FORM - 2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See Section 10 and Rule 13)
A WATER PURIFICATION DEVICE
HINDUSTAN UNILEVER LIMITED, a company incorporated under
the Indian Companies Act, 1913 and having its registered office
at 165/166, Backbay Reclamation, Mumbai -400 020, Maharashtra, India
The following specification particularly describes the invention and the manner in which it is to be performed.

Technical field:
The present invention relates to a water purification device and a process for water purification and in particular relates to a water purification device that may be used as a gravity fed system or adapted to be connected to the main water supply.
The invention has been developed primarily for use in drinking water application and will be described hereinafter with reference to this application. However, it will be appreciated that the invention is not limited to this particular field of use.
Background and Prior Art:
Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of the common general knowledge in the field.
A large population of people in the world live in countries where there is a severe shortage of hygienic potable water. People have to depend directly on ground water sources like wells, ponds and rivers. Often these water sources are contaminated by sewage, industrial effluents and agricultural by-products like pesticide residues. For water to be microbially safe, WHO recommends 6 log removal of bacteria, 4 log removal of virus and 3 log removal of cysts. Whilst bacteria and virus removal to the required extent is possible by using chemical disinfection {e.g. by contacting with halogen) or radiation-based disinfection (e.g. by exposure to

ultraviolet radiation) , these disinfection methods do not achieve 3 log removal of cysts.
Gravity fed devices are available where it is possible to achieve 6 log removal of bacteria, 4 log removal of virus and 3 log removal of cysts using filtration in combination with biocide action. Gravity fed devices function in the absence of pressurised and running water.
WO 2 005095284 (Unilever, 2005), discloses a gravity fed water purification system comprising a filtration unit adapted to separate particulate and soluble material from the input water and this is in the form of a carbon block and usually has an additional non-woven fabric filter, a chemical dispensing unit such that flow rate of water exiting the filtration unit is controlled by a flow control means before the water encounters a biocide dispensed by the chemical dispensing unit, the water thereafter being retained in a retention chamber for a predetermined period of time before exiting the water purification system through a scavenger means adapted to separate the dispensed biocide and its by-products from the exit water. This device is quite complex having a number of replaceable parts.
WO070 00238 (Unilever, 2 0 07), discloses a water purification device comprising an upper and a lower chamber comprising an outlet means for collecting purified water and a filter medium for removing suspended particulates and dissolved organics. The biocide system integral with it is a device which may dispense a unit dose of biocide and water may be fed into a chamber where the biocide could be dispensed. This designed only for a

solid biocide and can not be adopted for a liquid biocide. The disadvantage with solid biocides is that they degrade on exposure to air.
WO08083896 (Unilever, 2008) discloses a gravity fed water purification device which may incorporate controlled dosing of a liquid biocide. The device uses a dosing passage comprising a venturi where a top chamber is in fluid communication with a bottom chamber, and water may flow from the top chamber to the bottom chamber. The water in this system has to flow at a high flow rate and the dosing rate depends on the rate of flow of water. Dosing of the biocide is caused by a negative (suction) pressure at the discharge end of the liquid dosing tube, which is caused by water flowing through a venturi, which is connected to the discharge end of the tube in an air-tight manner. The air pressure in the compartment containing the liquid biocide, in this case, is at atmospheric pressure, which is "sucked" out of the biocide containing compartment by the negative pressure at its discharge end. In practice, the venturi based dosing system is highly sensitive to the physical dimensions, and control of dosage is more difficult. The system requires a lot of material for construction thus making it expensive.
EP2184263 (Unilever) discloses a gravity fed water purification device wherein reduction in the concentration of biocide or byproducts thereof in the downstream water and relatively longer lifetime of the scavenger media is achieved by the combination of features of positioning of outlet and the height of the wall separating the reservoir and the scavenger unit. The device comprises of a biocide unit having the biocide in fluid communication with the

