FORM 2
THE PATENTS ACT, 1970 (39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10, rule 13)
1. Title of the invention: FLUORIDE REMOVAL FOR WATER PURIFICATION
2. Applicant(s)
NAME NATIONALITY ADDRESS
TATA CONSULTANCY Nirmal Building, 9th Floor, Nariman Point,
Indian
SERVICES LIMITED Maharashtra 400021, India
3. Preamble to the description
COMPLETE SPECIFICATION
The following specification particularly describes the invention and the manner in which it
is to be performed.

TECHNICALFIELD
[0001] The present subject matter relates, in general, to purification of water and, in
particular, to removal of fluoride ions from water.
BACKGROUND
[0002] Generally, water available from natural sources, such as groundwater sources or
surface water sources, contains impurities and is not safe for human consumption. The impurities may include chemical impurities, such as fluoride and arsenic; and biological impurities, such as Escherichia coli, and can thus cause acute and chronic illnesses. Fluoride, for example, occurs in natural water in many countries.
[0003] Excessive exposure to fluoride can give rise to a number of adverse effects. These
effects range from mild dental fluorosis to crippling skeletal fluorosis as the level and period of exposure increases. Various health organizations have prescribed safe limits for fluoride concentration in drinking water. For example, the World Health Organization prescribes a value of 1.5 parts-per-million (ppm) as the safe limit for fluoride concentration in drinking water.
[0004] The prescribed safe limits for fluoride concentration often tend to be difficult to
achieve. A large population across the world, especially those in developing and underdeveloped countries, directly consumes contaminated water. Elevated fluoride concentrations usually occur in contaminated water, thus, subjecting the consumers of the contaminated water to the effects of fluorosis. Defluoridation plants may be set up for providing purified water for the population, but such plants usually get abandoned due to lack of proper maintenance. Point-of-use or household defluoridation devices that are available in the market are expensive and involve regular maintenance, which puts them beyond the reach of many households.
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 method for purification of water is described. In one
implementation, the method includes adjusting pH level of the water to provide conditioned water. The conditioned water is then passed through a primary adsorption media which adsorbs a first portion of fluoride ions present in the conditioned water to provide defluoridated water. A second portion of the fluoride ions present in the defluoridated water is subsequently adsorbed by a secondary adsorption media to provide purified water.
BRIEF DESCRIPTION OF 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) and 2(b) illustrate components of a connection mechanism for
connecting a water purification device to a source container for receiving water for purification, in accordance with an embodiment of the present subject matter.
[0010] Fig. 3 illustrates a water purification device of the apparatus for water
purification, according to one embodiment of the present subject matter.
[0011] Fig. 4 illustrates a pH conditioner of the water purification device, in accordance
with an embodiment of the present subject matter.
[0012] Fig. 5 illustrates a method for purification of water, according to an embodiment
of the present subject matter.
[0013] Fig. 6 illustrates a graph depicting performance of the water purification device
when used for removal of fluoride ions from water, in accordance with an embodiment of the present subject matter.

DETAILED DESCRIPTION
[0014] The present subject matter described herein relates to devices and methods for
purification of water. The devices and methods facilitate removal of ions, for example, fluoride ions, from water.
[0015] Fluoride ions (F¯) occur in both surface water, having concentrations ranging
from about 0.01 parts-per-million (ppm) to 0.3 ppm, and groundwater with concentrations varying from about less than 1 ppm to about more than 35 ppm. Prolonged ingestion of fluoride can lead to a number of adverse effects, such as dental fluorosis and skeletal fluorosis. Various health organizations have thus prescribed safe limits for fluoride concentration in drinking water. For example, the World Health Organization prescribes a value of 1.5 parts-per-million ppm as the safe limit for fluoride concentration in drinking water.
[0016] The prescribed safe limits for fluoride concentration are often difficult to achieve,
especially in rural areas. A large population across the world, especially in the rural areas in developing and underdeveloped countries, thus directly consumes water contaminated with fluoride ions. Various systems or methods may be implemented to provide purified water to the population, either at community level or for households. However, such systems or methods, typically, are expensive and involve frequent maintenance, which puts them beyond the reach of many households.
[0017] Conventionally, techniques such as reverse osmosis and membrane technology
have been implemented to reduce fluoride concentration in water. However, both the techniques require electricity, which may either be unavailable or be short in supply in rural areas of developing or underdeveloped countries. Furthermore, systems implementing such techniques are usually costly and, thus, beyond reach of the rural population.
[0018] Other conventional systems implement contact precipitation for fluoride removal
from water. In such systems, calcium and phosphate compounds are added to water and then brought in contact with an already saturated bone charcoal medium. Precipitation of calcium fluoride and fluorapatite is catalyzed in a contact bed of saturated bone charcoal that also acts as a filter for the precipitates. These systems can be used as a domestic unit as well as in a community plant. However, such systems are bulky and require skilled installation of fittings of

