GB2563202A

GB2563202A - Portable water purification system

Info

Publication number: GB2563202A
Application number: GB1708637.2A
Authority: GB
Inventors: Mason Colin; O'connor Cecil; Bryan Jotcham Richard
Original assignee: Axess Tech Ltd; P W CIRCUITS Ltd
Current assignee: Axess Tech Ltd; P W CIRCUITS Ltd
Priority date: 2017-05-31
Filing date: 2017-05-31
Publication date: 2018-12-12
Also published as: GB201708637D0

Abstract

A portable water treatment device comprises a photovoltaic panel (A), an input water storage tank, a filtration unit (D), and a UV irradiation unit. The UV irradiation unit is powered by the photovoltaic panel. Water is gravity fed from the input storage tank to the filtration unit and from the filtration unit to the UV irradiation unit. Optionally, water is gravity fed from the UV irradiation unit to an output water storage tank (H). Preferably, the filtration unit comprises a helical spring filter having an exclusion size of less than 40 microns. An array of UV LEDs may be utilised to suppress microbial growth in the output storage tank. The filtration unit and UV irradiation unit can be provided in drawers to facilitate removal from the device for cleaning, servicing or replacement. A photocatalyst, such as titania, may be utilised in the UV irradiation unit to generate free radicals in the presence of UV irradiation. The device may also comprise a rechargeable battery, which is charged by the photovoltaic panel when sufficient light is available, and which can power the UV irradiation unit when the unit is operational.

Description

Portable Water Purification System

Field of the Invention

The invention relates to the production of potable water from sources that may be harmful to health due to contamination with microorganisms. In particular, the invention relates to the provision and use of a portable, self-contained unit which is able to produce potable water and which is simple in design and solar-powered and, therefore, suitable for use "off the grid", for example in remote locations and/or developing countries.

Introduction

It is widely known that drinking water in many areas of the world contains bacteria arising from the contamination of the water supply by effluent, sewerage or the products of natural decomposition processes.

Often, this water may look and smell clean, but, if drunk, may result in serious health issues, such as dysentery and bacterial infection.

The World Health Organisation (WHO) estimates that 1.5 million people die every year due to water-borne disease. Examples of contaminants include:

Cryptosporidium, a protozoan parasite, that causes gastrointestinal upset and may be resistant to chlorination. Hepatitis A, a small enteric virus often sourced from sewerage, causing liver damage and sometimes death. Campobacteriosis, a bacterial infection caused by faecal contamination. Leptospirosis, a bacterium which thrives in water contaminated by animal urine and can cause meningitis and renal failure. These examples illustrate only a small proportion of the bacterial, viral and other microbial contaminants that can be present in untreated drinking water. Other contaminants, such as nematodes and tapeworms may also cause serious health problems.

Major water treatment plants are able to treat large volumes of water, rendering it safe to drink. However, for smaller and more remote communities, this may be completely impractical; resulting in the population being compelled to drink what is available.

Current solutions to this problem can involve boiling the water before drinking, treating with chemical disinfectants, and using sealed vessels to irradiate the water with sunshine. Boiling is effective, but takes time, creates hot water (not always desirable in a hot climate) and requires the use of an oven or fire, creating a serious health and safety hazard for children. A variation on this approach uses sunshine to evaporate the water to separate the clean from the contaminated water. Examples here include Solar Balls and the Cole Dobson Solar Water Purifier.

Chemical disinfectants, such as chlorine or sodium metabisulphate will destroy bacteria but involve adding potentially harmful chemicals to the drinking water. If these are not carefully monitored, then poisoning can occur. It is also difficult for the user to know what the optimum dose of chemical is. Too little and the water remains harmful and too much and the water may become unpalatable and possibly poisonous in its own right.

