Water purification device

1. A portable device ( 1 ) for water purification, the device ( 1 ) comprising a dirt water container ( 2 ) for accumulating dirt water and a purification unit ( 5 ) for purifying the dirt water, wherein the dirt water container ( 2 ) is arranged above the purification unit ( 5 ) for driving water through the purification unit ( 5 ) by gravity; wherein the purification unit ( 5 ) comprises a filter housing ( 5 ′) enclosing a purification medium that is separating an upstream side ( 52 ) of the purification unit ( 5 ) from a downstream side ( 53 ) of the purification unit ( 5 ) such that water in the purification unit ( 5 ) can flow from the upstream side ( 52 ) to the downstream side ( 53 ) only through the purification medium; the filter housing ( 5 ′) having a downstream outlet ( 29 A) from the downstream side ( 53 ); wherein the purification unit ( 5 ) is a filtration unit ( 5 ) and the purification medium is a microporous filtration membrane; wherein the dirt water container ( 2 ) has a container outlet ( 10 ), and the filter housing ( 5 ′) has an upstream inlet ( 19 ) to the upstream side, wherein the container outlet ( 10 ) and the upstream inlet ( 19 ) are fluid-flow-connected by a first flow connector ( 9 ) for receiving dirt water from the dirt water container ( 2 ) into the upstream side of the purification unit ( 5 ); wherein the device comprises a clean water tank ( 3 ) fluid-flow connected to the downstream side ( 53 ) through the downstream outlet ( 29 A) for receiving purified water from the downstream side ( 53 ), wherein a backwash tube ( 12 , 12 A) is provided which is connected to the upstream side ( 52 ) for receiving contaminated backwash water from the upstream side ( 52 ) of the filtration unit ( 5 ) and connected to a backwash receptacle ( 8 ) for dispensing the backwash water into the backwash receptacle ( 8 ) when water is pressed from the downstream side ( 53 ) of the filtration unit ( 5 ) through the membrane to the upstream side ( 52 ) by compression of a backwash bulb ( 7 ) and further from the upstream side ( 52 ) through the backwash tube ( 12 , 12 A) into the backwash receptacle ( 8 ); wherein the backwash receptacle ( 8 ) is different and separate from the dirt water container ( 2 ) and tube-connected only to the filter housing ( 5 ′), and wherein the backwash receptacle is configured so that it is detachable from the backwash tube and is emptyable and replaceable.

2. The device according to claim 1 , wherein a one way check valve ( 54 ) is provided between the dirt water container ( 2 ) and the upstream side ( 52 ) of the filtration unit ( 5 ) for preventing backwash water to be pressed into the dirt water container ( 2 ).

3. The device according to claim 1 , wherein the filtration unit ( 5 ) has an upstream outlet ( 23 ) in the filter housing ( 5 ′) for outlet of fluid from the upstream side, wherein a vent tube ( 12 ) is connected to the upstream outlet ( 23 ) for venting of air from the filter housing ( 5 ′) through the upstream outlet ( 23 ) and into the vent tube ( 12 ) when dirt water enters the filter housing ( 5 ′) through the upstream inlet ( 19 ), the vent tube ( 12 ) extending upwards and having a vent opening ( 22 ) into atmosphere for venting of air from the upstream side and from the vent tube, wherein the vent opening ( 22 ) is provided at a level closer to a top than to a bottom ( 16 ) of the dirt water container ( 2 ) for preventing dirt water to flow from the filter housing ( 5 ′) through the upstream outlet ( 23 ) through the vent tube ( 12 ) and out of the vent opening ( 22 ), wherein the backwash tube ( 12 , 12 A) is an integral part of the vent tube ( 12 ) for venting air from the upstream side and dispensing backwash water from the upstream outlet ( 23 ) through the backwash tube ( 12 , 12 A) into the back wash receptacle ( 8 ).

