SE1100791A1 - Procedure for purifying wastewater - Google Patents

Abstract

Method for purifying sewage water from a first water closet (211), comprising the steps: a) bringing the sewage water from the first water closet to a locally arranged collecting vessel (221) for sewage water; b) circulating a gas through the collecting vessel and thereby causing the gas to bring with it a share of the contents in the collecting vessel in the form of evaporated water vapour; c) in a dehumidification step (230,242), causing the said water vapour to condense and collecting the thus condensed water; d) using the condensed water for flushing in a second water closet, which may be the same as the first water closet; and e) removing the slurry which remains in the collecting vessel after the said evaporation from the collecting vessel for further treatment, wherein the gas in the dehumidification step (230,242) is cooled by a heat pump being caused to transfer thermal energy from the gas to a fluid which is circulated in an external loop (243, 244), and wherein the said fluid is caused to heat indoors air or tap water in a building (210). The invention also relates to a device.

Description

15 20 25 30 water wells. In addition, frequent sludge suction is required, which is costly.

Furthermore, it is often not advisable or permissible to use fresh water from watercourses or the sea for, for example, flushing a water toilet that is connected to an infiltration plant, as this can add unacceptably large amounts of nutrients and bacteria to the local environment at the property.

Furthermore, from the perspective of society, it is often desirable to collect. the nutritional and. the energy-bearing parts. of the wastewater, such as biological material and nutrients, for return to the larger cycle. A conventional treatment step, such as a so-called mini treatment plant, often removes a certain part of this desirable material by, for example, oxidation of carbonaceous material, collection of certain chemicals such as phosphorus in filters and the like which must later be deposited. can not be neras, and so on. is optimally utilized in the larger cycle.

The dry substance in wastewater from water toilets constitutes a valuable raw material for the production of, for example, biogas. As such, however, specific requirements are placed on, among other things, the degree of chemical contamination and the degree of dryness of the sewage sludge.

In addition, a conventional treatment step of the above-mentioned type is often, in addition to being expensive, connected directly to the sewage line, which means that malfunctions cause immediate stoppage of the treatment function, which either leads to wastewater-producing equipment, such as a water toilet or a dishwasher, not being used. i. the wait. on service technicians, or, which is worse, that the waste water from such equipment flows straight through the failed treatment stage and out into the application without the user receiving immediate information about this. In addition, such a purification step typically also consumes environmentally harmful chemicals, which must be disposed of or released into nature.

Many conventional sewer management systems for use in municipal box real estate. sewers further set specific requirements' on which. type of wastewater-producing equipment that can be used in buildings, such as requirements for low-flush water toilets. This not only infringes on the user's freedom, but also means that such systems are associated with increased installation costs.

The Swedish patent with number 531290 describes a procedure for maintaining the water balance in a property where wastewater. removed and fresh water, for local storage, is returned in the corresponding amount. This procedure requires, in addition to frequent sludge suction, regular external refilling of fresh water.

Finally, for reasons of convenience, there is a need for portable toilet facilities, including water toilets, in places that do not have a municipal sewer or other permanent way of disposing of waste water from a toilet. This applies, for example, to festivals and other temporary events, to construction sites, disaster sites and developing countries.

In summary, it is desirable to provide a method for managing wastewater from one or more water toilets that only minimally affects the local water. requires a minimum. of cycles and is reliable, maintenance and sludge suction, which can collect all the energy- Application application document 2013-04-02 110044EN 10 15 20 25 30 and. nutrient-containing fraction. and. son1 is cheap both to install and to operate.

The present invention solves the problems described above.

Thus, the invention relates to a method for purifying wastewater from a first water toilet, comprising the steps of a) transferring the waste water from the first toilet to a locally arranged waste water collection container b) circulating a gas through the collection container and thereby causing the gas to carry part of the contents of the collection container in the form. of evaporated water vapor; c) in a dehumidifying step causing said water vapor to condense and collect the water thus condensed; d) use the condensed water for flushing in a second water toilet, which may be the same as the first water toilet; and e) remove the sludge which. after said evaporation 'remains in the collection container from the collection container for further processing.

