Patent Publication Number: US-2021179468-A1

Title: System and method for purifying faecal-free and surfactant-containing domestic wastewater

Description:
The present invention relates to a system and a method for purifying fecal-free and surfactant-containing domestic wastewater comprising an electrochemical processing stage. 
     TECHNICAL FIELD 
     In the case of wastewater from the domestic sector, it would generally be desirable if it were at least partially possible to recycle the resulting wastewater, i.e. to purify it and to feed it to a renewed use. This would be particularly important, however, for mobile sanitary systems, such as, for example, in campers, mobile homes, on boats and ships, as well as in aircrafts. In the case of these, the amount of fresh water, which is to be carried along, could be drastically reduced, if it were possible to treat at least a portion of the generated wastewater such that it can be reused at least in individual regions of the sanitary systems. 
     PRIOR ART 
     Various approaches for this are known in the prior art. However, the opinion is generally prevalent that only fecal-free wastewater can be purified with reasonable effort and can thus be recycled. The so-called black water—wastewater from the toilet containing fecal matter—is thus typically considered to be waste. The same generally applies for wastewater from the sink and the dishwasher, but for a different reason. The grease accumulating when doing the dishes often cause problems when purifying. The so-called grey water, however, which originates from showers, bathtubs, hand washbasins, and washing machines, would be ideally suited for the treatment and reuse in light of the dirt load as well as in consideration of the fact that such wastewater is typically neither particularly greasy, nor is it loaded with bacteria or viruses. The below-mentioned documents in the prior art therefore deal predominantly with grey water recycling. 
     Various filter stages connected in series are used, for example, in US 2017/0297939 A1, in CN 105 421 527 A, and also in EP 2 295 649 A2. The latter also proposes biological water purification methods. 
     DE 10 2005 006 136 A1 discloses a grey water utilization system for an aircraft. Grey water accumulating in the hand washbasin is thereby treated to such an extent that it can be utilized for flushing the toilet in the aircraft. An electro-flotation stage is proposed for purifying the grey water. WO 2008/120963 A1 proposes a mechanical floatation stage for separating contaminants in grey water. Here, polymers are added in the form of flocks and are removed, after they are soaked with dirt particles. 
     In the case of the present invention, the development of a recycling system for campers was paramount. The camper market has greatly increased in recent years. Customers appreciate the freedom offered by a camper under various aspects. What also delights is in particular the freedom that the camper can also be parked once independently of camper sites or campgrounds and that, for example, one can stay for one night. However, it is important for this that sufficient water can be brought along in order to be able to perform the necessary bodily functions, i.e. to use the toilet, to take a shower, to wash, and optionally also to do the dishes. To reduce the fresh water consumption and thus the amount of fresh water to be brought along in a camper, it would thus be desirable if resulting wastewater could be purified for renewed use. As already described above, toilet wastewater cannot be used to recycle wastewater, and wastewater from doing dishes can only be used to a limited extent. It would be extremely desirable, however, if, for example, resulting shower water could be purified and treated, so that it could be used as shower water again. In addition, this would make it possible that one could also shower for a relatively long time, for example also for 10 minutes, in a camper, without depleting the water. 
     However, when implementing the known methods and systems, it became apparent that the surfactants, which are contained in the shower water, from the shampoo and from the soap, which is used for washing, caused problems during the treatment. If the purified water is only used again for flushing the toilet, as in the case of DE 10 2005 006 136 A1, it is irrelevant whether surfactant residues are still contained and the flushing water thus foams slightly. When taking a shower and washing hands, however, it is perceived to be unpleasant when the water comes out of the tap while already foaming. The person taking a shower then gets the impression that he is washing himself with unclean water. 
     OBJECT 
     As a result of this, the present invention has the object that the surfactants, which are contained in fecal-free domestic wastewater, are also removed as much as possible and that purified water is thus obtained, which is essentially surfactant-free and which at least does not foam when it is used for showering or for washing hands. The wastewater generated in a household is to further be recycled in the best possible way, in order to conserve water. 
     DESCRIPTION OF THE INVENTION 
     This object is met by a system according to patent claim  1  and a method according to patent claim  11 . Preferred embodiments are subject matter of the dependent claims. 
     The system according to the invention and the method according to the invention are provided for purifying fecal-free and surfactant-containing domestic wastewater. In the context of the present invention, the term “domestic wastewater” is understood to be wastewater from various sources, also referred to as consumers. The term does not only capture the classic private household, but in particular also a mobile household, for example in a camper, mobile home, or on a boat or ship, respectively. To an extended degree, this also includes wastewater from aircrafts and also from larger units, such as, for example, hotels, cruise ships, or entire residential complexes. However, industrial wastewater, as it results, for example, in manufacturing firms, is excluded from the definition. 
     The wastewater to be treated is fecal-free, i.e. black water, thus wastewater from the toilet, is excluded. It will typically be wastewater from the shower, from the bathtub, from the hand washbasin, from washing machines, thus grey water. It became clear, however, that wastewater from sinks and dishwashers can also be purified by means of the present invention, so that wastewater of this type is also included in the present definition. What is to be treated is thus wastewater from different consumers, provided that it is fecal-free wastewater. 