Various sunshine irradiation systems have been proposed, such as the Life Sack that utilises the SODIS (Solar Water Disinfection Process) or Solvatten that employs sunshine to undertake the disinfection. The main drawback with these is it is not always possible to know when the product is ready for drinking. If treatment is too short then it results in only warming up the water, which may encourage bacterial growth; the opposite of what it is trying to achieve. These systems tend to be batch processes and require long periods of extended sunshine (typically 6 hours) for them to be effective.

An example of a granted patent in this area is European Patent No. EP2004554filed by inventors C. O'Connor & C. Mason et al in the name of P.W. Circuits Ltd. This patent discloses a UV system for treating a fluid such as air or water, comprising ultraviolet light emitting diodes for the production of drinking water.

There is a need (described in the invention) for a portable, continuous, reliable, safe, low-cost and easy to operate water treatment system that can be installed very quickly in locations of need, or even transported on vehicles for emergency relief operations. Because water is a necessity for life, it is important that any treatment system employed in more remote rural areas, or in locations where relief is necessary, meets all of these criteria and not just some of them.

Summary of the Invention

According to a first aspect of the invention, there is provided a portable water treatment device comprising a photovoltaic panel, an input water storage tank, a filtration unit, a UV irradiation unit and, optionally, an output water storage tank, wherein the UV irradiation unit is powered by the photovoltaic panel and wherein water is gravity fed from the input water storage tank to the filtration unit and from the filtration unit to a UV irradiation unit and, optionally, from the UV irradiation unit to the output water storage tank.

According to a second aspect of the invention, there is provided a method of producing potable water, comprising use of a portable water treatment device according to the first aspect of the invention.

Brief Description of the Drawings

Figures 1, 2 and 3 illustrate the exemplary portable water treatment devices described in, respectively, examples 1 and 2.

Figure 4 shows, diagrammatically, a possible arrangement of the UV irradiating LEDs relative to the channels in a UV irradiation unit according to the invention.

Figure 5 shows, in cross-section, possible arrangements of the UV irradiating LEDs relative to various channel arrangements in a UV irradiation unit according to the invention.

Detailed Description of the Invention

According to a second aspect of the invention, there is provided a method of producing potable water comprising use of a portable water treatment device according to the first aspect of the invention.

Portable Device

The requirement that the device of the invention is portable is to be understood as meaning that it can be lifted and carried by a single person as a discrete device. This means that the device can be effectively deployed to where it is needed, without requiring specialist installation or transportation equipment. Typically, the device will weigh no more than 20kg, for example no more than 10kg (weighed without water in the tanks, or elsewhere in the device). Typically, the device is to be used in a domestic setting by a family unit and configured to produce at least 2, 3, 4, 5, 8, 10, 15 or 20 litres of water per day (but no more than 5, 10, 15, 20, 30, 40, 50 75, 100, 150 or 200 litres of water per day). The precise volume of water produced will depend on a number of factors, such as filter efficiency, amount of light incident on the photovoltaic panel and, perhaps, the level of contamination of the input water (because more heavily contaminated water may require a longer residency time in the UV irradiation unit). Whilst the device is scalable in that it can be made in different sizes, scalability also arises by running multiple devices side-by-side. A larger premises, for example a school, may be served by an array of multiple devices of domestic size. This is advantageous over the installation of a single large device in that it allows individual devices to be taken off-line for replacement and/or servicing without interrupting potable water production completely. According to certain embodiments, multiple devices may be electrically interlinked to allow the UV irradiation unit of one device to take power from another device, so that all devices may keep operating, even when the power available in an individual device would, otherwise, prevent an individual device from operating.

It is also possible to interconnect an array of devices, such that the potable water produced by each device is stored in a common water output tank.

According to certain embodiments, the device optionally includes features that facilitate its portability, for example carry handles or corner wheels, so that it may, respectively, be lifted and carried or wheeled along a surface. According to certain embodiments, the device includes a robust lid, for example a hinged lid, to cover and protect the photovoltaic panel from damage during transit and when otherwise not in use.

