosing valve 78 placed in an outlet 2005. The dosing valve 78 is shown connecting the concentrated water recovery tube 418 with the filtered water recovery tube 438. Analogous elements with the elements described in Figures 2, 3A, 3B, 3C and 4 have been represented with the same reference signs.

[0069] Figure 6 illustrate an example of a method 1000c for increasing the concentration of pathogens in a water sample. The method 1000c in Figure 6 comprises a rinsing step 110, a providing water step 101 , concentration steps 100c, a recovering step 105 and a cleaning step 106. The concentration steps 100c comprise a filtering step 102, a purging step 103, a backflushing step 104. The filtering step 102 is performed until at least one of the backflushing conditions occur, and the concentration steps 100c are performed until a stopping condition is met. The concentration steps 100c also comprise checking 124 backflushing conditions and checking 125 stopping conditions. As illustrated in Figure 6, the method 1000c is an iterative method: If the stopping conditions are not met, a new filtering step 102 is initiated after the backflushing step 104. Since part of the initial water have been filtered during the previous filtering step 102, the water at the concentration deposit 201 at the new filtering step 102 is more concentrated than on the previous filtering step 102. Since a purging step 103 was performed, solids, water and particles at the tubes and at the tangential flow filter 500 have been returned at the concentration deposit 201 . The tubes are clean. Since a backflushing step 104 was performed, the pathogens at the interface of the membrane have also been returned to the concentration deposit 201.

[0070] Figures 7A-7E illustrate the circulation of water during the steps of providing water at 101 (Fig. 7A), filtering at 102 (Fig. 7B), purging at 103 (Fig. 7C), backflushing at 104 (Fig. 7D) and recovering at 105 (Fig. 7E) disclosed in the methods 1000b and 1000c. These steps are described in relation with the device 200 of Figure 5 and are analogous to the steps performed in a device such as illustrated in Figure 4. Following, these steps, as well as the additional steps of rinsing at 110 and cleaning at 106 are described.

[0071] In the examples of Figures 7A-7E, the circulation of water is controlled by a controller 9. The controller 9 is configured to: perform any of the methods 1000a, 1000b, 1000c, receive data from level sensors 800, 801 , 802, 803 and from pressure probes 811 , 812, and based on the data received from the sensor, control the status of the valves 71 , 72, 73, 74, 75, 76, 77, 78 and the pumps 60, 61 , 63 of the device, and control said valves and pumps to perform the methods 1000a, 1000b, 1000c.

[0072] Figure 7A represents the circulation of water during an example of the providing water step 101. During the providing water step 101 , a water sample from a water source to be analysed is introduced into the concentration deposit 201. For example, the water provided has a volume of 3 litres or less. In an example, the step 101 of providing water may comprise suctioning the water from the water source and circulating the suctioned water into the concentration deposit 201 in order to fill the concentration deposit 201. To suction the water, the concentration deposit feed tube 441 is introduced into a water source and water from the water source is suctioned through the concentration deposit feed tube 441. In an example, the controller 9 activates a supplying pump 61 that suctions the water. After filling the concentration deposit 201 to a desired upper threshold, the suction is stopped. Then, the remaining water in the tube 441 is filled into the concentration deposit and the supplying pump 61 is stopped. The upper threshold can be detected by an upper-level sensor 800 of the concentration deposit 201. The upper-level sensor 800 can send data to the controller 9 to control the supplying pump 61 in order to stop the suction of water.

[0073] The providing water step 101 can also comprise prefiltering the water suctioned from the water source before filling the concentration deposit 201 . By prefiltering the water, bigger solids present in the water are filtered. In an example, the solid filters 504 are metal-mesh filters. In an example, the solid filter is configured to filter solids bigger than 100 pm so that solids bigger than 100 pm are not filled into the concentration deposit 201 . In another example, the solid filter is configured to filter solids bigger than 20 pm so that solids with a volume higher than 20 pm are filtered. In another example, the solid filter is configured to filter solids bigger than 5 pm. The size of the solid filter 504 can be adapted to the type of pathogen to be concentrated.

[0074] Figure 7B represents the circulation of water during an example of the filtering step 102. During the filtering step 102, the controller 9 disables the operation of the pump 61 and controls the peristaltic pump 60 in order to pump the fluid in a filtering direction. That is, water is circulated through the filter inlet tube 451 from the concentration deposit 201 to the tangential flow filter 500. The controller controls the valves 72, 73, 74 to allow the circulation of water through the pump 60 and through the filter inlet tube 451 and to impede the flow of water through the flow filter bypass tube 455, the backflush tube 435 and the concentrated water recovery tube 418.

