WO2013051013A2

WO2013051013A2 - Water purification device

Info

Publication number: WO2013051013A2
Application number: PCT/IN2012/000400
Authority: WO
Inventors: Rajshree PATIL; Dilshad Ahmad; Shankar Kausley; Chetan MALHOTRA
Original assignee: Tata Consultancy Services Limited
Priority date: 2011-07-28
Filing date: 2012-06-07
Publication date: 2013-04-11
Also published as: WO2013051013A3

Abstract

The subject matter described herein relates to a water purification device (104) for purification of water. The water purification device (104) includes a filtration unit (116), a primary disinfectant unit (118), and a secondary disinfectant unit (120). The filtration unit (116) includes a plurality of permeable membranes (302) and is configured to filter particulate matter present in the water to provide filtered water. The filtered water is treated by the primary disinfectant unit (118) having at least one metal disinfectant treated porous media (402) to inactivate a first portion of microbial contaminants present in the filtered water. Further, a second portion of the microbial contaminants present in the filtered water is inactivated by the secondary disinfectant unit (120) having at least one oxidizing agent releasing component (502).

Description

TECHNICAL FIELD

WATER PURIFICATION DEVICE

[0001] The present subject matter, in general, relates to a device for water purification and, in particular, to a device for removal of microbiological and particulate contaminants in water.

BACKGROUND

[0002] Generally, water available from natural sources, such as groundwater sources, or surface water sources, contains various contaminants, such as microbes like pathogenic bacteria, protozoan cysts; particulate matter; soluble salts; and heavy metals like barium, cadmium, chromium, lead, etc. Presence of excess contaminants in water makes the water unsuitable for human consumption as consumption of contaminated water may cause various waterborne diseases. Thus, various purification techniques have been developed conventionally to remove the contaminants.

[0003] To curb the spread of such waterborne diseases, contaminated water is treated at source, such as at municipal water treatment plants. Water from the source is distributed to various users for consumption. However, even after treatment at the source, contamination may occur during distribution. Therefore, to curb spread of waterborne diseases, various water purification devices are usually implemented at the point-of-use (POU) from where water can be directly consumed. The water purification devices based on technologies, such as reverse osmosis, membrane filtration, and ultra violet (UV) radiation usually need electricity and may also require elevated water pressure for operation, thus increasing the cost of the water purification devices and limiting the use of water purification devices.

[0004] In order to facilitate use of water purification devices, various low cost water purification devices, such as ceramic filters, activated carbon filters, and filters using chemical disinfection have been developed. However, these low cost water purification devices often use a single or sometimes even no disinfectant and are thus not capable of providing adequate purification. Additionally, the treatment of contaminated water may involve inactivating the microbiological contaminants by using high concentrations of disinfectants, which imparts pungency and objectionable taste to the treated water. Thus, additional steps are introduced during the purification process to remove the excess disinfectants before delivering it for consumption which adds to the size and cost of the purifier. Further, such water purification devices are often bulky and suffer from limitations, such as clogging and poor inactivation of microorganisms like bacteria, viruses, protozoan cysts, etc. SUMMARY

[0005] This summary is provided to introduce concepts related to water purification.

These concepts are further described below in the detailed description. This summary is neither intended to identify essential features of the claimed subject matter nor is it intended for use in determining or limiting the scope of the claimed subject matter.

[0006] In one embodiment, a water purification device for purification of water is described. The water purification device includes a filtration unit, a primary disinfectant unit, and a . secondary disinfectant unit. The filtration unit includes a plurality of permeable membranes and is configured to filter particulate matter present in the water to provide filtered water. The primary disinfectant unit includes a metal disinfectant treated porous media to inactivate a first portion of microbial contaminants present in the filtered water. Further, a second portion of the microbial contaminants present in the filtered water is inactivated by the secondary disinfectant unit having at least one oxidizing agent releasing component.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The detailed description is provided with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to reference like features and components.

[0008] Fig. 1 illustrates an apparatus for water purification, according to an embodiment of the present subject matter.

[0009] Fig. 2(a) illustrates a water purification device of the apparatus for water purification, according to one embodiment of the present subject matter.

[0010] Fig. 2(b) illustrates a water purification device of the apparatus for water purification, according to another embodiment of the present subject matter. [0011] Fig 3 illustrates a filtration unit of the water purification device, according to an embodiment of the present subject matter.

[0012] Fig. 4 illustrates a primary disinfectant unit of the water purification device, according to an embodiment of the present subject matter. [0013] Fig. 5 illustrates a secondary disinfectant unit of the water purification device, according to an embodiment of the present subject matter.

[0014] Fig. 6 illustrates a graph depicting performance of the water purification, device along with concentration of residual disinfectants in purified water, according to an embodiment of the present subject matter. DETAILED DESCRIPTION

[0015] The present subject matter relates to purification of water. The purification of water involves removing microbiological and physical particulate contaminants to make the water usable for various purposes, including human consumption.

[0016] Generally, consumption of contaminated water leads to spread of waterborne diseases. The spread of these diseases is likely to occur where water, used for consumption, gets contaminated by microorganisms, such as bacteria, viruses, and protozoan cysts. To curb the spread of such diseases, contaminated water is treated at source, such as at municipal water treatment plants. Water from the source is distributed to various users for consumption. However, even after treatment at the source, contamination may occur during distribution. Other ^' methods of water purification involve treating water by certain disinfectants, filtering, or combination thereof at point-of-use (POU) from where water can be directly consumed.

[0017] Various methods of water purification used at the POU typically involve using water purification devices based on low cost technologies, such as ceramic filters, carbonaceous filtering media coated with metal disinfectants, and halogen based disinfectants. Using such low cost water purification devices at the POU helps in reducing diarrhea and other waterborne diseases caused due to pathogenic bacteria, viruses, and protozoan cysts present in contaminated water. However, these low cost water purification devices suffer from various limitations. For example, water filtered through ceramic filters suffers from inadequate removal of microbiological contaminants. Further, high concentration of halogen based disinfectants may impart unacceptable taste and odor to water. In order to remove excess disinfectants before delivering the water for consumption, additional steps are introduced during water purification process. Such additional steps add to the cost and increase the size of the water purification devices. Additionally, the carbonaceous filtering media coated with metal disinfectants requires long contact times for complete inactivation of microorganisms up to such limits as considered safe for making water drinkable.