The invention also relates to a device for purifying waste water from a first water toilet, characterized in that the device comprises a locally arranged collection container for waste water arranged to receive waste water from the water toilet; a circulating means arranged to circulate a gas through the collecting container and thereby cause the gas to carry a part of the contents of the collecting container in the form of evaporated water vapor; and a dehumidifying step, arranged to cause said water vapor to condense and collect the water thus condensed, by the device being arranged. to carry the condensed water to a second water toilet, which may be the same as the first water toilet, for use for flushing therein, and by the fact that the device comprises emptying means for emptying and Disposal text 2013-04-02 110044EN 10 15 20 25 30 removal for further treatment of the sludge. which after said evaporation remains in the collecting container from the collecting container.

The invention will now be described in detail, with reference to exemplary embodiments of the invention and the accompanying drawings, Figures I-4 are schematic diagrams illustrating first, second, third and fourth exemplary embodiments of the present invention.

In all figures, the same last two digits in the reference numerals are used for the corresponding parts. The first number is attributable to the figure number. For example, the housing is indicated as I10 in Figures 1 and 21 in Figure 2. In the following description, description of such parts already described is sometimes omitted, in order to avoid unnecessary repetitions.

Figure I thus shows a house ll0 on the ground ll5, in the form of a detached house or a multi-family house. In the house 110 there is a toilet lll fixed and permanently installed. It will be appreciated that the house 110 may have more than one toilet lll fixed and permanently installed To which other toilets what is said herein is correspondingly applicable. The toilet lll is a water toilet, which is thus flushed with water. Preferably the toilet lll is not of the so-called ultra-low flushing type, i.e. the flush volume of the toilet is preferably at least 2 liters. Above all, it is preferred that the same toilet, as previously used in the property, also continues to be used as part of a plant according to the present invention after the plant in question has been installed, this means, for example, that the sealing layer in the wet room in which the toilet lll be present does not have to be broken.

Application text document 2013-04-02 110044EN 10 15 20 25 30 The wastewater. brought from the toilet. 111, via. a drain pipe 124, to a local, i.e. on the same property as, and preferably in the immediate vicinity of, the room in which the toilet 111 is installed, arranged collection container 121 for wastewater. It is preferred that the effluent is not passed on from the collection container 112 in any way, except that the water fraction is partially removed, as described below.

In addition, it is preferred that the remaining fraction, in other words the sludge remaining in the collection container 121, be emptied from time to time, when necessary when the volume of waste water becomes too high or its dry content becomes too high, and / or at regular intervals. preferably by conventional sludge suction via a connection 127, and removed from the collection container 121 for further treatment. Such further treatment consists, for example, of digestion into biogas, and is preferably carried out at a central plant. Thus, it is preferred that the entire residue in the collection container 121, after the evaporation of water described below, be removed from the container 121 in this way for central handling.

A gas which is preferably air but which can also be an inert gas in the form. of nitrogen or the like, is circulated according to the invention by. the collection container 121 and contacts therein with the waste water housed therein. The gas can circulate- such as by bubbling on and / or race genon1 themselves. the wastewater, a certain depth in the wastewater in the container 121, is circulated past the surface of the wastewater in the atmosphere present above this surface in the container 121.

By. contact with. the wastewater, the gas will absorb water vapor that has evaporated from the contents of the collection container- It is the liner 121, and thus carry with it such water vapor.

Application text docs 2013-04-02 110044EN 10 15 20 25 30 preferably that the gas is circulated at such a low speed in relation to its temperature that it becomes saturated to at least 40%, more preferably 50%, more preferably at least 90%, preferably substantially gen 100%, with water vapor, in which case the dry content of the contents of the container. 121 is a maximum of 50%, preferably a maximum of 25%. At such dry contents, it is also preferred that the gas circulated through. the container 121 with each flow increases the moisture content of the gas by at least 25% relative humidity, more preferably at least 50% relative humidity.