reservoir, the reservoir is separated from the scavenger unit having the scavenger media by a wall, and the scavenger unit is in fluid communication with the dispenser chamber by an outlet present on the partition which separates the scavenger unit from the dispenser chamber. In achieving this it is essential that at least 10 percent by weight of said media (M) is below the lowest level of the outlet (0), and the wall (W) extends above the highest level of the media and above the lowest level of the outlet. This document does not disclose or discuss how a biocide is to be dosed, and does not disclose a liquid biocide dosing system.
The present inventors have designed a liquid biocide dosing system as well as an arrangement for delaying the contact of water into which a biocide has been dispensed with a filter cum biocide scavenging means and adapting this to gravity fed water purification device.
WO04 074182A (Unilever) discloses a flow control means to control the leach of a solid biocide by controlling the flow of water into the solid biocide dispensing unit. This discloses a flow control means that provides a constant flow through the chemical dispensing unit so that uniform amounts of the solid biocide is leached out without being influenced by the head of input water in the top chamber. The dosing of the biocide into the water is by the gradual erosion of the solid biocide tablet by contact with water, whose flow is controlled by means of the flow regulator which in turn controls the erosion of the biocide tablet. It does not disclose how to control the dosing of a liquid biocide.

US4093551 (IFUO AB) , discloses a device for purifying water in small sewer systems includes means for automatic addition of a chemically active liquid to the water passing through the device. The invention eliminates the need of any movable parts by using two siphon tubes controlling the liquid supply. One of the siphon tubes is traversed by the sewer water and the corresponding flow generates a suction which is relied upon to transfer the chemically active liquid through the second siphon tube. This discloses a liquid disinfectant dosing system, wherein the liquid is dosed by a "suction" or negative pressure created within a siphon, as water flows through it. A second siphon, one end of which is dipped into a liquid biocide pool, has its discharge end placed within the first siphon. Hence liquid biocide is "sucked" into the siphons as water flows through the first siphon. Hence the two siphons used form the liquid dosing system.
The present inventors have designed two siphons to provide a means to delay the introduction of the biocide added water into the biocide scavenging section and these siphons do not control the dosage of the liquid biocide. These two siphons are not physically connected but simply provide a residence time, for the biocide to act on the microbes, while the liquid disinfectant dosage is caused by a positive pressure created by an air pocket.
The present inventors thus have designed a novel liquid dosing device that is controlled by a positive pressure created by hydrostatic head of water and providing two siphons arranged in a definite fashion it has been possible to provide an additional residence time to

enhance the interaction of the biocide with water to be purified.
Our co-pending Indian patent application 2126/MUM/2009 describes a water purification device wherein the required level of killing of microorganism is achieved by a liquid biocide dosing system. One of the essential features of this device is a fill cup, filling up of which allows the dosing system to dose the desired amount of biocide in the water purification chamber. It is not possible for the device to work properly without the fill cup. One of the disadvantages of having fill cup is that, the miniaturization of the device is difficult.
The present inventors have been able to design a novel biocide dosing system by using a pressure transmitting tube along with a siphon discharge mechanism. The relative position of the siphon discharge mechanism with respect to the pressure transmitting tube allows the purification device to work properly. Furthermore, the geometry of the tube along with its submerged length controls the biocide dosing. The present device is designed without the fill cup thus making it easier for miniaturization.
In the view of foregoing it is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art.
The object of the present invention is to provide a water purification device which is less complex and thus making it economical in its construction.

Another object of the present invention is to provide a water purification device that can be adapted to use both solid and liquid biocides.
Another object of the present invention is to provide a water purification device that can be used as gravity fed device as well as adapted to be used in inline systems.
It is yet another object of the present invention to provide a dwell time means inside a water purification device to ensue that even the first drop of water that is coming out from the water purification device is completely free of any harmful microorganisms.
Summary of the invention:
According to one aspect of the present invention there is provided a water purification device comprising a water purification chamber comprising:
a biocide dispensing box that is in fluid communication with a biocide storage compartment and a biocide dispensing port wherein the biocide dispensing box is connected to a pressure transmitting tube and the free end of said tube is extending downwards into the water purification chamber; said water purification chamber is in fluid communication with a filter chamber through an inverted 'U' shaped inflow siphon discharge mechanism with legs of unequal length; wherein the opening of the small leg of the inflow siphon discharge mechanism is above the bottom of the water purification chamber; the long leg extending into the filter chamber and the top of the inverted 'U' shaped inflow siphon discharge mechanism is above the free end of the tube.

