WO2012025943A1

WO2012025943A1 - Method for purifying water by contacting water with a porous rice husk ash and clay mixture and apparatus therefor

Info

Publication number: WO2012025943A1
Application number: PCT/IN2011/000579
Authority: WO
Inventors: Shankar Balajirao Kausley; Rajshree Amrut Patil
Original assignee: Tata Consultancy Services Limited
Priority date: 2010-08-27
Filing date: 2011-08-26
Publication date: 2012-03-01
Also published as: WO2012025943A4

Abstract

The subject matter described herein relates to purification of water. In one implementation, a disinfectant treated porous media (118) is provided for purification of water. The disinfectant treated porous media (118) includes at least one porous media treated with a disinfectant. Further, the at least one porous media further includes rice husk ash (RHA) and clay.

Description

METHOD FOR PURIFYING WATER BY CONTACTING WATER WITH A POROUS RICE HUSK ASH AND CLAY MIXTURE AND APPARATUS THEREFOR

TECHNICAL FIELD

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

BACKGROUND

[0002] Generally, consumption of untreated water leads to spread of waterborne diseases.

The spread of these diseases is likely occur where water, used for consumption, gets contaminated by microorganisms, such as b oteria, viruses, and protozoan cysts. To curb the spread of such diseases, untreated water <s 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.

[0003] Therefore, to curb spread of waterborne diseases, various water purification systems are usually implemented at a point-of-use (POU) from where water can be directly consumed. The water purification systems implement various technologies, such as reverse osmosis, ultra violet (UV) radiation, membrane filtration, and chemical disinfection to treat the untreated water. The technologies based on rever e osmosis, ultra violet (UV) radiation, and membrane filtration usually need electricity and may also require elevated water pressure for operation. Using such technologies thus increases the cost of the water purification systems and limits the use of the water purification syr.'ems.

|0004] Further, chemical disin "U!on involvfcs removing microbiological contaminants by using high concentrations of disinfectants, which imparts pur.^ency and objectionable taste to the treated water. Thus, additional stecs are introduced during water purification method to remove excess disinfectants before delivering treated water for consumption. These additional steps may further increase the size and cost of the water purification systems. Additionally, purifiers implementing such water purification methods are often bulky and suffer from limitations, such as clogging and poor trapping of microorganisms like bacteria, protozoan cysts, etc. SUMMARY

[0005] This summary is provided to introduce concepts related to purification of water, which is further described below in the detailed description. This summary is not 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 disinfectant treated porous media is described herein. The disinfectant treated porous media includes at least one porous media treated with a disinfectant. Further, the at least one porous media includes rice husk ash and clay.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The detailed description is described 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. la illustrates a water purification system for treating untreated water, according to an embodiment of the present subject matter.

[0009] Fig. l b illustrates a configuration of a disinfectant treated porous media of the water purification system, according to an embodiment of the present subject matter.

[0010] Fig. 2a and Fig. 2b illustrate cross sectional views of the water purification system, according to various embodiments of the present subject matter.

[0011] Fig. 3 illustrates a cross sectional view of the water purification system, according to another embodiment of the present subject matter.

[0012] Fig. 4a and Fig. 4b illustrate cross sectional views of the water purification system, according to various embodiments of the present subject matter.

[0013] Fig. 5 illustrates an apparatus for water purification implementing the water purification system, according to an embodiment of the present subject matter.

[0014] Fig. 6 illustrates an apparatus for water purification implementing the water purification system, according to another embodiment of the present subject matter. DETAILED DESCRIPTION

[0015] The present subject matter relates to purification of water. Generally, purification of water is a process of removing microbiological and particulate contaminants from untreated water. Microbiological contaminants, such as bacteria, viruses, and protozoan cysts, when present in water, for example, drinking water, contaminate the drinking water and cause waterborne diseases. Conventional methods of purification of water involve treating water at source. Other methods of water purification involve treating water by certain disinfectants, filtering, or combinations thereof at point-of-use (POU). The disinfectants used in such methods include chlorine and iodine which are effective against bacteria and viruses, but have limited effectiveness against other microorganisms such as protozoan cysts.

[0016] Also, the water purification process may introduce high concentrations of disinfectants in water, which may impart unacceptable taste and odor to water. In order to remove the excess disinfectants before delivering the water for consumption, additional steps are introduced during the water purification process. Such additional steps add to the cost and increase the size of a water purification system implementing such purification methods. Further, these water purification systems lose efficiency to trap the contaminants after a period of time.

[0017] A Method and a system for purification of water are described herein. According to an embodiment, a water purification system has an inlet, a purification device, and an outlet. The inlet is used for receiving water, which requires further treatment, from one or more water sources. The water may or may not have undergone prior treatment and is hereinafter referred to as untreated water. In one implementation, the inlet may be connected to a reservoir of water. The untreated water is subsequently received by the purification device for treatment, and the purified water exits from the purification device through the outlet. In one embodiment, the purification device has a primary purification unit and a secondary purification unit.

[0018] 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. [0019J Untreated water is initially purified. in the primary purification unit. The primary purification unit includes 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. Removing the particulate matter helps in avoiding direct exposure of the secondary purification unit to such particulate matter, thereby avoiding premature clogging of the secondary purification unit. Untreated water is thus filtered by the primary purification unit to receive filtered water.