     It should be noted that with respect to some wastewater, the classification of wastewater as being so well recyclable that it can be used again for showering or bathing, can depend on the respective circumstances. Wastewater from the shower and from the bathtub generally only contains a small amount of surfactants and it generally likewise only carries a small dirt load. Wastewater from the sink and from the dishwasher generally contains a large amount of surfactants and grease, and generally contains relatively high dirt loads. Depending on the affected household and the use of surfactants taking place there as well as on the dirt load to be cleaned, wastewater from washing machines and hand washbasins can be purified into virtually pure clear water from time to time and can thus be used, e.g. as shower water, or it is to be qualified as dirtier wastewater, and consequently the purified clear water is to only be used, e.g., for flushing the toilet. As a result, an exact classification of the wastewater of a consumer depends on the actual circumstances. 
     As described above, it became clear that the electro-flotation alone was not sufficient to remove surfactants contained in the wastewater to be purified. After a large number of tests, the inventors were surprised to find that the introduction of a gas, in particular of air and/or of ozone, and in particular in fine-bubble form, in combination with the electrochemical treatment makes it possible to remove the contained surfactants to such an extent that the obtained clear water is largely free from surfactants, and at least does not foam when it leaves the shower head or the faucet. 
     Water is split during the electro-flotation. The oxygen created thereby rises as small gas bubbles and reacts with present pollutants in the liquid phase and/or accumulates at undissolved components, such as dirt particles. The floatation is made possible thereby. Due to the fact that gas is already created in the wastewater during the floatation and gas is thus already present in the wastewater, it could not be assumed that further introduction of gas could result in an improvement of the purification effect. Instead, it would have been necessary to assume that a different processing type is to be sought in order to completely remove surfactants. It came as a surprise, however, that the introduction of gas, regardless of whether prior to, during, or after the electro-flotation stage, greatly improves the surfactant purification, so greatly that virtually surfactant-free clear water is created. Neither electrochemical processing alone, nor the introduction of gas, and subsequent skimming of the foam alone, brought the desired success. 
     By means of the present invention, fecal-free and surfactant-containing domestic wastewater is transferred into sterile and odorless clear water, which is largely free from active washing substances. The fact that it can subsequently be used again, for example for showering, results in the advantage that sufficiently clean water for showering is in each case available for each person, which is an advantage that has an advantageous effect, in particular in the case of campers, mobile homes, and yachts, but also in hotels and cruise ships. 
     It is highly advantageous that total water quantities, which are to be transported, are reduced by means of the present invention. Due to the fact that a larger portion of the water circulates and is treated again, it is possible to reduce the fresh water quantity as well as the wastewater quantity. Fresh water tanks and wastewater tanks in mobile units can thus be dimensioned to be suitably smaller and/or the service life can be extended, without tedious refilling of the fresh water tank and/or emptying of the wastewater tank. 
     Due to the separate guidance and storage of dirty water from different sources, i.e. originating from different consumers, as well as clear water from different sources, the water, which is present in the system, is optimally usable and recyclable. Extremely dirty and surfactant-polluted water can be used to flush the toilet when purified; and not very dirty and surfactant-polluted water can be used for showering, washing hands, or doing dishes when purified. The fresh water consumption in a household can be greatly reduced in this way. 
     The system and the method can be operated in circulation, quasi “online”, i.e. while a person showers, the treatment of his/her shower water takes place, which is subsequently fed immediately to the shower again. An essentially “endless” shower time can be provided in this way with a small amount of shower water, e.g. with 10 liters of water. 
     In the alternative, the water is stored in a clear water container after the treatment and is then used during the next showering process. Until this next showering process has concluded, the dirty water thereof is collected in a dirty water container and is treated subsequently or at any point in time, e.g. at night, and is fed to the clear water container again. “Endless” shower times are obviously not possible in this way. 
     It goes without saying that the invention can also be used and is advantageous in stationary households, such as private households, residential complexes, and hotels. In many parts of the world and also in Europe, more ground water is consumed than is reproduced, so that it would be extremely desirable, if wastewater is recycled in larger quantities. 
     According to the invention, at least two dirty water containers and at least two clear water containers are present. Each of them stashes away wastewater and clear water, which originates from different consumers or which is intended for different consumers, respectively. The wastewater originating from the shower and/or bathtub and/or washing machine is thereby collected in the one dirty water container, and the dirty water originating from the hand washbasin and/or the sink and/or dishwasher is collected in the other dirty water container. Wastewater from the hand washbasin, the sink, and the dishwasher is typically dirtier and often also contains a much larger quantity of surfactants than shower or bath water and optionally washing machine water. These types of wastewater are thus kept separate and are purified separately, because shower and bath water can be treated more easily, and can thus be treated to a higher purity than the wastewater from the sink, etc. Different types of wastewater originating from different consumers, can be stored separately, purified separately, and used again separately, and with the largest possibly flexibility by means of the present system, depending on the level of soiling thereof and the type of soiling thereof. 
     If the household requires it, more than two dirty water tanks and/or more than two clear water tanks can also be provided. On large ships or at camping sites, for example, it can be advantageous when, e.g., three types of dirty water tanks are present, one for dirty water from the showers, a second one for dirty water from the sinks, and a third one for dirty water from the hand washbasins and washing machines. Depending on the level of soiling, e.g. of the wastewater in the third dirty water container (dirty water from the hand washbasin), the clear water resulting after passing through the purification stages can be fed into the shower water-clear water container for showering, or into the toilet flushing water-clear water container. 
