The present invention relates to a method and a device for purifying sewage water from one or several water closets.

In general, during normal use a property gives rise to sewage water, from equipment installed in the property, in the form of both gray water and black water. Gray water producing equipments comprise washbasins, showers, dishwashers, etc. Black water producing equipments comprise water closets. For properties with no municipal sewage system, there is a problem to dispose of such sewage water in an environmentally friendly way. In a so called infiltration bed, sewage water is released, after slurry separation and filtration, into the ground. This is, however, not always possible because of current regulations, in particular for sewage water from water closets risking contamination of the ground and subsoil water with nutrient salts, bacteria and so forth. Upstream of an infiltration bed, a slurry separation step is often used, such as a conventional three-compartment septic tank. When the surrounding ground is waterlogged, such a step runs the risk of so called backflow, when water enters the step from down- stream thereof, and in the step contributes to unwanted sludge flight and potential ground contamination.

Another alternative is to install a closed storage tank for sewage water. The tank is emptied regularly or when needed, whereby the sewage water is transported away from the property for suitable treatment. This if often not allowed or advisable for properties lacking municipal water supply, since freshwater is then normally taken from the subsoil water via a local well, without being restored in equal amounts. There- by, subsoil unbalances arise, with risks of for instance salt water penetration and drying of wells. Moreover, frequent slurry exhaustion is necessary, to great cost. Also, it is often not advisable or allowed to exploit freshwater from water courses connected to the sea, such as for flushing of a water closet which is connected to an infiltration bed, since this may lead to unacceptable amounts of nutrition salts and bacteria in the local environment at the property.

It is furthermore, from the viewpoint of society, often desirable to collect the nutrition- and energy carrying parts of the sewage water, such as biological material and nutri- tion salts, for return to the larger circulation loop. A conventional purification step, such as a so called mini purification installation (Swedish "minireningsverk" ) , often removes a certain share of this desirable material through for instance oxidation of carbon containing material, collec- tion of certain chemicals such as phosphorous in filters and the like, which later must be deposited, and so on. This results in that these compounds cannot be exploited optimally in the larger cycle of materials. The dry substance in sewage water from water closets constitutes a valuable raw material for production of for instance biogas . As such, there are however specific requirements regarding for example content of chemical contaminants and degree of dryness of the sewage slurry.

Apart from being expensive, a conventional purification step of the above described type is also many times connected directly to the sewage pipe, which results in that operation faults cause an immediate interruption of the purification function, which either leads to that sewage water producing equipment such as a water closet or a dishwasher cannot be used before the visit of a service technician, or, which is worse, that sewage water from such equipment pours straight through the faulty purification step and out into nature without the user gaining immediate information about this. Moreover, such a purification step typically also consumes environmentally harmful chemicals that must be taken care of or be released into nature.

Furthermore, many conventional sewage handling systems for use in properties with no municipal sewage raise specific demands on the type of sewage water producing equipment that can be used in properties, such as requirements for water closets with low water consumption. This does not only limit the freedom of the user, but also results in that such systems are associated with high installation costs.

The Swedish patent no. 531290 describes a method for main- taining the water balance in a property, in which sewage water is removed and freshwater, for local storing, is returned in corresponding amounts. Apart from frequent slurry exhaustion, this method requires regular external replenishing of freshwater.

The Swedish patent application no. 1100791-1, which is not published at the application date of the present application, describes a method and a device for handling and purifying sewage water from one or several water closets, whereby the sewage water is allowed to evaporate, and condensed water is collected in a separate container for use as flushing water.

Finally, for reasons of convenience, there is a need for portable toilet arrangements, comprising water closets , in places lacking municipal sewage or other permanent ways to take care of sewage water from a toilet. This is for instance the case at festivals and other temporary events, at construction sites, scenes of disaster and in developing coun- tries .