the system and careful adjustment of flow rates in the system. Furthermore, such systems have limited durability and the fluoride ions break through after saturation of the bed. Such systems are thus unreliable for being used in households.
[0019] Another conventional defluoridation technique, which uses alum and lime, may
release fluoride ions back to purified water. Further, in such a technique, concentrations of aluminum and sulphate, used for treatment, are relatively high in the purified water. Disposal of produced toxic sludge, which also contains fluoride ions, poses environmental considerations. Additionally, mechanisms based on adsorption of fluoride ions using activated alumina, are often difficult to maintain. Such mechanisms often produce wastes containing fluoride ions that need to be disposed.
[0020] A method and a device for purification of water are described herein. 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 requires 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 water purification device for treatment. Purified water exits from the water purification device through the outlet. The water purification device selectively removes fluoride ions from water, for example to provide potable water for consumption or further use. In one embodiment, the water purification device has three stages of water purification.
[0021] A first stage of purification includes conditioning of untreated water to bring the
pH of the untreated water to about neutral pH. In one implementation, the untreated water is treated with a predetermined amount of a pH conditioning agent, hereinafter referred to as a pH adjuster. The pH adjuster, such as sodium bisulphate, adjusts the pH level of the untreated water to about neutral pH, for example, in a range of about pH 6.5 to about pH 7. Adjustment of the pH level of the untreated water makes the water suitable for drinking. Further, the pH adjustment facilitates in adsorption of fluoride ions in further stages of purification as adsorption media used in these stages become selective in adsorbing fluoride ions at about neutral pH level. The pH of the untreated water is thus adjusted at the first stage to receive pH conditioned water, interchangeably referred to as conditioned water.

[0022] The conditioned water is then at least partly defluoridated at a second stage of
purification. In one implementation, the second stage of purification includes treating the conditioned water with a primary adsorption media. The primary adsorption media selectively adsorbs a first portion of fluoride ions from the conditioned water. In one implementation, the primary adsorption media includes a fluoride adsorbing chemical composition, such as aluminum hydroxide capable of adsorbing fluoride ions from the conditioned water. The conditioned water is thus treated at the second stage to receive defluoridated water.
[0023] The defluoridated water is then purified at a third stage of purification. The third
stage of purification includes treating the defluoridated water using a secondary adsorption media. The secondary adsorption media adsorbs a second portion of fluoride ions from the defluoridated water. In one implementation, the secondary adsorption media includes a porous media, such as rice husk ash (RHA) treated with a fluoride removing chemical composition, such as ferric hydroxide, calcium phosphate, or aluminum hydroxide. Further, the secondary adsorption media may also reduce concentration of other ions, such as arsenic ions, both As+3 and As+5, from the defluoridated water. Purified water, thus received, exits through the outlet.
[0024] Although the terms primary and secondary have been used to identify the
adsorption media 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.
[0025] The water purification method and device, as described herein, keeps fluoride
concentrations in water below the prescribed safe limits throughout its rated life for wide ranges of input fluoride concentration, water pH level, and total dissolved solids (TDS) conditions. Water purification device based on the above described method of fluoride removal can be effectively employed as a household or community level purification device, does not require electricity, is cost effective, is easy to operate, and requires minimal maintenance.
[0026] 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 water purification can be implemented in any number of different water purification devices, the embodiments are described in the context of the following exemplary system(s).

[0027] 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 container 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 container 106 for receiving the purified water. In one implementation, the water purification device 104 may be connected to the source container 102 in a leak proof manner. Although the apparatus 100 has been described with reference to a single water purification device 104, it would be obvious to a person skilled in the art that a plurality of water purification devices, similar to the water purification device 104, may be connected to the apparatus for purifying water.
[0028] Untreated water from any source, such as ground water and other surface water
sources or any other source of drinking water may be poured in to the source container 102 through a water inlet 108. The untreated water from the source container 102 then enters the water purification device 104. In one embodiment, the water purification device 104 is connected to the source container 102 through a plug and play type connector 110 to receive the untreated water. The purified water from the water purification device 104 may then flow in and get collected in the collection container 106 through a water outlet 112. In an embodiment, the collection container 106 is provided with an outlet, such as a tap 114 from which the purified water may be drawn for consumption.
[0029] In one embodiment, the water purification device 104 of the apparatus 100
implements three stages of water purification. At a first stage, pH level of the untreated water is adjusted to provide pH conditioned water, hereinafter referred to as conditioned water. At a second stage and a third stage, the conditioned water is treated with different adsorption media to selectively adsorb fluoride ions from the conditioned water. In order to implement the three stages of water purification, the water purification device 104 includes a pH conditioner 116 to condition pH of the untreated water, a primary purification unit 118 to adsorb a portion of fluoride ions present in the conditioned water, and a secondary purification unit 120 to adsorb a remaining portion of the fluoride ions present in the conditioned 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.

