Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D65/00—Accessories or auxiliary operations, in general, for separation processes or apparatus using semi-permeable membranes
  • B01D65/10—Testing of membranes or membrane apparatus; Detecting or repairing leaks
  • B01D65/104—Detection of leaks in membrane apparatus or modules
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
  • B01D61/14—Ultrafiltration; Microfiltration
  • B01D61/20—Accessories; Auxiliary operations
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
  • B01D61/14—Ultrafiltration; Microfiltration
  • B01D61/22—Controlling or regulating
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2313/00—Details relating to membrane modules or apparatus
  • B01D2313/18—Specific valves
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2313/00—Details relating to membrane modules or apparatus
  • B01D2313/19—Specific flow restrictors
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2315/00—Details relating to the membrane module operation
  • B01D2315/18—Time sequence of one or more process steps carried out periodically within one apparatus

Definitions

• the invention relates to a method for monitoring the integrity of an ultrafiltration membrane in a filter module of an ultrafiltration system for drinking water treatment during its filter operation, the system having an untreated water inlet and a filtrate outlet, between which the filter module is located. Furthermore, the invention relates to an ultrafiltration system that is set up to carry out the method.
• Ultrafiltration systems for drinking water supply in buildings with filter modules working in parallel are known per se. They are used where a central supply of water of potable quality is not possible or not permanently possible.
• Residential and multi-family houses, hotels, hospitals, office buildings and public facilities are particularly noteworthy as buildings with such systems, which include a large number of water consumers such as washbasins, toilets, showers, bathtubs, etc. and therefore have extremely dynamic water consumption over the course of the day .
• a cruise ship is also to be understood as a building in the sense of a mobile hotel.
• Filter modules of an ultrafiltration system have an inlet connection on the raw water side for supplying raw water and an outlet connection on the filtrate side for supplying filtered water, referred to below as filtrate.
• filtrate filtered water
• filter membranes between the inlet and outlet connections, which filter out microorganisms and dirt particles in the raw water supplied.
• the filter membrane(s) thus spatially separate the raw water side from the filtrate side. Regardless of the actual number of filter membranes in the module, only “one” is Filter membrane spoken in the singular, although also two or a multiplicity of
• Filter membranes can/can be present.
• the main integrity tests used are air based, as the wet filter membranes are impermeable to air depending on the level of pressure applied. Air can either be sucked out to create a vacuum or introduced as compressed air. This can be done locally, ie specifically for a specific filter module, or globally for all or part of the system, ie for several filter modules at the same time. Furthermore, this can be done either from the raw water side or from the filtrate side. It is then examined or measured whether and, if so, how large the pressure drop over the membrane or the filter modules over time in order to make a statement about the integrity. The level of the applied transmembrane pressure in a pressure drop test determines the minimum size of the detectable defect.
• a pressure of 7 bar is required to check the retention of bacteria (0.45 ⁇ m) and a test pressure of 120 bar for viruses (25 nm). These high pressures cannot be achieved with conventional filter modules with, for example, a maximum permissible transmembrane pressure of 4 bar in terms of mechanical stability.
• a standard transmembrane pressure of 1 bar for integrity testing is only sufficient to detect defects down to a minimum size of 3 pm. If a large number of filter modules are tested simultaneously, the natural diffusion of air through the intact membrane wall into the water medium and mini-leakage outside the membrane wall reduce the sensitivity of the pressure drop measurement.
• a further disadvantage of this method is the not inconsiderable effort involved in carrying out the integrity test, because the filter module or modules must be emptied before the integrity test and then refilled. Some of the air also remains in the filter modules after the integrity test and reduces the filter efficiency. It must therefore be removed with an additional measure by appropriate venting.
• Another disadvantage of air-based testing methods is the need to shut down all or part of the operation of the filtration system during the test. As a result, it then supplies little or no drinking water, which, depending on the location of the system, e.g. for hotels, is unacceptable, or allows the process to be used only outside of the main consumption time, i.e. at night.
• An additional disadvantage is the technical effort required to carry out the process, since the system has to be equipped with the appropriate lines, valves and an oil-free compressed air supply, e.g. a compressor.
• a very sensitive integrity monitoring method consists of injecting a defined dose of molecular or particulate markers into the raw water and checking whether and, if so, to what extent these markers appear on the filtrate side.