To sum up, it is desirable to achieve a method for handling waste water from one or several water closets, which method is highly reliable and only minimally affects the local water circulation, which requires only a minimum of maintenance and slurry exhaustion, which can collect the total energy- and nutrition carrying fraction and which is inexpensive both to install and to operate. The present invention solves the above described problems.

Hence, the invention relates to a method for purifying sewage water from a first water closet, comprising the steps to a) bring the sewage water from the first water closet to a lo- cally arranged collecting container for sewage water; b) allow the sewage water in the collecting container to evaporate and again condense on a condensing surface; c) collect the condensed water in a locally arranged storing container for condensed water; d) use the condensed water for flushing in a second water closet, which may be the same as the first water closet; and e) from the collecting container remove the sludge which after said evaporation remains in the collecting container for further treatment; whereby when the amount of water in the collecting container exceeds a certain maximum amount, return the surplus amount of water to the collecting container .

The invention also relates to a combination container associ- ated with an upright operation orientation, comprising a collecting vessel for sewage water, arranged to receive and accommodate a certain maximum amount of sewage water, and a storing container for condensed water, arranged to receive and accommodate a certain maximum amount of condensed water, and is characterised in that the combination container furthermore comprises a condensing surface on which water, which has evaporated from the collecting container, can condense, in that the combination container, when it is oriented in the operation orientation, is arranged to, using gravity, lead the water condensed on the condensing surface to the storing container, and, when the amount of water in the collecting container exceeds the certain maximum amount condensed water, return the surplus amount to the collecting container by overflow from the storing container.

The invention will now be described in detail, with reference to exemplifying embodiments of the invention and to the enclosed embodiments, wherein:

Figure 1 is an outline diagram illustrating an exemplifying embodiment of the present invention.

Figures 2a and 2b show the fundamental structure of a first exemplifying combination container according to the invention. Figure 2b shows the container in figure 2a in cross- section .

Figures 3a and 3b show the fundamental structure of a second exemplifying combination container according to the invention. Figure 3b shows the container in figure 3a in cross- section. Figure 3c is a detail view of a part of figure 3b.

Figures 2a and 2b, and 3a, 3b and 3c, respectively, share reference numerals for corresponding parts. Figures 2a-3c are partly exploded and simplified outline diagrams. Figure 1 shows a house 110 on the ground 115, in the form of a small house or an apartment house. In the house 110, there is a water closet 111 fixedly and permanently installed. It is realized that the house 110 can have more than one water closet 111 fixedly and permanently installed, for which other water closets what is said herein is correspondingly applicable. The water closet 111 is a toilet of water closet type, which thus is flushed with water. Preferably, the water closet 111 is not of a so-called ultra-low flushing type, in other words the flushing volume of the toilet is preferably at least 2 liters. In particular, it is preferred that the same water closet 111 as was previously used in the property is still used as a part of an installation according to the invention after the installation of the present invention. For example, this results in that the moisture barrier in the sanitary room in which the water closet 111 is present does not have to be broken.

The sewage water is brought from the water closet 111, via a sewage pipe 124, to a locally arranged, that is arranged on the same property as, and preferably in immediate connection to, the locale in which the water closet 111 is installed, collecting container 121 for sewage water. The collecting container 121 preferably comprises one part of a combined container 120 for sewage water and condensed water, see below. It is preferred that the sewage water to no part is taken away from the collecting container 121, except that the water fraction is partly removed, as described below. Moreover, it is preferred that the remaining fraction, in other words the sludge which remains in the collecting container 121, every now and then, when so is needed as the volume of the sewage water becomes too large or its level of dryness becomes too high, and/or at regular intervals, is emptied, preferably via conventional slurry exhaustion, for instance by a lid 122 covering the container 121 being removed so that access to the inside of the container 121 is admitted, and is removed from the collecting container 121 for further treatment. Such further treatment may for example be in the form of anaerobic digestion to biogas, and is preferably carried out at a central plant. Thus, it is preferred that the whole remainder in the collecting container 121, after the evaporation of water described below, is removed from the container 121 this way for central treatment.