[0030] In one implementation, the pH conditioner 116 includes a pH conditioning agent,
hereinafter referred to as the pH adjuster, to condition pH of the untreated water. In one implementation, the untreated water is treated with a predetermined amount of the pH adjuster for adjusting the pH level of the untreated water to about neutral pH, for example, in a range of about pH 6.5 to about pH 7. The predetermined amount of the pH adjuster may be varied by the pH conditioner 116 based on, for example, the flow rate of the untreated water. Adjustment of the pH level of the untreated water facilitates in adsorption of fluoride ions in later stages of purification as adsorption media used in these stages become selective to fluoride ions at about neutral pH level. Further, adjusting the pH level of the untreated water to neutral pH makes the purified water, received form the water purification device 104, suitable for drinking. The pH of the untreated water is thus adjusted by the pH conditioner 116 to receive the conditioned water.
[0031] The primary purification unit 118 includes a primary adsorption media (not
shown in this figure) for adsorbing a first portion of fluoride ions present in the conditioned water. In one embodiment, the primary adsorption media may be formed as a porous bed comprising a fluoride adsorbing chemical composition capable of adsorbing fluoride ions from the conditioned water. Examples of the fluoride adsorbing chemical composition include, but are not limited to, activated alumina, granular aluminum hydroxide, granular ferric hydroxide, tamarind seed powder, bone char, synthetic tricalcium phosphate, florex, activated carbon soaked with alum solution, magnesium hydroxide, calcium hydroxide, manganese sulfate, and any combination thereof. As the conditioned water passes through the primary purification unit 118, the first portion of fluoride ions present in the conditioned water is adsorbed by the primary adsorption media to provide defluoridated water.
[0032] The secondary purification unit 120 includes a secondary adsorption media (not
shown in this figure) to adsorb a second portion of the fluoride ions. The secondary adsorption media includes a porous media, such as RHA treated with a fluoride removing chemical composition, such as ferric hydroxide, calcium phosphate, and aluminum hydroxide. As the defluoridated water passes through the secondary purification unit 120, fluoride ions that were not adsorbed by the primary adsorption media are adsorbed by the secondary adsorption media to provide the purified water. Further, the secondary adsorption media may also reduce concentration of other ions, such as arsenic ions, both As+3 and As+5, from the defluoridated

water. The purified water, thus received, exits through the water outlet 112 and gets collected in the collection container 106.
[0033] In one embodiment, the secondary purification unit 120 may be placed above the
primary purification unit 118 to enable reverse flow of the defluoridated water as will be discussed later. Using the synergistic action of the two adsorption media along with the pH adjuster facilitates in providing a water purification device having high efficiency and capacity for adsorbing fluoride ions. The water purification device 104 thus demonstrates high efficiency in adsorption of fluoride ions and good performance in maintaining fluoride concentrations in water below the prescribed safe limits throughout its rated life irrespective of input fluoride concentration and water pH level.
[0034] Although the terms primary and secondary have been used to identify the
adsorption media 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.
[0035] 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.
[0036] Fig. 2(a) and 2(b) illustrate components of the connector 110, in accordance with
an embodiment of the present subject matter. The connector 110, as previously described, connects the water purification device 104 to the source container 102 for receiving the untreated water for purification. Fig. 2(a) illustrates the connector 110 in operation, i.e., when the connector 110 is transferring the untreated water from the source container 102 to the water purification device 104. Fig. 2(b) illustrates components of the connector 110 when the connector 110 is not in operation. In one implementation, the connector 110 includes a plug 202 and an adaptor 204. The adaptor 204 includes an adaptor inlet 206 connected to the source container 102 to receive the untreated water and an adaptor outlet 208 to deliver the untreated water to the plug 202. The plug 202 includes a plug inlet 210 to receive the untreated water from