[0018] A device and a method for purification of water are described herein. The device employs a trace amount of oxidizing agent and a metal disinfectant to treat water, wherein the synergistic action of these two disinfectants, results in enhanced inactivation in lesser contact time without altering the aesthetic aspects of the water. According to an embodiment of the present subject matter, an apparatus for water purification includes a water purification device with an inlet and an outlet. The inlet is used for receiving water, which may or may not have undergone prior treatment and is hereinafter referred to as untreated water, from one or more water sources. In one implementation, the inlet may be connected to a reservoir of water. The untreated water is subsequently received by the water purification device for treatment. Purified water exits from the water purification device through the outlet. In one embodiment, the water purification device has three stages of water purification.

[0019] A first stage of purification includes filtering untreated water with a plurality of permeable membranes for removing particulate matter, for example, suspended particles and mud from the untreated water. In one implementation, the permeable membranes are cascaded in order of decreasing porosity so as to filter various particulate matters at different levels according to their size. Untreated water provided to the purification system is thus filtered at the first stage to receive filtered water.

[0020] The filtered water is then disinfected at a second stage of purification. In one implementation, the second stage of purification includes treating the filtered water with a metal disinfectant treated porous media. In one implementation, the metal disinfectant treated porous media may be formed by treating a porous media with different disinfectants, such as silver, copper, iron, zinc, zinc oxide, titania, aluminum, aluminum oxide or gold in the form of nano- particles. The porous media may be, for example, porous layers made of rice husk ash (RHA), clay or any other porous media known in the art. As the filtered water passes through the metal disinfectant treated porous media, the microbial contaminants present in the filtered water are inactivated by the disinfectants. The filtered water is thus disinfected to receive disinfected water.

[0021] The disinfected water is then purified at a third stage of purification. Here, any micro-organisms resistant to the disinfection action of the second stage of the purification system get inactivated due to presence of a different kind of disinfectant. In one implementation, the third stage of purification includes purifying the disinfected water using an oxidizing agent releasing component having an oxidizing agent, such as a halogen releasing compound. In one embodiment, the oxidizing agent releasing component is provided in the form of a tablet. When the disinfected water received at the second stage comes in contact with the tablet, a predetermined concentration of the oxidizing agent is released into the flowing water by the tablet. The microorganisms that were not inactivated in the second stage are thus inactivated at the third stage to receive purified water. In one embodiment, chlorine is used as an oxidizing agent and the concentration of chlorine is kept in the range of about 0.1 parts per million (ppm) to 0.5 ppm, which is acceptable for human consumption. Maintaining a low concentration of the oxidizing agent results in elimination of the additional step of removing excess oxidizing agent from the purified water, thus decreasing the size of the water purification device and in turn, the apparatus.

[0022] The water purification device described herein inactivates microorganisms present in the untreated water, requires nominal maintenance, has high efficiency, and low operating costs. The water purification device purifies the untreated water by inactivating microorganisms in the untreated water due to a synergistic action of two different disinfectants. Further, residual concentrations of the two different disinfectants, present in the purified water, also inhibit growth of microorganisms due to any post purification contamination of water. Additionally, using the metal disinfection treated porous media and the tablet decreases the contact time required to disinfect the untreated water, thus purifying the untreated water in a short period of time. Further, the water purification device is compact, efficient and requires no external source of energy for operation. The water purification device is suitable for use in a domestic setting or at a household level. These and other aspects are discussed in detail in conjunction with the following figures. [0023] In one embodiment, the stages of purification may be implemented in any order for purification of untreated water. For example, the second stage and third stage of purification may be placed interchangeably with respect to the filtered water coming through the first stage of purification. [0024] Fig. 1 illustrates an apparatus 100 for water purification, according to an embodiment of the present subject matter. In said embodiment, the apparatus 100 includes a source reservoir 102 for storing untreated water that may be contaminated, a water purification device 104 for purifying the untreated water to provide purified water, and a collection reservoir 106 for receiving the purified water. In one implementation, the water purification device 104 may be connected to the source reservoir 102 in a leak proof manner.

[0025] Untreated water from a suitable source like a municipal water supply source, a well, a bore-well, a river, or any other source of drinking water may be poured in to the source reservoir 102 through a water inlet 108. The untreated water from the source reservoir 102 then enters the water purification device 104 as shown by an arrow 110. In one embodiment, the untreated water may pass through the water purification device 104 at a predetermined rate. The purified water from the water purification device 104 may then flow in and get collected in the collection reservoir 106 as shown by an arrow 112. In an embodiment, the collection reservoir 106 is provided with an outlet, such as a tap 114 from which the purified water may be drawn for consumption. [0026] . In one embodiment, the water purification device 104 of the apparatus 100 implements three stages of water purification. At a first stage, particulate matter, for example, suspended particles and mud present in the untreated water are removed to provide filtered water. At a second stage and a third stage, the filtered water is treated with different disinfectants to inactivate microbial contaminants, such as microbes like pathogenic bacteria, viruses, and protozoan cysts. In order to implement the three stages of water purification, the water purification device 104 includes a filtration unit 116 to filter particulate matter present in the untreated water, a primary disinfectant unit 118 to inactivate a portion of microbial contaminants present in the filtered water, and a secondary disinfectant unit 120 to inactivate a remaining portion of the microbial contaminants present in the filtered water. Although the terms primary and secondary have been used to identify the purification units related to two stages of purification, it will be understood that these terms are used merely for the purpose of reference and not as descriptive of function or importance of the two stages of purification.

[0027] In one implementation, the filtration unit 116 includes a plurality of permeable membranes (not shown in this figure) cascaded in order of decreasing porosity. Such a placement^ of the permeable membranes facilitates in filtering various particulate matters at different levels according to their size. Untreated water provided to the apparatus 100 is thus filtered at the first stage to receive filtered water. As the untreated water passes through the permeable membranes, the particulate matters are removed to provide the filtered water. Removing the particulate matters at the filtration unit 116 protects the primary disinfectant unit 118 and the secondary disinfectant unit 120 from direct exposure to the particulate matters, thereby avoiding premature clogging of the water purification device 104.