[0020] The filtered water is then disinfected by the secondary purification unit. The secondary purification unit includes one or more disinfectant treated porous media to inactivate microbial contaminants present in the filtered water. As the filtered water passes through the secondary purification unit, the microbial contaminants are inactivated by the disinfectants incorporated in the disinfectant treated porous media. Further, the disinfectant treated porous media may have different porosities and strengths. In one implementation, one or more of the disinfectant treated porous media may 'lave pore sizes in the range of about 1 micron to 10 microns to trap contaminants, such as protozoan cyst, which are not only small in size, but also resistant to disinfectants. Thus, such disinfectant treated porous media facilitates removal of contaminants which earlier could not be inactivated using disinfectants or were inactivated only when a substantially high quantity of the disinfectants was used. Further, the disinfectant treated porous media are cascaded in such a manner that the pore size of the disinfectant treated porous media decreases in the direction of flow of the water. Upper layers of the disinfectant treated porous media trap bigger or coarser particles and lower layers of the disinfectant treated porous media trap fine particles, thereby preventing clogging of the pores of the lower layers by the coarser particles. The filtered water is thus disinfected to receive purified water.

[0021] The water purification system described herein inactivates microorganisms present in the untreated water, requires nominal maintenance, has high efficiency, and low operating costs. Further, the water purification system as described herein is durable and effective in trapping particulate and microbial contaminants. These and other advantages of the present subject matter would be described in greater detail in conjunction with the following figures. While aspects of described systems and methods for the water purification system can be implemented in any number of system(s), the embodiments are described in the context of the following exemplary system(s)

[0022] Fig. la illustrates a water purification system 100,^' according to an embodiment of the present subject matter. The water purification system 100 facilitates removal of contaminants, for example, particulate and microbiological contaminants from untreated water, thereby making the water suitable for consumption. The water purification system 100 includes an inlet 102 for receiving untreated water, a purification device 104 for removal of the contaminants from the untreated water, and an outlet 106 for providing purified water. The untreated water, entering the water purification system 100 through the inlet 102, is hereinafter interchangeably referred to as water.

[0023] In one implementation, one or more structural components of the water purification system 100 can be made from plastics, for example, polyethylene (PE), polypropylene (PP), acrylonitrile butadiene styrene (ABS), polycarbonate (PC), polyethylene terepthalate (PET), low density po!y h\'lene (LD^pE), high density polyethylene (HDPE). polystyrene, polyvinyl chloride (PVC , po^rtetrafluoroethylene (PTFE), nylons, polyesters, acrylics, polyolefins, polyurethanes, polyamides, polycarboxyamides, phenolics, polylactic acids, and any combination thereof. Additionally or alternately, one or more of the structural components of the water purification system 100 can also be made from metals, ceramics, or any combination thereof.

[0024] In one embodiment, the purification device 104 has a primary purification unit

108 and a secondary purification unit 1 10. The primary purification unit 108 and the secondary purification unit 1 10 are disposed such that the untreated water received by the inlet 102 first flows in the primary purification unit 108 and, from the primary purification unit 108, flows into the secondary purification unit 1 10. The secondary purification unit 1 10 is placed in such a way that an opening of the secondary purification unit 1 10 discharges into the outlet 106 to provide purified water for consumption. In one implementation, the primary purification unit 108 is placed between the inlet 102 and the secondary purif cation unit 1 10 to avoid direct exposure of the secondary purification unit 1 10 to suspended physical particles present in the untreated water. Avoiding direct exposure of the secondary purification unit 1 10 to suspended physical particles helps in preventing premature clogging of the secondary purification unit 1 10. [0025] Ingress of the untreated water in the purification device 104 via the. inlet 102 is indicated by an arrow 1 12. The untreated water initially passes through the primary purification unit 108. In one implementation, the primary purification unit 108 includes one or more permeable membranes, such as permeable membranes 1 14-1 and 1 14-2, hereinafter collectively referred to as the permeable membranes 1 14. In one implementation, the permeable membranes 1 14 can be made up of any material, such as, fabric, mesh, foam, cotton, canvas, felt, nylon, polypropylene, polyamide, polyester, sand, fired clay, ceramics, glass wool, rice husk ash, and activated charcoal. In addition, permeable membranes 1 14 may be formed in various shapes and sizes, for example, the shape of the permeable membranes 1 14 may be in the form of a cup having a cross section, such as cylindrical, triangular, rectangular, square, and the like. Different processes can be used to fabricate the primary purification unit 108, such as weaving, spinning, spun bound, needle punched, and melt blown processes. Further, the primary purification unit 108 can be formed in a woven or a non-woven manner.

[0026] In one implementation, the permeable membranes 1 14 are cascaded in decreasing order of porosity such that the pore size of a preceding layer of a permeable membrane is greater than the pore size of a subsequent permeable membrane. For example the permeable membrane 1 14-1 has a pore size greater than the p'r.ieable membrane 1 14-2. Owing to such cascading of the permeable membranes 1 14, the first permeable membrane 1 14-1 can trap bigger and coarser particles, thereby preventing the clogging of subsequent lower permeable membranes 1 14-2 which may trap fine particles. In one implementation, the pore size of the permeable membranes 1 14 decreases in the direction of the flow of water. Further, the permeable membranes 1 14 are placed such that they can be easily removed for cleaning purpose, which in turn facilitates easy installation and maintenance of the water purification system 100.

[0027] As the untreated water passes through the primary purification unit 108, the coarse and fine particulate matter, such as suspended particles, present in the untreated water are removed to provide filtered water. Subsequently, the filtered water enters the secondary purification unit 1 10 as indicated by an arrow 1 16.