     According to the invention, bath and shower wastewater is also collected in a separate clear water container after the purification, and the dirtier wastewater from the sink, etc. in a further separate clear water container after the purification. Water from the second clear water container, i.e. purified shower and bath water, can then be used to shower and bathe again, whereas in contrast, the clear water from the first clear water container, i.e. purified handwashing water, dishwashing water, and dishwashing machine wastewater is preferably used to flush the toilet. 
     The introduction of gas can take place, for example, with the help of a compressor, a pump, a stirrer, or, particularly preferably, by means of an aeration membrane, also referred to as venting membrane, in particular by means of a ceramic aeration membrane. It became clear that it is particularly advantageous when the gas is as fine-bubbled as possible, in order to provide the largest possible surface. Fine-bubble gas bubbles generated by means of ceramic aeration membranes have a diameter of, for example, approx. 50-100 μm. 
     A further improvement in the surfactant removal is attained in that in a preferred design, a calming zone or several calming zones, in which the purified water can calm to the extent that it can be discharged, exist within the electrochemical processing unit or immediately adjacent thereto. During the calming, small gas bubbles, which may still be present, originating from the electro-flotation as well as introduced in the form of fine bubbles, will rise to the top, and will thus entrain surfactants or pollutants, which may still be present. The calming zone is thus arranged in the floor area of the electro-flotation system and is separated via a separation. 
     The separated, i.e. floated foam, which is loaded with surfactants, possibly present harmful substances and dirt particles, is processed as wastewater and is fed to a wastewater tank or is discarded immediately, respectively. In a camper, for example, it could be processed like black water originating from the toilet and could be fed to a common wastewater tank. 
     The discharging of the floatable water constituents into the wastewater tank takes place, e.g., via an overflow pipe. The latter can simultaneously also serve as forced venting or can have such a forced venting, respectively, in order to guide the released hydrogen from the electro-flotation and the foam to the outside. 
     Prior to the introduction into the wastewater tank, the foam can be destroyed, in order to bring about a volume reduction. The destruction of the foam can take place, for example, by means of sonicating, by means of chemical anti-foaming agents, by means of mechanical methods, such as the guiding through a foam-destroying woven fabric or screen, by washing away or showering down by means of a corresponding liquid. This foam-destroying system is preferably mounted in the overflow pipe. 
     In the case of the system according to the invention, further pre-treatment and post-treatment stages can be added, such as, for example, various filtration stages. Typically, both a pre-processing will be performed by means of a pre-filter or coarse filter, and a post-processing will be performed by a post-filter. The pre-filter or coarse filter thereby predominantly filters out coarser particles; the post-filter generally serves to separate fines, which may still be present. Sand filters, microfiltration, nanofiltration, ultrafiltration, and reverse osmosis are thus preferably used as post-processing filtration units. For example screens and woven fabrics are possible as pre-filter and coarse filter. 
     In one embodiment, the clear water generated by means of the method according to the invention or the system according to the invention, respectively, which can also be referred to as industrial water, can also be used for backflushing the filtration system. 
     The fresh water container, i.e. the container in which water originating from communal water supply systems is stashed away, can be kept relatively small by means of the system according to the invention, and even more so by means of the system in the preferred embodiments. The predominant portion of the water supply, for example of a camper or of a yacht, can thus be covered via recycled water. One of the main problems when traveling for example on a yacht, the timely stashing away of water, is significantly simplified thereby. The yacht can thus travel much longer, without having to add water again, than if it did not have a recycling system according to the invention on board. 
     Moreover, a water shortage in the clear water tank, e.g. in an aircraft, can be capable of being detected via a sensor system, so that, for example via an electronic controller, a subsequent washing process in the hand washbasin in the lavatory can be lengthened, until this water shortage is fixed. For all intents and purposes, more dirty water and thus clear water is thus intentionally generated by increased consumption of fresh water. 
     Moreover, a grey water feed and the electro-flotation device can be connected to one another on the floor side according to the principle of the communicating tubes. According to an exemplary embodiment, the electro-flotation device and the filtration stage are connected on the surface side according to the overflow principle. From the dirty water container, the polluted water flows into the cleaning, i.e. into the pre-filter, if present, or directly into the electro-flotation stage, according to the principle of the communicating tubes. 
     The layer thickness of the generated and removed foam, i.e. the floated, can take place, for example, by means of an optical measurement, for example in the form of a light barrier or in the form of an ultrasonic measurement. 
     To avoid that an aluminum or iron hydroxide layer attaches to the anodic plates, the polarity thereof is reversed within certain time intervals. 
     The filling level of the liquid containers—dirty water containers, clear water containers, fresh water containers, wastewater containers—is preferably monitored, e.g. via a float gauge or via a different fill level sensor. For example when reaching a fill maximum in the clear water tank for feeding into the shower, a float valve can thus be opened by means of a corresponding float gauge, which floats upwards, wherein the excess liquid is either transferred into a clear water tank, more precisely into the clear water tank for flushing the toilet, or is fed to the wastewater container. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The invention will be explained and described in more detail below on the basis of the enclosed drawing, in which: 
         FIG. 1  shows a first exemplary embodiment of a domestic wastewater recycling system according to the invention, and 
         FIG. 2  shows a second exemplary embodiment of a domestic wastewater recycling system according to the invention. 
     
