WO2006046074A1

WO2006046074A1 - Water purification apparatus

Info

Publication number: WO2006046074A1
Application number: PCT/GB2005/004195
Authority: WO
Inventors: Barry Robert East
Original assignee: Barry Robert East
Priority date: 2004-10-29
Filing date: 2005-10-31
Publication date: 2006-05-04
Also published as: GB0423985D0

Abstract

Lightweight man-portable water purification apparatus consists of a tank, a pre-filter (2), an ultra-filtration module (4) and a pneumatically operated pump (3) to cause contaminated water to be passed through the pre-filter (2) and ultra-filtration module (4) to produce potable water.

Description

WATER PURIFICATION APPARATUS

This invention relates to water purification apparatus, particularly to such apparatus which can be configured to be man-portable, i.e. able to be handled and transported by a single person without external aid, and able to be operated without any external power supply, i.e. by purely mechanical means.

There is a need to be able to purify any available non-brackish water, in any location regardless of how remote, anywhere in the world to provide pure, clean drinking water which conforms to World Health Organisation standards. Large-scale systems for such purification, powered by vehicle generators, are known, e.g., as used in the Field Missions division of NATO, but these are expensive, and cannot always reach locations where the pure water is needed.

Portable units, able to run without external power sources, would be better, as they can be quickly and easily transported to any location, and set up and operated.

According to the present invention, there is provided apparatus for water purification which comprises at least one tank for receiving water to be purified, a pre-filter arranged to receive water from the tank(s) and having a filtered water outlet, at least one ultra-filtration module connected to the outlet of the pre-filter, and having outlets for filtrate and concentrate, and a pneumatically driven pump arranged to pump water from the tank(s) successively through the pre-filter and the ultra-filtration module(s) to produce filtered purified water at the filtrate outlet(s) of the ultra-filtration module(s).

The pre-filter may be configured as a guard filter and is designed to remove particles which could clog up the ultra-filtration module(s). It is preferably located in a pre-filter unit configured to contain organic substances, prevent growth of bacteria and other microorganisms and prevent algal and other growths. It may additionally be configured to remove most heavy metals.

The ultra-filtration module may be of any known type compatible with the desired configuration of the overall apparatus. For man-portable such apparatus, it is preferred to use commercially available crossflow ultra¬ filtration units. These generally consist of an outer casing having inlet and outlet ports for liquid and, internally of the casing, a filter element consisting of an array of parallel microporous tubes. These are conventionally arranged in a rigid porous support with the ends of the tubes being coplanar in two parallel planes spaced apart by the length of the tubes, and with a water-impermeable baffle sealed to each tube at its ends, the two baffles extending across the chamber of the unit and being sealed to the walls of the chamber so as to divide the chamber into three sections, viz. an inlet section into which the inlet port of the ultra-filtration unit debouches, a central section containing the porous support and having an outlet port for filtrate in the chamber wall at an appropriate position, and an outlet chamber into which water flowing through the tubes may pass and from which water may be abstracted via the outlet port of the ultra-filtration unit itself. When water is pumped under pressure through the tubes, it can flow through the tube walls into the porous support and be collected from the central chamber. The unit is called a crossflow unit because of this transverse movement of the water. The contaminated water flowing through the tubes is accordingly concentrated and collects in the outlet chamber through which it passes via a restrictor valve either to a waste concentrate outlet, or it may be recycled into the tank(s). The restrictor valve may be of an adjustable type and the unit preferably has a pressure gauge fitted between the outlet and the restrictor valve to enable adjustment to a desired back pressure, this being essentially the pressure across the walls of the tubes which drives the ^• water through the porous tube walls.

The diameter and wall thickness of the porous tubes may be chosen appropriately. The smaller the tubes, which may even be capillary tubes, the greater the overall surface area in the ultra-filtration unit, but, equally, the greater the tendency to clog and the greater the pressure drop from inlet chamber to outlet chamber. Larger tubes provide less pressure drop, but, likewise, less surface area. The tubes may be produced in known fashion, for example by the process set out in US-A-4042359. The pore size is preferably less than 0.01 mμ so that nothing of size greater than that can pass into the filtrate. However, the dissolved natural minerals and salts which are usually present in the contaminated water and which are important to retain as components of healthy drinking water are able to pass through the microporous material without difficulty.