[0028] In one embodiment, the secondary purification unit 1 10 includes one or more disinfectant treated porous media 1 18-1 and 1 18-2, hereinafter collectively referred to as the disinfectant treated porous media 1 18. The disinfectant treated porous media 1 18 may be fabricated in the form of. a flat structure, which can be of any suitable cross-section, such as circular, square, rectangular, triangular, and the like. For example, the disinfectant treated porous media 1 18 can be fabricated to have a circular cross-section and therefore may be in the form of a disc, as illustrated in Fig. l b.

[0029] In one implementation, the disinfectant treated porous media 1 18 are incorporated within the secondary purification unit 1 10 in such a manner that there is no gap between an inner surface of the secondary purification unit 1 10 and an outer surface of the disinfectant treated porous media 1 18, thereby preventing leakage of the filtered water. In one implementation, a sealant or a washer (not shown in the figures) may be introduced between the inner surface of the secondary purification unit 1 10 and the outer surface of the disinfectant treated porous media 1 18 to prevent any leakage.

[0030] In one example, the disinfectant treated porous media 1 18 are formed by treating a porous media with a suitable disinfectant to inactivate microbial contaminants. The examples of the disinfectant that may be used for treating the porous media may include, but are not limited to, metal salts like silver nitrate, silver chloride, copper sulphate, and zinc sulphate; metal oxides like aluminum oxide, copper oxide, titanium dioixde, and ferric oxide; 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 hydroxides, such as ferric hydroxide and aluminum hydroxide; peracetic acid; performic acid; lactic acid; potassium permanganate; quaternary ammonium compounds like quaternary ammonium chloride; halogen containing compounds like calcium hypochlorite, sodium hypochlorite, chloramine, iodine, chloramine T, halazone, sodium dichloroisocyanurate, and trichloroisocyanuric acid; and oxygen releasing compounds like hydrogen peroxide, magnesium peroxide, and sodium perborate. Further, naturally occurring disinfectants, such as extracts of medicinal plants may also be used for treating the porous media.

[0031] Examples of the porous media include, but are not limited to, RHA, 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, and any combination thereof. [0032] In one implementation, the disinfectant treated porous media 1 18 are fabricated using a combination of RHA and clay. The RHA, as will be known to a person skilled in the art, is a residue obtained after combustion of rice husk, which is a renewable agro-waste. The RHA includes mainly silica and carbon, and trace amounts of various metal oxides, such as alkali, alkali earth metal, and iron oxides. The RHA may be produced by burning rice husk in heaps, in a step grate furnace, fluid ized bed furnace, or tube-in-basket burner. Additionally, the RHA may also be obtained from boiler and brick kilns. Further, different types of clay such as kaolin, i.e., white clay, red clay, black clay, synthetic clay, and combinations thereof may be used in fabrication of the disinfectant treated porous media 1 18. Using the combination of low cost raw materials, such as RHA and clay, for making the disinfectant treated porous media 1 18 provides for reduction in manufacturing cost of the water purification system 100.

[0033] In one implementation, in order to strengthen the binding of RHA and/or clay to metal disinfectants, the RHA and/or clay are pre-treated, for example, by functionalizing surface of the RHA and/or clay. In one embodiment, the surface of RHA and/or clay is silanized with 3- aminopropyltriethoxysilane (APTES). The silanization is carried out by soaking the RHA and/or clay with an aqueous solution of APTES, where, the concentration of APTES used may be in the range of about 0.1 % to 30 % by weight. The RHA and/or clay are mixed with the aqueous solution of APTES to form a slurry. After uniform mixing, the RHA and/or clay slurry may be kept at ambient temperature for at least 3 hrs. The RHA and/or clay slurry may be subsequently dried at a temperature in the range of 20 to 250 °C. The dried mass of clay may then be grinded to fine powder and sieved to get particles of the size in the range of 10 micrometer (μπι) to 800 micrometer (μηπ). The dried mass of RHA is sieved to get particles of the size in the range of about 10 μπι to 800 μπι. Such RHA and/br clay functional ized with APTES have strong binding to metal disinfectants. Pre-treated RHA and pre-treated clay thus received are treated with the disinfectants.

[0034] In one implementation, in order to incorporate the disinfectants, at least one of

RHA, clay, pre-treated RHA, and pre-treated clay are soaked in the disinfectants. However, other methods of incorporating disinfectants, for example, passing a disinfectant solution through a bed of at least one of RHA, clay, pre-treated RHA, and pre-treated clay; painting or spraying at least one of RHA, pre-treated clay, pre-treated RHA, and pre-treated clay with the disinfectant solution; and in-situ synthesis of the disinfectants such as nanometals within at least one of RHA, clay, pre-treated RHA, and pre-treated clay may also be used. In one embodiment, at least one of RHA, clay, pre- treated RHA and pre-treated clay may be incorporated with different disinfectants to make them effective against a variety of contaminants.

[0035] In one embodiment, the disinfectant treated porous media 1 18 are fabricated by mixing disinfectant treated RHA and disinfectant treated clay in a predetermined ratio with continuous addition of a predefined quantity of water to get a wet mixture. In another embodiment, the disinfectant treated porous media 1 18 are fabricated by mixing RHA and disinfectant treated clay in a predetermined ratio vith continuous addition of a predefined quantity of water to get a wet mixture. In yet another embodiment, the disinfectant treated porous media 1 18 are fabricated by mixing disinfectant treated RHA and clay in a predetermined ratio with continuous addition of a predefined quantity of water to get a wet mixture. The wet mixture is compacted in a mould under a predefined force to form a compact layer. For example either clay or disinfectant treated clay in the range of about 10 % to 90 % by weight is mixed with either RHA or disinfectant treated RHA in the range of about 10 % to 90 % by weight with continuous addition of a predefined quantity of water to form the wet mixture. The water is added in the range of about 5 % to 90 % of total weight of RHA and clay mixture. The wet mixture is then compacted in a mould under force in the range of 10 kg to 200 kg to form a compact layer. The compact layer is then heated in two stages, first in the temperature range of about 20 °C to 250 °C and then in the range of about 500 °C to 1500 °C, to obtain the disinfectant treated porous media 1 18.