    
    
     DESCRIPTION OF THE FIGURES 
       FIG. 1  shows a wastewater purification system, which could be realized, for example, in a camper or a yacht. Two dirty water containers are present, one shower dirty water tank  1 , and one general dirty water tank  21 . Wastewater from the shower  25  reaches into the shower dirty water tank  1 . Wastewater from a washbasin  15  and from a sink  13  are fed to the dirty water tank  21 . 
     The dirty water from the two dirty water containers  1  and  21  can be fed to a pre-filter  2 . The wastewater from the two dirty water containers  1  and  21  can thereby be fed to the pre-filter  2  in a combined manner or can be kept separate and can in each case be guided separately through the purification stages. Coarser dirt particles and other coarser substances in the wastewater, such as, e.g., hair, are separated in the pre-filter  2 . 
     After the wastewater has passed through the pre-filter  2 , it is fed to an electrochemical processing unit  3 . On the way there, chemicals can also be added, if necessary, such as, for example, chemicals for the water treatment and splitting agents. The adding unit for chemicals is identified with reference numeral  19 . 
     In the embodiment of  FIG. 1 , the electrochemical processing unit  3  is equipped with plate electrodes  16 . The plate electrodes are aligned parallel to one another. 
     In the electrochemical processing unit  3 , gas in the form of fine bubbles is introduced via a venting membrane  14 . For example ozone from an ozone ventilation  11  can be used as gas. Ozone is a strong oxidizing agent, so that germs, which may be contained, are killed. For example iron, manganese, and organic substance is furthermore oxidized thereby. In the alternative or simultaneously, air can be used as gas for the introduction of gas, identified by reference numeral  12 . 
     As can be seen, the unit for introducing gas is arranged within the electrochemical processing unit  3 , namely the venting membrane  14 , in the preferred embodiment. It is also possible, however, that the air is introduced in the form of fine bubbles in the pipe system, which leads directly into the electrochemical processing unit, i.e. between adding unit for chemicals  19  and electrochemical processing unit  3 , or upstream of the adding unit for chemicals  19  in the feed pipe. 
     Foam is created in the electrochemical processing unit  3 , both by means of the electro-flotation itself, and by means of the fine gas bubbles, as suggested in  FIG. 1 . The foam is compressed via a foam compression  17  and is discharged via an overflow pipe  7  and is fed to a wastewater tank  9 . 
     A calming zone  18 , in which the water is collected prior to the discharge from the electrochemical processing unit and can calm, so that gas, which may still be contained, escapes, and foam rises to the top, is likewise entered in  FIG. 1 . The calming zone  18  is separated from the remaining interior of the electrochemical processing unit  3  via a separation. Water thus enters into this calming zone  18  from the bottom, very close to the floor of the electrochemical processing unit  3 . 
     An automatic level raise  27  serves for and improves the foam discharge. 
     Water purified in the electrochemical processing unit is finally fed to a fine filter  4 , for example a sand filter, or to a microfiltration unit, and to an activated carbon filter  5 . The purified water is finally fed to one of the two clear water containers or to both of them, namely to the clear water tank  6  or to the toilet clear water tank  22 . For example, the shower  25  is fed from the clear water tank  6 , or also a separate faucet  23  of the sink  13 , in order to pre-clean dishes, for example. Water from the toilet clear water tank  22  is fed to the toilet flusher  24  with the help of a pressure cylinder  10 . 
     It can be seen that the two dirty water containers  1  and  21  as well as the two clear water containers  6  and  22  can be processed separately. For example, the dirty water from the shower dirty water tank  1  can thus be guided through the purification stages and can be fed to the clear water tank  6  or to the toilet clear water tank  22 . The same applies for wastewater from the second dirty water tank  22 . 
     If necessary, fresh water can be used directly from a fresh water tank  20 , for example also for showering or for doing dishes. If necessary, the clear water tanks  6  and  22  can furthermore also be replenished by fresh water from the fresh water tank  20 . 
     Filtration systems can preferably be backflushed, in order to remove residues adhering during the filtration process, and in order to thus reestablish the filtration pipe. A backflushing pipe  8  is provided for this purpose, so that treated clear water can be used for backflushing, for example for backflushing the activated carbon filter  5 . In the alternative, fresh water from the fresh water tank  20  can also be used for backflushing. 