[0028] The primary disinfectant unit 118 includes one or more metal disinfectant treated porous media (not shown in this figure) for inactivating microbial contaminants present in the filtered water. In one embodiment, the metal disinfectant treated porous media may be formed by treating a porous media, such as RHA, activated carbon, clay, sand, foam, wo ven/non woven cloth, resin or combinations thereof, with a disinfectant, such as metal salts, metal nano-particles, metal oxides, and metal hydroxides. In another embodiment, the metal disinfectant treated porous media may be fabricated in the form of discs made of porous media, such as RHA or clay, treated with the disinfectant, such as nano particles of silver.

[0029] As the filtered water passes through the metal disinfectant treated porous media, a portion of the microbial contaminants present in the filtered water is inactivated by the disinfectants to provide disinfected water. In one embodiment, the metal disinfectant treated porous media is prepared such that a predetermined amount of the disinfectant is released in the filtered water, thus controlling the concentration of the disinfectant below a permissible level.

[0030] The secondary disinfectant unit 120 includes at least one oxidizing agent releasing component (not shown in this figure) to inactivate another portion of the microbial contaminants. The oxidizing agent releasing component may include one or more oxidizing agents, such as halogens and halogen releasing compounds. When the disinfected water received from the primary disinfectant unit 118 at the second stage passes through the secondary disinfectant unit 120, a predetermined concentration of the oxidizing agent is released into the flowing water. The microorganisms that were not inactivated by the primary disinfectant unit 1 18 are thus inactivated to receive the purified water. Further, in order to control the concentration of the oxidizing agent, the oxidizing agent releasing component may be formulated in such a way as to have a predetermined dissolution rate. Maintaining a low concentration of the oxidizing agent results in elimination of the additional step of removing excess oxidizing agent from the purified water, thus decreasing the size of the water purification device 104. In one embodiment, chlorine is used as an oxidizing agent with the concentration of the chlorine kept in the range of about 0.1 ppm to 0.5 ppm thus making the purified water acceptable for human consumption.

[0031] Using the synergistic action of the two disinfectants at low concentrations along with the filtration unit 116 facilitates in inactivating pathogens from untreated water at required levels within a shorter period of time. The water purification device 104 thus demonstrates high efficiency in inactivation of microbial contaminants, good performance in treating water from various sources, and long lasting residual disinfection effect. Further, the water purification device 104 does not require the additional step of removing residual disinfectants, i.e., disinfectants present in water after purification, thus decreasing the size of the water purification device 104 and in turn of the apparatus 100 having the water purification device 104.

[0032] Further, the stages of purification may be implemented in any order for purification of untreated water. For example, the second stage and the third stage of purification may be interchanged with respect to the filtered water coming through the first stage of purification. For instance, in order to interchange the second stage and the third stage, the position of the primary disinfectant unit 1 18 and the secondary disinfectant unit 120 may be interchanged in the water purification device 104.

[0033] Additionally, it will be understood that although the water purification device 104 has been shown to function as a part of the apparatus 100 for purposes of discussion, the water purification device 104 may be separately connected to any reservoir or tap for purification of water.

[0034] Fig. 2(a) illustrates the water purification device 104 according to one embodiment of the present subject matter. As previously described, the water purification device 104 includes the filtration unit 1 16, the primary disinfectant unit 118, and the secondary disinfectant unit 120. In said embodiment, the purification stages are placed such that the filtered water received from the filtration unit 116 is disinfected at the primary disinfectant unit 118 to provide the disinfected water to the secondary disinfectant unit 120. The filtration unit 116 is provided with a first inlet 202 for receiving the untreated water from the source reservoir 102 and a first outlet 204 for providing the filtered water to the primary disinfectant unit 118. The . primary disinfectant unit 118 receives the filtered water through a second inlet 206 connected to the first outlet 204 of the filtration unit 116 to receive the filtered water for disinfection and provides the disinfected water to the secondary disinfectant unit 120 through a second outlet 208. The second outlet 208 is in turn connected to a third inlet 210 of the secondary disinfectant unit 120 for further purifying the disinfected water. The secondary disinfectant unit 120 then provides the purified water to the collection reservoir 106 through a third outlet 212.

[0035] Fig. 2(b) illustrates the water purification device 104 according to another embodiment of the present subject matter. In said embodiment, the secondary disinfectant unit 120 is used as the second stage of purification and the primary disinfectant unit 118 is used as the third stage of purification. In order to implement said embodiment, the third inlet 210 of the secondary disinfectant unit 120 is connected to the first outlet 204 of the filtration unit 116 to receive the filtered water for disinfecting. Further, the third outlet 212 of the secondary disinfectant unit 120 is connected to the second inlet 206 of the primary disinfectant unit 118 for providing the disinfected water. The primary disinfectant unit 118 then provides the purified water to the collection reservoir 106 through the second outlet 208. The collection reservoir 106 stores the purified water which may be drawn through the tap 114 for consumption.

[0036] The purification stages of the water purification device 104 may thus be implemented in any order for treatment of untreated water. However, for the sake of clarity and _s not as a limitation, working of the water purification device 104 has been described in accordance with the embodiment described in fig. 2(a).

[0037] Fig. 3 illustrates components of the filtration unit 116 of the water purification device 104, according to an embodiment of the present subject matter. The filtration unit 116 as described herein includes one or more permeable membranes 302-1 and 302-2, hereinafter referred to as permeable membrane(s) 302. In one implementation, the permeable membranes 302 are cascaded in such a manner that a first permeable membrane, say the permeable membrane 302-1 has pore size greater than that of subsequent permeable membranes, such as the permeable membrane 302-2. Owing to such cascading of the permeable membranes 302, the first permeable membrane 302-1 can trap bigger and coarser particles thereby preventing the clogging of subsequent permeable membranes, which trap finer particles.

