WO2007115988A1 - Small scale reverse osmosis system with concentrate management - Google Patents

Abstract

The invention relates to a method for operating a small scale reverse osmosis system comprising a system controller, wherein a reverse osmosis module (4) is supplied with untreated water by means of an untreated water inlet (1), from which a partial amount, designated as a concentrate, is discharged via a concentrate outlet (9) and another partial amount, designated as a permeate, is filtered by a membrane and is discharged via a permeate outlet (21) from the reverse osmosis module (4). According to the invention, an additional amount is added to a continuous concentrate flow, which is less than the amount required to operate the system in a safe manner, said additional amount being adjusted on a user interface in accordance with the membrane performance and the degree of hardness of the untreated water.

Description

Small volume reverse osmosis plant with concentrate management

The invention relates to a small-volume reverse osmosis system, comprising a reverse osmosis module, which has a membrane and a raw water inlet and a concentrate outlet, both arranged on one side of the membrane, and a permeate outlet, the reverse osmosis module on the other side of the membrane is arranged. In order to avoid blockage of the membrane, the reverse osmosis module must be flushed regularly or it must be permanently operated with a clear excess of water, so that the permeate yield is in a very low ratio to the raw water volume used and the operation of the reverse osmosis plant is accordingly economical unfavorable. In this case, the ratio of raw water used to usable permeate is referred to as yield or else as efficiency, eg. B. 50%, if the used raw water amount of 100% in 50% concentrate and 50% permeate divided. The ratio of discarded concentrate to recoverable permeate may be referred to as the effluent ratio, that is, 1: 1 in the case described above, which means the same yield. Typical small quantities of plants work in a ratio of 3: 1 and worse, which corresponds to a yield of 25% and less.

A small-scale plant is a so-called "point-of-use" plant, which is installed directly at the end consumer, eg in restaurants or private households, and produces permeate amounts of about 20 l to about 1000 l per day Such a system is described, for example, in European Patent EP 0 567 751 B1 or European Patent EP 0 672 448 B1.

Especially with devices for the end user, it is desirable because of the different specifications for the local hardness of the raw water and the individual membrane performance, since a single general setting almost always leads to non-optimal yields. The discrepancy to the optimum yield can be considerable. In the small-scale systems used today, it is not yet possible, the yield of the system without the change of components or automatically to different membrane performance, and raw water qualities adapt. In addition, it is necessary to adjust the yield to the raw water temperature. A higher temperature greatly increases the quantity output, so that it is then necessary to adjust the amount of concentrate in proportion to the amount of meat. It would be necessary to precisely adapt the device technology on site.

For this reason, in the case of small systems, a setting is usually used which also fits worst conditions and maximum water temperatures, so that blocking of the membrane is ruled out. As a result, the system works but only under these conditions with the best possible efficiency. At lower water temperatures efficiency would be worse by the lower production and a possible adaptation to a more advantageous for the operation raw water quality does not take place with it. A change in membrane performance would immediately require a redesign of the system.

In practice, this means that a plant designed for 25 ° C raw water temperature to a yield of 25% works in areas with a water temperature of 12 ° C only with a yield of about 15%, with favorable water quality with soft water but actually up to 75% yield would be possible. An adjustment of the production quantity to increased demand or an optimization of the efficiency could only be carried out by trained specialist personnel with a lot of time and material expenditure. It requires a huge assortment of different systems and components, which hinders the development of a low-cost mass-produced product.

The object of the invention is to improve a generic reverse osmosis system in such a way that it overcomes the disadvantages indicated above.

According to the invention, it is proposed to provide a method for operating a small-volume reverse osmosis system with a system controller, in which raw water is supplied to a reverse osmosis module by means of a raw-water inlet, of which one partial quantity designated as concentrate flows via one concentrate outlet and another, is filtered out of the reverse osmosis module through a membrane called a permeate subset via a Permeatauslauf, wherein an addition amount is added to a continuous concentrate flow, which is below the necessary amount necessary for the safe operation of the plant, which can be adjusted depending on the membrane performance and the hardness of the raw water at a user interface.

In a further embodiment of the invention it is proposed to replace a part of the user interface by a sensor which determines a value correlating to the membrane performance and then incorporates this value for the calculation of the necessary total concentrate flow.

A value correlating to the membrane performance can also be determined according to the invention by determining the respective quality of the raw water and the concentrate and / or permeate and their comparison.

In an alternative embodiment of the invention, it is proposed to replace a part of the user interface by a sensor that determines the degree of hardness of the raw water and then incorporate this value for the calculation of the necessary total concentrate flow.

Furthermore, it is proposed to equip a small-volume reverse osmosis system, with a reverse osmosis module, which has a raw water inlet, a concentrate outlet and a permeate outlet, with sensors which detect the water quality as described above, and by a plant control, which also as described above total concentrate flow automatically adapts to the amount required for the amount of permeate produced, as well as by a user-operable and effectively connected to the plant control interface, by means of which adaptation to the degree of hardness and the membrane performance on site are possible.