the adaptor 204 and a plug outlet 212 connected to the water purification device 104 to provide the untreated water.
[0037] The connector 110, when in operation as shown in Fig. 2(a), receives the
untreated water through the adaptor inlet 206 as shown by an arrow 214 and delivers it to the water purification device 104 through the plug outlet 212 as shown by an arrow 216. The plug 202, in such a condition, is connected to the adaptor 204 in a leak proof manner through a suitable mechanism. When not in operation, as shown in Fig. 2(b), the plug 202 is detached from the adaptor 204 and flow of the untreated water entering into the adaptor 204 through the adaptor inlet 206 is stopped within the adaptor 204 by a suitable mechanism such as a non returnable valve. The connector 110 may thus be easily operated as a plug and play device resulting in an easy removal and attachment of the water purification device 104 to any source container, such as the source container 102 of the apparatus 100.
[0038] Fig. 3 illustrates components of the water purification device 104, according to
one embodiment of the present subject matter. The water purification device 104 includes a water inlet 302, the pH conditioner 116, the primary purification unit 118, the secondary purification unit 120, and the water outlet 112. In one implementation, the pH conditioner 116, the primary purification unit 118, and the secondary purification unit 120 are placed inside a vessel 304 to make the water purification device 104 compact and easy to install and uninstall. The water inlet 302 receives the untreated water from a source of water, as indicated by an arrow 306, and provides the untreated water to the pH conditioner 116 via the connector 110.
[0039] The pH conditioner 116 starts dosing the pH adjuster in the untreated water as
soon as the untreated water starts passing through it and stops the dosing when the untreated water stops flowing. In one implementation, the untreated water passes through the pH conditioner 116 at variable flow rates ranging from about 0.01 liters per hour to 15 liters per hour. As the untreated water starts passing through the pH conditioner 116, a predetermined amount of the pH adjuster is released into the untreated water to adjust the pH of the untreated water to about neutral pH in the range of about pH 6.5 to pH 7. In one implementation, the predetermined amount of the pH adjuster is in proportion to the flow rate of the untreated water. Adjusting the pH level of the untreated water not only makes the untreated water suitable for drinking but also facilitates in adsorption of fluoride ions. Adjusting the pH level makes the

primary and the secondary adsorption media selective for adsorbing the fluoride ion, thus increasing the capacity of the water purification device 104 as the adsorption media now mainly adsorb the fluoride ions. Further, the pH adjuster may be dosed in either liquid or solid form. In one implementation, the pH adjuster may be any acidic salt, such as sodium bisulfate, poly aluminum chloride, aluminum sulfate, ferric chloride, and ferric sulfate capable of lowering the pH of the untreated water to neutral pH in the range of about pH 6.5 to pH 7. The pH conditioned water exits the pH conditioner 116 through a pH conditioner outlet 308.
[0040] The pH conditioned water from the pH conditioner 116 enters a central tube 310
via the pH conditioner outlet 308. A first end of the central tube 310 is connected to the pH conditioner outlet 308 to receive the conditioned water, while a second end of the central tube 310 is connected to a bottom chamber 312 to provide the conditioned water for purification. In one implementation, the bottom chamber 312 is positioned just below the primary purification unit 118 such that the conditioned water received from the pH conditioner 116 initially collects in the bottom chamber 312 before entering the primary purification unit 118. Collecting the conditioned water in the bottom chamber 312, before entering the primary purification unit 118, ensures that the conditioned water always enters the primary purification unit 118 uniformly across the primary adsorption media 316 in order to ensure optimum contact of the conditioned water with the primary adsorption media 316 in the primary purification unit 118.
[0041] The conditioned water collected in the bottom chamber 312 subsequently enters
into the primary purification unit 118 through a first mesh 314 and passes through the primary adsorption media 316 in an upward direction. Providing such a flow of the conditioned water through the primary adsorption media 316 in a direction against the force of gravity helps in achieving better adsorption of the fluoride ions. Additionally, such a flow allows a longer and uniform period of contact between the conditioned water and a purification bed of the primary adsorption media 316. Further, such a reverse flow of the conditioned water also prevents formation of channels within the primary adsorption media 316 and consequently provides a more uniform purification throughout the life of the water purification device 104.
[0042] The primary adsorption media 316 may be any porous bed comprising the
fluoride adsorbing chemical composition capable of adsorbing fluoride ions from the conditioned water. In one implementation, the porous bed may be formed by granules of the fluoride