The pneumatically driven pump which is arranged to pump water through the pre-filter and the ultra-filtration module to the portable water outlet may be of any convenient type, but is preferably one which is light in weight, has adequate volumetric flow and, in particular, can pump against the substantial back pressure generated by pumping water through the ultra-filtration module at a desired high rate. An air-powered diaphragm pump is preferred, designed to operate at an output pressure of 1 to 2 bar. The supply of air under pressure to operate such a pump may be provided by a simple mechanical hand or foot pump, so enabling the apparatus to be used in locations where there is no electrical power supply. A simple pneumatic foot pump is preferred as this enables the pneumatically driven pump to be operated to produce an adequately high output of portable water essentially "on demand". If a power supply is available, the pneumatic supply for the pneumatically driven pump may be provided by a compressor which may be electrically driven or, e.g., attached to an internal combustion engine, for example one in a vehicle.

An electrically driven compressor may in turn be powered by a rechargeable battery which is charged during the day by an external solar panel and which will thus allow the apparatus to be operated at night.

The components of the pneumatically driven pump which come into contact with the water should, of course, be manufactured from appropriate materials so as not to prejudice the potability of the water finally produced.

Preferably the pre-filter, ultra-filtration unit and the pneumatically operated pump are all located inside the tank(s) with a view to enabling a simple man- portable unit to be configured. The apparatus may also include a coarse filter or sieve for removing large size debris, fibres or the like from the contaminated water before it passes to the pre-filter.

The tank(s) may be configured to enable a foot pump for powering the pneumatic water pump, to be stowed inside, to save space during transportation. A collapsible water bucket for collecting treated water and/or a collapsible bellows for receiving and storing the treated water, can be likewise thus stowed.

Sealed collapsible water containers are preferably used with the apparatus of the present invention, as these provide various benefits, including those of easy storage and protection against re-contamination. Such containers are formed from a water-impermeabie membrane, for example a suitable food- grade plastics film. Known collapsible containers such as those used for storing wine and other drinkable products may be used for collecting and storing the purified drinking water. As water is drawn from such a container, the container collapses so no air can enter the container, i.e. the bag effectively gets smaller as the water volume is diminished, which keeps the water fresh and this prevents contamination of the purified water by airborne pathogens or pollutants and from airborne germs, such as from sneezes, and from other contaminants like human hair from heads, beards, etc.

It also prevents contamination from "dipping" of unclean implements or hands into the purified water, lapping by animals, or the laying/breeding of mosquito eggs/larvae, and thus enables the purified water to be safely stored.

An ultra violet lamp may be fitted or located in the storage vessel if a power supply to operate it is available, so as to kill off any bacteria or other micro¬ organisms that may try to develop.

The tank(s) and all pipework are preferably produced from strong, non-brittle polyethylene plastic approved for use in food processing.

Preferably the various components of the apparatus are designed to ensure that the entire apparatus is sufficiently light in weight to be man-portable, thus enabling a single apparatus to be shared between multiple communities within a reasonable geographic area, thereby enabling the supply of purified water to a larger number of people.

Preferably each of the components of the apparatus is designed to be fitted to the others, so that, if desired, the apparatus may be quickly dismantled without the need for tools, and the weight of the apparatus thus shared between several people.

A particularly preferred design is to configure the tank(s) to be mounted on a backpack carry frame, with all other components being stowed or nested inside the tank(s) or mounted to the carry frame. The total weight is preferably designed not to exceed around 25 kg. Alternatively or additionally, the apparatus can be mounted on a wheeled luggage frame with optional foldaway or stowaway wheels as in conventional luggage.

The unit can be used for the purification of surface water and ground water sources to produce quality drinking water meeting World Health Organisation standards without removal of necessary life-supporting minerals, but with effective removal of e.g. colloidal solids, bacteria, viruses, protozoa, parasitic worms, pesticides, herbicides, arsenic and heavy metals.