According to the invention, a system is provided with a single basic device design which is easy to install and always achieves the highest possible yield despite temperature-induced variable membrane performance and changing water quality. Today, in household appliances and smaller professional applications, membrane capacities of 24 to 400 liters per day are available, all of which can be installed in the same housing. The inventive method and the system according to the invention ensure that without further ren replacement of components such a range of services installed and optimized can be operated.

In contrast to installations used for large industrial purposes, in which the water quality is measured and in which, depending on the measured values, the delivery of concentrate is influenced by means of regulating valves, a considerably cheaper configuration of the installations is made possible according to the proposal. While the large-scale industrial plants have considerable minimum flow rates, comparable control valves would have to work very accurately according to laboratory standards in order to be adapted to the small-volume reverse osmosis system. That is precisely with the price specifications for the mass market of small plants not transferable. In practice, it may be necessary or desirable to set an average concentrate flow in the range of less than 50 ml / min, and the highly accurate measurement and control technique required would be disproportionately expensive relative to the price of the remainder of the equipment.

According to the invention is designed by a proposed reverse osmosis system, the system in a first step with common components for the lowest power and efficiency, that the design would usually lead to blocking of the membrane. The plant is equipped with a plant controller according to the present invention which monitors the concentration of solutes at the most important points of the system and monitors the concentration by comparing the values. The blocking index of the raw water can be entered into the system manually or via an interface from a measuring device via a user interface. A statement about the Verblockungsindex would be simply by measurements with common hardness gauges possible, as it is already carried out during the commissioning of a dishwasher by the consumer. The system control then acts on a control valve, which may be designed here as a simple solenoid valve, and controls via flushing pulses the actual concentrate flow of the system always to the best possible efficiency, taking into account a desired by the system manufacturer maximum concentration in the measured or detected Verblockungsin- dex. Advantageously, the flushing process can be carried out as a pulse flush with a sudden change in flow rate or flow rate. These changes as well as the resulting pressure fluctuations ensure an intensive rinsing effect and a correspondingly reliable cleaning of the membrane.

With this proposed procedure, it is possible to minimize the concentrate flow of the plant, which is so low that it is not sufficient to operate the plant in continuous operation. The fact that a rinse cycle is carried out regularly, the membrane is regularly cleaned and protected against blocking, so that the functionality of the system as well as the advantageous high yield is ensured for a long time.

The sensory detection of the water quality can for example affect the quality of the concentrate. A concentrate sensor can be provided in the housing, in which the membrane is also arranged, for example integrated on the membrane or in the membrane. This proximity to the membrane ensures responsive measurement results with a change in concentrate quality.

A manufacturing technology particularly simple arrangement of the sensor, which does not require a change in the reverse osmosis module itself, can be done in a line section through which the concentrate is guided by the membrane.

In order to be able to carry out the measurement in such a line section without problems and with a meaningful result, it is advantageously provided to set a certain minimum flow of the concentrate as so-called basic flushing amount, so that the respective line section is always flowed through by concentrate and the measurement is not carried out in a standing liquid will be recorded in the quality changes only with great delay.

In addition, a sensory detection of raw water quality can be carried out, so that a quality ratio between raw water and concentrate can be taken into account.

For example, measured values such as the electrical conductivity or other water quality readings are compared, and when certain limits are reached, the rinse cycle is triggered.

The invention is based on the assumption that a decrease in the quality of the permeate accumulated in a reservoir can not be measured even if the concentrate already has too low a quality to permit further operation with this concentrate quality, for example shortly before the first crystal formations take place. The timely purging of the reverse osmosis module thus ensures firstly the technical feasibility of the reverse osmosis module and in particular its membrane, and secondly the desired water quality of the permeate.

Alternatively to the above-described measurement of the concentrate quality, it may be provided to carry out a very accurate measurement of the permeate quality. Since in the above-mentioned memory there is always a thorough mixing with permeate already present there and the quality measurement made there is correspondingly slow, it is advantageously possible to carry out the measurement of the permeate quality in the membrane, e.g. by a conductivity sensor integrated in the membrane, or it can be carried out on or near the membrane. If there is the slightest impairment of the permeate quality, the automatically initiated rinsing cycle can then take place.

The automatic adaptation of the plant to the given local conditions can be carried out in a simple manner by the referencing of the permeate quality being carried out after such a rinsing cycle, so that individual quality values for the quality of the raw water used depend on the quality of the plant and on the quality Permeate are determined, which then serve as a reference for the further operation of the system.