According to another preferred aspect of the present invention there is provided a water purification device according to the invention wherein the inflow siphon discharge mechanism is in fluid communication with the filter chamber through a residence time chamber and in turn with an outflow siphon discharge mechanism wherein the outflow siphon discharge mechanism is encased in the residence time chamber.
The term "comprising" is meant not to be limiting to any subsequently stated elements but rather to encompass non-specified elements of major or minor functional importance. In other words the listed steps, elements or options need not be exhaustive. Whenever the words "including" or "having" are used, these terms are meant to be equivalent to "comprising" as defined above.
Brief description of the figures:
Figure 1 is an embodiment of the water purification device according to the invention.
Figure 2 is a further preferred embodiment of the water purification device according to the invention with a dwell time providing means.
Figure 3 is another embodiment of the water purification
device according to the invention wherein the biocide
dispensing unit is encased inside the water purification
chamber.

Detailed Description of the invention:
Thus the present invention provides for a water purification device comprising a water purification chamber comprising:
a biocide dispensing box that is in fluid communication with a biocide storage compartment and a biocide dispensing port wherein the biocide dispensing box is connected to a pressure transmitting tube and the free end of said tube is extending downwards into the water purification chamber; said water purification chamber is in fluid communication with a filter chamber through an inverted 'U' shaped inflow siphon discharge mechanism with legs of unequal length; wherein the opening of the small leg of the inflow siphon discharge mechanism is above the bottom of the water purification chamber; the long leg extending into the filter chamber and the top of the inverted 'U' shaped inflow siphon discharge mechanism is above the free end of the tube.
The tube may be of different' shapes and sizes and may have different cross-sections. The tube cross-section may have rectangular, circular, polygonal, elliptical or different other geometrical shapes. The tube may be tapered along any direction completely or partially.
The device of the present invention can be manufactured in different capacity and sizes e.g. l, 2, 3, 5 liters or larger.
The biocide may be provided as a solid or in a liquid form. When it is in the solid form the device is designed to dissolve right amount of the solid to provide the

correct quantity of liquid biocide in the biocide dispensing box. The biocide is preferably selected from any halogen releasing compounds and preferably chlorine releasing biocide including chlorinated trisodium phosphate, Sodium or Potassium or calcium hypochlorite, the various N-chlorinated compounds known in the art to release active chlorine such as sodium or potassium dichloroisocyanurate, trichlorocyanuric acid, monochloramine, dichloramine, [(monotrichloro)-tetra(monopotassium dichloro)] pentaisocyanurate, 1,3-dichloro-5,5-dimethylidanotone, Chloramine T, p-toluene-sulfodichloroamide, thrichloromelamine, N-chloramine, N-chlorosuccinimide, N,N'- dichloroazodicarbonamide, N-chloroacetyl-urea, N,N-dichloroazo-dicarbonamide, N-chloroacetyl-urea,N,N-dichlorbiurile,chlorinated dicyandiamide, hydrogen peroxide or its derivatives, peroxy acetic acid.
Suitable liquid biocides that can be used in the device of the invention include aqueous solutions of sodium hypochlorite, sodium dichloro-isocyanuric acid, iodine, quaternary ammonium compounds or gluteraldehyde. Most preferred liquid biocide is an aqueous solution of sodium hypochlorite. When sodium hypochlorite is the liquid biocide . used, it is added in the biocide storage compartment at a concentration in the range of 0.01 to 50 weight %, more preferably in the range of 1 to 2 0 weight % in water. With the use of the device of the invention, it is possible to get the concentration of the biocide in the water purification chamber in the range of 0.5 to 100 ppm by weight, more preferably in the range of 1 to 50 ppm by weight in water.

According to one of the preferred aspect of the present invention the filter can be combined together with a biocide scavenger. The filter-cum-biocide scavenger preferably comprises an activated carbon block filter media. The activated carbon block filter media comprises powder activated carbon (PAC) and a binder which are well mixed and made into a block by pressure and heat treatment. The PAC is preferably selected from bituminous coal, coconut shell/wood charcoal, petroleum tar. Preferably, the PAC used has a size uniformity coefficient of less than 2, or more preferably less than 1.5, a carbon tetrachloride number exceeding 50%, more preferably exceeding 60%.
The filter-cum-biocide scavenger is further provided with a particulate filter that is a single or multi-layered non-woven fibrous-fabric filter wherein the outermost layer is pleated. The filter could alternately comprise of a combination of a pleated and. spirally wound fabric filter.