     Foam from the overflow pipe  7  is collected in the wastewater tank  9 . Wastewater collected in the dirty water tank  21 , i.e. sink wastewater and hand washbasin wastewater, can furthermore also be transferred directly into the wastewater tank  9 , when, for example, heavy dirt loads are contained temporarily. 
     In a preferred embodiment, a showering process has two parts. First of all, water from the clear water tank  6  is used for showering, i.e. the body is moistened. After lathering, water from the clear water tank  6  is still used to rinse off the soap, and fresh water from the fresh water tank  22  is subsequently used to rinse again. 
     The toilet flusher  24  preferably has fine nozzles. It is supplied with clear water from the toilet clear water tank  22  with the help of a pressure cylinder  10 , in particular by means of a high-pressure cylinder or by means of a water pump. 
     The electrochemical processing unit  3  comprises a direct current voltage source, the polarity of which can be reversed. The polarity of said direct current voltage source can be reversed in a time- or state-controlled manner, in order to prevent an attachment of hydroxides to the electrodes  16 . A reversal of the polarity also serves the purpose of ensuring an even wear of the electrodes  16 , thus of anodes and cathodes. 
     The electrochemical processing unit  3  is encapsulated in the upper region, i.e. provided with a cover  26 . 
     The electro-flotation stage can also comprise oxidizing agents, by means of which free hydrogen molecules within the wastewater treatment are oxidized into water. It is also possible to use atmospheric oxygen to convert the released hydrogen via a catalytic converter into water, wherein the atmospheric oxygen reaches into the system via a ventilation, e.g. via the overflow pipe. 
     An alternative embodiment of a domestic wastewater purification system is illustrated schematically in  FIG. 2 . 
     Two dirty water tanks are present—a first dirty water tank  121 , in which wastewater from a washbasin  115  and a sink  113  is collected, and a second dirty water tank  101 , also referred to as shower dirty water tank, in which wastewater from the shower  125  is collected. 
     Yet a further wastewater tank is provided, the wastewater tank  109 , in which the wastewater to be discarded is collected, e.g. toilet wastewater. Wastewater from the first dirty water tank  121  can be purified as well as discarded. In the latter case, it is fed to the wastewater tank  109 . 
     Wastewater to be purified, e.g. from the second dirty water tank  101 , is initially guided via a coarse filter  130 . There, coarse pollutants, such as sand or hair, are removed. With the help of a pump P 1 , it subsequently reaches into the electrochemical processing unit  103 , where the electro-flotation is performed. 
     The pump P 1  is arranged in a container  131 . The dirty water is temporarily stored therein and is fed to the first one of the two tubular electrochemical processing units  103  by means of the pump P 1 . The container  131  has a buffer function. If the system is turned off, too much dirty water arrives, or if the system produces too little power, this buffer flows over and dirt water reaches directly into the wastewater tank  109  without processing. For example in the case of failures in the system, it can thus be ensured that showering can continue without interferences. 
     In the embodiment of  FIG. 2 , tube assemblies are used as electrochemical processing units  103 , which are in each case covered by means of a cover  126 . Tubular electrodes  116  have the advantage that, compared to plate electrodes, they have a smaller space requirement with the same reaction surface, which is an advantage, which becomes noticeable in particular in the case of campers, mobile homes, aircrafts, or yachts. In the embodiment of  FIG. 2 , two tube assemblies are connected in series. 
     After passing through the electrochemical processing unit, the wastewater to be treated reaches into a relaxation container  128 . A relaxation floatation is performed there. For this purpose, gas is introduced via a venting membrane  114 . In the present case, ozone can be introduced via an ozone ventilation  111  and air can be introduced via a unit for introducing air  112 . Ozone and air can in each case be introduced separately as well as combined. Which gas is to be used depends on the wastewater, which is to be treated, and can be easily determined by the expert by means of simple tests. 
     Chemicals can also be added in the relaxation container with the help of the adding unit for chemicals  119 , if required. 