[0038] The permeable membranes 302 may be made up of any material, such as, fabric, mesh, foam, cotton, canvas, felt, nylon, polypropylene, polyamide, polyester, fired clay, ceramics, RHA, activated charcoal, woven cloth, and non woven cloth. In one implementation, the filtration unit 116 may be placed just above the second stage of purification with the permeable membranes 302 placed in the form of layers. In another implementation, the shape of the filtration unit 116 may be in the form of a cup having a cross-section of any shape, such as cylindrical, triangular, rectangular, square, and like.

[0039] Ingress of the untreated water in the filtration unit 116 via the inlet 202 is indicated by an arrow 304. The untreated water then passes through the permeable membranes 302 as indicated by arrows 306-1 and 306-2. As the untreated water passes through the permeable membranes 302, the coarse and fine particulate matter, such as suspended particles, present in the untreated water are removed to provide the filtered water. Subsequently, the filtered water is removed through first outlet 204, as indicated by an arrow 308, for further purification.

[0040] Fig. 4 illustrates components of the primary disinfectant unit 118, according to an embodiment of the present subject matter. As previously described the primary disinfectant unit 118, in one embodiment, may be used as the second stage of purification for treating the filtered water. In another embodiment, the primary disinfectant unit 118 may be used as the third stage of purification for treating the disinfected water. However, for the sake of clarity and not as a limitation, working of the primary disinfectant unit 118 has been described as would be in the second stage of purification in accordance with the embodiment described in fig. 2(a).

[0041] The primary disinfectant unit 118 includes the second inlet 206 for receiving the filtered water, the second outlet 208 for providing the disinfected water, and one or more metal disinfectant treated porous media 402-1, 402-2, 402-3, and, 402 -n, hereinafter referred to as the metal disinfectant treated porous media 402, for inactivating microbial contaminants. In one implementation, the metal disinfectant treated porous media 402 may be any solid, porous or granular substrate formed by treating a porous media with a disinfectant. Examples of porous media include, but are not limited to, RHA, clay, sand, foam, woven/nonwoven cloth, resin, activated carbon, charcoal powder, saw dust, ceramics, cellular plastics, zeolites, silicates, organosilicas, silicon, alumina, aluminosilicates, metals, metal foams, metal oxides, clay minerals, carbons and carbon nanotubes, synthetic and natural organic polymers, cloth fabrics, fiber, and combinations thereof.

[0042] The disinfectant used for treating the porous media may include, metal salts like silver nitrate, silver chloride, copper sulphate, and zinc sulphate; metal nanoparticles like nano silver, nano copper, nano zinc, nano aluminum, nano copper oxide, nano iron oxide, nano aluminum oxide, and nano titanium dioxide; metal oxides like aluminum oxide, copper oxide, titanium dioixde and ferric oxide; metal hydroxides, such as ferric hydroxide and aluminum hydroxide.

[0043] In one implementation, in order to obtain the metal disinfectant treated porous media, the porous media are soaked in these disinfectants. However, other methods of incorporating disinfectants, for example, passing the disinfectant solution through the porous media, painting or spraying the porous media with disinfectants, and in-situ synthesis of disinfectants such as nanometals within the porous media, may also be used. In addition, raw materials used for fabrication of the porous media may be soaked in the disinfectants before fabricating. Further, in order to strengthen the binding of the disinfectants to surface of the porous media, such as clay and/or RHA the surface of the porous media can be functionalized before treatment with the disinfectant. The surface of the porous media can be functionalized, for example, by silanization using a silane compound such as 3-aminopropyltriethoxysilane (APTES). The silanization is carried out by soaking the porous media in an aqueous solution of APTES. In one implementation, the concentration of APTES may be in the range of about 0.1 % to 40 %. In another implementation, the concentration of APTES may be in the range of about 0.5 % to 10 %. The soaked porous media is then dried at a temperature in the range of about 50 °C to 200 °C to remove moisture from the porous media to form a functionalized porous media. The functionalized porous media may be further treated with the disinfectant to get the metal disinfectant treated porous media. Further different layers of porous media may be treated with different disinfectants to obtain the metal disinfectant treated porous media 402 effective against a variety of contaminants in order to achieve the inactivation of a broad range of micro organisms. [0044] Further, the metal disinfectant treated porous media 402 can be formed in various shapes and sizes by treating the porous media under heat or by addition of a binder, such as polyvinyl alcohol, epoxy resin, gum, maltodextrin, lactose, polyethylene, polypropylene, polyolefin, cellulose ethers, bentonite , and polyvinylpyrrolidone (PVP) such as PVP K-30 is used to form a given structure.

[0045] In one embodiment, the porous media is fabricated by mixing the RHA and clay in a predetermined ratio with continuous addition of a predefined quantity of water to obtain a wet mixture. The wet mixture is compacted in a mould under a predetermined pressure to form a compact layer of the RHA and clay. The compact layer is then dried at a predetermined temperature, for example, in a temperature range of around 20 °C to 250 °C for removal of moisture. The dried compact layer may then be subsequently heated at higher temperature in the range of around 500 °C to 1500 °C to obtain a porous layer. Further, the porous layer may have different pore size and porosity depending upon the size and amount of RHA and heating temperature. In one implementation, the porous layer is prepared by mixing 80 % of -212 + 75 μιη sized clay and 20 % of -75 + 37 μιη sized RHA with sufficient amount of water to form a wet mixture. The wet mixture is compacted, dried, and subsequently heated at a temperature of around 1350 °C. The porous layer thus obtained is effective against removing protozoan cysts and fine particulate matter in the range of 1 to 10 micron.

[0046] In one embodiment, the metal disinfectant treated porous media 402 may include a plurality of porous layers in the forms of discs fabricated using rice husk ash and clay treated with nano silver. In said embodiment, the nano silver treated clay discs are fabricated using rice husk ash and clay which have been heat treated in the range of 500 °C to 1500 °C.