As a further alternative when operating the reverse osmosis system, the change in the solutes, ie the Ausfilterrate the reverse osmosis system via sensors in the raw water and in the permeate can be compared, and depending on the determined ratio of the rinse cycle can be automatically activated. Alternatively, the change in the Ausfilterrate can be determined based on comparative measurements of concentrate and permeate. Advantageously, a user interface can be provided, so that the operator of the reverse osmosis system can set the limit, which serves to trigger the rinsing process, for. As the amount of maximum accumulation in the concentrate, and so that the operator of the reverse osmosis system can influence the duration of the rinsing phase. In this way, the reverse osmosis system can be adjusted by the user or commissioning of service personnel on the local water hardness, which allows further optimization of the yield, ie the ratio of raw water used or discarded concentrate on the one hand and won permeate on the other ,

From the determined measured values for the permeate and the concentrate or for the permeate and the raw water, or for all three mentioned measured variables, an evaluation of the filter effect can also be carried out, which is expressed as a percentage or over a threshold value, for example on a display accessible to the user can be.

By means of the proposed embodiment of the reverse osmosis system, it is possible to put the system into operation without first adjusting it to the respective place of use by selecting and assembling certain technical components. Rather, it may possibly be provided to select a specific hardness range of the raw water used on site. Subsequently, the system always automatically adjusts to the best possible yield.

Plant technology is economically advantageous that only a single purge system for a wide performance range of reverse osmosis systems is needed, which significantly reduces the cost of production and positional position of the manufacturer of reverse osmosis systems. In addition, it is possible for the operator in an economically advantageous manner, to achieve significantly better yield values than with "rigid" set to certain operating conditions systems.

The cost of a proposed self-regulating, automatically rinsing triggering reverse osmosis system are currently hardly any higher than that of a commercial reverse osmosis system with a commercial automatic rinsing and a conductivity comparator. Even with a tenfold increase in membrane performance, the basic configuration of the system can remain unchanged an automatic adaptation to the respective conditions takes place. This ten-fold increase in membrane performance can be made possible, for example, by using a housing design of the reverse osmosis module with different membrane inserts, ie with different sized effective membrane surfaces, which is also possible with currently commercially available reverse osmosis modules , In the case of proposals designed according to this change, however, this change is particularly easy, without having to make a change or adjustment of the entire system.

It is advantageous for the manufacturer that, for example, not 20 or more different concentrate regulators need to be provided in order to adapt the respectively to be delivered reverse osmosis system to the respective local water quality, which is found at the customer.

Another advantage of the proposed system is the automatic adaptation of the system to different raw water qualities and raw water temperatures.

In contrast to a tailored to the local water quality, but "rigid" ready-made system in which, for example, by the selection and adjustment of the respective concentrate regulator such an adjustment has been made when operating a proposed system even with changing raw water qualities automatically an adjustment the plant done by depending on the particular circumstances in each case the flushing of the reverse osmosis module in time, so that in each case the optimal intersection between see the highest possible yield on the one hand and the highest possible permeate water quality on the other hand is maintained.

Exemplary embodiments of small-volume reverse osmosis systems are explained in more detail below with reference to the purely schematic illustrations. It shows

1 is a simple system,

2 shows a plant with a concentrate recycling, and FIG. 3 shows a plant with a permeate pump.

In the drawings, 1 denotes a prefilter, in the corresponding the drawn arrow direction raw water is led, for example, from a public drinking water supply network. The filtered raw water passes to a raw water solenoid valve 2, to a raw water sensor 3 and from there into a reverse osmosis module 4. The raw water solenoid valve 2 is automatically opened and closed depending on demand by means of an electronic system control.

Passed through the membrane of the module 4 permeate passes to a permeate sensor 5 and from there for further use. It can be used directly or stored in a memory.

At the reverse osmosis module 4 also falls to concentrate, which passes a concentrate sensor 6 and passes to a flow restrictor 7, which also serves as a pressure holding valve for the reverse osmosis module 4.

A bypass line 8 leads the concentrate past the flow restrictor 7 to an outlet line 9 if a rinse water solenoid valve 10 is open. Basically, the flushing water solenoid valve 10 is closed. It is automatically opened and closed by the system controller. The open solenoid valve 10 allows the short-term outlet of larger amounts of concentrate, so that in a kind of pulse flushing the reverse osmosis module 4, in particular its membrane, can be rinsed.

Deviating from the illustrated embodiment, the solenoid valve 10 may be combined with the flow restrictor 7, so that the required installation costs can be reduced.