     During the relaxation floatation in the relaxation container  128 , components of the wastewater, e.g. surfactants, which are precipitated in the electro-flotation or which are bound to small oxygen or hydrogen bubbles, which are generated, e.g. during the electro-flotation, are enriched and are collected via a foam compression  117 . Flocks and particles carrying dirt loads accumulate in this way in the upper region of the container  128 , because the flocks and particles rise up due to the attachment of gas bubbles in the water. Purified clear water thus remains in the lower region of the container, below the venting membrane  114 , referred to as calming zone  118 . The collected foam is removed via an overflow pipe  107  and is guided through a foam destroyer  129 . The foam is destroyed there, e.g. by means of sonication or with the help of chemicals. The separated portion of the purified dirty water subsequently reaches into the wastewater tank  109 . 
     In the present embodiment, the purified water, which is removed in the lower region of the relaxation container  128 , is finally guided past three filtration systems, where the water is further purified. The individual filtration stages become increasingly finer thereby. First of all, the water purified in the two floatation stages reaches into a pre-filter  102 , then into an activated carbon filter  105 , and finally into a fine filter  104 . 
     Instead of the further purification, the water, which was thoroughly purified in the two floatation stages, can also be discharged, in that it is pumped into the wastewater tank  109  via a corresponding valve, here V 2 , with the help of a pump P 2 . 
     The clear water, which has run through all purification stages, is either fed to the toilet clear water tank  122  after the last purification stage or is fed directly to the shower system—either in that it is stashed away in a clear water tank  106  or in that it is fed directly to the shower  125 . Corresponding valves V 7 , V 3 , V 4 , and V 5  ensure the desired feed. 
     A separate faucet  123 , to which clear water purified in the system can be fed, is further provided at the sink  113 . Recycled water can thus be used, e.g. for pre-rinsing dishes, cutlery, and pots, or it can be used as water for cleaning. 
     Water stashed away in the toilet clear water tank  122  is used to flush the toilet  124 . In mobile systems, a pressure cylinder  110  is provided for this purpose, which sprays the water in the toilet  124  while saving water. 
     A fresh water tank  120  is furthermore also provided. If not enough recycled clear water is present or, e.g. when concluding a showering process, fresh water from the fresh water tank  120  can be fed to the shower  125 . 
     Fresh water from the fresh water tank  120  or clear water from the clear water tank  106  can be used via a backflushing pipe  108 , in order to backflush the system, in particular the three filtration stages  102 ,  104 , and  105 . 
     According to the invention, two dirty water tanks are present, provided with reference numerals  121  and  101 . This makes it possible that different types of wastewater can be kept separate and can be treated separately. Two clear water tanks, reference numerals  106  and  122 , are furthermore also present, whereby clear water of different origins can be kept separate and can be used separately. In a preferred embodiment, wastewater from the hand washbasin  115  and sink  113  is stored in the dirty water tank  121 . After the treatment thereof with the help of the above-described system, the resulting clear water is typically stored in the toilet clear water tank  122  and will be used to flush the toilet  124 . Wastewater from the sink and from the hand washbasin is possibly not completely clean, even after passing through all purification stages, so that it is unsuitable for showering or bathing. The same also applies, for example, for wastewater from the dishwasher. The situation is different for wastewater from the shower, collected in the dirty water tank  101 . These types of wastewater can be treated well in this way because they are relatively lightly contaminated, so that they can subsequently be used again for showering. Shower wastewater, which has passed through the system, is thus collected in the clear water tank  106  and is then fed to the shower  125  again, or it is fed directly to the shower  125 . The above also applies for bath water, which is generally dirty only very slightly. 
     Some valves and pumps are also entered in the schematic illustration, and are accordingly identified as P 1 , P 2 , etc., and V 1 , V 2 , etc. 
     An even larger independence on communal systems results in that in a further preferred embodiment, which is not graphically presented, however, sea or river water can be drawn in and can be guided through the wastewater purification. For example, a further separate dirty water container would be provided for this purpose. Rain water can also be treated in this way and can be used as industrial water, for example for showering or for flushing the toilet. 
     