Particularly preferred carbon block filter media are those disclosed in GB2390987, more preferably that disclosed in our co-pending application 320/MUM/2004. The co-pending application describes a carbon block filter media for use in gravity fed filters comprising powder activated carbon (PAC) having a particle size such that 95 wt% of the particles pass through 50 mesh and not more than 12% passes through 200 mesh and a binder material having a Melt Flow Rate (MFR) of less than 5. Further preferred carbon block filter media has 55 to 80 wt % of the PAC particles in the particle size range of 100 to 200 mesh in the lower 50 volume% of the carbon block filter media.
The discharge mechanism may be a tap or a bellow actuated hand pump discussed later.
The invention will now be illustrated with help a specific non-limiting example of a water purification device according to the Invention In Figures 1-3.
Detailed Description of the figures:
Figure 1 is an embodiment of the water purification device according to the invention. The device has a water purification chamber (1) which is provided with a cover (6), opening which will expose the inlet port which will allow the user to pour water into the water purification chamber. The water purification chamber comprises of a biocide dispensing box (3) which is in fluid communication with a biocide storage compartment (5) and a biocide dispensing port (4). The biocide dispensing box is connected to a pressure transmitting tube (2) which is

extended downwards into the water purification chamber.
The tube is in fluid communication with the biocide
dispensing box. The water purification chamber is in fluid
communication with a filter chamber (10) having filter-
cum-biocide scavenger (7} through an inverted 'U' shaped
inflow siphon discharge mechanism (13). The opening of the
small leg of the inflow siphon discharge mechanism is
above the bottom of the water purification chamber. The
filter is positioned on the partition wall that separates
the water purification chamber and the pure water
discharge chamber. The inflow siphon discharge mechanism
is provided to operatively connect the water purification
chamber and the filter chamber such that the water from
the water purification chamber flows into the filter
chamber only through the inflow siphon discharge
mechanism. The air vent (12} provided at the filter
chamber allows the inflow siphon discharge mechanism to
operate by allowing an upwardly directed passage for air
to exit the filter chamber. The exit of water from the
filter chamber is through the filter-cum-biocide
scavenger, while the entry of water into the filter
chamber occurs through the inflow siphon discharge
mechanism. The top of the inverted 'U' shaped inflow
siphon discharge mechanism is above the free end of the
tube to ensure that no water should pass through siphon
discharge mechanism without the addition of required
amount of biocide. The water tight cover (11} provided at
the filter chamber ensures that water enters the filter
Chamber only through the inflow siphon discharge
mechanism. As the water purification chamber (1) fills-up
to the top of the inflow siphon discharge mechanism, the
inflow siphon discharge mechanism begins to discharge
water into the filter chamber. As the water with biocide

fills the filter chamber, water flows through the filter-cum-biocide scavenger which removes colloidal impurities from the water as well as the residual biocide, and discharges water into the pure water discharge chamber (8) , pure water devoid of biocide is available from pure water discharge chamber, through a dispensing means such as a tap (9).
When water flows into the water purification chamber through the inlet port of the water purification chamber and fills up the same, the level of water in water purification chamber creates an air pressure in the tube and enables the discharge of the biocide from the biocide dispensing box into the water purification chamber through the biocide dispensing port.
Figure 2 is another embodiment of the water purification device according to the invention with a dwell time providing means. Figure 2 is showing a water purification chamber (1), provided at its bottom inner section a filter chamber (10) that encloses the filter-cum-biocide scavenger (7) . The filter chamber is provided with a water-tight cover (11) and an air vent (12). The biocide dispensing box (3), biocide dispensing port (4), biocide storage compartment (5), and tube (2) are in their respective position as described in Figure 1. In Figure 2 there is provided a residence time chamber (14) with an outflow siphon discharge mechanism (15). The outflow siphon discharge mechanism is encased in the residence time chamber. The residence time chamber is having an air vent (16) . The air vent provided at the residence time chamber allows the outflow siphon discharge mechanism to operate by allowing an upwardly directed passage for air

to exit the residence time chamber. The inflow siphon discharge mechanism (13) is operatively connected with the residence time chamber. The inflow siphon discharge mechanism is in fluid communication with the filter chamber through the residence time chamber and in turn with the outflow siphon discharge mechanism. The device of Figure 2 is designed in such a manner by way of dual residence time, it ensures that even for the first drop of water that is coming out from the pure water discharge chamber is free from all harmful microorganisms.
In use, filling of water purification chamber creates an air pressure in the tube which is then transmitted in the biocide dispensing box causing dosing of biocide through the biocide dispensing port. After the level of water in the water purification chamber reaches the highest level of inflow siphon discharge mechanism, the water mixed with biocide then enters into the residence time chamber through the inflow siphon discharge mechanism. After entering into the residence time chamber water starts to fills up the residence time chamber. When the water level in the residence time chamber reaches the highest level of outflow siphon discharge mechanism, the water mixed with biocide then enters into the filter chamber through the outflow siphon discharge mechanism, thereby providing dual residence time. After removing the residual biocide and filtering it in the filter chamber, the pure water can be discharged from the pure water discharge chamber by opening the tap.
Figure 3 is another embodiment of the water purification device according to the present invention. All the features and characteristics of Figure 3 are same as