The collecting container 121 is arranged to hold the sewage water as a sewage water volume 128 with an open surface 130. Thereby, the water contained in the sewage water will contin- uously pass on to the atmosphere arranged in the container 120. The evaporated water is recondensed onto a condensing surface, which preferably comprises an inside of the container 120, in other words and among other things at an inside of the lid 122. Moreover, other surfaces which are in contact with the atmosphere above the liquid surface 130 of course are also included, such as the upper parts of the inner side walls of the container 120 as illustrated in figure 1.

From this condensing surface, the condensed, liquid water is thereafter collected, and is brought to a storing container 123 for condensed water. In the storing container 123, a volume of condensed water 129 is hence present, which part may also comprise a share of freshwater which has not been supplied via condensation, see below. From there, the con- densed water is then brought, via a conduit 125 and a pump 112, to a second water closet, which may be the same as the first water closet 111, and which water is used for flushing in the said second toilet. The pump 112 may also be arranged at other locations between the container 123 and the water closet, such as drowned in the container 123. It is also noted that the first and the second water closets are in the figures both shown as the water closet 111, but it is realized that any number of water closets may for instance share the same purification installation according to the present invention, and may thereby use the same collecting container 121, etc. It is preferred that the storing container 123 constitutes the only source of flushing water for the second water closet, preferably for all water closets being in- stalled in the same house 110 and preferably on the same property .

Hence, it is the sludge which after the said evaporation remains in the collecting container 121 which is removed from the collecting container 121 for further treatment.

In order to increase the rate of evaporation, it is preferred that a device for supply of external thermal energy is present, in order to, when so is needed, supply such energy to the collecting container 121. A preferred way of supplying such energy is by using an electric immersion heater 117. However, it is realized that other ways, such as a closed heat carrier circuit, in which the heat carrier is heated using a heat exchanger (not shown) connected to an external energy source, or directly using solar heating, may be used. It is preferred that the said energy supply device is arranged to be switched on only in connection to an increased need for flushing water, such as when more persons than those who normally live on the property in question are planning on being on the property during a limited time period. It has turned out that an externally energy supply of as little as or equal to 1000 W, more preferably equal to or less than 500 W, more preferably equal to or less than 200 W, preferably equal to or less than 100 W, is enough to sufficiently in- crease the rate of evaporation in order to be able to cover temporary peaks in the flushing water requirements. It is preferred that the container 121, or at least the container

120, is insulated in case external thermal energy can be supplied. It is preferred that the thermal energy is supplied at or in connection to the surface 130, for instance by the heating step 117 being in the form of a floating heat loop, such as an electric resistance heater arranged to float on the surface 130, such as a heat cable arranged inside a water filled tube of floating plastic material. This results in, among other things, decreased thermal losses to the container 123.

When the amount of water in the storing container 123 for condensed water exceeds a certain predetermined maximum amount, the surplus amount is, according to the invention, brought back to the collecting container 121 for sewage water . Hence, all contents in the containers 121, 123 will originate from the water closet 111 and any other water closets on the property. Since the flushing water in the water closet 111 is completely constituted by evaporated and recondensed water, except any initially supplied amount of freshwater (see be- low) , no additional water is supplied to the containers 121, 123 via the flushing water. Instead, it is only the material, in the form of urine, feces and so forth, which is supplied above and beyond the flushing water itself to the containers

121, 123. Since the flushing water is recirculated in a closed circuit, the net addition to the collecting container

123 during continuous operation consists essentially only of this material. Depending on the evaporation rate in combination with the rate of restoration of condensed water, a cer- tain amount of flushing water may also be supplied to the container 121.