Water Quality

Preferably, the device and method of the invention produces output water of potable water quality as defined by a suitable standard or recommendation. For example, by the EU Drinking Water Directive or the WHO Guidelines for Drinking Water Quality. With regard to microorganisms, the "gold standard" for potable water is "water free from any micro-organisms and parasites which [...] constitute a potential danger to human health" (from UK legislation). In practice, drinking water quality is often monitored by measuring the levels of specific organisms, such as total coliforms or total faecal coliforms or E. coli, which are used as indicators of probable sewage contamination by a wider range of pathogens. According to certain embodiments, the output water from a device of the invention contains no more than 100, 50, 20, 15, 10, 5, 2 or 1 viable E. coli cells per 100 cm3. Most preferably, it produces water of a quality such that no more than 5% of samples of 100 cm3 of water contain any viable E. coli cells.

Photovoltaic Panel

The device according to the invention comprises a photovoltaic panel. Any suitable panel may be used that is designed to absorb the sun's rays as a source of energy for generating electricity including crystalline solar cells, thin film technologies & flexible cells.

The panel is preferably dimensioned to fit over substantially the whole of the top surface of the unit, for example it may be approximately 200 mm by 300 mm. Preferably, it is securely fixed to the top of the device, although, in some embodiments, it may be detachable from the rest of the device and linked, via a power cable, to allow the photovoltaic panel to be sited remote to the rest of the device. For example, the panel may be placed outside, for example on a roof and the rest of the device may be placed inside a building for reasons of convenience or security.

Battery

The device optionally includes a rechargeable battery, which is arranged to be chargeable from the photovoltaic panel and which is also configured to power the UV irradiation unit. This allows the UV irradiation unit to operate via the battery when the photovoltaic panel may not be producing enough power and provides the power to all of the control electronics & the UV LED's.

Input Water Storage Tank

Devices of the invention comprise an input water storage tank. This is preferably located above the filtration unit so that water can flow into the filtration unit under gravity. The input water tank may be equipped with features to facilitate its filling with input water, for example it may comprise a filling spout, or a filling valve, or a filling pump. The tank volume may be 1 to 50 litres, 1 to 20 litres or 1 to 5 litres in certain embodiments.

Filtration Unit

The filtration unit is preferably located below or inside the input water storage tank. The filtration unit comprises at least one filter. According to certain embodiments, it comprises at least 2 filters, a coarse initial primary filter and a secondary finer filter. According to certain preferred embodiments, the prefilter or primary filter may be a coarse mesh filter with 50 to 500 micron apertures, for example 75 to 200 micron apertures, for example 100 to 150 micron apertures. This may be static with the water flowing through it under gravity as shown in Figure 1 or it may be connected to a plunger that is pushed through the water storage tank isolating the largest debris at one end of the tank where it can be removed as shown on Figure 2.

According to certain embodiments, the secondary filter has 5 to 50 micron apertures. In some embodiments, it is a sand filter, in other embodiments, it is a filter comprising a series of metal discs or a helical spring arrangement, such that the discs or coils of the helical spring are spaced by a controlled distance (for example 15, 20, 25, 30, 35, 40 microns) to prevent passage of larger particles. Such a filter may be easily cleaned by separating the discs and stretching out the spring so that the coils come apart, and then wiping or rinsing them.

The filtration unit serves to remove larger contaminants from the water including the larger bacteria. It may also clarify the water making it more transparent to the UV used in the UV irradiation unit, thereby ensuring better irradiation.