The gas is then passed, according to the invention, to a dehumidification step, where the gas vapor content of the gas is at least partially caused to condense to liquid water. The water thus condensed is then collected, and passed to an equalization vessel 122 for condensed water. From there, the condensed water is then conveyed, via a line 125 and a pump 112, to a second water toilet, which may be the same as the first water toilet 111, and is used there for flushing in said second toilet. It is noted that in the figures the first and the second water toilet are both shown as the toilet 111, but it is understood that an optional number of water toilets can, for example, share the same treatment plant according to and thus using the present invention, the same collection container 121, etc. it is preferred that the container 122 be the sole source of flushing water for the second water toilet, preferably for all water toilets which are installed in the same housing 110 and preferably on the same property.

It is preferred that the equalization container 122, via a connection 128, is initially supplied with a certain amount of fresh water, so that the water toilet 111 can be flushed already at the time of commissioning.

Application text document 2013-04-02 110044EN 10 15 20 25 30 It is also preferred for collection and location reasons that the collection container. 121 and the leveling container 122 form two separate parts of one and the same container 120, 120, 121, 122 separated by a partition 123. The containers are preferably buried in the ground and at least arranged frost-free above or below ground.

Since the water toilet 111, through its use, supplies more water than the used rinsing water, in some applications over time an excess of condensed water will arise in the equalization tank 122. It is preferred, especially in the preferred case when the waste water in the collection container 121 is derived only from one or more water toilets and not from other waste water producing units and washing machines, showers, such as dishwashers, etc., that excess water is carried, by overflow, pumping or otherwise, from the equalization container 122, via a line 101 to an infiltration bed 102 in the ground 115. The levels of environmentally harmful chemicals and microorganisms in such condensed water have in many cases proved to be acceptably low for infiltration. Alternatively, the excess water is used for irrigation.

Figure 1 illustrates in fact a design of a plant according to the invention which is arranged to be operated in two phases in order to dehumidify the gas circulating through the collecting container 121. with. by means of sorption dehumidification. Filled arrows illustrate in Figure 1 the flow direction of the gas in the first phase, unfilled arrows illustrate the corresponding flow direction, in the second phase. Corresponding flow direction arrows are also found in Figures 2-4. to flow The gas is thus brought, by means of a fan 132, out of the container 121, via a filter 131.

Application text docs 2013-04-02 110044EN 10 15 20 25 30 Thereafter, the gas flows, via a pipe 133, to a sorption dehumidification stage 130, comprising a per se conventional, moisture-absorbing body of material 135, such as a foam rubber block.

The circulating gas, comprising the evaporated water vapor from the container 121, is passed through a heating device 134, for example in the form of an electric heating element, the heating function of which is switched off during the first phase, through a tube 137 and 121. valve 136, a filter 137a, back to the collecting container Thereby a certain proportion of the moisture contained in the gas is absorbed by the material body 135, so that the gas returning to the container 121 is drier after passage through the material body 135.

In the second phase, which is initiated after a certain time, for example, the moist gas is conveyed from the container 121, via the tube 133, to the heating device. 134 whose heating function. now is on. Thus, by passing therethrough, the gas is heated to a higher temperature before it again passes through the moist material body 135, thereby drying out the liquid from the material body 135, the moisture content of the material body 135 absorbed in the first phase being absorbed by the heated gas via the valve. 136 by evaporation. The gas is then passed, and a pipe 138, to a per se conventional condensing device 139, such as a per se conventional cooling pipe, arranged to condense the occupied water vapor. The condensed water is passed, through a pipe 141 and a filter 141a to the container 122 which is thereby filled.

The gas is in turn then, via a pipe 140 and a filter 140a, returned to the container 121, whereby the gas is circulated in a closed cycle through the collection container 121, to whereby the gas is conveyed from the collection container 121, Application text document 2013-04-02 The humidification step, which in this case includes both step 130 and the condenser 139, and eats to the collection container 121 after separation of condensed water to the equalization container 122. Note that a closed circuit is also present for the gas during the first phase. .

After a certain time, or when, for example, the block of material 135 is sufficiently dry, the first phase is started again as above, the process continuing in an iterative manner.