[0036] In another embodiment, the disinfectant treated porous media 1 18 are fabricated by mixing RHA and clay in a predetermined ratio with contir.uous addition of a predefined quantity of water to get a homogeneous wet mixture. The wet mixture is compacted in a mould under a predefined force to form a porous media. The size of the RHA and clay particles may vary across different layers. The porous media is then dried at a predefined temperature, for example, in the temperature range of about 20 °C - 250 °C. The porous media can be dried by different methods, such as open air drying, sun drying, oven drying, hot air drying, microwave drying, and combinations thereof. The dried layers are then heated at a predefined temperature, for example, in the temperature range of about 500 °C to 1500 °C providing appropriate heating rates and holding times to obtain the porous media. Holding time may be understood as the time for which the dried porous layers are kept in the furnace after reaching the predefined temperature. The holding time affects the strength and porosity of the porous layer and is typically in the range of 0 minutes to 8 hours.

[0037] Further, the dried layers are heated in various environments environment, such as inert gases, vacuum, oxidizing, reducing environments, and combinations thereof, inside one or more heating device including, but not limited to furnace, kiln, masonry oven, and combinations thereof. Such fabrication processes used for fabricating the disinfectant treated porous media 1 18 are simple and cost effective, thereby reducing the cost of the water purification system 100.

[0038] In one implementation, surface of the porous media can be functional ized using a silane compound such as APTES before treatment *vith the disinfectant. The silanization is carried out by soaking the porous media in an aqueous solution of APTES to obtain a soaked porous media. In one implementation, the concentration of APTES may be in the range of about 0.1 % to 30 %. The soaked porous media is then heated in a temperature range of about 20 °C to 250 °C to obtain a pre-treated porous media. The pre-treated porous media may be further treated with the disinfectants to get the disinfectant treated porous media 1 18.

[0039] In one implementation, in order to incorporate the disinfectants, the pre-treated porous media are soaked in the disinfectants. However, other methods of incorporating disinfectants, for example, passing a disinfectant solution through a bed of the pre-treated porous media, painting or spraying the pre-treated porous media with the disinfectant solution, and in- situ synthesis of the disinfectants, such as nanometals, within the pre-treated porous media, may also be used. In one embodiment, different disinfectant treated porous media 1 18 may be incorporated with different disinfectants to make them effective against a variety of contaminants. Although method for obtaining the disinfectant treated porous media has been described in relation to incorporating disinfectants in the pre-treated porous media, it will be understood that the disinfectant treated porous media may be obtained by incorporating disinfectants in the porous media directly without the process of pre-treating. Further, the disinfectant treated porous media may be obtained using one pre-treated porous media and one porous media that has not been pre-treated. [0040] Further, the disinfectant treated porous media 1.18 may have different porosities and strength. In one implementation, different strength of the disinfectant treated porous media 1 18 may be achieved by using sintering techniques. The use of sintered material enhances the strength of the disinfectant treated porous media 1 18 and makes them resistant against structural damages. The porosities of the disinfectant treated porous media 1 18 may be varied, for example, by changing the particle sizes of the RHA and clay. The disinfectant treated porous media 1 18 is prepared by mixing clay and RHA with sufficient amount of water to form a wet mixture. In one implementation, wet mixture is prepared by mixing clay of size in the range of about 10 μπι to 800 μπι in the range of about 10 % to 90 % by weight with RHA of size in the range of about 10 μπι to 800 μιη in the range of about 10 % to 90 % by weight. The wet mixture is compacted, dried, and subsequently heated at temperature in the range of about 500 °C to 1500 °C.

[0041] In another implementation, the disinfectant treated porous media 1 18 is prepared by mixing clay of size in the range of abo.'t 50 μπι to 425 μητι in the range of about 40 °/o to 60 % by weight and RHA of size in the range c ^l bout 50 (. :>\ to 425 μητι in the range of about 40 % to 60 % by weight with sufficient amount of vater to form a wet mixture. The wet mixture is compacted, dried, and subsequently heat .'d at temperature in the range of about 1000 °C to 1500 °C. The disinfectant treated porous media 1 18, thus formed, is effective against removing protozoan cysts and fine particulate matter in the range of about I to 10 micron. In one example, proportions of RHA, clay, and water in the wet mixture and/or the fabrication condition, such as heating time and heating temperature may be changed to fabricate the disinfectant treated porous media 1 18 to obtain a desired porosity and strength.

[0042] Further, the disinfectant treated porous media 1 18 are cascaded in such a manner that a first layer, such as the disinfectant treated porous media 1 18-1 has pore size greater than a subsequent disinfectant treated porous media, such as the disinfectant treated porous media 1 18- 2. Owing to such cascading of the disinfectant treated porous media 1 18, the first disinfectant treated porous media 1 18-1 can trap bigger and coarser particles thereby preventing the clogging of subsequent disinfectant treated poroi'a media 1 18, which trap finer particles. Thus, the primary purification unit 108 and the secondary purification unit 1 10 work in tandem to remove particulate matter and microbes. [0043) In one embodiment, the disinfectant treated porous media 1 18 are fabricated by mixing the RHA and clay with a binder selected from polyvinyl alcohol, epoxy resin, gum, maltodextrin, lactose, polyvinylpyrrolidone (PVP) such as PVP K-30, polyethylene, polypropylene, polyolefin, cellulose ethers, and bentonite.