adsorbing chemical composition; coating of the fluoride adsorbing chemical composition on a suitable substrate, such as sand, RHA, activated carbon; or as a compact media formed by adding a suitable binder, such as sucrose, lactose, starch, cellulose, microcrystalline cellulose, hydroxypropyl cellulose, sorbitol, mannitol, gelatin, polyvinylpyrrolidone (PVP), and polyethylene glycol (PEG) to the fluoride adsorbing chemical composition.
[0043] In one embodiment, the primary adsorption media 316 is formed using aluminum
hydroxide granules. The aluminum hydroxide granules are prepared by mixing a 5 % to 25 % of poly aluminum chloride with 1 Molar (M) to 5 M sodium hydroxide solution to provide an aluminum hydroxide floc. The resulting aluminum hydroxide floc is subsequently separated by decantation and dried at a temperature in the range of about 50 °C to 100 °C. Dried aluminum hydroxide thus received is then heated to a temperature in the range of about 100 °C to 500 °C to make an aluminum hydroxide cake. The aluminum hydroxide cake is then sieved to get the aluminum hydroxide granules having size in the range of about 50 µm to 500 µm to form the primary adsorption media 316.
[0044] In an embodiment, the primary adsorption media 316 is formed by filling granules
of the fluoride adsorbing chemical composition between the first mesh 314 and a second mesh 318 disposed above and below the primary purification unit 118, respectively. The granules can be of any size in a range of about 50 micrometer (µm) to 500 µm. The first mesh 314 and the second mesh 318 may be of any suitable material, such as fabric, mesh, foam, cotton, canvas, felt, nylon, polypropylene, polyamide, and polyester with a pore size in the range of about 10 µm to 200 µm.
[0045] As the conditioned water enters through the first mesh 314 and passes through the
primary purification unit 118, the first portion of fluoride ions present in the conditioned water is adsorbed by the primary adsorption media 316 to provide the defluoridated water. In one implementation, the primary adsorption media 316 is configured to adsorb about 10% to 90 % of the fluoride ions present in the conditioned water. The defluoridated water from the primary purification unit 118 subsequently exits via the second mesh 318 and collects into a middle chamber 320 for further purification.

[0046] In one implementation, the middle chamber 320 is positioned just above the
primary purification unit 118 and just below the secondary purification unit 120 thus separating the primary purification unit 118 and the secondary purification unit 120. The defluoridated water received from the primary purification unit 118 initially collects in the middle chamber 320 before entering into the secondary purification unit 120. Collecting the defluoridated water in the middle chamber 320, before entering the secondary purification unit 120, ensures that the defluoridated water always enters the secondary purification unit 120 uniformly across the secondary adsorption media 324 in order to ensure optimum contact of defluoridated water with the secondary adsorption media 324 in the secondary purification unit 120.
[0047] The defluoridated water collected in the middle chamber 320 enters into the
secondary purification unit 120 via a third mesh 322 and subsequently passes through a secondary adsorption media 324 in an upward direction, i.e., in a direction opposite to the direction of force of gravity. Providing the defluoridated water in a direction against the force of gravity ensures that optimum contact is maintained between the defluoridated water and the secondary adsorption media 324. Further, such a reverse flow of the defluoridated water also prevents formation of channels within the secondary adsorption media 324 and consequently provides a more uniform purification throughout the life of the water purification device 104.
[0048] In one embodiment, the secondary adsorption media 324 is filled in the secondary
purification unit 120 as a porous bed of the fluoride removing chemical composition capable of adsorbing fluoride ions from the defluoridated water. In one implementation, the porous bed may be formed by granules of the fluoride removing chemical composition, coating of the fluoride removing chemical composition on a suitable substrate, such as sand, RHA, activated carbon; or as a compact media formed by adding a suitable binder, such as sucrose, lactose, starch, cellulose, microcrystalline cellulose, hydroxypropyl cellulose, sorbitol, mannitol, gelatin, polyvinylpyrrolidone (PVP), and polyethylene glycol (PEG) to the fluoride removing chemical composition. In another implementation, the secondary adsorption media 324 may be formed by coating the fluoride removing chemical composition on a porous media, such as RHA and heating the fluoride removing chemical composition coated porous media.
[0049] In one embodiment, heat treated aluminum hydroxide coated RHA is used as the
secondary adsorption media 324. The heat treated aluminum hydroxide coated RHA may be

formed by coating aluminum hydroxide on RHA and heating aluminum hydroxide coated RHA in a temperature range of about 50 °C to 200 °C for a period of about 30 minutes to 2 hours. In one implementation, aluminum hydroxide used for coating RHA can be formed by addition of any suitable base, such as potassium hydroxide, barium hydroxide, cesium hydroxide, sodium hydroxide, strontium hydroxide, calcium hydroxide, magnesium hydroxide, lithium hydroxide, rubidium hydroxide, sodium carbonate, ammonium chloride, and ammonium hydroxide to any suitable aluminum salt, such as poly-aluminum chloride, aluminum sulfate, potash alum, and aluminum chloride etc. The aluminum hydroxide coated RHA can then be obtained by adequately mixing RHA in an aluminum hydroxide floc prepared as describe above. Alternatively, the aluminum hydroxide coated RHA can be prepared by mixing the basic solution into an aqueous mixture of RHA and the aluminum salt.
[0050] In one implementation, the aluminum hydroxide coated RHA is prepared by
soaking RHA of size in the range of about 100 µm to 600 µm in a 0.2 M to 1 M aluminum sulfate solution followed by stirring to ensure adequate absorption of the aluminum sulfate solution into RHA. A 2 M to 8 M sodium hydroxide solution is subsequently added to above mixture till the resulting solution becomes neutral. The resulting mixture is then filtered into a liquid part and a solid part. The solid part is then dried in a temperature range of about 50 °C to 200 °C for a period of about 4 to 15 hours to obtain the secondary adsorption media 324.
[0051] In an embodiment, the secondary adsorption media 324 is formed by filling
aluminum hydroxide coated RHA inside the secondary purification unit 120, i.e., between the third mesh 322 and a fourth mesh 326 provided over the middle chamber 320. The third mesh 322 and the fourth mesh 326 may be of any suitable material, such as fabric, mesh, foam, cotton, canvas, felt, nylon, polypropylene, polyamide, and polyester with a pore size in the range of about 10 µm to 200 µm.
[0052] As the defluoridated water enters through the third mesh 322 and passes through
the secondary purification unit 120, the second portion of fluoride ions present in the defluoridated water is adsorbed by the secondary adsorption media 324 to provide the purified water. Further, other ions and suspended mater present in the defluoridated water may be additionally removed in the secondary purification unit 120. The purified water from the secondary purification unit 120 subsequently exits via the fourth mesh 326 and collects into a top