If further purification is required, i.e. for the removal of specific contaminants such as water-soluble arsenic, these can be coupled in series with the apparatus of the invention. Other known purification units, such as osmosis units, can be incorporated. However, these require pressures which may not be obtainable from pneumatically driven pumps powered by portable electrical power sources which are solar powered or user generated, and the output purified water may then require mineral additions to render it suitable for drinking.

The invention is illustrated by way of example with reference to the accompanying drawings, in which:

Figure 1 shows diagrammatically a first embodiment of an apparatus according to the invention;

Figure 2 shows an alternative arrangement of the main components of an alternative embodiment of the invention; and Figure 3 shows a further embodiment, diagrammatically.

Referring to Figure 1 , the apparatus consists basically of a tank 1 in which are located a pre-filter 2, a pneumatic pump 3 and an ultra-filtration module 4. The ultra-filtration module 4 has a permeate outlet fitted with a shut-off tap 5 to facilitate changing of a sealed water bag 6 which acts as a receiving vessel. Water bag 6 has a shut-off valve 14 for dispensing purified water.

Water to be purified is first poured into tank 1 , preferably via a strainer 11 to trap coarse materials. It is then pumped by pump 3 from tank 1 through pre- filter 2 and ultra-filtration module 4 to the bag 6. Contaminants and source water rejected by the ultra-filtration module 4 pass through to a concentrate outlet pipe with a restrictor valve 7 and a pressure manometer 8. Where source water is scarce, the concentrate from the outlet pipe may be recycled back into tank 1 for re-processing; otherwise it is merely disposed of.

Pump 3 is driven by compressed air provided by a mechanical foot or hand pump 9 or alternatively by an electrically powered air pump 10, and supplied via a pipe 17.

Battery back-up 12 may be provided in known fashion to enable use of the pump 10 during non-daylight hours with the battery being recharged by a solar panel 13 during daylight hours. Charging of battery 12, and its use to power pump 10, may be controlled by a control unit 15.

The apparatus may also include a UV light sterilizer, for example a 9 Watt UV unit in a robust housing which can be placed in the purified water collection vessel or bag 6 to prevent growth of algae or other micro¬ organisms and enable the purified water to be stored safely in bag 6 for a considerable period of time. Such a steriliser may also act in the same way if placed by one or more bags 6, so long as the bags 6 are constructed of UV transparent material. A typical apparatus shown in Figure 1 may be designed and constructed to weigh less than 25 kg while being capable of treating up to 350 litres water per hour. Depending on the condition and degree of contamination of the feed water, approximately 65% of the processed water becomes drinking water (permeate), the remainder being returned to the original source, giving a yield of up to 240 litres/hour.

The apparatus should be designed to operate satisfactorily at operating temperatures of 5 to 60^°C and at up to 100% humidity (non-condensing).

The capillary tube membranes forming part of ultra-filtration module 4 should be chosen to tolerate water temperatures of 5 to 3O⁰C with pH values of 6 to 9, and to have a chlorine tolerance of 5,000 ppm.

If the apparatus is to be stored for any length of time between uses, a 1 gram chlorine tablet may be added to approximately 25 litres of water in tank 1 and then pumped through the ultra-filtration module to promote sterile conditions prior to storage. This may need to be repeated before using the apparatus after a stored period.

Referring to Figure 2, this shows in diagrammatic simplified form an alternative way of arranging the major components of water purification apparatus according to the present invention. The unit illustrated consists of a pair of cylindrical water tanks 20 which are connected by a welded plate 22 to a pre-filter module 2. Module 2 has a removable cap 21 to enable the changing of a filter cartridge when necessary.

An outlet pipe 23 receives water from the pre-filter module 2 and feeds it into the upper ends of a pair of ultra-filtration units 24 mounted adjacent each tank 20. The filtrate outlets from the ultra-filtration units 24 are joined by a pipe 25 having a spout 26 from which purified water may flow. Turning now to Figure 3, this shows diagrammatically another embodiment of water purification apparatus according to the invention which is designed to be entirely man-powered. In the drawing, components analogous to those shown in Figure 1 are identified by the same reference numbers.

Thus, as shown, located in a tank 1 are a pre-filter module 2 and an ultra¬ filtration module 4.