[0044] As the filtered water flows through the secondary purification unit 1 10, the microbial contaminants present in the filtered water are inactivated and residual particulate and microbial contaminants are trapped in the pores of the disinfectant treated porous media 1 18- 1 and 1 18-2. The purified water thus received is provided by the outlet 106 as indicated by the arrow 120. The purified water may be stored, for example, in a reservoir for consumption and distribution. The water purification system 100 can handle a large volume of water while maintaining a good flow of water throughout its operational life.

[0045] In an embodiment, a carbonaceous adsorbent material, such as activated charcoal, charcoal powder, RHA, or any combination thereof may be incorporated at the outlet 106 of the water purification system 100. Such materials facilitate removal of color and odor from the purified water.

[0046] 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.

[0047] Fig. 2a and Fig. 2b illustrate the water purification system 100 according to various embodiments of the present subject matter. As previously described, the water purification system 100 includes the inlet 102, the purification device 104, and the outlet 106. In one embodiment, the purification device 104 has a lid 202, which may be used, for example, to remove the primary purification unit 108 from the purification device 104 for cleaning purpose. Further, the lid 202 may be a removable or an openable lid. The easy removal of the lid 202 facilitates regular cleaning of the primary purification unit 108. Thus, the particles trapped in the primary purification unit 108 are removed regularly, thereby increasing the operational life of the water purification system 100. In one embodiment, the lid 202 can be attached to the top of the purification device 104, as illustrated in Fig 2a. In another embodiment, the lid 202 may be attached to a base of the purification device 104, as illustrated in Fig. 2b.

[0048] The primary purification unit 108, as discussed has one or more permeable membranes, such as the permeable membrane 1 14-1 and the permeable membrane 1 14-2. For the purpose of explanation only two permeable membranes 1 14 are illustrated in Fig. 2a and 2b; however it will be understood that the primary purification unit 108 may have any number of permeable membranes 1 14. In one implementation, the permeable membrane 1 14-1 is connected to adaptors 204-1 and 204-2. The adaptors 204-1 and 204-2 can further be removably attached to holders 206-1 and 206-2, respectively, provided in the lid 202. Similarly, the permeable membrane 1 14-2 is connected to adaptors 204-3 and 204-4, which are removably attached to holders 206-3 and 206-4, respectively, provided in the lid 202. The adaptors 204-1 , 204-2, 204-3, and 204-4 are collectively referred to as the adaptors 204. Likewise, the holders 206- 1 , 206-2, 206-3, and 206-4 are collectively referred to as the holders 206. In one implementation, the permeable membranes 1 14 may be attached to the top of the purification device 104, as illustrated by Fig. 2a. In another implementation, the adaptors 204 may be directly placed in between the lid 202 and the purification device 104 in a leak proof manner. In yet another implementation, the permeable membranes 1 14 can be attached to the base of the purification device 104 so that they envelope the secondary purification unit 1 10, as illustrated in Fig. 2b.

[0049] In operation, the untreated water enters through the inlet 102 as indicated by the arrow 1 12 and flows through the primary purification unit 108. As the untreated water flows through the permeable membranes 1 14, particulate matter present in the untreated water is trapped in the permeable membranes 1 14. As illustrated in Fig. 2b, since the permeable membranes 1 14 are placed at the bottom of the purification device 104, the water can enter the primary purification unit 108 laterally as well as from an upward direction.

[0050] The filtered water from the primary purification unit 108 then enters the secondary purification unit 1 10 as indicated by the arrow 1 16. In one embodiment, the secondary purification unit 1 10 includes a receptacle 208 which further incorporates the disinfectant treated porous media 1 18. For the purpose of explanation only two disinfectant treated porous media 1 18-1 and 1 18-2 are illustrated in Fig. 2a and 2b, however it will be understood that the receptacle 208 may have any number of t'.e disinfectant treated porous media 1 18. As discussed previously, the disinfectant treated porous media 1 18 are treated with disinfectants to inactivate microbial contaminants. In one embodiment, the disinfectant treated porous media 1 18 may be cascaded in the order of decreasing porosity with respect to the flow of the filtered water. For example, the disinfectant treated porous media 1 18-1 has more porosity than the disinfectant treated porous media 1 18-2. Further, porosity of the disinfectant treated porous media 1 18 may be lesser than the porosity of the permeable membranes 1 14.

[0051] In one implementation, the receptacle 208 may be placed such that an outlet of the receptacle 208 coincides with the outlet 106 of the water purification system 100. The receptacle 208 further includes an opening 210 for the entry of the filtered water from the primary purification unit 108. In one implementation, the opening 210 is a perforated opening. As the filtered water flows through the disinfectant treated porous media 1 18, the microbial contaminants present in the filtered water are inactivated by the disinfectants present in the disinfectant treated porous media 1 18. The microbes and the residual particulate matter are then trapped in pores of the disinfectant treated porous media 1 18. Subsequent to purification by the secondary purification unit 1 10, the purified water exits the water purification system 100 through the outlet 106 as indicated by an arrow 212.