chamber 328. Purified water from the top chamber 328 exits via the water outlet 112 as indicated by an arrow 330 and can be either collected into a collection reservoir for consumption or directly consumed. The water purification device 104 can thus be used at point-of-use for providing potable water.
[0053] Using the synergistic action of the two adsorption media along with the pH
adjuster facilitates in providing a water purification device having high efficiency and capacity for adsorbing fluoride ions. The pH adjuster makes the two adsorption media selective to the fluoride ions ensuring that the adsorption media mainly adsorb fluoride ions, thus increasing the life and capacity of the adsorption media. Further, using the aluminum hydroxide as the primary adsorption media 316 and the RHA treated with a fluoride removing chemical composition as the secondary adsorption media 324 increases the capacity and efficiency of the water purification device 104. Additionally, increasing the capacity and efficiency of the water purification device 104 facilitates in making the water purification device 104 compact and less expansive as compared to the conventional water purification devices. The water purification device 104 thus demonstrates high efficiency in adsorption of fluoride ions and good performance in maintaining fluoride concentrations in water below the prescribed safe limits throughout its rated life.
[0054] Fig. 4 illustrates components of the pH conditioner 116, in accordance with an
embodiment of the present subject matter. As described previously, the pH conditioner 116 is configured to condition the untreated water by adjusting the pH level. In said embodiment, the pH conditioner 116 includes a chemical cartridge 402 containing the pH adjuster, a doser 404 to release a predetermined amount of the pH adjuster in the untreated water, a water level metering chamber 406 to control level of the untreated water inside the pH conditioner 116, and a mixing chamber 408 for mixing the pH adjuster with the untreated water.
[0055] In one embodiment, the chemical cartridge 402 includes the pH adjuster soaked in
a fibrous matrix 410, for example, made of felt fiber. The pH adjuster can be hygroscopic or non-hygroscopic in nature and include, but are not limited to, sodium bisulfate, poly aluminum chloride, aluminum sulfate, ferric chloride, and ferric sulfate. Further, the pH adjuster may be provided in the form of granules, powder, or paste. In one implementation, diameter of the felt fiber used for the fibrous matrix 410 is in the range of about 5 µm to 100 µm. The chemical

cartridge 402 holds the fibrous matrix 410 soaked in the pH adjuster and allows a controlled release of the pH adjuster through it.
[0056] In one implementation, the chemical cartridge 402 is kept inside a casing 412 to
make the pH conditioner 116 leak proof. The casing 412 includes a pH conditioner inlet 414 for receiving the untreated water from a source of water and the pH conditioner outlet 308 to provide the conditioned water to the primary purification unit 118. The casing 412 further includes a breathing orifice 416 to maintain equal pressure between the casing 412 and the water level metering chamber 406.
[0057] The doser 404 is attached to the chemical cartridge 402 such that it receives one
end of the fibrous matrix 410. The fibrous matrix 410 thus establishes a physical link between the doser 404 and the chemical cartridge 402 facilitating transfer of the pH adjuster to the doser 404 for being dosed in the untreated water. In one implementation, the doser 404 is in the shape of a circular cylinder and is provided with a slanted tip 418 having an elliptical cross section. The slant of the slanted tip 418 is made in such a way that the amount of the pH adjuster dosed in the untreated water varies in proportion to the flow rate of the untreated water into the pH conditioner 116. Varying the amount of the pH adjuster in proportion to the flow rate of the untreated water helps in ensuring that a controlled amount of the pH adjuster is dosed in the untreated water thus ensuring that pH of the untreated water is lowered only to a desired level.
[0058] In one implementation, the water level metering chamber 406 is provided such
that it houses the doser 404. The water level metering chamber 406 is configured to control the level of the untreated water flowing in the pH adjuster 116 in order to control the area of the slanted tip 418 dipped in the untreated water. For the purpose, the water level metering chamber 406 includes level metering orifices 420-1, 420-2, and 420-3, hereinafter collectively referred to as orifices 420. The orifices 420 are provided to drain out water from the water level metering chamber 406 into the mixing chamber 408 in order to maintain a level of the untreated water in the water level metering chamber 406. The orifices 420 thus also work as a water outlet for the water level metering chamber 406. The rise of water level in the water level metering chamber 406 is controlled in such a way that the area of the slanted tip 418 dipped in the untreated water is proportional to the flow rate of the untreated water. Controlling flow rate of the untreated water and the area of the slanted tip 418 dipped in the untreated water ensures proportional