described in Figure 1. The only difference between the embodiment of Figure 1 and Figure 3 is, in Figure 3 the biocide storage compartment (5), the biocide dispensing box (3) , the biocide dispensing port (4) all are encased inside the water purification chamber.
Examples:
Effect of the tube geometry and submerged tube height on liquid biocide dosing:
In this example submerged tube height means the length of the tube that is immersed in the water of the water purification chamber i.e. the distance between the highest level of water in the water purification chamber and the lowest point of the pressure transmitting tube. In Table 1, Ll and L2 means two different sides of the rectangle and the square.
Table 1, below depicts the effect of tube geometry and submersed tube height on biocide dosing.
Table 1

Shape of Ll, mm L2, mm Submerged Volume
Tube- tube Dosed, ml
cross height,
Section mm
Rectangle 28 14 4 4
Square 13 13 5 3.5
Square 10 10 6 3.5
From the data in Table 1 it is evident that with changing the tube geometry and the submerged tube height, the

biocide dosage changes. So it is possible to control the volume of biocide dosed precisely depending on the capacity of the water purification device.
Effect of the residence time chamber to increase the contact time of the biocide with the unpurified (input) water:
Using devices constructed as shown in Figures 1 to 3, the time taken for the water containing the biocide dispensed from the biocide dispensing box before passing through the filter which is referred to as the contact time. This contact time will be the duration when the biocide will be acting on the microbes in the input water.
Table 2 summarizes the contact time with and without the residence time chamber.
Table 2

Different embodiments of Time required for
the purification device the input water to
according to the touch the filter
invention chamber
Figure 1 Less than 1 minute
Figure 2 5 minutes or more
Figure 3 Less than 1 minute
From the data in Table 2, it is evident that by providing the residence time chamber as shown in the preferred embodiment of Figure 2 it is possible to increase the contact time. It has been found that this feature ensures that even the first drop that is coming out from the water

purification device of the invention is free from any harmful microorganism.

Claims
1. A water purification device comprising a water
purification chamber (1} comprising:
a biocide dispensing box (3) that is in fluid communication with a biocide storage compartment (5) and a biocide dispensing port (4} wherein the biocide dispensing box (3) is connected to a pressure transmitting tube (2) and the free end of said tube is extending downwards into the water purification chamber (1); said water purification chamber (1) is in fluid communication with a filter chamber (10) through an inverted 'U' shaped inflow siphon discharge mechanism (13) with legs of unequal length; wherein the opening of the small leg of the inflow siphon discharge mechanism is above the bottom of the water purification chamber (1) ; the long leg extending into the filter chamber (10) and the top of the inverted 'U' shaped inflow siphon discharge mechanism (13) is above the free end of the tube.
2. A water purification device as claimed in claim 1 wherein the inflow siphon discharge mechanism is in fluid communication with the filter chamber through a residence time chamber (14) and in turn with an outflow siphon discharge mechanism (15) wherein the outflow siphon discharge mechanism is encased in the residence time chamber.
3. A water purification device as claimed in claim 2 wherein there is provided an air vent (16} at the residence time chamber.

4. A water purification device as claimed in any one of the preceding claims wherein the water purification chamber is provided with an inlet port adopted to receive input water in the water purification chamber.
5. A water purification device as claimed in any one of the preceding claims wherein the biocide dispensed from the biocide dispensing box is in the liquid form.
6. A water purification device as claimed in any one of the preceding claims wherein the filter (7) is encased in a filter chamber comprising an air vent (12) .
7. A water purification device as claimed in any one of the preceding claims wherein the filter comprises an activated carbon block filter media.
8. A water purification device as claimed in any one of the preceding claims wherein the filter comprises a single or multiple layers of pleated or non-pleated fabric filter, where the fabric comprises of nonwoven polymeric fibers.
9. A water purification device as claimed in any one of the preceding claims wherein the filter is a composite filter having layers of non-woven fabric and bound activated carbon element