[0075] In the filtering step 102, the water from the concentration deposit enters the tangential flow filter 500 by the feed inlet 501 of the filter into the feed chamber 511 . Part of the water (concentrated water) which comprises pathogens cannot permeate the membrane 510 of the tangential flow filter, exits the tangential flow filter by the retentate outlet 502, and is circulated back to the concentration deposit 201 through the first filter outlet tube 452. Part of the water (filtered water) permeates the membrane 510 into the permeate chamber 513 of the tangential flow filter and exits the tangential flow filter 500 by the permeate outlet 503. During the filtering step 102, the valve 76 of the second filter outlet tube 453 is open, while the filtered outlet valve 77 is closed to allow the circulation of filtered water to filtered water deposit 203 through the second filter outlet tube 453. In the example shown, some part of the filtered water remains in the tangential flow filter bypass tube 455, without entering the filter inlet tube 451 due to the valve 74 being closed.

[0076] During the filtering step 102, the flow of fluid passing through the tangential flow filter can be advantageously controlled by controlling the pressure between the two sides of the membrane 510 of the filter (corresponding to the feed chamber 511 and the permeate chamber 513 of the filter). A higher pressure in the feed chamber results in a higher fluid flow from the feed chamber to the permeate chamber.

[0077] The pressure probes 811 , 812, placed respectively in the first filter outlet tube 452 and the second filter outlet tube 453, send to the controller 9 a signal corresponding to the pressure in said tubes 452, 453. The pressure detected by the first probe 811 corresponds to the pressure on the feed chamber 511 and the pressure detected by the second probe 812 corresponds to the pressure on the permeate chamber 513. The proportional valve 75 is associated with the pressure probe 811 placed on the first filter outlet tube 452. The controller 9 controls the proportional valve 75 so that the relative pressure between the feed chamber and the permeate chamber is of between an upper limit and a lower limit. In that example, when the relative pressure is higher than the upper limit, the controller sends the instruction to increase the aperture of the proportional valve 75, while when the relative pressure is lower than the lower threshold, the controller 9 sends the instruction to reduce the aperture of the proportional valve. Preferably, the upper limit is 0.8 bar, and the lower limit is 0.6 bar.

[0078] The water of the concentration deposit is continuously filtered by the tangential flow filter, increasing the concentration of pathogens in the water of the concentration deposit over time as a permeate part of the water permeates the membrane 510 and is conducted to the filtered water deposit 203. Each time water of the concentration deposit passes through the tangential flow filter, small particles present in the water may remain in the membrane of the filter clogging it. Pathogens may also be stuck in the membrane 510 by its feed chamber 511 side.

[0079] The filtering step 102 is performed until at least one of the backflushing conditions occur. During the filtering step 102, a checking 124 of whether the backflushing conditions occurs is performed. When at least one backflushing condition occur, the filtering step 102 is stopped, and the purging step 103 and later the backflushing step 104 are initiated. To stop the filtering step 102, the controller stops the peristaltic pump 60. The checking 124 for backflushing conditions can be performed in every filtering step 102. An example of a backflushing condition includes when a predetermined maximum time lapses. The predetermined maximum time lapse can be, for example, between 600 and 800 seconds, preferably 700 seconds. The predetermined maximum time lapse may be, for example, between 10 and 35 minutes. Another example of backflushing condition includes when a predetermined pressure or flow rate is measured at any of the tubes.

[0080] If, after the predetermined maximum time is lapsed, the membrane 510 of the filter 500 is clogged, the filtering step 102 is stopped. In that case, the backflushing step 104 is not initiated directly. The controller 9 opens the proportional valve 75 in order to lower the pressure on the feed chamber 511. When the pressure has been lowered to a desired value, the backflushing step 104 is initiated, the filter 500 is cleaned and the filtering step 102 initiated again. That is, the method 800 is an iterative method.

[0081] Figure 7C illustrates the circulation of water (black arrows) and air (white arrows) during an example of the purging step 103. The utilization of a single pump 60 during the filtering step 102 and the backflushing step 104 implies that some tubes of the device receive a circulation of flow of fluid during both the filtering step and the backflushing step, such as the filter inlet tube 451. The purging step 103 comprises purging the tangential flow filter 500 removing solid particles stuck in it and purging tubes placed between the concentration deposit 201 and the tangential flow filter 500, through which water from the concentration deposit was circulated during the filtering step 102. During the purging step 103, pathogens present in the tubes and in the tangential flow filter are also dislodged.

[0082] The purge of the tangential flow filter, as well as the conduits, ensures that the water used during the backflushing step 104 does not comprise pathogens, or concentrated water, which could be present in said filter or conduits since the filtering step 102. The cleanliness of the device during the backflushing step 104 is improved. If a purging step 103 were not performed, these pathogens would circulate to the tangential flow filter in a backflushing direction during the backflushing step, and the pathogens could be stuck in the side of the membrane corresponding to the feed chamber 511 of the tangential flow filter, clogging the tangential flow filter. In embodiments where the backflushing step is performed by conducting water from the filtered water deposit into the tangential flow filter through the permeate tube, for example by using a secondary pump, the conduction of water during the backflushing step utilizes different conduits than the ones used during the filtering step. In that case few or no pathogens remain on the tubes used for backflushing and therefore the purging step can be avoided.