increase in amount of the pH adjuster dosed in the untreated water. The untreated water drained by the orifices 420 is received by the mixing chamber 408. The mixing chamber 408 mixes the pH adjuster with the untreated water so as to achieve uniform pH level of the conditioned water received from the pH conditioner outlet 308 as shown by an arrow 422.
[0059] Thus, a constant concentration of the pH adjuster may be maintained in the
untreated water irrespective of the flow rate of the untreated water. Maintaining a constant concentration of the pH adjuster in the untreated water helps in ensuring that pH level of the untreated water is lowered to a desired level irrespective of the flow rate of the untreated water. Maintaining the pH level of the untreated water to a desired level in turn facilitates in ensuring that fluoride concentration in the purified water is maintained below the prescribed safe limits for improved life of the water purification device 104, irrespective of the pH level of the untreated water. Additionally, synergistic effect of using the pH adjuster, the primary adsorption media 316, and the secondary adsorption media 324 ensures that the water purification device 104 has high efficiency and capacity for adsorbing the fluoride ions.
[0060] Although, the pH conditioner 116 has been explained with reference to the above
embodiment, it would be understood that any dosing mechanism capable of providing controlled dosing of the pH adjuster may be used as the pH conditioner 116. For example, a siphon based mechanism, a flow/ pressure triggered mechanism, and the like may be used to dose the pH adjuster.
[0061] Table 1 illustrates effect of the pH level of the untreated water on performance of
adsorption media, such as the primary adsorption media 316. As can be observed, when the untreated water has a basic pH of 7.5-8.0, the capacity of the adsorption media is less. As the pH level of the untreated water is decreased to slightly acidic pH of about 6.5 the fluoride adsorption capacity of the adsorption media increases.

Table 1

pH value of untreated water Fluoride Adsorption Capacity of Aluminum hydroxide granules (mg/g)
7.7 3.0
6.5 5.2
Thus it can be seen from Table 1 that the pH conditioning of the untreated water increases the fluoride adsorption capacity of the adsorption media 316.
[0062] Fig. 5 illustrates a method 500 for adsorbing fluoride ions from untreated water,
in accordance with an implementation of the present subject matter. The order in which the method is described is not intended to be construed as a limitation, and any number of the described method blocks can be combined in any order to implement the method, or an alternate method. Additionally, individual blocks may be deleted from the method without departing from the spirit and scope of the subject matter described herein. Furthermore, the method is not restricted to the present water purification device 104 and can be implemented in any suitable water purification device.
[0063] At block 502, untreated water received from a source of water is conditioned to
adjust pH level of the untreated water. In one implementation, the untreated water may be received from any source of water, such as ground water and other surface water sources or any other source of drinking water. In one implementation, the untreated water is treated with a predetermined amount of a pH conditioning agent, such as sodium bisulphate. The pH conditioning agent adjusts the pH level of the untreated water to about neutral pH, for example, in a range of about pH 6.5 to about pH 7. Adjustment of the pH level of the untreated water facilitates in adsorption of fluoride ions in later stages of the method 500 as adsorption media used in these stages become selective in adsorbing fluoride ions at about neutral pH level. Further, the pH adjustment makes the water suitable for drinking. The pH of the untreated water is thus adjusted to receive pH conditioned water, also referred to as conditioned water.
[0064] At block 504, the conditioned water is then defluoridated using a primary
adsorption media, for example, the primary adsorption media 316. In one implementation, a first