[0047] In operation, as the filtered water received from the filtration unit 1 16 is passed through the primary disinfectant unit 118, the filtered water enters through the second inlet 206. In one implementation, the second inlet 206 is provided at the bottom of the primary disinfectant unit 1 18 such that the filtered water flows through the metal disinfectant treated porous media 402 in an upward manner as indicated , by arrows 404-1, 404-2, and 404-3. In another implementation, the filtered water may flow downwards through the metal disinfectant treated porous media 402. As the filtered water passes through the metal disinfectant treated porous media 402, the disinfectants incorporated in the metal disinfectant treated porous media 402 inactivate microbial, contaminants present in the filtered water. Further, a predetermined amount of metal disinfectant incorporated in the metal disinfectant treated porous media 402 may leach out into the filtered water. Controlling the amount of disinfectant helps in maintaining the level of residual disinfectant in the purified water under permissible limits required for drinking water. 5 In one implementation, the amount of residual disinfectant, say silver, is less than 100 parts per billion (ppb). The disinfected water thus received exits the primary disinfectant unit 118 via the second outlet 208.

[0048] The primary disinfectant unit 118 thus inactivates a first portion of microbial contaminants and removes protozoan cysts present in the filtered water using the silver nano 0 particles as disinfectants in the metal disinfectant treated porous media 402. Further, maintaining the amount of residual silver at a concentration of less than 100 ppb prevents post purification microbial contamination of water.

[0049] Fig. 5 illustrates components of the secondary disinfectant unit 120, according to an embodiment of the present subject matter. As previously described the secondary disinfectant 5 unit 120, in one embodiment, may be used as the second stage of purification for treating the filtered water and in another embodiment may be used as the third stage of purification for treating the disinfected water. However, for the sake of clarity and not as a limitation, working of the secondary disinfectant unit 120 has been described to perform the third stage of purification in accordance with the embodiment described in fig. 2(a).

Ό [0050] The secondary disinfectant unit 120 includes, the third inlet 210 for receiving the disinfected water, the third outlet 212 for providing the purified water, an oxidizing agent releasing component 502 for inactivating the microbial contaminants, a plunger 504 having a plug 506 in contact with a top surface of the oxidizing agent releasing component 502 to hold the oxidizing agent releasing component 502 firmly over a base 508. The plunger 504 is supported 5 by a spring 510 placed near the top surface of the secondary disinfectant unit 120. Further, the oxidizing agent releasing component 502, the plunger 504, and the spring 510 are enclosed in a casing 512 attached to the base 508.

[0051] The base 508 includes one or more supports 514-1 and 514-2, hereinafter collectively referred to as support(s) 514, to rest the oxidizing agent releasing component 502, an D inlet passage 516 for transporting the disinfected water received from the third inlet 210 to a central opening 518, radial channels (not shown in the figure) for the passage of water, as indicated by arrows 520-1, 520-2, and to control dissolution of the oxidizing agent releasing component 502, and one or more outlet passage 522-1 and 522-2, hereinafter collectively referred to as outlet passage(s) 522 to carry the purified water from the radial channels to the third outlet 212. In one implementation, the secondary disinfectant unit 120 is configured to release chemicals, such as oxidizing agents, from a composition, such as the oxidizing agent releasing component 502 provided in the form of a tablet, at a predetermined rate in to the water flowing through it.

[0052] The oxidizing agent releasing component 502 includes at least one oxidizing agent which acts as a disinfectant for inactivating the microbial contaminants that were not removed by the primary disinfectant unit 118 and are thus still present in the disinfected water. Examples of the oxidizing agents include, but are not limited to, halogens such as chlorine, iodine and bromine; halogen releasing compounds, such as calcium hypochlorite and sodium hypochlorite; chlorine dioxide; peroxides such as hydrogen peroxide, magnesium peroxide, and calcium peroxide; potassium permanganate; potassium peroxymonosulfate; peracetic acid; performic acid and combinations of thereof. In one embodiment, the oxidizing agent may be chlorine in the form of chlorine releasing compounds.

[0053] Further, the oxidizing agent releasing component 502 may be dosed in the form of liquid, solid or gas. In one embodiment, the oxidizing agent releasing component 502 is in the form of a tablet of any shape including, but not limited to, cubical, cylindrical, disc, and prism shape. The oxidizing agent releasing tablet may be composed of a combination of oxidizing agent releasing component 502, additives, lubricants, and binders. In one embodiment, the oxidizing agent in the oxidizing agent releasing component 502 may be chlorine. In another embodiment the oxidizing agent may be a chlorine releasing compound. The chlorine releasing compound may include calcium hypochlorite, sodium dichloroisocyanurate, chloramine-T, chlorinated trisodium phosphate, lithium hypochlorite, trichloroisocyanuric acid, and combinations of thereof.

[0054] The additives, in one example, may include calcium sulphate, magnesium sulphate, calcium carbonate, magnesium carbonate, sodium persulphate, potassium phosphate, dibasic calcium phosphate, aluminium sulphate, ferric sulphate, aluminium hydroxide, ferric hydroxide, adipic acid, boric acid, cyanuric acid, cellulose, starch, glucose, lactose, mannitol, Sorbitol, and combinations thereof. Further, the additives may be added in the range of about 0 % to 90 % by weight.

[0055] Examples of the binders include, but are not limited to, sucrose, lactose, starch, cellulose, microcrystalline cellulose, hydroxypropyl cellulose, sorbitol, mannitol, gelatin, polyvinylpyrrolidone (PVP), PVP K-30, polyethylene glycol (PEG), and combinations thereof. Further, the binders may be added in the range of about 0 % to 60 % by weight of the oxidizing agent releasing compound 502. For example, polyvinylpyrrolidone (PVP), such as PVP K-30, may be added in the range of in the range of about 0 % to 60 % by weight.

[0056] The lubricants, in one example, may include talc, silica, sodium stearate, magnesium stearate, stearic acid and combinations of thereof. Further, the lubricants may be added in the range of about 0 % to 60 % by weight.

[0057] In accordance with an embodiment of the present subject matter, the oxidizing agent releasing component 502 is composed of a chlorine releasing compound such as calcium hypochlorite, sodium hypochlorite, and trichloroisocyanuric acid in the range of about 5% to 100% by weight, an additive such as calcium sulphate, as a diluent to slow down the tablet dissolution rate, in the range of about 0% to 90% by weight, PVP K-30 in the range of about 0% - 60% by weight to function as a binder, and magnesium stearate in the range of about 0% - 60% by weight to function as a lubricant.