[0083] The purging step 103 starts after the filtering step 102 has been stopped, for example after a backflushing condition such the lapse of a predetermined time, e.g. 700 seconds, occurred. During the purging step 103, the controller 9 controls the peristaltic pump 60 to pump fluid in a direction opposite than the direction pumped during the filtering step 102. In this case, during the filtering step 102 and the backflushing step 104 the pump pumps water towards the tangential flow filter 500, while during the purging step 103 the pump pumps water in an opposite direction. The controller 9 also maintains the same status of the valves 72, 73, 74, 76 than during the filtering step 102. During the purging step 103, the fluid present along the tangential flow filter 500 and along the filter inlet tube 451 is returned back into the concentration deposit 201.

[0084] In the example of Figure 7C, air is injected to the device 200 during the purging step 103 to improve the circulation of the fluid through the tubes of the device. The injection of air is performed through an air entrance 403 connected to an outlet of the filtered water deposit 203. The air enters the device through the air entrance 403, passes through the second inlet filter tube 453 into the feed chamber of the tangential flow filter 500 by its retentate outlet 503, penetrates the membrane of the filter and contacts the fluid, which at this point flows through the feed chamber of the filter. Preferably, the air is ambient air. After contacting the fluid, both the air and the fluid circulate through the filter inlet tube 451 and through the peristaltic pump 60 into the concentration deposit 201. Injecting air through the permeate chamber 513 of the tangential flow filter 500 helps to impulse solids, particles and pathogens that blind or clog the membrane 510 on its other side corresponding to the feed chamber, detaching them from the membrane. The purging step 103 stops after the water in the tubes has been returned into the concentration deposit 201. The purging step 103 is a fast step and can last in between 10-20 seconds, preferably around 15 seconds. The controller 9 can be configured to stop the pump 60 to stop the purging step 103 after a predetermined time, for example after 20 seconds.

[0085] Purging the device empties the tangential flow filter 500 and the filter inlet tube 451. Therefore, no concentrated water will be present in those tubes during the backflushing step. Purging is performed due to a part of the filter inlet tube 451 being used during both the filtering step 102 and the backflushing step 104. If these filtering step 102 and the backflushing step 104 used different tubes from circulating water, for example by using two different pumps, the purging step 103 may be avoided.

[0086] Figure 7D represents the circulation of water during an example of the backflushing step 104. After the purging step 103 has finished, the backflushing step 104 starts. During the backflushing step 104, filtered water from the filtered water deposit 203 is circulated through the tangential flow filter in a backflushing direction to remove pathogens from the tangential flow filter. Thus, during the backflushing step 104 the filtered water from the filtered water deposit is circulated from the permeate outlet 503 of the tangential flow filter to the retentate outlet 502 of the tangential flow filter. As the water used in the backflushing step 104 is filtered water, containing none or a small quantity of pathogens, no pathogens are stuck in the membrane of the tangential flow filter by the side of the membrane corresponding to the feed chamber of the tangential flow filter 500. In addition, water that remained in the tangential flow filter bypass tube 455 during the filtering step 102 is also pumped. The backflushing step 104 is quick, and lasts less than 30 seconds, in an example between 15 and 30 seconds, in an example around 20 seconds. This time depends on the amount of filtered water used and the type of pathogen to be concentrated.

[0087] The controller 9 controls the peristaltic pump 60 and the position of the valves 73, 74, 76 to pump fluid in a direction opposite than the direction pumped during the purging step 103. That is, the controller 9 controls the peristaltic pump 60 to pump fluid in the same direction than during the filtering step 102. The peristaltic pump 60 pumps the filtered water from the filtered water deposit 203 through the backflush tube 435 into the pump feed tube portion 4511 of the filter inlet tube 451 , though the peristaltic pump 60 into the filter feed tube portion 4512 until the three-way valve 74, through the tangential flow filter bypass tube 455, through the membrane of the tangential flow filter 500 in a backflush direction and through the first filter outlet tube 452 into the concentration deposit 201 .

[0088] In the example, the three-way valve 73 is set to allow the pass of fluid from the backflush tube 435 to the peristaltic pump 60, the three-way valve 74 is set to impede the pass of fluid to the feed inlet 501 of the tangential flow filter and to allow the pass of fluid through the tangential flow filter bypass tube 455 and the valve 76 is closed to allow the pass of fluid from the tangential flow filter bypass tube 455 to the permeate outlet 503 of the tangential flow filter 500. The three-way valve 74 also impedes the pass of fluid from the tangential flow filter 500 through it. The status of the valves is set by the controller 9.