In Fig. 2, a system is shown, which is basically constructed as the system of FIG. 1, but is equipped with an additional pump 11 to increase the pressure. This pump 11 increases the pressure in the reverse osmosis module 4 beyond the normal pressure of the public drinking water supply network. This makes it possible, via the flow restrictor 7, to recycle the concentrate before the pressure-increasing pump 11 against the pressure prevailing in the drinking water supply network. In the reverse osmosis module 4, therefore, a high flow can be generated without a correspondingly high consumption of raw water, ie without correspondingly high water losses at the outlet 9 Concentrate quality can be detected by means of the concentrate sensor 6, so that a flushing process can be initiated by opening the flushing water solenoid valve 10 with appropriate concentrate values. The installation control system used for this exemplary embodiment illustrated in FIG. 2 is advantageously extended over the installation control system that can be used for the exemplary embodiment of FIG. 1 such that it includes the actuation of the pressure increase pump 11.

Fig. 3 shows a plant, as it is basically comparable to the system of Fig. 1. The permeate passes behind the permeate sensor 5 into a permeate pump 12. From this, the permeate is conveyed into a pressure accumulator 13. If the permeate is used, it passes through a post-filter 14, in which it is post-treated and can then be removed from a sampling tap 15 under pressure.

To drive the permeate pump 12, the energy, in particular the pressure, of the concentrate is utilized: A membrane 16 separates a concentrate chamber 17 within the permeate pump 12 from a permeate chamber 18. Control valves 19 and 20 serve to control the permeate pump 12. These are mutually dependent, namely position-dependent from the position of the membrane 16, controlled. On the side of the permeate chamber 18, the pump valves 21 and 22 serve as non-return valves for conveying the permeate into the storage tank 13.

The permeate which has passed through the membrane in the reverse osmosis module 4 fills the permeate chamber 18 of the permeate pump 12, the permeate passing through the pump valve 22 into the permeate chamber 18. The membrane 16 of the permeate pump 12 is deflected to the left, ie into the concentrate chamber 17. The control valve 19 is closed in this phase. The control valve 20, however, is open, so that the increasing permeate within the permeate pump 12 displaces the concentrate from the concentrate chamber 17 to the outlet 9.

By reversing the valves 19 and 20, this process is terminated when the membrane 16 has reached its intended deflected to the left end position. For this purpose, a sensory connection between the valves 19 and 20 on the one hand and the membrane 16 on the other hand can be provided. Since the valve 20 is now closed and thus the connection to the outlet 9 is interrupted, concentrate flows through the open valve 19 in the concentrate chamber 17 of the permeate pump 12. In this case, the membrane 16 is pushed back from its maximum to the left deflected position to the right. The permeate accumulated in the permeate chamber 18 is thereby forced out of the permeate pump via the pump valve 21 and flows into the storage tank 13. This process continues until the membrane 16 has been moved to its right-deflected end position and the permeate is largely conveyed out of the permeate chamber and is conveyed into the storage tank 13. Subsequently, when the valves 19 and 20 again reversed and the above-described filling of the permeate chamber 18, at the same time the emptying of the concentrate chamber 17, starts from the beginning.

The above-described processes can in principle be repeated until the pressure in the storage tank 13 has reached the inlet pressure of the water supply, ie the public drinking water supply network, or until the supply to the reverse osmosis module 4 via the solenoid valve 2 is closed. The solenoid valve 2 can be controlled for example via a pressure switch 23. Since the effective surface of the membrane 16 to the two concentrate and permeate chambers 17 and 18 is the same size, the same amount of concentrate is delivered as the amount of meat in the storage tank 13 is promoted. This concentrate flow makes it possible to detect the concentrate quality at the concentrate sensor 6.

Claims

claims: 1. A method for operating a small-volume reverse osmosis system with a plant control, wherein a Umkrosmosemodul (4) by means of a raw water inlet (1) raw water is supplied, of which a designated as concentrate subset via a concentrate outlet (9) and another, filtered through a membrane and referred to as permeate subset via a permeate outlet (21) is led out of the reverse osmosis module (4), characterized in that a continuous concentrate flow, which is below the necessary amount that is necessary for the safe operation of the system, an additional amount is added, which can be adjusted depending on the membrane performance and the hardness of the raw water at a user interface. 2. The method according to claim 1, characterized in that a part of the user interface is replaced by a sensor that determines a value correlating to the membrane performance and then this value can be included for the calculation of the necessary total concentrate flow. 3. The method according to claim 2, characterized in that the correlating to the membrane performance value is determined by determining the respective quality of the raw water and the concentrate and / or permeate. 4. The method according to any one of the preceding claims, characterized in that a part of the user interface is replaced by a sensor that determines the degree of hardness of the raw water and then incorporate this value for the calculation of the necessary total concentrate flow. 5. small-volume reverse osmosis system, with a reverse osmosis module, which has a raw water inlet, a concentrate outlet and a Permeatauslauf, characterized by sensors (3, 5, 6), which detect the water quality according to one of the preceding claims, and by a plant Control, which according to one of the preceding claims automatically adjusts the total concentrate flow to the amount required for the amount of permeate produced, as well as an interface operable by a user and operatively connected to the plant control, by means of which adaptation to the degree of hardness and membrane performance is possible on site are.