[0058] In accordance with another embodiment of the present subject matter, the oxidizing agent releasing component 502 is composed of a chlorine releasing compound such as trichloroisocyanuric acid in the range of about 5% to 100% by weight, an additive such as boric acid in the range of about 0% to 90% by weight to function as a diluent to slow down the tablet dissolution rate, aluminum hydroxide in the range of about 0% to 50% by weight to function as another additive, cyanuric acid in the range of 0% to 50% by weight to function as another additive to slow down the tablet dissolution rate, PVP K-30 in the range of about 0% - 60% by weight to function as a binder, and magnesium stearate in the range of about 0% - 60% by weight to function as a lubricant.

[0059] In accordance with yet another embodiment of the present subject matter, the oxidizing agent releasing component 502 is composed of a chlorine releasing compound such as sodium dichloroisocyanurate in the range of about 0 to 60% by weight, another chlorine releasing compound such as calcium hypochlorite in the range of about 0% to 60 % by weight, and magnesium stearate in the range of about 0 % to 60 % by weight to function as a lubricant.

[0060] Further, the oxidizing agent releasing component 502 may be produced in the form of a tablet by mixing all the aforementioned ingredients thoroughly, followed by grinding for about 10 to 20 min to get some fine powder. The fine powder may then be compressed in the form of a die at a pressure of about 10 kg to 10 tons. Alternatively, the tablet may also be made using an automated tablet making machine. In accordance with an embodiment, the weight of an individual tablet may be in the range of about 1 gram (gm) to 20 gm. In another embodiment, the weight of an individual tablet may be in the range of about 1 gm to 5 gm.

[0061] In operation, as the disinfected water enters the secondary disinfectant unit 120, it passes through the third inlet 210 into the base 508. The disinfected water then starts moving in an upward direction through the inlet passage 516 towards the oxidizing agent releasing component 502 as shown by an arrow 524. Subsequently, the disinfected water exits through the central opening 518 and gets distributed into the radial channels as indicated by the arrows 520-1 and 520-2, thereby touching and in a controlled way dissolving the bottom surface of the oxidizing agent releasing component 502. The microorganisms that were not inactivated by the primary disinfectant unit 118 are then inactivated by the oxidizing agent releasing component 502 to provide the purified water. Further, a controlled contact of the disinfectant water with the oxidizing agent releasing component 502 ensures that a predetermined amount of the oxidizing agent is dosed into the disinfected water. In one embodiment, the oxidizing agent releasing component 502 is designed to release around 0.2 ppm of chlorine in a continuous flow of water at a flow rate of about 2 - 6 lit per hour. The purified water thus obtained then comes down through the outlet passages 522, as indicated by arrows 526-1, 526-2 and exits the secondary disinfectant unit 120 through the third outlet 212. As the oxidizing agent releasing component 502 gets consumed, the spring 510 starts expanding, pushing the plunger 504 and the oxidizing agent releasing component 502 downwards.

[0062] Further, the shape, size and composition of the oxidizing agent releasing component 502 are designed such that the oxidizing agent releasing component 502 dissolves completely in a predefined volume of water. Thus giving an indication of life of the water purification device 104 to the user. As the oxidizing agent releasing component 502 gets consumed, the plug 506 comes in contact with the central opening 518 and stops the flow of the disinfected water through it. At this point, the untreated water stops flowing through the water purification device 104 and provides an indication for replacement of the water purification device 104. In one implementation, the oxidizing agent releasing component 502 may be replaced in the water purification device 104 instead of replacing the water purification device 104. Additionally, the casing 512 may be made using a transparent material to provide a visual indication of the life of the water purification device 104 and stoppage of water flow through the water purification device 104. [0063] Stopping the purification process ensures that the water purification device 104 is not used beyond a safe prescribed limit thus ensuring that the purified water received from the apparatus 100 is always safe for drinking. Further, using three stages of purification facilitates in removing various contaminants, such as particulate matter and protozoan cysts and inactivates microbes like pathogenic bacteria. Additionally, synergistic effect of the two different disinfectants, i.e., the metal disinfectant and the oxidizing agent at two stages of the purification process ensures that all the microbial contaminants present in the untreated water are removed or inactivated. For example, most of Gram negative pathogens responsible for water borne disease e.g. E. coli, Pseudomonas aeruginosa, Vibrio cholera, Salmonella typhi, Shigella dysenteriae and poliovirus show sensitivity to silver and can thus be inactivated using silver as the disinfectant. Chlorine, on the other hand, can be used to inactivate Gram positive group of microorganisms, heterotrophic group of microorganism, and Hepatitis A virus present in the untreated water.

[0064] In addition, using two different disinfectants helps in purifying the untreated water using a small amount of the disinfectants, reducing the amount of residual disinfectants in the purified water. Reducing the amount of residual disinfectants helps in eliminating an extra step of removing excess residual disinfectants. Furthermore, due to the synergistic effect between the two disinfectants the contact time for purifying the untreated water reduces as compared to the contact time taken by each of the disinfectants individually.

[0065] Table 1 illustrates performance of a silver treated porous media, such as the metal disinfectant treated porous media 402 when used individually for treating water and performance of the silver treated porous media when used along with 0.2 ppm chlorine releasing tablet at contact times of 30 minutes, 1 hour, 2 hours, and 3 hours. As can be observed, the usage of both silver and chlorine based disinfectants leads to a substantial reduction in microbial count in 1 hour, which is similar to the reduction in microbial count obtained in 3 hours from using silver alone.

Table 1

[0066] Thus it can be seen from Table 1 that the metal disinfectant acts synergistically with the oxidizing agent at low concentrations to provide effective water purification. [0067] Fig. 6 illustrates a graph 600 depicting performance of the water purification device 104, according to an embodiment of the present subject matter. The graph 600 further depicts concentration of residual disinfectants in the purified water. In the graph 600, amount of water passed through the water purification device 104 is taken as a reference position and is represented along a horizontal axis 602, while log reduction of contaminants in the water, concentration of residual silver, and concentration of residual chlorine is represented on vertical axis 604-1, 604-2, and 604-3, respectively.