The filtration unit may also have a secondary role of controlling the rate at which water is fed by gravity into the UV irradiation unit so that a flow rate which would be too fast for full irradiation is not encountered. In certain embodiments, a flow restrictor may be provided to limit the rate of water flow into the UV irradiation unit as an alternative to, or in addition to, using the filtration unit for that purpose. UV Irradiation Unit UV light has been used to sterilise water in two different ways, namely direct disinfection, whereby light of approximately 254 nm wavelength, which is directly destructive of micro-organisms is used and also by using UV light in conjunction with a photocatalyst to make free-radicals in the water which are destructive of micro-organisms. The optimum wavelength for this second mechanism should be chosen to match that of the photocatalyst employed. However, the wavelength is typically longer than lOOnm and up to 450nm at which UV LEDs are especially efficient. Any suitable photocatalyst may be employed including titania and doped titania. The optimum UV wavelength for titania to produce free radicals is approximately 350 to 380 nm. Photocatalytic titania is a well understood material utilized in the production of self-cleaning glass and the like . UV Sources

The UV irradiation unit may use any appropriate UV source, but it preferably uses UV LEDs due to their stability, long-life, durability, efficiency and low cost. LEDs may be controlled to enable pulsing of the emitted light at a duty cycle of less than 100%, thereby allowing the LEDs to operate above their maximum rated power, providing enhanced treatment capabilities without affecting LED life expectancy.

Channels

Preferably, the UV irradiation unit of the invention comprises channels down which water is trickled, during which transit time it is irradiated. The channels may be manufactured from a range of materials including metals, composites and ceramics and may contain grooves, ridges or other irregularities of their surface to increase water turbulence. Preferably, the UV irradiation is provided to irradiate the water as it trickles down the channels in contact with a photocatalyst, for example titania .

Photocatalyst

The photocatalyst may be provided as a surface coating of the channels, which may, themselves, be made of any suitable material including metal, glass, plastic or ceramic. Alternatively, it may be provided as the body of the channels themselves, for example as ceramic titania, or as solid inserts to be placed into the channels. Various configurations are possible and some exemplary arrangements are shown in figures 3 and 4. Figure 5 shows different channel shapes (K) down which, or past which water flows. LEDs are placed above or into each channel so that water flowing down them is irradiated. Figure 4 shows a diagrammatic plan view whereby an array of LEDs (J) on a substrate (for example a PCB) may be arranged so that it can be placed into a set of channels comprising channel walls (K).

The channels are preferably removable and replaceable and the UV irradiation unit preferably comprises channels as described herein having a photocatalyst and a UV irradiating LED array producing UV light at a wavelength compatible with the photocatalyst.

Optionally, the UV irradiation unit includes a safety interlock whereby the LEDs are switched off if the UV irradiation unit is removed from the device, or opened, so as to prevent exposure of users to UV.

Output Water Storage Tank

According to certain preferred embodiments, the device of the invention further comprises an output water storage tank. Preferably, this is located below the UV irradiation unit so that water from the UV irradiation unit flows under gravity into it. According to certain embodiments, the volume of the output water storage tank is approximately equal to that of the input water tank (i.e. both tanks are 1 to 20, 1 to 10, 1 to 5 litres in volume). Optionally, the output water storage tank may be fitted with a tap.

Maintaining Water in Output Storage Tank

According to certain embodiments, microbial growth in the output water storage tank is suppressed by using UV irradiation of the water in the tank. The irradiation is preferably carried out by UV LEDs of the nature described in respect of the UV irradiation unit of the invention. It will, however, be appreciated that suppressing microbial growth in already portable water is less demanding than initial decontamination. Therefore, the use of a photocatalyst system as described above is probably not required and LEDs producing light of approximately 254 nm (say lOOnm to 300 nm or 225 to 275 nm) wavelength are likely to be sufficient when used to provide direct disinfection without the use of a photocatalyst, for example for 20 minutes or more, once, twice or more per day.