Thereby, the degree of dryness in the collecting container 121 will after a certain period of continuous operation in general be relatively low, and can also be controlled within a relatively narrow interval. For instance, the level of dryness can be kept at a level which at least corresponds to that for sewage water, including flushing water, originating from a so called ultra-low flushing water closet, which uses considerably less than 2 liters of flushing water per flushing, such as less than 1 liter per flushing. This is very desirable for anaerobic digestion, since conventional purifying plants must perform expensive drying of sewage sludge before such digestion. Hence, the water contents in the concentrated latrine in the collecting container 121 can be regulated to accomplish optimal prerequisites for energy and/or nutrient recycling in a central purifying plant. At the same time, essentially all organic constituents will remain in the collecting container 121, which is desirable in view of a later anaerobic digestion- or dehygienization step.

The amount of sludge in the collecting container 121 at the time of sludge evacuation also becomes less; preferably, it is maximally 50%, rather maximally 30%, of the total amount of sewage water which is supplied from the water closet, counting the flushing water. This results in that one and the same sludge evacuation truck can serve more properties than previously, which leads to financial and environmental gains.

Since the flushing water is constituted by recycled black water from the water closet 111, the local water balance is not burdened, despite the fact that a conventional water closet of standard type is used. That no ultra-low flushing water closet has to be installed does not only result in increased user comfort, but also that existing moisture barriers can be kept in the bathroom. This latter, and the fact that an existing water closet of standard type can be kept during the installation of a system for performing a method according to the present invention, results in considerable cost savings. The low number of required moving parts in the system also leads to low operation costs and high availability.

Furthermore, the system does not lead to any environmental load in the form of emissions into the local environment, neither in the form of water, nor of residual compounds from local purification steps.

It is preferred that the orifice 126 of the sewage pipe 124 is arranged essentially in the center of and above the sur- face 130, at a height above the bottom of the collecting container 121 of only a few centimeters, such as maximally 10 cm, higher than the maximum sewage water depth. It is also preferred that the orifice 126 is arranged so that the sewage water is supplied essentially vertically downwards from the orifice 126. This minimizes the amount of splashing during supply of sewage water, which in turn increases the cleanness of the condensed water.

Moreover, it is preferred that the condensed water on its way between the storing container 123 and the second water closet passes an active coal filter 116, in other words a filter through which the water is forced to flow through porous active coal. This removes smelly substances of the condensed water, as well as certain other impurities, which for example results in that the flushing water does not smell bad in the toilet .

It is preferred that the storing container 123 and the col- lecting container 121 are arranged as one single, connected space. In figure 1, this is the case since the containers are connected to each other via a hole 131. The container 120 is arranged to lead water which has condensed on the inside of the lid 122, via pouring along the inner walls of the con- tainer 120, down to a gutter 127 which preferably runs around all of the sides of the container 120, and which gutter 127 also slants downwards towards the location along the gutter 127 where the hole 131 down to the storing container 123 is arranged. This way, all condensed water is led down to and along the gutter 127, to the hole 131 and there through down to the storing container 123.

Since the containers 121, 123 are only connected to each other via the hole 131, all condensed water will be brought to the storing container while the possibility of contamination from the collecting container 121 to the storing container 123 is limited. It is furthermore preferred that the container 120 is manufactured from a material which is essentially opaque to sunlight, and most preferably that the ma- jority or the whole of the container 120 is buried in the ground 115. This way, the space formed by the containers 121, 123 will be dark, whereby fouling of bacteria, algae and so on will be limited to sufficiently low levels without using chemicals .

According to a preferred embodiment, the above mentioned restoration of condensed water from the storing container 123 back to the collecting container 121 takes place by the con ^¬ tents of the storing container 123 overflowing to the col- lecting container 121, in the embodiment illustrated in figure 1 via the hole 131. Such overflowing means that the restoration can take place in a reliable and automatic way, when so is needed, without requiring any moving parts . It is noted that the maximum level for the sewage water in the container 121 must be selected to be lower than the height for the hole 131, since no liquid from the liquid body 128 can be allowed to pour directly from the body 128 down into the container 123.