[0089] The concentration steps 100b comprises checking 125 the stopping conditions. When a stopping condition occur, the filtering step 102 or backflushing step 104 are stopped. If no stopping condition occurs, the filtering step 102 is initiated again after the backflushing step 104 so that the concentration of the water sample can be continued. That is, the process is an iterative process. When a stopping condition occurs, the filtering step 102 is not initiated again, and the recovering step 105 is initiated.

[0090] One stopping condition is that the volume of water in the concentration deposit 201 reaches a predetermined volume e.g. less than 50 mL, e.g. less than 30 mL. The predetermined volume can be selected as the volume of water enough to be later analysed. In an example, the water sample provided in the concentration deposit during the providing water step 101 has a volume of 3 litres and the predetermined volume is a volume of 30 mL. A water volume two orders of magnitude lower than the volume of the water sample usually ensures that the volume of water recovered have a concentration of pathogens adequate for its analysis by a biosensor. In an example, during the backflushing step 104, an amount of between 2-70 mL, for example 40 mL, of filtered water from the filtered water deposit is circulated.

[0091] The controller 9 is configured to check the stopping conditions based on the data obtained from the lower-level sensor 801. The lower-level sensor 801 detects if the volume of water in the concentration deposit 201 reaches a predetermined lower threshold, which indicates that the water remaining in the concentration deposit 201 is highly concentrated water. When the lower-level sensor 801 detects that the water on the concentration deposit is low, the controller 9 stops the pump. Then a purging step 103 is carried out again to collect the fluid from the tubes, so there is always a little more concentrated liquid than required.

[0092] Figure 7E represents the circulation of water during an example of the recovering step 105. During the recovering step 105, the controller 9 controls the three-way valve 72 to allow the pass of fluid from the concentrated deposit through the concentrated water recovery tube 418 into an outlet 2005 of the device 200, obtaining a highly concentrated sample which is concentrated enough to be analysed. In an example, the recovering of the water from the concentration deposit 201 is by gravity.

[0093] During the recovering step 105, the proportional valve 75 and the second outlet filter valve 76 are advantageously open. The aperture of these valves allows the concentration deposit to be connected at ambient pressure due to its connection with the air entrance 403. The difference of pressure between the upper part of the concentration deposit and its lower part eases the recovering of the water in the deposit when the valve 72 is opened. During the recovering step 105, air from outside the device is conducted to the concentration deposit 201 through the air entrance 403, to further improve the recovering of the water from the concentration deposit 201. In an example, the recovering step 105 also comprises recovering the filtered water from the filtered water deposit 203 by opening a filtered outlet valve 77 which allows the filtered water to circulate through the filtered water recovery tube 438 into an outlet 2003 of the device. A lower-level sensor 805 can send data to the controller to control when the filtered water deposit is empty. In an example, the device may comprise an additional discharge pump 63 to pump the filtered water during the recovering step.

[0094] As illustrated in Figure 6, in addition of the above-mentioned steps, the method 1000c comprises a cleaning step 106 after the recovering step 105, and a rinsing step 110 before providing the water sample to the concentration deposit.

[0095] During the cleaning step 106, cleaning product is used to clean the device after the highly concentrated water has been recovered, in order to dislodge the solids, particles and pathogens present in the tubes of the device.

[0096] In the cleaning step 106, cleaning product is introduced through the concentration deposit feed tube 441 into the concentration deposit 201. The cleaning product can be stored in a cleaning product deposit 204 fluidically connected to the deposit feed tube 441 through a cleaning product three-way valve 71. The cleaning product is pumped by the supplying pump 61 into the concentration deposit, and into the pump feed tube portion 4511 of the filter inlet tube 451. The upper-level sensor 800 of the concentration deposit 201 can send a signal to the controller 9 to close the valve 71 and stop the supplying pump 61 when the volume of cleaning product in the deposit 201 reaches a predetermined level. The cleaning product three-way valve 71 and the supplying pump 61 are controlled by the controller 9. In an example, the cleaning product is ethanol at 70%.

[0097] The cleaning step 106 comprises performing a filtering cleaning step, a purging cleaning step and a backflushing cleaning step. In an example, in the filtering cleaning step the cleaning product circulates from the concentration deposit through a tangential flow filter, with part of the cleaning product permeating the membrane and circulating to the filtered water deposit 203 and another part of the cleaning product circulating back to the concentration deposit 201 , analogous to the concentration filtering step 102. The purging cleaning step and the backflushing cleaning step are also analogous to the concentration purging step 103 and the concentration backflushing step 104. During the purging cleaning step and the backflushing cleaning step, the tangential flow filter is cleaned in both the filtering direction and the backflushing direction. By performing a filtering cleaning step, the purging cleaning step and the backflushing cleaning step, the tubes used during the concentration steps are cleaned. Therefore, after the backflushing cleaning step, most of the cleaning product have not permeated yet the membrane of the filter and remains in the concentration deposit, while the filtered water deposit comprises a small amount of cleaning product. In an example, the duration of the filtering cleaning step, the purging cleaning step and the backflushing cleaning step are analogous to the duration of the concentration filtering step 102, purging step 103 and backflushing step 104.