Figure 2 illustrates an alternative or complementary embodiment to that shown in Figure 1, wherein the condenser 139 comprises or is replaced by a cooling device 242 which, by heat exchange to a fluid circulating in an external loop 243, 244, transfers heat energy from the gas to said fluid so that the gas is thereby cooled. Alternatively, the device 242 comprises a heat pump which is arranged. to transfer heat energy from the gas to the fluid with corresponding results. The fluid is then used to heat indoor air or domestic hot water in a house in which the first and / or second water toilet 211 is installed. In this way, an efficient cooling of the gas can be achieved, and thus also efficient condensation, at the same time as the residual heat is useful in the property operation. via a filter 246 and a tube 222.

The condensed water is returned, 247, to the equalization tank. The dried gas is led, via a pipe 245 and a filter 245a, back to the collection tank 221 so that the gas cycle is thereby closed.

Figures 3 and 4 illustrate further exemplary embodiments of the invention, according to which the circulating gas is caused to circulate in only one, continuous phase, pure 321, and to be heated before it is passed. 421. comprising both a device 350 dehumidification stage and a heating stage, further comprising a heat pump 354 arranged to transfer heat energy from the gas passing through the dehumidifying stage to the gas passing past the heating stage, where the heating stage is arranged between the dehumidification step l2l. and, more specifically, the collecting container, the gas is conveyed, again by means of a fan 332, via a filter 331 and a pipe 333, to a first heat exchanger 351, further via a pipe 352 to a second heat exchanger 353, and again via a pipe 337 and a filter 337a to the container 121. The heat pump 354 is arranged to transfer heat energy from the heat exchanger 351 to the heat exchanger 353, the gas flowing through the heat exchanger 351 being cooled at the same time as the gas flowing downstream thereof flows through heat exchange 35. In other words, the heat exchanger 354 establishes a temperature difference between the gas which has just passed the heat exchanger 351 and the gas which has just passed the heat exchanger 353.

Through the cooling in the heat exchanger 351, a part of the evaporated water vapor is condensed out of the air, and is led via a pipe 355 and a filter 356 to the equalization container 322. Thus, the heat exchanger 351 constitutes a cooling step.

Genon1 the heating j_ the heat exchanger 353, which. thus constituting a heating step, the gas returned to the container 321 will be hotter than the gas after the cooling step, which increases the evaporation, in the container 321 and also restores the capacity of the gas to carry evaporated water vapor back to the cooling step.

Application text document 2013-04-02 110044EN 10 15 20 25 30 12 The mentioned temperature difference can be used in different ways, by. appropriate selection of the characteristics of the heat pump 354 and the heat exchangers 351, 353 and by the use of any additional, inherently conventional, cooling and heating devices. For example, the temperature of the gas can be arranged to be higher than the ambient temperature in the space in which the container zone 1 the ground temperature, if the 321 is present, the container 321 is buried. In this case, it will thus be possible to increase evaporation, and an equilibrium with respect to the temperature profile inside the container 321 will be achieved after a period of continuous operation. This equilibrium temperature profile will include elevated temperatures relative to the ambient temperature if the cooling caused by the evaporation in the container 321 does not compensate for the heat energy supplied by the hot gas. According to an alternative example, the temperature of the gas returning to the container 321 may be substantially the same as the ambient temperature of the container 321, with no energy being used to heat the interior of the container 322. Alternatively, the temperature of the heated gas is lower than the ambient temperature, with the environment contributing heat energy to heat the evaporating liquid in the container 321. In all these, and in other examples, the temperature difference created by the heat pump 354 may be of the same order of magnitude. , so that the gas after the cooling step is preferably between 5 and 15 ° C lower than after the heating step.

An advantage of such a method is that the temperature of the gas which is passed through the pipe 337 back to the container 321 can be temporarily regulated up, in order to temporarily increase the performance of the plant to a higher energy cost if necessary.

Application text docc 2013-04-02 110044EN 10 15 20 25 30 l3 Figure 4 illustrates an alternative way of achieving the cooling and heating of the circulating gas described in connection with Figure 3.