• the molecular or particulate size of a marker is larger than the nominal pore size of the filter membrane, so that the marker does not reach the filtrate side, if the membrane is intact, or only to a minimal extent.
• This method has the advantage that it can be used during filtration operations.
• the method requires additional equipment for dosing and injection as well as additional sensors or subsequent laboratory analysis on the filtrate side in order to detect the presence of the marker in the filtrate.
• the marker reduces the filter efficiency because it does not get through the filter membrane, but instead contributes to increased fouling of the membrane.
• such a method is not permitted for drinking water, since the suitability for drinking of the water could be restricted by the marker.
• TMP transmembrane pressure
• an object of the present invention to provide a simple method for reliably monitoring the integrity of an ultrafiltration membrane in a filter module during the Filter operation and can be used without interrupting it and uses only existing pressure sensors. Furthermore, it is the object of the invention to provide a corresponding ultrafiltration system for carrying out the method.
• the method for monitoring the integrity of an ultrafiltration membrane in a filter module of an ultrafiltration system for drinking water treatment during its filter operation provides that filtered drinking water flows from the filter module via a backflow preventer to the filtrate outlet, which has a known opening pressure with a filtrate flow, the pressure difference between the pressure determined in the raw water inlet and the pressure in the filtrate outlet and a loss of integrity is assumed if the pressure difference is below a limit value that is greater than the opening pressure. A comparison is thus made between the pressure difference and the limit value and a loss of integrity is assumed if the pressure difference is less than the limit value.
• the core idea of the invention is therefore to connect the filter module or modules of the ultrafiltration system via a backflow preventer to the filtrate line, which directs the filtrate to the consumers.
• the filter module and the backflow preventer are therefore connected in series.
• the backflow preventer only allows a volume flow in the direction of the filtrate line. For structural reasons, it only opens above a certain opening pressure. It then forms hydraulic resistance during the flow of filtrate, so that a pressure drop equal to said opening pressure occurs across it. This is regularly perceived as a disadvantage because attempts are always made to avoid hydraulic resistance in order to minimize hydraulic losses and maximize efficiency.
• the invention uses the opening pressure of or the pressure loss at the backflow preventer as an advantage in order to determine whether something is flowing through it or the filter module.
• a filtrate flow is determined via the pressure.
• the pressure drop across the system is considered, more precisely, the pressure difference between the inlet and outlet, between which the at least one filter membrane to be monitored is located.
• the opening pressure of the non-return valve contributes to this pressure difference in every operating state with water extraction, so that it can be evaluated as to whether the non-return valve, and thus also the filter module, is being flown through.
• TMP transmembrane pressure
• the filter membrane If the integrity of the filter membrane has been lost due to significant defects, such as cracks, larger pores or several severed hollow fibers, it has no hydraulic resistance or the filter module only has a negligibly low hydraulic resistance, so that the transmembrane pressure is zero. As a result, the pressure drop across the system is only in the range of the opening pressure of the non-return valve. Consequently, the finding that the pressure difference between the pressure in the raw water inlet and the pressure in the filtrate outlet is in the range of this opening pressure is an indication of a loss of integrity of the filter membrane.
• the integrity test method according to the invention requires less effort than other test methods. It is not air-based, so there is no need to perform a drain, refill and bleed of the filter module, nor does it use a marker. Furthermore, neither a special nor an additional sensor or measurement technology is required in the system. Rather, a pressure determination in the inlet line and the is sufficient to carry out the method Filtrate line, which is usually already implemented in conventional ultrafiltration systems for their control.
• Another advantage of the method is that the integrity monitoring can be performed continuously and not at specific times (1-2 times a day) as in air-based methods or prior art use of markers. A significant membrane defect can thus be detected immediately and the contamination caused by it can be minimized. Finally, the method according to the invention can be carried out during filter operation, which does not have to be stopped for this purpose. This means that the supply of drinking water is not interrupted. At the same time, integrity monitoring is also uninterrupted.
• the filter module can have one, two or more filter membranes, preferably a large number of hollow fiber membranes.
• the ultrafiltration system can have one, two or more parallel filter modules, which are each connected to the filtrate outlet or the filtrate line via a backflow preventer.
• the filter modules are preferably connected together to form groups. For example, two, three or more groups of two, three or more parallel filter modules can be located in parallel.
• the raw water inlet of the system is at the same time the raw water inlet of the groups or the filter modules.