Additionally located in the tank 1 are a pneumatically driven water pump 3 and a coarse filter 30 adapted to stop particulate contaminants in the water getting into the pump 23. Pump 23 is driven by pneumatic pressure generated by a foot pump 27 which is connected via an air line 28 including a one-way valve 29 to the pneumatic supply port of the pump 3.

The coarse filter 30 has an outlet pipe 31 which is connected to the supply side of the pump 3, with the delivery side of pump 3 being connected via a lead 32 to the pre-filter module 2 which is, in turn, connected via a pipe 35 to the ultra-filtration module 4. The filtered purified water which emerges from the ultra-filtration module is delivered via a pipe 37 to a beaker 40. The still contaminated water which emerges from the ultra-filtration module 4 may be fed away via a pipe 38 and e.g. disposed of into a soil drain 39 or returned to tank 1.

The operation of the apparatus shown in Figure 3 is very straightforward. Once assembled, the tank 1 is filled to an appropriate level with water and pump 27 then operated. This causes the pump 3 to draw water through coarse filter 30 and lead 31 and eject it under pressure through lead 32, pre- filter 2, pipe 35, the ultra-filtration module 4 and pipe 37 into the beaker 40.

By careful design, the apparatus shown in Figure 3 may be produced in a form which is sufficiently lightweight to enable it to be all easily carried by a backpack, quickly unpacked and assembled when needed, filled with water and then operated rapidly to produce potable water. The following are typical design and dimensional data for such apparatus:

Main tank capacity 75 litres Ultra filtration module: membrane chosen for 5-30^°C operating temperature range to process water at pH 6 to 9 and chlorine tolerance of 5000 ppm.

Pneumatic pump: capacity 5 litres/mm, input pressure 1 to 1.5 bar

Pre-filter: active carbon, 200 cm³ volume Foot pump: standard auto tyre inflation pump

A system of this type can produce up to 350 litres per hour of potable water.

Claims

1. Apparatus for water purification which comprises at least one tank for receiving water to be purified, a pre-filter arranged to receive water from the tank(s) and having a filtered water outlet, at least one ultra-filtration module connected to the outlet of the pre-filter, and having outlets for filtrate and concentrate, and a pneumatically driven pump arranged to pump water from the tank(s) successively through the pre-filter and the ultra-filtration module(s) to produce filtered purified water at the filtrate outlet(s) of the ultra-filtration module(s).

2. Apparatus according to Claim 1 wherein the ultra-filtration module(s) is/are a cross-flow unit(s).

3. Apparatus according to Claim 1 or 2 wherein the pneumatically driven pump has an output pressure of the order of 1 to 2 bars.

4. Apparatus according to any one of Claims 1 to 3 wherein the pneumatically driven pump is powered by hand or foot pump..

5. Apparatus for water purification according to any one of Claims 1 to 4 in which the ultra-filtration module(s) and the pneumatically driven pump are mounted inside the tank(s).

6. Apparatus according to any one of Claims 1 to 5 in which the pre-filter unit is mounted inside the raw water tank(s).

7. Apparatus according to Claim 5 or 6 wherein the water tank(s) is/are adapted for mounting to a backpack carry frame and the remaining components of the apparatus to stow or nest inside the main tank or mount to the carry frame.

8. Apparatus according to any one of Claims 1 to 4 wherein the ultra¬ filtration module(s) and the pre-filter unit are mounted exterior to the tank(s).

9. Apparatus for water purification according to any one of the preceding Claims and including a sealed collapsible water container comprises at least one sealed water-impermeable membrane.

10. Apparatus for water purification according to any one of the preceding Claims and including an electrically powered air pump adapted to drive the pneumatically driven pump.

11. Apparatus for water purification according to Claim 9 and including rechargeable batteries for storing electrical power adequate to operate the air pump.

12. Apparatus according to any one of the preceding Claims and including a filter cartridge adapted to remove arsenic from the water.

13. Apparatus according to any one of the preceding Claims and weighing less than 25 kg.

14. Apparatus according to any one of the preceding Claims and in which the components are configured to be snap-fitted together to form the working apparatus.