The gas is thus carried, with. by means of a fan 432, through a filter 431 and a pipe 433, to a heat exchanger 460 of the counter-current or cross-current type. From there the gas is forced through. a cooling coil 461 buried in the ground 415, alternatively immersed in, a natural body of water such as a stream or sea, and back through the heat exchanger 460. Thus, the gas coming from the pipe 433 is cooled by the cooled gas coming from the cooling coil. 46l. The resulting condensed water is passed, through a pipe 465 and a filter 466, the container 422. 462, to the equalizer. The cooled gas is further passed, through a pipe to a solar collector device 463 which is arranged to heat the gas by means of solar energy, which is then returned to the container 421 through a tube 464 and a filter 464a.

This means that no additional energy must be supplied to the system externally, except for energy to maintain the circulation of the gas.

It is preferred that the first and second water toilets, the waste water collection container, the condensed water equalization container, the dehumidification step described above in its various forms, all the cooling coils, pumps, fans, pipes, valves and filters described herein, the possible heating step, and so on , all are made to constitute permanently installed parts of a fixed and permanently installed facility for handling wastewater in a property that does not have a municipal sewer.

It is further preferred that only waste water from one or more water toilets is supplied to the collection container Application text doc. 2013-04-02 110044EN 10 15 20 25 30 14 for waste water, and that no waste water originating from other types of waste producing units is transferred to said collection container. Namely, it has been shown that wastewater from toilets after evaporation, passage through a carbon filter and condensation is generally clean enough to be discharged into an infiltration bed in nature. However, even if wastewater is allowed from both water toilets and from other sewage-producing units *, the condensed water is sufficiently clean to be used safely for flushing in the toilet, even if the condensed water does not maintain food quality.

It is preferred that the equalization tank for wastewater has a volume of at least 0.5 m, preferably 1 m 3, in order to be able to accommodate the wastewater from the at least one water toilet.

A control device 114, 214, 314, 414 is provided. to control the operation of the pumps, fans and valves described herein. and from It is preferred that all gas connections to the collection container 121, 221, 321, 421 for wastewater be provided with filters 131, 137a, 140a, 231, 237a, 245a, 331, 337a, 431, 464a of a type which prevents at least 99% , preferably at least 99.9%, of the possible bacterial content of the gas to pass the filter in question. A suitable type of such filters are filters of the so-called HEPA type (High-Efficiency Particulate Air filters). This means that parts of the plant which are arranged externally in relation to the container 121, 221, 321, 421 do not risk being clogged due to growth.

It is further preferred that the condensed water used for flushing in the water closet. is filtered genon1 a filter with activated carbon, ie. a filter through which the air Application textdocx 2013-04-02 110044EN 10 15 20 25 30 l5 is forced to flow through. porous activated carbon. This removes foul-smelling constituents of the condensed water, as well as certain other contaminants, which means, for example, that To achieve this 356, the flushing water does not smell bad in the toilet. it is preferred that the filters 14a, 246, 466 through which the condensed water is passed on its way to the condensing tank 222, 422 for condensed water are 222, 322, of such type with activated carbon. It is also possible to use such an activated carbon filter along the pipe 125, 425 between the container 222, 222, 322, 225, 325, 422 and the toilet.

The purified water in the container 222 is thus used to flush in the toilet 111, and is thus returned to the container 112 for re-purification, whereby a cycle is achieved. By using both the collection container l11 for wastewater and the equalization container l22 for purified water, it is possible that the water toilet lll can be made self-sufficient with regard to flushing water, despite the flow from and. to the water toilet lll is intermittent while the flow of condensed water to the container l22 is rather limited per unit of time but on the other hand more or less continuous.

Thus, it is achieved by such a procedure and such a device that a property which is not connected to a municipal sewer can be arranged with one or more water toilets.

Instead, it is sufficient that the much more limited amounts of sludge in the container l2l are emptied when necessary. Such emptying can take place at regular intervals, alternatively when the contents reach a certain minimum volume and at the same time a desired degree of dryness. The volume of the container l1l can suitably be monitored by means of a measuring equipment ll3, for example in the form of a counter or a flow meter, which measures the number of flushes or the amount of flushed water in the toilet lll, to the control device ll4. At the same time, the volume in the container Application text docc 2013-04-02 110044EN 10 15 20 25 30 16 121 can be measured by one placed in it. measuring device 126, such as. a level sensor, which also communicates * measurement data to the control device 114. The degree of dryness can then be estimated with sufficient accuracy. comparing the amount of flushed wastewater with the current volume of wastewater in the container 121.