       
         
           
               
            
               
                   
               
               
                 List of Reference Numerals 
               
            
           
           
               
               
            
               
                 Reference Numeral 
                 name 
               
               
                   
               
               
                 1, 101 
                 shower dirty water tank 
               
               
                 2, 102 
                 pre-filter 
               
               
                 3, 103 
                 electrochemical processing unit 
               
               
                 4, 104 
                 fine filter 
               
               
                 5, 105 
                 activated carbon filter 
               
               
                 6, 106 
                 clear water tank 
               
               
                 7, 107 
                 overflow pipe 
               
               
                 8, 108 
                 backflushing pipe 
               
               
                 9, 109 
                 wastewater tank 
               
               
                 10, 110 
                 pressure cylinder 
               
               
                 11, 111 
                 ozone ventilation 
               
               
                 12, 112 
                 unit for introducing air 
               
               
                 13, 113 
                 sink 
               
               
                 14, 114 
                 venting membrane 
               
               
                 15, 115 
                 washbasin 
               
               
                 16, 116 
                 electrodes 
               
               
                 17, 117 
                 foam compression 
               
               
                 18, 118 
                 calming zone 
               
               
                 19, 119 
                 adding unit for chemicals 
               
               
                 20, 120 
                 fresh water tank 
               
               
                 21, 121 
                 dirty water tank 
               
               
                 22, 122 
                 toilet clear water tank 
               
               
                 23, 123 
                 separate faucet 
               
               
                 24, 124 
                 toilet flusher 
               
               
                 25, 125 
                 shower 
               
               
                 26, 126 
                 cover 
               
               
                  27 
                 level raise 
               
               
                 128 
                 relaxation container 
               
               
                 129 
                 foam destroyer 
               
               
                 130 
                 coarse filter 
               
               
                 131 
                 container