• the filtrate outlet of the system is at the same time the filtrate outlet of the groups or the filter modules.
• the filter membranes, filter modules or groups are always between the raw water inlet and the filtrate outlet.
• a known opening pressure is a nominal opening pressure specified by the manufacturer for the non-return valve.
• this terminology takes into account the fact that a physical quantity never exactly reaches a specific value when measured in practice.
• the actual opening pressure is not identical, even in the case of identical non-return valves, rather it varies.
• the temperature of the water also plays a role, or rather its temperature-dependent density and dynamic viscosity, so that the actual Opening pressure of the non-return valve fluctuates compared to the nominal value. For this reason, a limit value is used as a decision criterion according to the invention, which takes into account the scatter and temperature-related fluctuation of the opening pressure and is therefore greater than the opening pressure.
• the limit is at most 20% above the known cracking pressure.
• the limit may be 20%, 10%, or 5% above the known cracking pressure. It thus forms the upper limit of a possible fluctuation range of the opening pressure. This fluctuation range is to be understood as the "range of the opening pressure".
• the first-mentioned limit value to form an upper limit of a tolerance band, the lower limit of which is defined by a further limit value, with the loss of integrity being assumed only if the pressure difference lies within the tolerance band.
• the double comparison is made as to whether the pressure difference is greater than the further limit value and smaller than the first limit value.
• the further limit value is preferably at most 20% below the opening pressure.
• the further limit value can be 20%, 10% or 5% less than the known opening pressure.
• a time duration can be taken into account in addition to the pressure comparison, for which the pressure difference may be below the first-mentioned limit value. Provision can thus be made for a loss of integrity to be assumed only if the value falls below the limit value for at least a predetermined period of time. This determination can be realized, for example, with the help of a counter, which is started when the limit value is undershot and, when a counter reading corresponding to the duration of time is reached, a message about exceeding the permissible limit value outputs time duration.
• the counter can be an up counter (stopwatch) or a down counter (countdown).
• the duration can be between 5 and 20 minutes, for example.
• the duration As an additional decision criterion, it makes sense to differentiate between the times of day, since the characteristics of water consumption change significantly over the course of the day. So there is either no or only minimal water withdrawal at night. In contrast, water withdrawal during the day is high on average and changes very dynamically. This is the main consumption time. The fact that very low volume flows occur during the main consumption time is rather improbable, but at least more improbable than an occurrence outside the main consumption time, especially at night. against this background, in order to quickly identify a loss of integrity, the duration of falling below the limit value used as a further decision criterion for a loss of integrity can be shorter for the main usage time than outside of the main usage time.
• the loss of integrity is assumed when the limit value is not reached during a main consumption time for a first predetermined time period or outside of the main consumption time for a second predetermined time period, the second time period being longer than the first time period .
• the duration during the main usage time can be between 5 and 10 minutes and thus form a first duration. Outside of the main consumption time, it can be between 15 and 20 minutes and thus be a second duration.
• the period between 6 a.m. and 6 p.m. can be regarded as the main consumption time.
• the period outside of the main consumption time hereinafter also referred to as secondary consumption time, is then between 6 p.m. and 6 a.m.
• a warning message can be issued if the loss of integrity is accepted. This can be done with an acoustic, visual or electronic warning signal. If necessary, an electronic message can also be sent (SMS, e-mail).
• the invention also relates to an ultrafiltration system for drinking water treatment, comprising at least one filter module with an ultrafiltration membrane, an untreated water inlet and a filtrate outlet, between which the filter module is located. It comprises a backflow preventer between the filter module and the filtrate outlet, a sensor system for determining the pressure difference between the pressure in the raw water inlet and the pressure in the filtrate outlet and a monitoring unit for monitoring the integrity of the ultrafiltration membrane, the monitoring unit being set up to carry out the method described above according to the invention .
• the sensors can be a pressure sensor in the raw water inlet and in the filtrate outlet.
• the monitoring unit can be a PLC (programmable logic controller) or a microcomputer.
• FIG. 1 an ultrafiltration system according to the invention
• FIG. 3 a flow chart of the method according to the invention
• FIG 1 shows an ultrafiltration system 1 for drinking water treatment using three parallel ultrafiltration modules 3a, 3b, 3c.
• only one ultrafiltration module or two or more than three parallel ultrafiltration modules can be present.