[0068] The graph 600 shows the results obtained after experiments were performed for testing performance of the water purification device 104. The water purification device 104 was tested at a flow rate of 3 - 5 L hr by passing up to 1853 liters of untreated water received by artificially spiking ground water with a bacterial culture Escherichia coli (E. coli) ATCC 1 1229 at a concentration of about 10⁶ colony forming units per milliliter of water (CFU/ml). A sample of the untreated water was collected in a sterile container to check the input load. The output water, i.e., the purified water from the water purification device 104 was collected in a separate sterile container to determine its microbial load, i.e., to determine the effectiveness of the water purification device 104 in treating the untreated water. Further, the performance of water purification device 104 was evaluated by comparing the bacterial count in the purified water and the untreated water. It should be noted that even though the test has been performed by measuring bacteria count, it will be understood that other microorganisms can also be removed.

[0069] Curve 606 represents the log reduction of contaminants in the purified water received by purifying the untreated water provided to the water purification device 104. Curve 608 and curve 610 represent concentration of residual silver and concentration of residual chlorine, in the purified water respectively. Log reduction is a mathematical term which shows the relative number of live microbes eliminated from a medium, i.e., water by purification methods. For example, a "6-log reduction" means lowering the number of microorganisms by a million fold, that is, if a water sample has 1,000,000 pathogenic microbes per milliliter, a 6-log reduction would reduce the number of microorganisms to one per milliliter.

[0070] The graph 600 shows that the purified water is substantially free from bacterial contaminants with a reduction of input count by 6 logs for more than 1853 litres of water passed through the water purification device 104. Further, the low concentrations of residual silver and chlorine in the purified water are acceptable for human consumption even with respect to qualitative parameters, such as taste and odor, thus making the purified water fit for human consumption.

[0071] Although implementations of a water purification device have been described in language specific to structural features and/or methods, it is to be understood that the appended claims are not necessarily limited to the specific features or methods described. Rather, the specific features and methods are disclosed as implementations of the water purification device.

Claims

I/We Claim:

A water purification device (104) for purification of water, the water purification device (104) comprising:

a filtration unit (116) comprising a plurality of permeable membranes (302), to filter particulate matter present in the water to provide filtered water;

a primary disinfectant unit (1 18) comprising at least one metal disinfectant treated porous media (402) to inactivate a first portion of microbial contaminants present in the filtered water; and

a secondary disinfectant unit (120) comprising at least one oxidizing agent releasing component (502) to inactivate a second portion of the microbial contaminants present in the filtered water.

The water purification device (104) as claimed in claim 1, wherein the at least one metal disinfectant treated porous media (402) comprises a porous media treated with a metal disinfectant, and wherein the metal disinfectant is at least one of a metal salt, a metal nano- particle, a metal oxide, and a metal hydroxide.

The water purification device (104) as claimed in claim 1, wherein the at least one metal disinfectant treated porous media (402) comprises a porous media treated with a metal disinfectant, and wherein the metal disinfectant is at least one of a silver nitrate, silver chloride, copper sulphate, zinc sulphate, copper oxide, titanium dioxide, aluminum oxide, ferric oxide, nano silver, nano copper, nano aluminum, nano zinc, nano copper oxide, nano iron oxide, nano aluminum oxide, nano titanium dioxide, ferric hydroxide, and aluminum hydroxide.

The water purification device (104) as claimed in claim 1, wherein the at least one metal disinfectant treated porous media (402) comprises at least one porous media selected from rice husk ash (RHA), clay, sand, foam, woven/nonwoven cloth, resin, activated carbon, charcoal powder, saw dust, ceramics, cellular plastics, zeolites, silicates, organosilicas, silicon, alumina, aluminosilicates, metals, metal foams, metal oxides, clay minerals, carbon nanotubes, synthetic and natural organic polymers, cloth fabrics, and fiber.

The water purification device (104) as claimed in claim 4, wherein the at least one metal disinfectant treated porous media (402) includes a binder selected from a group consisting of polyvinyl alcohol, epoxy resin, gum, maltodextrin, lactose, polyvinylpyrrolidone (PVP), polyethylene, polypropylene, polyolefin, cellulose ethers, bentonite , and combinations thereof.

6. The water purification device (104) as claimed in claim 1, wherein the at least one metal disinfectant treated porous media (402) is fabricated by heating a mixture of RHA and clay in a temperature range of about 500 °C to 1500 °C, to form a porous layer.

7. The water purification device (104) as claimed in claim 1, wherein the at least one metal disinfectant treated porous media (402) is fabricated using a method comprising

soaking a porous media in an aqueous solution of 3-aminopropyltriethoxysilane (APTES) to obtain a soaked porous media, wherein the concentration of the APTES is in range of about 0.1 % to 30 %;

treating the soaked porous media with a metal disinfectant.

8. The water purification device (104) as claimed in claim 1, wherein pore size of the at least one metal disinfectant treated porous media (402) varies based on size of RHA.

9. The water purification device (104) as claimed in claim 8, wherein the size of the RHA is selected from the range of about 10 micrometer to 600 micrometer, to form a porous layer to trap protozoan cysts and fine particulate matter with a mean size in the range of about 1 to 10 micro meters.

10. The water purification device (104) as claimed in claim 1, wherein the at least one oxidizing agent releasing component (502) comprises an oxidizing agent selected from a group consisting of a halogen, a halogen releasing compound, a peroxide, and a combination thereof.

1 1. The water purification device (104) as claimed in claim 1, wherein the at least one oxidizing agent releasing component (502) comprises an oxidizing agent selected from a group consisting of chlorine, iodine, bromine, calcium hypochlorite, sodium hypochlorite, sodium dichloroisocyanurate, chloramine-T, chlorinated trisodium phosphate, lithium hypochlorite, trichloroisocyanuric acid, calcium peroxide, magnesium peroxide, hydrogen peroxide, chlorine dioxide, potassium permanganate, potassium peroxymonosulfate, peracetic acid, performic acid, and combinations thereof

12. The water purification device (104) as claimed in claim 1, wherein the at least one oxidizing agent releasing component (502) is a tablet.