[0098] After performing the filtering cleaning step, the purging cleaning step and the backflushing cleaning step, the cleaning product is circulated from the concentration deposit 201 into the dosing valve 78 placed at the outlet 2005 of the device, for example by gravity, cleaning the concentrated water recovery tube 418. After that, the controller 9 controls the three-way valves 72, 73 so that the remaining cleaning product in the concentration deposit 201 is circulated to the filtered water deposit 203 through the backflush tube 435, for example by pumping the cleaning product. By this circulation, the remaining cleaning product reaches the filtered water deposit 203. Then, the dosing valve 78 is opened so that the cleaning product in the concentrated water recovery tube 418 is discharged through the outlet 2005. Finally, the filtered outlet valve 77 is opened and the discharging pump 63 is activated so that the cleaning product from the filtered water deposit 203 is circulated through the filtered water recovery tube 438, cleaning said tube 438, and discharged through the outlet 2003.

[0099] The rinsing step 110 is performed at the beginning of the method 1000c to concentrate a water sample. During the rinsing step 110, water is used to rinse the device 200, removing the cleaning agent, e.g. ethanol that may remain in the tubes of the device from the previous utilization of the device for concentrating a different sample. The rinsing step 110 ensures that the pathogens of the water sample are not killed with the cleaning agent remaining inside the device, which will make the results of a later analysis of the resultant highly concentrated water to not correspond with the actual pathogen concentration of the water sample. By virtue of performing the rinsing step at the beginning of the method 1000c instead than after the cleaning step 106, avoid the generation of pathogens, in the hypothetical case that the equipment was to remain stopped for a while, which could render the results of the analysis a new water sample inaccurate due to the added pathogens. In the example, the rinsing step 110 comprises performing rinse concentration steps and a rinsed water recovering step. The rinse concentration steps are analogous to the concentration steps 100a, 100b. The rinsed water recovering step is analogous to the recovering step 105 of the methods 1000a, 1000b described. For example, the rinse concentration steps may comprise a filtration rinsing step, a purging rinsing step and a backflushing rinsing step, while the recovering step may comprise recovering the concentrated water from the concentration deposit 201 and the filtered water from the filtered water deposit 203. The overall length of the process is much shorter than the concentration steps 100a, 100b. The controller 9 controls the pump 60 until the upperlevel sensor 800 detects that the concentration deposit is filled. A filtering, purging and backflushing process is carried out with this liquid to rinse all the concentrate process pipes. Finally, a concentrated product discharge process and another filtered product discharge process are carried out to clean the rest of the pipes.

[0100] Figure 8 shows an analysis method 1001 that comprises a method 1000 for concentrating pathogens in a water sample according to any of the methods 1000a, 1000b, 1000c described according to the first aspect of the disclosure and analysing at 109 the recovered water with a biosensor. As stated before, the methods 1000 for concentrating pathogens in a water sample comprise a providing water step 101 , a concentration step 100a, 100b and a recovering step 105.

[0101] The highly concentrated water sample resultant from the methods 1000a, 1000b, 1000c is has a concentration of pathogens able to be detected by the biosensor in a brief period of time. Therefore, during the analysing step 109, the highly concentrated water sample is analysed with a biosensor. By virtue of its high concentration, the analysing step 109 can take less than 30 minutes.

[0102] In an example, the biosensor is a gold nanoparticle (AuNP) based optical biosensor. Gold nanoparticle-based optical biosensors can also be referred as gold nanoparticlebased colorimetric biosensors. Gold nanoparticle based optical biosensors are preferred due to their non-reactive nature. When a sample to be analysed is added in a gold nanoparticle based optical biosensor to detect the pathogen, the gold nanoparticles change their colour. Thus, they do not require the addition of additional reagents for the detection of pathogens. Cleaning and maintenance of a gold nanoparticle based optical biosensor is also simpler than with other biosensors.

[0103] For reasons of completeness, various aspects of the present disclosure are set out in the following numbered clauses:

[0104] Clause 1 . Method for increasing the concentration of pathogens in a water sample, wherein the method comprises:

[0105] - providing a water sample containing pathogens in a concentration deposit,

[0106] - performing concentration steps comprising:

[0107] ■ filtering water from the concentration deposit, the filtering step comprising:

[0108] • circulating water from the concentration deposit through a tangential flow filter to obtain a permeate of filtered water and a retentate of concentrated water, and

[0109] • circulating the retentate back to the concentration deposit and the permeate to a filtered water deposit.