• each of these ultrafiltration modules 3a, 3b, 3c can represent a group formed from two or more parallel ultrafiltration modules. Each group can be understood as an ultrafiltration unit.
• all ultrafiltration units preferably have the same number of ultrafiltration modules 3a, 3b, 3c.
• the ultrafiltration modules of the same ultrafiltration unit can be structurally combined in a common holder, also called a rack.
• the ultrafiltration system 1 can have two, three or more ultrafiltration units or racks in one embodiment variant, which are hydraulically connected in parallel to one another. It makes sense for all ultrafiltration modules 3a, 3b, 3c to be structurally identical.
• the ultrafiltration system 1 is fed from a source 20 with raw water.
• This source 20 may be a local water utility or a local water reservoir such as a tank or cistern.
• a central supply line 2 which forms the raw water inlet here, connects the ultrafiltration modules 3a, 3b, 3c to the source 20, with a pressure booster system 21 being arranged in the supply line 2 in order to provide an inlet pressure Pzu of, for example, 10 bar on the inlet side of the ultrafiltration system 1 .
• the latter is necessary above all in tall buildings and/or extensive drinking water distribution networks within the building, since even the supply pressure provided by any supplier alone is not sufficient to ensure sufficient flow pressure, e.g. 2 bar, at the highest or most distant tapping points or consumers to guarantee.
• the pressure boosting system is only symbolized by a pump 21 here.
• a local supply line 2a, 2b, 2c in each of which an inlet valve Za, Zb, Zc lies.
• the local supply lines 2a, 2b, 2c each end at inlet connections 4au, 4ao, which open into an untreated water side 5a of the corresponding ultrafiltration module 3a, 3b, 3c.
• inlet connections 4au, 4ao instead of the two inlet connections 4au, 4ao, only one inlet connection can also be present in another embodiment variant.
• the raw water side 5a is separated from the filtrate side 5b by at least one ultrafiltration membrane 6, from which an outlet connection 4bo leads out.
• the ultrafiltration modules 3a, 3b, 3c are connected via a respective local filtrate line 8a, 8b, 8c, starting from the outflow connection 4bo, to a central filtrate line 8, which leads to the consumers 40.
• the filtrate line 8 thus forms a filtrate outlet here.
• Consumers 40 can be washbasin fittings, toilets, showers, tubs, etc., for example.
• the ultrafiltration modules 3a, 3b, 3c produce filtrate from the raw water, in that the raw water passes through the membrane 6 and particles in the raw water remain adhering to the raw water side 5a or to the membrane 6.
• the water or filtrate permeated to the filtrate side 5b is conducted through the local filtrate lines 8a, 8b, 8c to the central filtrate line 8, which then forwards the filtrate to the consumers 40.
• each ultrafiltration module 3a, 3b, 3c can be operated independently of the other ultrafiltration modules 3a, 3b, 3c in a backwash operation, in which the filter membrane 6 is flown through backwards, ie from the filtrate side 5b to the raw water side 5a.
• the filtrate used for this comes from at least one of the other ultrafiltration modules 3a, 3b, 3c.
• each ultrafiltration module 3a, 3b, 3c is connected via a local retentate line 7a, 7b, 7c, in which there is a retentate valve Ra, Rb, Rc , Connected to a central retentate line 7, which leads to a free outlet 30 where the retentate is deposited.
• a volume meter 17 also known colloquially as a water meter or water meter.
• the determination of which ultrafiltration module should filter at a time and which should be cleaned by backwashing is done by setting the inlet valves Za, Zb, Zc and the retentate valves Ra, Rb, Rc, these valves being related to each ultrafiltration module 3a, 3b, 3c be controlled inverted.
• the inlet valve Za, Zb, Zc assigned to an ultrafiltration module 3a, 3b, 3c is open, while the retentate valve Ra, Rb, Rc assigned to it is closed, and vice versa.
• all three ultrafiltration modules 3a, 3b, 3c deliver filtrate. So you are in filtration mode.
• the arrows on the various lines and within the ultrafiltration modules 3a, 3b, 3c indicate the respective direction of flow.
• the valve positions are thus as follows:
• the advantage of such an ultrafiltration system 1 is that backwashing of the individual ultrafiltration modules 3a, 3b, 3c can take place during operation of the ultrafiltration system 1, i.e. while filtrate is being delivered to the consumers 20, so that they experience no or at least no significant impairment. There is therefore no standstill or interruption of the filtrate delivery to the consumers 20. Furthermore, the ultrafiltration system 1 according to the invention does not require a backwash tank and a backwash pump, which reduces the complexity and costs of producing it.