[0052] Fig. 3 illustrates the water purification system 100, according to an embodiment of the present subject matter. In one implementation, the water purification system 100 resides inside and proximate the base of a reservoir 502. As previously mentioned, the untreated water enters the primary purification unit 108 through the inlet 102 as indicated by the arrow 1 12. In the present embodiment, the inlet 102 is provided close to the base of the purification device 104. Further, the inlet 102 may include multiple holes provided at the periphery of the purification device 104 as illustrated in the Fig. 3. The untreated water enters the primary purification unit 108 and flows through the permeable membranes 1 14. The coarse and fine particles, such as the suspended particles are removed by purification performed by the primary purification unit 108. The filtered water received from the primary purification unit 108 enters the secondary purification unit 1 10.

[0053] The secondary purification unit 1 10 includes the disinfectant treated porous media

1 18 provided inside the receptacle 208. The filtered water enters the receptacle 208 through the opening 210. In one implementation, the opening 210 is a perforated opening. As the filtered water flows through the disinfectant treated porous media 1 18, the . microbes present in the filtered water are inactivated by the disinfectant in the disinfectant treated porous media 1 18. Further, the physical contaminants and microbes of small size are trapped in the pores of the disinfectant treated porous media 1 18. The purified water received after purification from the secondary purification unit 1 10 exists via the outlet 106 as indicated by an arrow 308.

[0054] Fig. 4a and Fig. 4b illustrate the water purification system 100 according to various other embodiments of the present subject matter. In said embodiments, the water purification system 100 resides inside and proximate the base of the reservoir 302. The untreated water from the reservoir 302 enters the purification device 104 through the inlet 102. In said embodiments, the inlet 102 is located close to a base of the purification device 104. The untreated water enters the purification device 104 in horizontal direction as indicated by the arrow 1 12. The untreated water enters the primary purification unit 108 and flows through the permeable membrane 1 14 located within the primary purification unit 108. In one implementation, the permeable membranes 1 14 are placed in such a way that they form an enclosure around the receptacle 208.

[0055] The purification performed at the primary purification unit 108 facilitates removal of coarse and fine particulate matter, such as suspended particles from the untreated water. The filtered water received from the primary purification unit 108 enters the secondary purification unit 1 10 as indicated by an arrow 402. The filtered water enters the receptacle 208 through the opening 210. In said embodiments, the opening 210 is provided at the base of the receptacle 208, while the top of the receptacle 208 is closed. As the filtered water enters the receptacle 208, the water level in the receptacle 208 starts increasing and the filtered water passes through the disinfectant treated porous media 1 18 as indicated by an arrow 404.

[0056] In the present embodiment, the disinfectant treated porous media 1 18 are cascaded in such a manner that the pore size of the disinfectant treated porous media 1 18 decreases in the direction of flow of water, for example, a lower layer, such as the disinfectant treated porous media 1 18-1 is more porous than a subsequent layer, for example, the disinfectant treated porous media 1 18-2. As the filtered water flows through the disinfectant treated porous media 1 18, the microbial contaminants present in the filtered water are inactivated. Further, the disinfectant treated porous media 1 18 traps the residual particulate contaminants and microbes that are not inactivated by the disinfectants present in the disinfectant treated porous media 1 18. As the level of water in the receptacle 208 goes above the level of the disinfectant treated porous media 1 18, the purified water exits through a channel 406 in a downward direction as indicated by an arrow 408. In said embodiments, the disinfectant treated porous media 1 18 and the channel 406 may be understood to be connected to form a siphon, thereby facilitating the egress of the purified water. The egress of the purified water may be discontinued when the level of the water falls below the level of the inlet 102. In one implementation, the channel 406 is positioned at the centre of the receptacle 208 as illustrated by Fig. 4a. In another implementation, the channel 406 is positioned at lateral side of the receptacle 208, as illustrated by Fig. 4b. The receptacle 208 is placed such that the channel 406 coincides with the outlet 106.

[0057] Fig. 5 illustrates an apparatus 500 implementing the water purification system

100, according to an embodiment of the present subject matter. In said embodiment, the water purification system 100 is disposed between a first reservoir 502 and a second reservoir 504. The first reservoir 502 holds the untreated water and the second reservoir 504 holds the purified water received after being treated by the water purification system 100. In one implementation, the water purification system 100 may be connected to the first reservoir 502 and the second reservoir 504 in a leak proof manner using a sealer or washers.

[0058] The untreated water enters the first reservoir 502 through an inlet 506. The inlet

506 may be closed through a lid 508. In one embodiment, the first reservoir 502 includes a filter 510 that facilitates filtration of the untreated water prior to ingress of water in the first reservoir 502 and hence prior to the purification of the water by the water purification system 100. The filter 510 may be, for example, a fabric, a mesh, or a foam. The filter 510 may be made of materials, such as cotton, canvas, feit, nylon, polypropylene, polyamide, polyester, or any combination thereof. The filter 510 can be fabricated using different methods, such as weaving, spinning, spun bound, melt blown, and needle punched process. Further, the filter 510 can be formed in a woven or a non woven manner.

[0059] Thus, the water entering the first reservoir 502, as indicated by an arrow 512, is treated by the filter 510. The filter 510 removes large suspended particle and may also reduce turbidity present in the untreated water. Water, received after treatment of the untreated water by the filter 510, enters the water purification system 100 as indicated by an arrow 514. The water enters the purification device 104 through the inlet 102. The water is initially treated by the primary purification unit 108, which removes suspended and coarse particles present in the water to provide the filtered water. Subsequently, the filtered water enters the secondary purification unit 1 10. The disinfectant treated porous media 1 18 in the secondary purification unit 1 10 inactivate microbial contaminants and capture fine particulate matter present in the water. After being treated by the secondary purification unit 1 10, the purified water exits through the outlet 106 and flows in the second reservoir 504 as indicated by an arrow 516. In one implementation, the purified water exits the second reservoir 504, as indicated by an arrow 518, through a faucet 520, such as a tap for consumption purposes.