It is furthermore preferred that an amount of freshwater corresponding to the maximum amount of water in the storing container 123 in an initial step is supplied to the storing container 123. In other words, the storing container 123 is full at the outset of the operation. Hence, when sewage water is supplied to the collecting container 121 and condensed water pours down into the hole 131, none of this water will end up in the storing container 123, which is filled to the brim already. To the contrary, when flushing water is sup- plied to the water closet 111, room arises for further condensed water, which thereafter continuously fills the container 123 up to a point when this is again filled to the brim. In other words, the storing container 123 is continuously filled, during operation, with condensed water up to the maximum amount of water in the storing container 123, after which any additionally supplied condensed water results in that the surplus amount of water in the storing container 123 is brought back to the collecting container 121. The solution illustrated in the figures, in which gravity is used to bring water both from the container 121 to the container 123 and vice versa, is especially advantageous, since the container 120 can then be made passive, with no moving parts . However, it is realized that instead of overflow from the container 123, it would also be possible to for instance arrange a separate pump or the like, in order to bring back the surplus water from the container 123 to the container 121.

Thus, an amount of water roughly corresponding to the initially supplied amount of freshwater will always be present in the container 123, and the contents of the collecting container 121 will always, in terms of chemical composition and degree of dryness, essentially correspond to the material supplied apart from the flushing water in the water closet 111, irrespective of the total amount of sewage water in the container 121. This gives a fraction with predictable properties, in the container 121 in turn leading to good anaerobic digestion and dehygienization results.

It is preferred that the first and second water closets, the collecting container 121 for sewage water, the collecting container 123 for condensed water, as well as all pumps 112, pipes 124, 125, valves 340 and filters 116 described herein, the possible heating step 117, and so on, all constitute fixedly installed parts of a fixedly and permanently in- stalled installation for handling of sewage water in a property which lacks a municipal sewage system.

Moreover, it is preferred that only sewage water from one or several water closets is brought to the collecting container 121 for sewage water, and that no sewage water originating from other types of sewage water producing units is brought to the said collecting container 121. This gives good prerequisites both for energy and nutrient recycling. Furthermore, a control device 114 is arranged to control the operation of the pump 112 and any other necessary moving parts, such as valves, other pumps, and so on. Also, the control device 114 is arranged to in a suitable way control and supply the heating arrangement 117 with energy.

The purified water in the container 123 is thus used for flushing the water closet 111, and is thereby restored to the container 121 for repurification, whereby a closed circuit is achieved. By using both the collecting container 121 for sewage water and the collecting container 123 for purified water, the water closet 111 can be made self-supporting in terms of flushing water, despite the flow from and to the water closet being intermittent while the flow of condensed water to the container 123 being rather limited per time unit but on the other hand more or less continuous.

Hence, by such a method and such an arrangement it is achieved that a property which is not connected to a munici- pal sewage system can be equipped with one or more water closets. Instead, it is sufficient to, when so is needed, empty the considerably more limited amounts of sludge in the container 121. Such emptying can take place at regular intervals, alternatively when the contents reach a certain small- est volume and at the same time holding a desired degree of dryness. Conveniently, the volume in the container 121 can be monitored using a measuring equipment 113, for instance in the form of a counter or a fluxmeter, measuring the number of flushes or the amount of flushed water in the water closet 111, and communicating these data to the control device 114. At the same time, or alternatively, the volume in the container 121 can be measured by a measurement arrangement 132 arranged therein, such as a level meter, which also communicates measurement data to the control device 114. Figures 2a-2b and 3a-3c, respectively, illustrate the operation principle of two different embodiments of the container 120 illustrated in figure 1, in the form of a combination container 200 and 300, respectively, containing, respectively, both collecting containers 220, 320, for sewage water, arranged to accept and accommodate a certain maximum amount of sewage water, and storing containers 230, 330, for condensed water, arranged to accept and accommodate a certain maximum amount of condensed water.