In particular, the same degree of dryness can be achieved with respect to the waste water in the container 121 with. use of normal or low-flush toilets (approximately 2-8 liters per flush) which can be achieved with so-called ultra-low-flush toilets (ie flushing amounts of approximately 1 liter or less). Thus, a plant according to the present invention is a perfect alternative to installing such ultra-low-flush toilets, which leads both to the sealing layer in the wet space having to be broken and to a less pleasant experience for the user.

The two leveling containers 121, 122 constitute, according to the embodiment illustrated in the figures, two chambers * separated by means of a partition 123 in one and the same container 120. Such a container 120, which is suitably made as an elongate cylinder of plastic material comprising two opposite end walls and the partition 123 in between, are described, for example, in the Swedish patent with number 531290, and entail simple and inexpensive manufacture and installation.

Preferred embodiments have been described above. However, it will be apparent to those skilled in the art that many changes may be made to the described embodiments without departing from the spirit of the invention.

Thus, the embodiments illustrated in each of the figures. 1-4 are combined where applicable. For example, an electric heater according to figure * 1 or * a heat pump according to Application 3 doc. 2013-04-02 110044EN 10 15 20 l7 figure 3 can be used as a support heat at a plant according to figure 4, for use when the sun is not shining. Another example is that any excess heat from the heating of the gas by means of a heat exchanger 354 according to Figure 3 can be dissipated to an external loop by means of a device 242 in the manner described above in connection with Figure 2.

In addition. it is possible to design a facility according to the invention as a portable installation for use on boats, quays and in natural harbors, on construction sites or other places where there is a need for a water toilet but no municipal sewer. In this case, the excess water can be discharged from the container 122 during, for example, the period of use. before it is one. day well, and. the plant's necessary to sludge suction container l2l becomes long.

Thus, the invention should not be limited to the embodiments described, but may be varied within the scope of the appended claims.

Application text document 2013-04-02 110044EN

Claims (13)