• a special feature of the ultrafiltration system according to the invention in Figure 1 is that each ultrafiltration module 3a, 3b, 3c not only on the local filtrate line 8a, 8b, 8c, but also via a second line 8', 8a', 8b', 8c' parallel thereto to the central filtrate line 8.
• the second lines each consist of a module-related, first section 8a′, 8b′, 8c′, which combine to form a common second section 8′, which then opens into the central filtrate line 8 .
• the second lines 8', 8a', 8b', 8c' are from this common section 8' connected to the filtrate line 8 and from individual lines 8a', 8b', 8c outgoing to the individual ultrafiltration modules 3a, 3b, 3c ' educated. While the local filtrate lines 8a, 8b, 8c serve to discharge the filtrate in filtration operation, the second lines 8', 8a', 8b', 8c' are provided for a filtrate feed line in backwash operation. For example, filtrate from two of the ultrafiltration modules 3b, 3c can be fed to the third ultrafiltration module 3a via the corresponding second line 8', 8a' of the filtrate side 5b.
• a pressure reducing element in particular a pressure reducer, in the common section 8' of the second lines 8', 8a', 8b', 8c' 10 arranged.
• flushing valve Sa, Sb, Sc in each of the individual lines 8a', 8b', 8c' in order to separate the pressure-unreduced filtrate side 5b of the ultrafiltration modules 3b, 3c supplying the filtrate from the filtrate side 5b of the ultrafiltration module 3a to be backflushed , since the pressure reducing member 10 is otherwise bypassed.
• the flushing valves Sa, Sb, Sc can be designed identically to the inlet valves Za, Zb, Zc, the retentate valves Ra, Rb, Rc and/or the filtrate valves Fa, Fb, Fc.
• the flushing valves Sa, Sb, Sc are formed by non-return valves.
• the inlet valves Za, Zb, Zc and/or retentate valves Ra, Rb, Rc can be controlled, in particular switchable (open/closed) or adjustable (0...100%) control valves which are actuated, for example, electrically, electromagnetically or pneumatically will.
• the control valves are controllable engine valves.
• the filtrate valves Fa, Fb, Fc are formed by non-return valves. This has the advantage that no active activation of the filtrate valves Fa, Fb, Fc is required.
• This design also makes use of the fact that the local filtrate lines 8a, 8b, 8c and the second lines 8a', 8b', 8c' are or may only be flowed through in one direction, depending on the operating case "filtering" or " Backwash” alternative.
• the non-return valves Fa, Fb, Fc allow flow in only one direction due to their directional nature, they are particularly suitable for the ultrafiltration system 1 according to the invention. They are arranged in the local filtrate lines 8a, 8b, 8c in such a way that their input side is connected to the corresponding ultrafiltration module 3a, 3b, 3c and their output side is connected to the central filtrate line 8.
• the corresponding non-return valve Fa, Fb, Fc opens independently of the volume flow.
• This opening pressure PRFV is, for example, approx. 0.3 bar even for the smallest volume flows. From this property, which is perceived as disadvantageous in professional circles, the advantage arises within the scope of the present invention that the backflow preventers Fa, Fb, Fc can be used as flow indicators. While the opening pressure of normal backflow preventers is above the measuring tolerance of simple and inexpensive pressure sensors and can therefore be reliably detected, minimal volume flows can only be measured with special, expensive volume flow sensors.
• backflow preventers Fa, Fb, Fc between the ultrafiltration modules 3a, 3b, 3c and the central filtrate line 8 eliminates the need for a volume flow rate detection for a flow indication. Rather, it allows the pressure difference across the series connection of ultrafiltration module 3a, 3b, 3c and associated Backflow preventer Fa, Fb, Fc a statement about an opening or non-opening of the backflow preventer Fa, Fb, Fc and thus also a statement about the flow or non-flow of filtrate even with the smallest volume flows. This in turn opens up the possibility of recognizing whether and when the ultrafiltration membrane 6 is damaged, ie has lost its integrity.
• the thickness of the lines in FIG. 1 symbolizes the pressure on the corresponding water-carrying line, the pressure being greater the thicker the line is.
• the dashed lines carry no water in the operating case shown, because the corresponding valve is closed.