[0060] Fig. 6 illustrates another apparatus 600 implementing the water purification system 100, according to an embodiment of the present subject matter. As illustrated, the water purification system 100 is connected to a reservoir 602 which holds the untreated water. In one implementation, the inlet 102 of the water purification system 100 may be connected to an outlet of a faucet 604 of the reservoir 602. Thus, the untreated water enters the water purification system 100 via the faucet 604, as indicated by an arrow 606. The untreated water is treated in the water purification system 100 to provide the purified water. The purified water exits through the outlet 106 as indicated by an arrow 608. In one implementation, the purified water can be stored in a reservoir. In another implementation, the purified water exiting through outlet 106 can be directly used for consumption. In said embodiment, the water purification system 100 may be used as an on-tap water purification system.

[0061] Table 1 illustrates performance of the water purification system 100 when connected to a reservoir of untreated water as illustrated by Fig. 6. The untreated water used for the experiment contained the bacterium Escherichia coli (E. coli) (ATCC 1 1229). Further, the performance of the water purification system 100 was tested at a flow rate of 2.5 - 3 L/hr. The test was conducted at a loading recommended by the National Science Foundation (NSF) P248 standard for microbiological water purifiers. 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 system 100 was collected in a separate sterile container to determine its microbial load, i.e., to determine effectiveness of the water purification system 100 in treating the untreated water. The performance of the water purification system 100 was evaluated by comparing the bacteria 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. The test results are illustrated in table 1 .

Table 1

[0062] Thus, it can be gathered from table 1 that the output water purified by the water purification system 100 is substantially free from bacterial contaminants and is fit for human consumption. Log reduction is a mathematical term which shows the relative number of live microbes eliminated from a medium, vw-.ich is water in present subject matter, by purification methods. For example, a "5-log reduction" means lowering the number of microorganisms by 100,000-fold, that is, if a medium has 100,000 pathogenic microbes, a 5-log reduction would reduce the number of microorganisms to one.

[0063] Hence, the water purification system 100 as described herein is efficient, compact, inexpensive and easy to use. Further, the water purification system 100 can be used at point of use operation and may be effectively used for example, in developing and underdeveloped countries where proper water purification facilities are not available. Furthermore, since the water purification system 100 is cost effective, therefore it can be readily used across various regions, for example, rural regions, where cost effectiveness is a primary concern.

[0064] Moreover, as the porosity of the primary purification unit 108 is greater than that of the secondary purification unit 1 10 large suspended particles are trapped at the primary purification unit 108 thus preventing clogging of the secondary purification unit 1 10. Owing to varying porosities of the various layers in the primary purification unit 1 08 and the secondary purification unit 1 10; a large range of contaminants are trapped without requiring separate units of purification for trapping these contaminants, thus reducing the cost and size of the water purification system 100. Also, different disinfectants may be incorporated within the disinfectant treated porous media 1 18 in the secondary purification unit 1 10 due to which a large range of microbial contaminants may be inactivated without requiring separate units of purification for inactivating these contaminants, thus also reducing the cost and size of the water purification system 100.

[0065] Additionally, since the water flows through the water purification system 100 owing to the action of gravity, no additional energy is required to keep the water flowing in and out of the purification device 104, which in turn further reduces the operational cost of the water purification system 100. Also, the water purification system 100 does not require additional storage unit as the inlet 102 can be attached directly to the source of the untreated water and the outlet 106 can be connected directly to the point of use thereby reducing the size and the cost of the water purification system 100.

[0066] As mentioned previously, the water purification system 100 is cost effective since it uses raw materials like rice husk and clay. Further, the fabrication process used in making the permeable membranes 1 14 and the disinfectant treated porous media 1 18 is simple, thereby reducing the cost of the water purification system 100. Further, as the water purification system 100 has an openable lid 202, the primary purification unit 108 can be easily removed and cleaned thereby increasing the life of the purification device 104.

[0067] Although implementations of a water purification system 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 system.

Claims

1/We claim:

1. A disinfectant treated porous media ( 1 18) comprising:

at least one porous media treated with a disinfectant, wherein the at least one porous media comprises rice husk ash (RHA) and clay.

2. The disinfectant treated porous media ( 1 18) as claimed in claim I , wherein the at least one porous media comprises:

the RHA in the range of about 10 % to 90 % by weight; and

the clay in the range of about 10 % to 90 % by weight.

3. The disinfectant treated porous media ( 1 18) as claimed in claim I , wherein the at least one disinfectant treated porous media ( 1 18) is fabricated by heating a mixture of RHA and clay in a temperature range of about 500 °C to 1500 °C.

4. The disinfectant treated porous media (1 18) as claimed in claim 1 , wherein the at least one porous media further comprises a binder selected from the group consisting of polyvinyl alcohol, epoxy resin, gum, maltodextrin, lactose, polyvinylpyrrolidone (PVP). polyethylene, polypropylene, polyolefin, cellulose ethers, bentonite, and combinations thereof.

5. The disinfectant treated porous media ( 1 18) as cfaimed in claim 1 , wherein the disinfectant is at least one of a metal salt, a metal nano-particle, a metal oxide, and a metal hydroxide.

6. The disinfectant treated porous media ( 1 ! 8) as claimed in claim 1 , wherein the 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.