18 P A TP E li T K I {.A V A method of purifying wastewater from a first water toilet (111; 211; 311; 411), comprising the steps of: a) transferring the waste water from the first toilet to a locally arranged waste container (12l; 221; 321; 421) for wastewater; b) circulating a gas through the collection container and thereby causing the gas to carry part of the contents of the collection container in the form of evaporated water vapor; c) in a dehumidification step (130,139; 230,227; 35l; 460,461) causing said water vapor to condense and collect the water thus condensed; d) use. the condensed water for flushing j. a second water toilet, which may be the same as the first water toilet; and e) removing the sludge remaining after said evaporation in the collection container from the collection container for further treatment, characterized in that said gas is circulated in a closed circuit through the waste water collection container, the gas being passed from the collection container to the dehumidification step and back to the collection container after separation of condensed water, by bringing all of the first water toilet, the second water toilet, the collection container, the leveling container and the dehumidification step to form permanently installed parts of a fixed and permanently installed wastewater treatment plant in a property that lacks municipal sewage, by causing the gas in the dehumidification stage (230,242) to be cooled by causing a heat pump to transfer heat energy from the gas to a fluid circulating in an external loop (243,244), and by causing said fluid to Application text document 2013-04-02 110044EN 10 15 20 25 30 35 l9 heat indoor air or a house (210). up hot water in A method according to claim 1, characterized in that the entire residue in the collection container (l1l; 22l; 32l; 42l) for the waste water after the evaporation of water is removed in step e), the sludge being removed to a central plant for further treatment. 3. A method according to claim 1 or 2, characterized in that the gas which in said circulation is introduced into or the collecting container (121; 221; 321; 421) (131, 137a, 140a; 231, 237a, 245a; 331, 337a); 431, is brought out to pass a filter 464a) son1 is arranged to separate. at least 99% of the bacteria possibly contained in the gas. 4. A method according to any one of the preceding claims, characterized in that the condensed water is brought to a leveling container (222; 222; 322; 422) for condensed water from which condensed water is fed to the second water toilet for use in flushing. therein, and by transferring an excess of condensed water from the condensed water equalization vessel to an infiltration bed (102; 202; 302; 402) in the ground (ll5; 2l5; 3l5; 415). 5. A method according to any one of the preceding claims, k.ä n n e - t e c k n a t a v 'to said. circulating gas is heated before passing through the waste water collection container (32l; 42l). Method according to claim 5, characterized (354) in that a heat pump is arranged to transfer heat energy (351) to (353) from the gas passing through the dehumidification step the gas passing past a heating point Application text docs 2013-04-02 110044EN 10 15 20 25 30 20 arranged between and (321). dehumidification step the collection container 7. A method according to claim 5, characterized in that the gas is caused to be heated by means of solar energy which is absorbed via a solar collector (463). 8. Procedure according to any! the preceding claim, characterized in that the gas in the dehumidification step (460,46l) is caused to be cooled by transferring heat energy from the gas (415) or to a natural body of water with (461). to the ground using a cooling coil A method according to any one of the preceding claims, characterized in that the housing (210) in which indoor air or domestic hot water is caused to be heated by means of said fluid is a housing (210) in which the first and / or the second water toilet ( 211) is installed. A method according to any one of the preceding claims, characterized in that said dehumidification step (130, 139) comprises a sorption dehumidification step, wherein circulating gas comprising the evaporated water vapor in a first sorption operating phase is passed through. a moisture absorbing material body (135), wherein a gas in a second sorption operating phase with a higher temperature than said circulating gas had in the first sorption operating phase been passed through said material body, wherein moisture content absorbed by the material body from the circulating gas in the first sorption operation phase. evaporation is taken up to said hot gas, and the water vapor taken up in the second sorption operating phase is caused to condense to form said condensed water. Application text document 2013-04-02 110044EN 10 15 20 25 30 2l 11. ll. A method according to any one of the preceding claims, characterized in that only waste water from one or more water toilets (lll; 2ll; 3ll; 4ll) is fed to the collection container (l1l; 22l; 32l; 42l) for waste water, and that no waste water originating from other types of sewage-producing units is transferred to said collection container. Device for purifying wastewater from a first water toilet (III; 211; 311; 411), locally where the device comprises an arranged collection container (112; 22l; 321; 42l) for wastewater arranged to receive wastewater from the water toilet ; a circulating means (132; 232; 332; 432) arranged to circulate a gas through the collecting container and thereby causing the gas to carry a part of the contents of the collecting container in the form of evaporated water vapor; and a dehumidification step (130, 139; 230,227; 35l; 460,46l), arranged to cause said water vapor to condense and. collecting the water thus condensed, by the fact that the device is arranged to carry the condensed water to a second water toilet, which may be the same as the first water toilet, for use in flushing therein, (227; 227; 327; 427) and by the fact that the device comprises the discharge means for emptying and removal for further treatment of the sludge remaining after said evaporation in the collection container from the collection container, characterized in that the circulation device is arranged to circulate the gas in a closed circuit through the collection container for waste water, wherein is transferred from the collection container, to the dehumidification stage and back to the collection container after separation of condensed water the second water, in that all of the first water toilet, water toilet, collection container, equalization container and dehumidification stage form permanently installed parts of a fixed and permanently installed in a property that does not have a municipal sewer, by the dehumidification step (230,242) is arranged to cool the gas by means of a heat pump which is arranged to transfer heat energy from the gas to a fluid which is circulated in an external loop (243,244), and. of said fluid. is arranged. to heat indoor air or domestic hot water (210). 13. Device according to claim 12, characterized in that the device is arranged to circulate the gas in a closed cycle through. the collection container (l1l; 22l; 32l; 42l) for which the gas is forced from the collection container, (l30, l39; 230,227; 35l; 460,46l) waste water, to the dehumidification step and back to the collection container after separation of condensed water. Application text document 2013-04-02 110044EN