• the ultrafiltration modules 3a, 3b, 3c are formed from an elongate, essentially cylindrical housing. They each have a large number of hollow fiber membranes 6 between the raw water side 5a and the filtrate side 5b, with the interior of the hollow fiber membranes belonging to the raw water side 5a and the space outside the hollow fiber membranes 6 to the filtrate side 5b in this embodiment variant.
• Each of the two sides 5a, 5b has the two connections already mentioned, which are each arranged on opposite axial ends of the housing.
• each ultrafiltration module 3a, 3b, 3c thus has a lower inlet connection 4au and an upper inlet connection 4ao each for the raw water side 5a, as well as an upper outlet connection 4bo and a lower inlet connection 4bu each for the filtrate side 5b there.
• the ultrafiltration system 1 also includes an inlet pressure sensor 11 for measuring the inlet pressure Pzu in the supply line 2 and an outlet pressure sensor 12 for measuring the outlet pressure Pab in the central filtrate line 8.
• another pressure sensor 14 is connected to the common section 8' of the second line 8 ', 8a, 8b, 8c connected to measure the backwash pressure PSP.
• the measurement signals from these pressure sensors 11 , 12 , 14 are fed to a system controller 9 .
• This comprises an evaluation unit 13 and a monitoring unit 16 in the form of functional units.
• the pressure difference APAN is then fed to the monitoring unit 16 in order to evaluate it to determine whether there is a loss of integrity in an ultrafiltration membrane 6 of one of the ultrafiltration modules 3a, 3b, 3c.
• FIG. 2 illustrates various operating cases A, B, C and D of the ultrafiltration system 1, in which the volume flow Q on the one hand and the pressure difference APAN on the other hand are considered.
• operating case A no drinking water is drawn off.
• the pressure Pab in the central filtrate line 8 is identical to the pressure Pzu in the central supply line 2, so that the pressure difference APAN is zero, i.e. no pressure drop across the system.
• no membrane defect can be detected in this state, no raw water then flows unfiltered through the membrane 6.
• the secondary consumption time is the period outside of the main consumption time. Essentially, the main consumption time coincides with the day and the secondary consumption time with the night. For example, the main usage time is between 6 a.m. and 6 p.m., the secondary usage time is between 6 p.m. and 6 a.m.
• Operating case C represents the main operating case during the day.
• the TMP together with the opening pressure PRFV of the backflow preventer Fa, Fb, Fc forms the Pressure drop APAN across the system 1 .
• the pressure drop across each of the series circuits of ultrafiltration module and backflow preventer 3a + Fa, 3b + Fb, 3c + Fc is equal to the pressure drop APAN across the system 1, so that considering one of the series circuits is sufficient .
• Other pressure drops, for example due to pipe friction losses, are negligibly small and are not taken into account here for the sake of simplicity.
• the calculated pressure difference PAN is divided between the TMP PTMP and the opening pressure PRFV, so that:
• the pressure difference PAN is thus significantly greater than the opening pressure PRFV of the non-return valve Fa, Fb, Fc.
• the integrity is OK.
• the integrity of the filter membrane 6 has been lost (here it is sufficient if just one of several membranes 6 in the filter module 3a, 3b, 3c is damaged). It has no hydraulic resistance, or the filter module 3a, 3b, 3c only has a negligibly small hydraulic resistance, so that the TMP PTMP is approximately equal to zero.
• the nominal opening pressure PRFV is around 0.3 bar.
• production-related tolerances and temperature influences allow this to vary in practice.
• a tolerance T of ⁇ 10% can be taken into account, which defines a tolerance band 15 around the nominal opening pressure PRFV with an upper limit of the value PRFV+T and a lower limit of the value PRFV ⁇ T.
• a limit value PRFV+T which corresponds to the upper limit of the tolerance band 15, is used to determine a loss of integrity.
• a higher value between the upper limit and the sum of the nominal opening pressure PRFV and TMP with a clean membrane 6 can also be used.
• a counter is started when the limit value is not reached in order to check how long this condition lasts. If a certain period of time T1, e.g. 5 minutes, is exceeded, a loss of integrity can be assumed with certainty.
• Operating case B relates to consumption outside of the main consumption time, especially at night, which is usually characterized by no or minimal water withdrawal. It is therefore more the case here that the pressure difference PAN is in the range of the opening pressure PRFV.