A respective hole 231, 321 is arranged to lead in the sewage pipe 124, and a respective bottom hole 232, 332 is arranged to connect the pipe 125. It is realized that it is also pos- sible to arrange the hole 232, 332 in other locations than in the bottom of the container 200, 300.

The combination containers 200, 300 are associated with a respective upright operation orientation, in which the combi- nation containers are oriented as illustrated in the figures, with a respective lid 210, 310 upwards.

The combination containers 200, 300 furthermore comprise a respective condensing surface 213, 313, onto which water, which has evaporated from the collecting container 220, 320 to a space 212, 312 arranged above a free liquid surface in the container 220, 320 for sewage water, can condense.

When the respective combination container 200, 300 is orient- ed in the said operation orientation, it is according to the invention arranged to lead the water condensed onto the condensing surface 213, 313 to the storing container 230, 330. Then, when the amount of water in the storing container 230, 330 exceeds the certain maximum amount of condensed water, the respective combination container 200, 300 is arranged to bring back the surplus amount to the collecting container 220, 320. As described above, it is preferred that the respective storing container 230, 330 and the respective collecting container 220, 320 are designed as only single, connected space.

Such as has also been described above, it is preferred that the respective combination container 200, 300 is arranged to restore the surplus amount of water in the storing container 230, 330 back to the collecting container 220, 320 by overflowing from the storing container 230, 330. In the combination container 200, this takes place by the container 220 being arranged as a stand-alone container, arranged on legs 221 inside the container 230. A space 225 of between 1-5 cm around the container 220 allows condensed water to pour along the condensing surface 213 and on, along the inner walls of the container 230, down into a space 233 in the container 230 located below the container 220. The overflow then takes place by the water level in the container 230 rising all the way up to the upper edge of the walls of the container 220, after which the overflow takes place. Such a construction is simple and therefore inexpensive to manufacture .

In the combination container 300, the restoring takes place by the container 330 being arranged below and in the direc- tion of extension of the container 320. An edge along the sides of the container 320 forms a draining gutter or surface 324, which both slopes downwards and outwards from a space 323 in the container 320 which is intended for collection of sewage water, and also slopes along the sides of the contain- er 320 towards a location along the gutter 324 where a hole 325 is arranged, which hole 325 leads downwards down to the container 330 and to a space 333 therein for condensed water. Hence, the gutter 324 is arranged to capture and lead con- densed water from the condensing surface 313 to the hole 325. Overflow takes place when the water level in the container 330 reaches and passes the level for the hole 325, possibly the edge of the gutter 324. Such a construction, where the communication between the containers 320 and 330 is limited to one single location, minimizes the contamination from the container 320 to the container 330 of sewage water. Moreover, a suitable valve 340, such as a valve which is tightly sealed as long as a certain minimum pressure is not applied in any direction, is arranged in the hole 325 in order to addition- ally minimize the risk of contamination. The valve 340 is best seen in figure 3c. It is preferred that the communication between the containers 320 and 330, irrespective of whether it is limited to one or several holes, is limited to a total cross-sectional area of maximally 100 cm ² , rather maximally 10 cm ² , most preferably maximally 1 cm ² , most preferably maximally 0.1 cm ² .

As is clear from the figures 2a-3c, it is preferred that the condensing surface 213, 313 in the respective combination container 200, 300 comprises the inner surface of a roof which is convex upwards as seen from outside, which in the said operation orientation is arranged essentially vertically above the collecting container 220, 320, and also covering the collecting container 220, 320. Along the roof, water which has condensed onto the surface 213, 313 can then pour down along the sides of the roof, and then be brought back to the collecting container 230, 330 as described above. Since the roof is upwards convex as seen from outside, it can be designed so that all or substantially all water which is condensed onto the condensing surface 213, 313 is led through runoff down to the storing container 230, 330 rather than back to the collecting container 220, 320 through dripping. A preferred convex design is a domed, such as a semi-circular, shape. The shape can be domed in one horizontal dimension, such as in the examples illustrated in figures 2a-3c, or in two horizontal dimensions, such as a semi-spherical shape.