[0110] ■ backflushing the tangential flow filter by circulating filtered water from the filtered water deposit through the tangential flow filter in a backflushing direction to remove pathogens from the tangential flow filter.

[0111] - recovering the water from the concentration deposit as a concentrated water sample.

[0112] Clause 2. Method, according to clause 1 , wherein the filtering step is performed until at least one backflushing condition occur, such as when a predetermined maximum time lapses.

[0113] Clause 3. Method, according to clause 2, wherein the method comprises a detection step of detecting a blockade of the tangential flow filter, wherein the detection step comprises comparing the pressure of a tube where the retentate of concentrated water is circulating with a predetermined pressure value.

[0114] Clause 4. Method, according to any of clauses 1 to 3, wherein the method comprises initiating again the filtering step after the backflushing step.

[0115] Clause 5. Method, according to any of clauses 1 to 4, wherein the concentration steps are stopped when at least one stopping conditions, such as when the volume of water in the concentration deposit reaches a predetermined volume, occur.

[0116] Clause 6. Method, according to clause 5, wherein the predetermined volume of water in the concentration deposit is of 50 millilitres or lower, preferably 30 millilitres or lower. Clause 7. Method comprising to any of clauses 1 to 6, wherein performing concentration steps comprises a purging step, wherein the purging step comprises purging the tangential flow filter.

[0117] Clause 8. Method, according to clause 7, wherein the purging step is performed between the filtering step and the backflushing step.

[0118] Clause 9. Method, according to clause 7 or 8, wherein the purging step comprises purging tubes between the concentration deposit and the tangential flow filter.

[0119] Clause 10. Method, according to any of clauses 7 to 9, wherein the purging step comprises forcing air towards the tangential flow filter.

[0120] Clause 11. Method, according to any of clauses 1 to 10, wherein during the filtering step the water is pumped by a peristaltic pump.

[0121] Clause 12. Method, according to any of clauses 1 to 11 , wherein during the backflushing step the water is pumped by a peristaltic pump.

[0122] Clause 13. Method, according to clauses 11 and 12, wherein during the filtering step and the backflushing step, the water is pumped by the same peristaltic pump.

[0123] Clause 14. Method, according to any of clauses 7 to 13, wherein during the purging step the water is pumped by a peristaltic pump.

[0124] Clause 15. Method, according to clauses 13 and 14, wherein during the filtering step, the purging step and the backflushing step, the water is pumped by the same peristaltic pump, wherein during the filtering step and the backflushing step the pump pumps water towards the tangential flow filter, and wherein during the purging step the pump pumps water in an opposite direction.

[0125] Clause 16. Method, according to any of clauses 1 to 15, wherein the tangential flow filter is a membrane filter, e.g. a disc membrane filter.

[0126] Clause 17. Method, according to any of clauses 1 to 16, wherein the water provided during the providing water step has a volume of 3 litres or less.

[0127] Clause 18. Method, according to any of clauses 1 to 17, wherein the providing water step comprises prefiltering the water.

[0128] Clause 19. Method, according to any of clauses 1 to 18, wherein the pathogens to be concentrated is at least one of faecal coliforms, Escherichia coli spp, Legionella spp, Clostridium spp, Salmonella spp, Listeria spp, Campylobacter spp, Pseudomonas aeruginosa, etc, preferably Escherichia coli spp.

[0129] Clause 20. Method, according to any of clauses 1 to 19, wherein the method is a method for concentrating water samples from a wastewater treatment plant.

[0130] Clause 21. Method, according to any of clauses 1 to 18, wherein the providing water step 101 comprise prefiltering the water sample to filter solids with a volume higher than 20 pm, the prefiltering step being performed by a pretreatment tangential filter, preferably higher than 5 pm)

[0131] Clause 22. Method, according to any of clauses 1 to 21 , wherein the method further comprises a rinsing step before providing the water sample to the concentration deposit.

[0132] Clause 23. Method, according to any of clauses 1 to 22, wherein the method further comprises a cleaning step after the recovering step.

[0133] Clause 24. Method, according to any clause 23, wherein the cleaning step comprises performing a filtering cleaning step, a purging cleaning step and a backflushing cleaning step.

[0134] Clause 25. Method, according to any of clauses 1 to 24, wherein the method is an automated method.

[0135] Clause 26. Method for analysing a water sample, the method comprising: a method for concentrating pathogens in a water sample according to clauses according to any of clauses 1 to 25, analysing the recovered water with a biosensor.

[0136] Clause 27. Method for analysing a water sample according to clause 26, wherein the biosensor is a gold nanoparticle-based optical biosensor.

[0137] Clause 28. Device for increasing the concentration of pathogens in water, the device comprising: a concentration deposit; a filtered water deposit; a tangential flow filter; a filter inlet tube connecting an outlet of the concentration deposit with a feed inlet of the tangential flow filter. a first filter outlet tube connecting the retentate outlet of the tangential flow filter with the concentration deposit. a second filter outlet tube connecting the permeate outlet of the tangential flow filter with the filtered water deposit.