4. A portable device ( 1 ) for water purification, the device ( 1 ) comprising a dirt water container ( 2 ) for accumulating dirt water and a purification unit ( 5 ) for purifying the dirt water, wherein the dirt water container ( 2 ) is arranged above the purification unit ( 5 ) for driving water through the purification unit ( 5 ) by gravity; wherein the purification unit ( 5 ) comprises a filter housing ( 5 ′) enclosing a purification medium that is separating an upstream side ( 52 ) of the purification unit ( 5 ) from a downstream side ( 53 ) of the purification unit ( 5 ) such that water in the purification unit ( 5 ) can flow from the upstream side ( 52 ) to the downstream side ( 53 ) only through the purification medium; the filter housing ( 5 ′) having a downstream outlet ( 29 A) from the downstream side ( 53 ); wherein the purification unit ( 5 ) is a filtration unit ( 5 ) and the purification medium is a microporous filtration membrane; wherein the dirt water container ( 2 ) has a container outlet ( 10 ), and the filter housing ( 5 ′) has an upstream inlet ( 19 ) to the upstream side, wherein the container outlet ( 10 ) and the upstream inlet ( 19 ) are fluid-flow-connected by a first flow connector ( 9 ) for receiving dirt water from the dirt water container ( 2 ) into the upstream side of the purification unit ( 5 ); wherein the device comprises a clean water tank ( 3 ) fluid-flow connected to the downstream side ( 53 ) through the downstream outlet ( 29 A) for receiving purified water from the downstream side ( 53 ), wherein the filtration unit ( 5 ) has an upstream outlet ( 23 ) in the filter housing ( 5 ′) for outlet of fluid from the upstream side, wherein a vent tube ( 12 ) is connected to the upstream outlet ( 23 ) for venting of air from the filter housing ( 5 ′) through the upstream outlet ( 23 ) and into the vent tube ( 12 ) when dirt water enters the filter housing ( 5 ′) through the upstream inlet ( 19 ), the vent tube ( 12 ) extending upwards and having a vent opening ( 22 ) into atmosphere for venting of air from the upstream side and the vent tube, and wherein the vent opening ( 22 ) is provided at a level closer to a top than to a bottom ( 16 ) of the dirt water container ( 2 ) for preventing dirt water to flow from the filter housing ( 5 ′) through the upstream outlet ( 23 ) through the vent tube ( 12 ) and out of the vent opening ( 2 ), wherein a one way check valve ( 54 ) is provided between the dirt water container ( 2 ) and the upstream side ( 52 ) of the filtration unit ( 5 ) for preventing backwash water from being pressed into the dirt water container ( 2 ) when backwash water is pressed through the filter and through the upwardly extending vent tube and into the backwash receptacle.

5. A portable device ( 1 ) for water purification, the device ( 1 ) comprising a dirt water container ( 2 ) for accumulating dirt water and a purification unit ( 5 ) for purifying the dirt water, wherein the dirt water container ( 2 ) is arranged above the purification unit ( 5 ) for driving water through the purification unit ( 5 ) by gravity; wherein the purification unit ( 5 ) comprises a filter housing ( 5 ′) enclosing a purification medium that is separating an upstream side ( 52 ) of the purification unit ( 5 ) from a downstream side ( 53 ) of the purification unit ( 5 ) such that water in the purification unit ( 5 ) can flow from the upstream side ( 52 ) to the downstream side ( 53 ) only through the purification medium; the filter housing ( 5 ′) having a downstream outlet ( 29 A) from the downstream side ( 53 ); wherein the purification unit ( 5 ) is a filtration unit ( 5 ) and the purification medium is a microporous filtration membrane; wherein the dirt water container ( 2 ) has a container outlet ( 10 ), and the filter housing ( 5 ′) has an upstream inlet ( 19 ) to the upstream side, wherein the container outlet ( 10 ) and the upstream inlet ( 19 ) are fluid-flow-connected by a first flow connector ( 9 ) for receiving dirt water from the dirt water container ( 2 ) into the upstream side of the purification unit ( 5 ); wherein the device comprises a clean water tank ( 3 ) fluid-flow connected to the downstream side ( 53 ) through the downstream outlet ( 29 A) for receiving purified water from the downstream side ( 53 ), and wherein the dirt water container ( 2 ) is rigid, wherein the clean water tank ( 3 ) is rigid, wherein the device ( 1 ) has a modular build-up with mutually stackable dirt water container ( 2 ), intermediate module ( 4 ), and clean water tank ( 3 ), wherein the intermediate module ( 4 ) is supported by the clean water tank ( 3 ) and, in turn, supports the dirt water container ( 2 ) when in stacked condition to form an integrated three-module system, wherein the dirt water container ( 2 ) is arranged above the clean water tank ( 2 ) and with a clearance of at least 5 cm between the clean water tank ( 3 ) and the dirt water container ( 2 ), wherein the filtration unit ( 5 ) has an upstream outlet ( 23 ) in the filter housing ( 5 ′) for outlet of fluid from the upstream side ( 52 ), wherein a vent tube ( 12 ) is connected to the upstream outlet ( 23 ) for venting of air from the filter housing ( 5 ′) through the upstream outlet ( 23 ) and into the vent tube ( 12 ) when dirt water enters the filter housing ( 5 ′) through the upstream inlet ( 19 ), the vent tube ( 12 ) extending upwards and having a vent opening ( 22 ) into atmosphere for venting of air from the upstream side and the vent tube, and wherein the vent opening ( 22 ) is provided at a level closer to a top than to a bottom ( 16 ) of the dirt water container ( 2 ) for preventing dirt water to flow from the filter housing ( 5 ′) through the upstream outlet ( 23 ) through the vent tube ( 12 ) and out of the vent opening ( 22 ).

6. The device according to claim 5 , wherein the device is a portable device with dry weight of less than 30 kg, with a volume of the dirt water container of less than 30 liters, and with a volume of the clean water tank of less than 30 litres.