Irradiation Controls and Indicators

The device of the invention carries the risk that if UV irradiation is insufficient the water may not be fully decontaminated. The device of the invention is preferably provided with a battery and a control means, which detects when there is sufficient charge in the battery for a full and effective UV irradiation. In some embodiments, the detection of sufficient charge in the battery for a full and effective UV irradiation triggers an indicator to the user, for example an indicator light on a panel. The user is instructed to only fill the input water tank and allow the water decontamination process to start when that indicator is given. In other embodiments, there is alternatively or additionally provided a valve upstream of the UV irradiation unit which only opens when the device detects sufficient charge in the battery for a full and effective UV irradiation and water disinfection.

Drawers

According to certain preferred embodiments, the filtration unit and the UV irradiation unit are provided in drawers within the device which are arranged to slide out or be removed so that the units may be serviced, cleaned or replaced. According to such embodiments, the device of the invention may comprise a stack of drawers wherein the filtration unit is located in a drawer above the drawer containing the UV irradiation unit. One or more of the drawers may be provided with interlocking switches so that they need to be closed before the UV irradiation is switched on and/or so that, if they are opened, the user is given an indication that the water UV Purifier is switched off.

Charging Station

The device may, optionally, contain a power output port such as a USB port suitable for powering and/or charging low power electric articles such as mobile phones, tablets or low power domestic lighting. Such an arrangement is especially useful where the user lacks an alternative power source. Optionally, the device of the invention contains a battery and an electronic control system configured so that this power source is only available when there is sufficient power available in the battery to disinfect a batch of water so that water purification is always prioritized and the powering of other electronic articles only takes place using "spare" power, for example, power where the battery is sufficiently charged but the photovoltaic panel is generating additional power.

Methods of the Invention

The invention provides a method of producing potable water comprising use of a portable water treatment device of the invention.

Examples

The invention is further described by reference to the following non-limiting examples.

Example 1

Figure 1 illustrates a portable water treatment device comprising a series of removable drawers, drawer 1, drawer 2 and drawer 3. The outer casing includes a solar panel (Item A), typically 300 mm long by 200 mm wide (although any size solar panel may be used) that provides the power supply for the whole device. A hinged cover that can protect the solar panel during transport may be included (not shown). The casing may be made of metal or rigid plastic.

The top drawer consists of an input water tank for storage of raw, untreated water. It includes an inlet (Item B) that can accept batches of water or water can be dribbled continuously into it. The inlet feeds a storage tank, typically of up to 5 litres volume (although any dimensions may be used).

The raw untreated water flows by gravity through a pre-filter (Item E) situated at one end of the storage tank. Typically, this pre-filter is a 200 mm by 100 mm frame containing a mesh filter of 125 micron aperture (although other filter sizes and aperture dimensions are suitable). The filter frame slides into a removable chute (Item F) for easy access and cleaning. The aperture size chosen needs to permit water flow through the pre-filter using gravity only.

The central drawer contains a fine filter (Item D) that removes particles above 25 microns. It also serves to slow down the flow rate of the water to a rate that allows for optimum subsequent UV treatment. The filter system shown comprises a series of metal discs spaced by a controlled distance (typically 25 microns) preventing any particle larger than this from passing. There is easy access to this filter system by removing the central drawer, ensuring that the filters can be quickly and simply cleaned.

After passing through the filter the water is directed to the treatment channels (Item C). These comprise a plurality of ceramic, metal or other rigid material channels containing an activation coating (such as titania) or other component, reactive material or coating. The activation components are stimulated by the spectrum of UV light generated from the LEDs (Item J) to produce direct destruction & also produce free radicals that disinfect the water flowing past from both bacteria and viruses and other pollutants. The shape or profile of the channels can be selected to provide the maximum turbulent flow down each channel. Typically, the flow rate through the channels is approximately 1 litre / hour, although this is dependent on the size of the water treatment unit.

The bottom drawer consists of an output water storage tank (Item H) where the water is directed after UV treatment and may be tapped off for consumption.

At the back of this drawer is a sealed unit (Item G) containing the electronics and control components of the water treatment system.

Typically, the configuration of the drawers can be changed by altering the positions of the electronics and battery.