7. The disinfectant treated porous media ( 1 18) as claimed in claim 1 , wherein the disinfectant is at least one of a quaternary ammonium compound, halogen containing compound, an oxygen releasing compound, and a natural disinfectant.

8. The disinfectant treated porous media ( 1 18) as claimed in claim 1 , wherein the disinfectant is at least one of a potassium permanganate, peracetic acid, performic acid, lactic acid, quaternary ammonium chloride, calcium hypochlorite, sodium hypochlorite, iodine, chloramine T, sodium dichloroisocyanurate, tri chloroisocyanuric acid, hydrogen peroxide, magnesium peroxide, sodium perborate, and extract of medicinal plants.

9. The disinfectant treated porous media ( 1 18) as claimed in claim 1 , wherein pore size of the at least one disinfectant treated porous media ( 1 18) is based on size of the RHA.

10. The disinfectant treated porous media ( 1 18) as claimed in claim 1 or claim 3, wherein the size of the RHA is selected from the range of about 10 micrometer (μπι) to 800 μπι, 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 μπι.

1 1 . A water purification system ( 100) for purification of water, the water purification system ( 100) comprising:

a primary purification unit ( 108) comprising a plurality of permeable membranes ( 1 14), to filter particulate matter present in the water to provide filtered water; and

a secondary purification unit ( 1 10) comprising a plurality of disinfectant treated purification media ( 1 18) as claimed in any of the preceding claims, wherein the disinfectant treated purification media ( 1 18) is configured to inactivate microbial contaminants present in the filtered water.

12. The water purification system ( 100) as claimed in claim 1 1 , wherein the primary purification unit ( 108) encloses the secondary purification unit ( 1 10).

13. The water purification system ( 100) as claimed in claim I I , wherein the plurality of permeable membranes ( 1 14) are made of at least one of a fabric, mesh, foam, cotton canvas, felt nylon, polypropylene, polyamide, polyester, woven cloth, nonwoven cloth, sand, fired clay, ceramics, glass wool, rice husk ash, and activated charcoal.

14. The water purification system ( 100) as claimed in claim 1 1 , wherein the plurality of disinfectant treated purification media ( 1 18) are cascaded in decreasing order of porosity, wherein the porosity decreases in the direction of flow of water.

15. The water purification system ( 100) as claimed in claim 1 1 further comprising a channel (406) for providing purified water purified by the secondary purification unit ( 1 10), wherein the channel (406) and the secondary purification unit ( 1 10) are connected to form a siphon.

16. The water purification system ( 100) as claimed in claim I I further comprising an outlet ( 106) for providing purified water, and wherein the outlet ( 106) comprises a carbonaceous adsorbent material selected from at least one of an activated charcoal and RHA to facilitate removal of color and odor from the purified water;

17. The water purification system (100) as claimed in claim 1 1 , wherein the water purification system (100) is made from a material selected from the group consisting of plastics, metals, ceramics, and combinations thereof.

18. A method comprising:

treating at least one of RHA and clay to obtain at least one of disinfectant treated RHA and disinfectant treated clay, respectively;

mixing, with water, at least one of: the RHA and the disinfectant treated clay, the disinfectant treated RHA and the clay, and the disinfectant treated clay and the disinfectant treated RHA, to get a wet mixture; and

heating the wet mixture to obtain a disinfectant treated porous media (1 18).

19. The method as claimed in claim 18. vherein the treating comprises exposing at least one of the RHA and the clay to the disinfectant using a method comprising at least one of:

passing a disinfectant solution through a bed of at least one of the RHA and the clay; soaking at least one of the RHA and the clay in the disinfectant solution;

spraying the disinfectant solution at least one of the RHA and the clay;

painting the disinfectant solution on at least one of the RHA and the clay; and synthesizing nano particles of the disinfectant in situ within at least one of the RHA and the clay.

20. The method as claimed in claim 18 or 19, wherein the RHA comprises pre-treated RHA obtained by a method comprising:

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

heating the soaked RHA the in a temperature range of about 20 °C to 250 °C to obtain pre-treated RHA.

21. The method as claimed in claim 18 or 19, wherein the clay comprises pre-treated clay obtained by a method comprising:

soaking the clay in an aqueous solution of APTES to obtain soaked clay, wherein concentration of APTES is in a range of about 0.1 % to 30 %; and

heating the soaked clay the in a temperature range of about 20 °C to 250 °C to obtain pre-treated clay.

22. A method comprising: .

mixing clay with RHA and water to get a wet mixture;

heating the wet mixture to obtain a porous media; and

treating the porous media with a disinfectant to obtain a disinfectant treated porous media ( 1 18).

23. A method comprising:

mixing clay with RHA and water to get a wet mixture;

heating the wet mixture to obtain a porous media;

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

heating the soaked porous media in a temperature range of about 20 °C to 250 °C. to obtain a pre-treated porous media; and

treating the pre-treated porous media to the disinfectant.

24. The method as claimed in claim 22 or claim 23 wherein the treating comprises exposing at least one of the pre-treated porous media and the porous media to the disinfectant using a method comprising one of,

passing a disinfectant solution through at least one of the pre-treated porous media and the porous media;

soaking at least one of the pre-treated porous media and the porous media in the disinfectant solution;

spraying the disinfectant solution on at least one of the pre-treated porous media and the porous media;

painting the disinfectant solution on at least one of the pre-treated porous media and the porous media; and

synthesizing nano particles of the disinfectant in situ within at least one of the pre- treated porous media and the porous riedia.