It is preferred that the respective lid 210, 310 is connected either to the storing container 230 or to the collecting container 320 using a connection 211 and 311, respectively, which at least is liquid tight with respect to condensed water pouring downwards along the inner surfaces of the lid 210, 310 and which passes the connection 211, 311.

As is not illustrated in the figures 2a-3c, but on the other hand is principally illustrated in figure 1, the condensing surface may comprise a corrugated surface 133, for instance in the form of a corrugated plastic insert arranged to lead condensed water off, through pouring, towards and down along the inner walls of the container 120 for further transport to the container 123. Such a corrugated surface 133 increases the total condensing surface, which improves the turnover velocity in the container 120.

As is illustrated both in figures 2a-2b and in figures 3a-3c, the respective combination container 200, 300 preferably comprises a double bottom structure, with an outer bottom 234, 334 and an inner bottom 222, 322, where, in the said operation orientation, the space 233, 333 between the outer 234, 334 and the inner 222, 322 bottom constitutes the storing container 230, 330, and where the inner bottom 222, 322 constitutes the bottom in the collecting container 220, 320. In general, such a construction admits a simple construction with both containers 220, 230; 320, 330 in one and the same combination container 200, 300, rather than as two containers that during operation are separately arranged. This is preferred since it is difficult to install two such separate containers completely or partially buried in the ground 115 without problems arising with relative sliding and resulting leaks .

Moreover, it is preferred that, as in figures 2a-2b and 3a- 3c, respectively, the double bottom structure is designed with a passage 225, 325 between the inner 222, 322 and the outer 234, 334 bottom, arranged along the outer edge of the double bottom structure, so that, when the combination container 200, 300 is oriented in the said operation orienta- tion, condensed water can pour from the condensing surface 213, 313 and down into the storing container 230, 330 through the passage 225, 325.

It is preferred that the collecting container 121, 220, 320 for sewage water has a maximum volume for sewage water of at least 0.5 m ³ , rather at least 1 m ³ , rather at least 2 m ³ , in order to be able to accommodate the sewage water from the at least one water closet 111. The volume of the collecting container should be at least 0.2 m ³ , rather at least 0.5 m ³ , rather at least 2 m ³ .

Above, preferred embodiments have been described. However, it is apparent to the skilled person that many modifications may be made to the described embodiments without departing from the basic idea of the invention.

For instance, it is possible to design an installation according to the invention as a portable installation for use on boats, on quays and in natural harbours, at construction sites or in other places where there is a need for a water closet but where there is no municipal sewage. In this case, the sewage water is emptied from a water closet, such as a water closet installed on board on a boat or a water closet installed in a portable water closet, into the collecting container for sewage water, and flushing water for use in said water closet is filled from the storing container for condensed water. It is also possible to design a combination container according to the invention as illustrated in figures 2a-2b, having a collecting container which is arranged inside the space defined by the storing container, but where the collecting container is kept in place using a fastening means along its upper edge rather than using legs supported by the bottom of the storing container. Such a combination container can advantageously also be equipped with a gutter of the type illustrated in figures 3a-3c. With respect to the combination container, furthermore the collecting container and the storing container may be arranged as two separate containers, for instance for burying in the ground, between which containers a flexible connection, such as a flexible rubber tube, is arranged. In order to achieve the above described gravity driven transport of condensed water to the storing container, it is in this case necessary that the respective connection points of the flexible connection are arranged so that the connection to the collecting container is not lower than the connection to the storing container.

Hence, the invention shall not be limited to the described embodiments, but may be varied within the scope of the en- closed claims .