Example 2

Figure 2 illustrates a variation to Example 1 to include the addition of a plunger arrangement (Items L and M), comprising a mesh plunger (Item M) on a handle (Item L). The mesh plunger preferably contains a mesh through which water is able to freely flow (i.e. from inlet B to filter D), but which holds back larger contaminants such as stones, twigs, leaves etc. When pushed inwards the handle (Item L) moves the plunger to the left of the drawing carrying trapped contaminants with it. Those contaminants may be removed from the left hand end of the input tank, for example via optional port N, which is normally closed, but which may be opened for the expulsion of contaminants, preferably once most of the water has left the input tank and been processed, but before the input tank has been refilled. The filter mesh may be similar in construction to that used in a cafetiere plunger and may have a cut-off size of 1mm, 0.5mm, 0.25mm, 0.2mm, 0.1mm, or the like.

Example 3

Figure 3 illustrates a variation to Example 1, which is also applicable as a variation to the arrangement shown in Example 2, to include an additional array of LEDs positioned at the top of the storage tank (Item H). This would ensure that water stored over a period of time continues to be treated up until the time it is removed for consumption. The wavelengths of the LEDs in the treatment channels will be selected to result in both direct micro-organism destruct and optimum free radical production for indirect micro-organism destruct, whereas the LEDs in the storage area may be selected to have wavelengths that provides direct bacterial destruction, thereby inhibiting re-growth.

Claims

1. A portable water treatment device comprising a photovoltaic panel, an input water storage tank, a filtration unit, a UV irradiation unit and, optionally, an output water storage tank, wherein the UV irradiation unit is powered by the photovoltaic panel and battery and wherein water is gravity fed from the input water storage tank to the filtration unit and from the filtration unit to a UV irradiation unit and, optionally, from the UV irradiation unit to the output water storage tank.

2. A portable water treatment device according to claim 1, wherein said filtration unit comprises a helical spring filter having an exclusion size of less than 40 microns, for example less than 30 microns.

3. A portable water treatment device according to claim 1 or claim 2, wherein said array of UV irradiation unit comprises a number of channels down which water flows whilst being UV-irradiated, wherein the water in said channels is in contact with catalytic compounds which generate reactive free radicals in the presence of UV irradiation.

4. A portable water treatment device according to any of claims 1 to 3, comprising an output water storage tank having an array of UV-disinfection LEDs included to suppress microbial growth in the output water storage tank.

5. A portable water treatment device according to any of claims 1 to 4, wherein the filtration unit and the UV irradiation unit and, optionally, the input water storage tank and, optionally, the output water storage tank are provided in drawers to allow easy removal from the device for cleaning, servicing or replacement.

6. A portable water treatment device according to any of claims 1 to 5, wherein the photovoltaic panel is provided on the top of the device, optionally under a removable protective cover.

7. A portable water treatment device according to any of claims 1 to 5, further comprising a rechargeable battery, which is arranged to be charged from the photovoltaic panel when sufficient light is available and to power the UV irradiation unit when the unit is operational.

8. A portable water treatment device according to claim 7, further comprising a power output, for example a USB socket, suitable for powering lower power ancillary electrical equipment, such as domestic lighting or a mobile phone.

9. A portable water treatment device according to claim 7 or claim 8, further comprising a power input port for charging the rechargeable battery.

10. A portable water treatment device according to any of claims 1 to 9, further comprising a visual indicator that indicates when there is sufficient power available to operate the UV irradiation unit.

11. A portable water treatment device according to any of claims 1 to 10, further comprising a valve in line between the input water storage tank and the filtration unit and between the filtration unit and the UV irradiation unit, said valve being configured so as to open, thereby permitting water to flow under gravity into the UV irradiation unit only when there is sufficient power available to operate the UV irradiation unit.

12. A method of producing potable water comprising use of a portable water treatment device according to any of claims 1 to 11.