13. The water purification device (104) as claimed in claim 12, wherein the tablet comprises an additive selected from a group consisting of calcium sulphate, magnesium sulphate, calcium carbonate, magnesium carbonate, sodium persulphate, potassium phosphate, dibasic calcium phosphate, aluminium sulphate, ferric sulphate, aluminium hydroxide, ferric hydroxide,

5 adipic acid, boric acid, cyanuric acid, cellulose, starch, glucose, lactose, mannitol, sorbitol, and combinations thereof.

14. The water purification device (104) as claimed in claim 12, wherein the tablet comprises a binder selected from a group consisting of sucrose, lactose, starch, cellulose, microcrystalline cellulose, hydroxypropyl cellulose, sorbitol, mannitol, gelatin,0 polyvinylpyrrolidone (PVP), PVP K-30, polyethylene glycol, and combinations thereof.

15. The water purification device (104) as claimed in claim 12, wherein the tablet comprises a lubricant selected from a group consisting of talc, silica, sodium stearate, magnesium stearate, stearic acid, and combinations thereof.

16. The water purification device (104) as claimed in claim 12, wherein the tablet comprises, 5 a chlorine releasing compound in the range of about 5 % to 100 % by weight, wherein the chlorine releasing compound is at least one of a calcium hypochlorite, sodium dichloroisocyanurate, and trichloroisocyanuric acid;

calcium sulphate in the range of about 0 % to 90 % by weight;

PVP K- 30 in the range of about 0 % to 60 % by weight; and

0 magnesium stearate in the range of about 0 % to 60 % by weight.

17. The water purification device (104) as claimed in claim 12, wherein the tablet comprises, trichloroisocynuric acid in the range of about 5-% to 100 % by weight;

boric acid in the range of about 0 % to 90 % by weight;

aluminum hydroxide in the range of about 0% to 50% by weight;

'5 cyanuric acid in the range of about 0% to 50%; and

magnesium stearate in the range of about 0 % to 60 % by weight.

18. The water purification device (104) as claimed in claim 12, wherein the tablet comprises, sodium dichloroisocyanurate in the range of about 10 % to 50 % by weight;

calcium hypochlorite in the range of about 10 % to 50 % by weight; and

0 magnesium stearate in the range of about 0 % to 60 % by weight. — , u u υ H u U

19. The water purification device (104) as claimed in claim 1, wherein the at least one metal

disinfectant treated porous media (402) releases a predetermined amount of metal disinfectant in the filtered water. '

20. The water purification device (104) as claimed in claim 19, wherein the at least one metal 5 disinfectant treated porous media (402) releases a predetermined amount of silver to have a

• residual concentration of less than 100 parts per billion.

21. The water purification device (104) as claimed in claim 1, wherein the at least one oxidizing

agent releasing component (502) releases a predetermined amount of an oxidizing agent in the filtered water.

0 22. The water purification device (104) as claimed in claim 21, wherein the at least one

oxidizing agent releasing component (502) releases a predetermined amount of chlorine in the range of about 0.1 parts per million (ppm) to 0.5 ppm.

23. The water purification device (104) as claimed in claim 1, wherein the secondary

disinfectant unit (120) comprises,

5 a base (508) comprising,

a third inlet (210) for receiving the water;

an inlet passage (516) to carry the water from the third inlet (210) to a central opening (518);

radial channels to allow passage of water from the central opening (518) and.0 control dissolution of the at least one oxidizing agent releasing component (502);

outlet passages (522) to carry the water from the radial channels to a third outlet (212); and

supports (514) to rest the at least one oxidizing agent releasing component (502); and

'5 a casing (512) attached to the base (508), the casing (512) comprising,

the at least one oxidizing agent releasing component (502);

a plunger (504) with a plug (506) to hold the at least one oxidizing agent releasing component (502); and

a spring (510) to support the plunger (504).

0 24. The water purification device (104) as claimed in claim 23, wherein the at least one

oxidizing agent releasing component (502) is dissolved in a controlled way, and wherein on a complete dissolution of the at least one oxidizing agent releasing component (502), the plug (506) of the plunger (504) comes in contact with the central opening (518) to stop the flow of water into the secondary disinfectant unit (120).

25. The water purification device (104) as claimed in claim 1, wherein a second inlet (206) of the primary disinfectant unit (118) is connected to a first outlet (204) of the filtration unit

(116) to receive the filtered water for disinfecting, and wherein a second outlet (208) of the primary disinfectant unit (1 18) is connected to a third inlet (210) of the secondary disinfectant unit (120) to provide disinfected water to the secondary disinfectant unit (120) for purification.

26. The water purification device (104) as claimed in claim 1, wherein a third inlet (210) of the secondary disinfectant unit (120) is connected to a first outlet (204) of the filtration unit (1 16) to receive the filtered water for disinfecting, and wherein a third outlet (212) of the secondary disinfectant unit (120) is connected to a second inlet (206) of the primary disinfectant unit (1 18) to provide disinfected water to the primary disinfectant unit (118) for purification.

27. The water purification device (104) as claimed in claim 1, wherein the plurality of permeable membranes (302) are made of at least one of fabric, mesh, foam, cotton, canvas, felt, nylon, polypropylene, polyamide, polyester, fired clay, ceramics, RHA, activated charcoal, polyvinyl alcohol, woven cloth, and non woven cloth.

28. A method for purification of water for consumption comprising:

filtering particulate matter present in the water to provide filtered water;

inactivating a first portion of microbial contaminants present in the filtered water using at least one metal disinfectant treated porous media; and

inactivating a second portion of the microbial contaminants present in the filtered water using at least one oxidizing agent releasing component, wherein the at least one oxidizing agent releasing component releases a predetermined amount of an oxidizing agent to keep a concentration of the oxidizing agent below a predefined value.

29. The method as claimed in claim 28, wherein the metal disinfectant treated porous media is treated with silver, and wherein the method comprises releasing a predetermined amount of silver to have a residual concentration of less than 100 parts per billion.

0. The method as claimed in claim 28, wherein the oxidizing agent is chlorine, and wherein the method comprises releasing a predetermined amount of chlorine in a range of 0.1 parts per million (ppm) to 0.5 ppm.