[0138] Clause 29. Device, according to clause 28, wherein the device comprises a tangential flow filter bypass tube connecting the filter inlet tube with the second filter outlet tube.

[0139] Clause 30. Device, according to any of clauses 28 to 29, wherein the device comprises a backflush tube connecting the filtered water deposit with the filter inlet tube.

[0140] Clause 31. Device, according to any of clauses 28 to 30, wherein the device comprises a peristaltic pump configured to pump the water through the filter inlet tube, the first filter outlet tube, and through the second filter outlet tube.

[0141] Clause 32. Device, according to clause 31 , wherein the peristaltic pump is configured to pump the water through the filter inlet tube, the first filter outlet tube, the second filter outlet tube, the tangential flow filter bypass tube and through the backflush tube.

[0142] Clause 33. Device, according to any of clauses 31 to 32, wherein the peristaltic pump is placed on the filter inlet tube.

[0143] Clause 34. Device, according to any of clauses 28 to 30, wherein the device comprises a pump configured to pump filtered water from the filtered water deposit (203) through the tangential flow filter in a backflushing direction to remove pathogens from the tangential flow filter, wherein the backflushing direction is defined by the direction from the permeate outlet (503) of the tangential flow filter to the retentate outlet (502) of the tangential flow filter so that solids, particles and pathogens are dislodged from the tangential flow filter and circulated towards the concentration deposit.

[0144] Clause 35. Device, according to clause 34, wherein the pump is a peristaltic pump.

[0145] Clause 36. Device, according to any of clauses 34 to 35, wherein the pump is configured to pump the water through the filter inlet tube, the first filter outlet tube, and through the second filter outlet tube.

[0146] Clause 37. Device, according to clause 36, wherein the peristaltic pump is configured to pump the water through the filter inlet tube, the first filter outlet tube, the second filter outlet tube, the tangential flow filter bypass tube and through the backflush tube.

[0147] Clause 38. Device, according to any of clauses 36 to 37, wherein the pump is placed on the filter inlet tube.

[0148] Clause 39. Device, according to any of clauses 28 to 38, wherein the device comprises a concentrated water recovery tube to recover the water from the concentration deposit.

[0149] Clause 40. Device, according to any of clauses 28 to 39, wherein the device comprises a filtered water recovery tube to recover the water from the filtered water deposit.

[0150] Clause 41. Device, according to any of clauses 28 to 40, wherein the device comprises valves to regulate and / or impede the flow of water through the tubes.

[0151] Clause 42. Device, according to any of clauses 28 to 41 , wherein the device comprises a proportional valve placed in the first filter outlet tube configured to regulate the pressure of a feed chamber of the tangential flow filter.

[0152] Clause 43. Device, according to any of clauses 28 to 42, wherein the device comprises a three-way valve placed in the filter inlet tube, connecting the filter inlet tube with the flow filter bypass tube, the three-way valve preferably placed between the peristaltic pump and the feed inlet of the tangential flow filter.

[0153] Clause 44. Device, according to any of clauses 28 to 43, wherein the device comprises a three-way valve placed in the filter inlet tube, connecting the filter inlet tube with the backflush tube.

[0154] Clause 45. Device, according to clause 44 in combination with any of clauses 31 to 33 or 35 to 44, wherein the three-way valve is placed between the peristaltic pump and the concentration deposit. Clause 46. Device, according to clause 44 in combination with clause 34, wherein the three-way valve is placed between the pump and the concentration deposit.

[0155] Clause 47. Device, according to any of clauses 28 to 46, wherein the device comprises a concentration deposit feed tube connecting the concentration deposit with an inlet of the device.

[0156] Clause 48. Device, according to any of clauses 28 to 47, wherein the device comprises a cleaning product deposit to store a cleaning product.

[0157] Clause 49. Device, according to clauses 47 to 48, wherein the device comprises a solid filter placed on the concentration deposit feed tube.

[0158] Clause 50. Device, according to any of clauses 28 to 49, wherein the device comprises a biosensor placed in fluidic connection with an outlet of the device.

[0159] Clause 51 . Device, according to clause 46, wherein the biosensor is a gold nanoparticle based optical biosensor.

[0160] Clause 52. Device, according to any of clauses 28 to 51 , wherein the device comprises a controller configured to control at least one pump and / or at least one valve of the device.

[0161] Clause 53. Device, according to clause 52, wherein the controller is configured to: perform a method for increasing the concentration of pathogens in a water sample according to any of clauses 1 to 25, and / or receive data from level sensors placed on the concentration deposit and / or in the filtered water deposit, and / or receive data from pressure probes, and analyse data received from the sensors and probes and, based on the data received, control the status of the valves and the pumps of the device to perform the method for increasing the concentration of pathogens in a water sample.