• a counter timer is also started here when the limit value is undershot in order to check how long this state lasts. If a certain period of time T2, e.g. 15 minutes, is exceeded, a loss of integrity can be assumed with certainty.
• the time duration T1 is selected to be shorter than the time duration T2, because due to the usually high water withdrawal and strong dynamics in the main consumption time, a minimum volume flow or a pressure difference APAN across the system 1 in the range of the opening pressure PRFV of the backflow preventer Fa, Fb, Fc should only be available for a short time.
• FIG. 3 illustrates the process sequence of the integrity monitoring according to the invention during filter operation of the ultrafiltration system 1. The process can even be carried out when the system 1 is backwashing one of the filter modules 3a, 3b, 3c.
• step S1 The method thus begins in the filtration mode, step S1.
• the calculated pressure difference PAN is made available to the monitoring unit 16, which checks the pressure difference APAN to see whether it lies between an upper and a lower limit value, in particular within the tolerance band 15, step S3.
• the upper limit here corresponds to the opening pressure PRFV of the non-return valve Fa, Fb, Fc plus a tolerance T, e.g. +10%. However, it can also be higher, as previously described.
• the lower limit here corresponds to the opening pressure PRFV of the non-return valve Fa, Fb, Fc minus a tolerance T, e.g. +10%. However, it can also be lower or even be zero.
• the pressure difference APAN is compared with the upper limit value, more precisely, a check is made as to whether the pressure difference APAN is below the upper limit value.
• the comparison of the pressure difference APAN with the lower limit value that takes place in the second sub-step, more precisely the check as to whether the pressure difference APAN is above the lower limit value, serves to distinguish the integrity error from operating case A, ie the case of no water withdrawal.
• the second comparison can thus be viewed as a verification of the “integrity error” assumption from the first comparison.
• the second sub-step can also consist of checking whether the pressure difference APAN is greater than zero. If the pressure difference APAN is above the upper limit value or below the lower limit value, then the integrity of the membrane 6 is OK (no branch) and the determination “no loss of integrity” is made in step S9.
• step S4 If the pressure difference PAN is between the upper and lower limit values, a further check is made as to whether the main consumption time is currently present, step S4. If this is the case, the method continues with step S5 (yes branch), otherwise with step S8 (no branch). In the case differentiation in step S4, it is only decided which duration T1 is to be taken into account for the main consumption time or T2 for the secondary consumption time in the subsequent step S5, S8.
• step S5 For the duration T1, in step S8 for the duration T2. More precisely, in these steps S5, S8 a counter is first started and then step S2 and the test are repeated and carried out alternately as to whether the pressure difference APAN remains below the upper limit value until the corresponding duration T1, T2 is reached. If the pressure difference APAN rises above the upper limit value again within the corresponding period T1, T2 (no branch of S5, S8), the brief undershooting of the upper limit value was merely the result of minimal water removal and there is no loss of integrity, step S9. The method is then continued again at the beginning at step S1, since the integrity monitoring is continuously active in the filtration operation.
• a loss of integrity can thus be reliably detected for each of the filtration operations in a simple manner. It should be noted that the method described only establishes that or if there is a loss of integrity in any membrane 6 of an ultrafiltration module 3a, 3b, 3c. In order to find out where or in which filter module 3a, 3b, 3c this is the case, these can be taken out of operation one after the other by closing the inlet valves Za, Zb, Zc one after the other. If the inlet valves Za, Zb, Zc of that ultrafiltration module 3a, 3b, 3c that has the defective membrane 6 is closed, the pressure difference APAN rises above the upper limit value again. This means that the location of the integrity error has also been tracked down.
• the invention also includes any changes, alterations or modifications of exemplary embodiments which have the exchange, addition, alteration or omission of elements, components, method steps, values or information as their subject matter, as long as the basic idea according to the invention is retained, regardless of whether the change, alteration, or modifications improves or degrades an embodiment.

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• Engineering & Computer Science (AREA)
• Water Supply & Treatment (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Separation Using Semi-Permeable Membranes (AREA)

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• 2020
  • 2020-12-21 EP EP20841704.8A patent/EP4200063A1/de active Pending
  • 2020-12-21 CN CN202080107452.3A patent/CN116457074A/zh active Pending
  • 2020-12-21 WO PCT/EP2020/087492 patent/WO2022135670A1/de active Application Filing

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