[0162] Clause 54. Device, according to any of clauses 28 to 53, wherein the device is a portable device.

[0163] Clause 55. Device, according to any of clauses 28 to 54, wherein the concentration deposit (201) has a volume of less than 3 L, preferably a volume of less than 2.5 L.

Claims

CLAIMS1. Method (1000a, 1000b, 1000c) for increasing the concentration of pathogens in a water sample, wherein the method (1000a, 1000b, 1000c) comprises:- providing (101) a water sample in a concentration deposit;- performing (100a, 100b) concentration steps comprising:■ filtering (102) water from the concentration deposit, the filtering step comprising:• circulating water from the concentration deposit through a tangential flow filter to obtain a permeate of filtered water and a retentate of concentrated water; and• circulating the retentate back to the concentration deposit and the permeate to a filtered water deposit;■ backflushing (104) the tangential flow filter by circulating filtered water from the filtered water deposit through the tangential flow filter in a backflushing direction to remove pathogens from the tangential flow filter;- recovering (105) the water from the concentration deposit as a concentrated water sample, wherein the backflushing direction is defined by the direction from a permeate outlet of the tangential flow filter to a retentate outlet of the tangential flow filter so that solids, particles and pathogens are dislodged from the tangential flow filter and circulated towards the concentration deposit.

2. Method (1000b, 1000c), according to claim 1 , wherein performing concentration steps (100b) comprises a purging step (103), and wherein the purging step (103) comprises purging the tangential flow filter so that water from the tangential flow filter is returned back from the tangential flow filter to the concentration deposit.

3. Method (1000a, 1000b, 1000c), according to any of claims 1 to 2, wherein during the filtering step (102) the water is pumped by a peristaltic pump and wherein during the backflushing step (104) the water is pumped by the same peristaltic pump.

4. Method (1000b, 1000c), according to claim 2 in combination with claim 3, wherein during the filtering step (102), the purging step (103) and the backflushing step (104), the water is pumped by the same peristaltic pump,wherein during the filtering step (102) and the backflushing step (104) the pump pumps water towards the tangential flow filter, and wherein during the purging step (103) the pump pumps water in an opposite direction.

5. Method (1000a, 1000b, 1000c), according to any of claims 1 to 4, wherein the method comprises initiating again the filtering step after the backflushing step.

6. Method (1000a, 1000b, 1000c), according to any of claims 1 to 5, wherein the method is an automated method.

7. Method (1001) for analysing a water sample, the method (1001) comprising: a method (1000a, 1000b, 1000c) for concentrating pathogens in water according to claims according to any of claims 1 to 6, analysing (109) the recovered water with a biosensor.

8. Method (1001) for analysing a water sample according to claim 7, wherein the biosensor is a gold nanoparticle-based optical biosensor.

9. Device (200) for increasing the concentration of pathogens in water, the device comprising: a concentration deposit (201); a filtered water deposit (203); a tangential flow filter (500); a filter inlet tube (451) connecting an outlet of the concentration deposit (201) with a feed inlet (501) of the tangential flow filter (500). a first filter outlet tube (452) connecting the retentate outlet (502) of the tangential flow filter (500) with the concentration deposit (201). a second filter outlet tube (453) connecting the permeate outlet (503) of the tangential flow filter (500) with the filtered water deposit (203), a pump configured to pump filtered water from the filtered water deposit (203) through the tangential flow filter in a backflushing direction to remove pathogens from the tangential flow filter, wherein the backflushing direction is defined by the direction from the permeate outlet (503) of the tangential flow filter to the retentate outlet (502) of the tangential flow filter so that solids, particles and pathogens aredislodged from the tangential flow filter and circulated towards the concentration deposit10. Device, according to claim 9, wherein the device comprises a tangential flow filter bypass tube (455) connecting the filter inlet tube (451) with the second filter outlet tube (453), and a backflush tube (435) connecting the filtered water deposit (203) with the filter inlet tube (451).11 . Device, according to claim 10, wherein the device comprises a peristaltic pump (60) configured to pump the water through the filter inlet tube (451), through the first filter outlet tube (452), through the second filter outlet tube (453), through the tangential flow filter bypass tube (455) and through the backflush tube (435).

12. Device (200), according to any of claims 9 to 11 , wherein the device (200) comprises a controller configured to perform the method for increasing the concentration of pathogens in a water sample of claims 1-5.

13. Device (200), according to any of claims 9 to 12, wherein the device (200) comprises valves to regulate and / or impede the flow of water through the tubes, and wherein the device (200) comprises a controller (9) configured to control at least one pump and / or at least one valve of the device (200).

14. Device (200), according to any of claims 9 to 13, wherein the device (200) comprises a biosensor placed in an outlet of the device.

15. Device (200), according to any of claims 9 to 14, wherein the device (200) is a portable device.

Images