portion of fluoride ions present in the conditioned water is adsorbed by the primary adsorption media 316. The primary adsorption media 316 includes a fluoride adsorbing chemical composition, such as aluminum hydroxide, capable of adsorbing the fluoride ions from the conditioned water. The conditioned water is thus treated at block 504 to receive defluoridated water.
[0065] At block 506, the defluoridated water is purified using a secondary adsorption
media, for example, the secondary adsorption media 324. The secondary adsorption media 324 adsorbs a second portion of the fluoride ions from the defluoridated water. In one implementation, the secondary adsorption media 324 includes a porous media, such as RHA treated with a fluoride removing chemical composition, such as ferric hydroxide, calcium phosphate, or aluminum hydroxide. Purified water, thus received, exits through the outlet.
[0066] Fig. 6 illustrates a graph 600 depicting performance of the water purification
device 104 when used for removal of fluoride ions from water, in accordance with an embodiment of the present subject matter. In the graph 600, a total amount of water, in liters, passed through the water purification device 104 is taken as a reference position and is represented along a horizontal axis 602, while concentration of fluoride ions, in parts per million (ppm), present in the water is represented on a vertical axis 604.
[0067] 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 using 500 liters of untreated water contaminated with about 10 ppm of fluoride ions. The performance was measured using known methods of measuring ionic concentration.
[0068] Curve 606 represents concentration of fluoride ions in the untreated water
provided to the water purification device 104 for defluoridation. Curve 608 depicts concentration of fluoride ions in the purified water received from the water purification device 104. The graph 600 shows that concentration of the fluoride ions in the purified water is about 0.02 ppm for almost whole amount of the untreated water provided for purification up to about 500 liters of water, which was the detection limit of the instrument used for measuring. As can be seen, the fluoride concentration is well below the permissible safe limit set by various health organizations. For example, the concentration of fluoride ions is well below the safe limit of 2

ppm, set forth by United States Environmental Protection Agency (USEPA); and 1.5 ppm set forth by similar standards in India and by the WHO.
[0069] 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.

I/We claim:
1. A water purification device (104) comprising:
a pH conditioner (116) comprising a pH conditioning agent to adjust pH level of untreated water to provide conditioned water;
a primary purification unit (118) comprising a primary adsorption media (316) to adsorb a first portion of fluoride ions present in the conditioned water received from the pH conditioner (116), to provide defluoridated water, wherein the primary adsorption media (316) comprises a fluoride adsorbing chemical composition; and
a secondary purification unit (120) comprising a secondary adsorption media (324) to adsorb a second portion of the fluoride ions present in the defluoridated water received from the primary purification unit (118), to provide purified water, wherein the secondary adsorption media (324) comprises a porous media coated with a fluoride removing chemical composition.
2. The water purification device (104) as claimed in claim 1, wherein the pH conditioning agent is at least one of a sodium bisulfate, poly aluminum chloride, aluminum sulfate, ferric chloride, and ferric sulfate.
3. The water purification device (104) as claimed in claim 1, wherein the pH conditioning agent conditions the untreated water to provide the conditioned water having a pH level in the range of about 6.5 to 7.
4. The water purification device (104) as claimed in claim 1, wherein the fluoride adsorbing chemical composition is selected from a group consisting of activated alumina, granular aluminum hydroxide, granular ferric hydroxide, tamarind seed powder, bone char, synthetic tricalcium phosphate, florex, activated carbon soaked with alum solution, magnesium hydroxide, calcium hydroxide, manganese sulfate, and any combination thereof.
5. The water purification device (104) as claimed in claim 1, wherein the primary adsorption media (316) comprises at least one of: granules of the fluoride adsorbing chemical composition, a substrate coated with the fluoride adsorbing chemical composition, and a compact media comprising a binder and the fluoride adsorbing chemical composition.

6. The water purification device (104) as claimed in claim 1, wherein the secondary adsorption media (324) comprises at least one of: granules of the fluoride removing chemical composition, a substrate coated with the fluoride removing chemical composition, and a compact media comprising a binder and the fluoride removing chemical composition.
7. The water purification device (104) as claimed in claim 5 or claim 6, wherein the substrate comprises at least one of sand, rice husk ash (RHA) and activated carbon.
8. The water purification device (104) as claimed in claim 5 or claim 6, wherein the binder is selected from a group consisting of sucrose, lactose, starch, cellulose, microcrystalline cellulose, hydroxypropyl cellulose, sorbitol, mannitol, gelatin, polyvinylpyrrolidone (PVP), and polyethylene glycol (PEG), and any combination thereof.
9. The water purification device (104) as claimed in claim 1, wherein the primary adsorption media (316) is formed using aluminum hydroxide granules, wherein size of the aluminum hydroxide granules is selected from the range of about 50 micrometer (µm) to 500 µm.
10. The water purification device (104) as claimed in claim 9, wherein the aluminum hydroxide granules are prepared using a 5 % to 25 % of poly aluminum chloride with 1 Molar (M) to 5 M sodium hydroxide solution followed by decantation and heat treatment at a temperature in the range of about 50 °C to 500 °C.
11. The water purification device (104) as claimed in claim 1, wherein the secondary adsorption media (324) is fabricated by heating aluminum hydroxide coated RHA in a temperature range of about 50 °C to 200 °C.
12. The water purification device (104) as claimed in claim 11, wherein aluminum hydroxide used for preparing the aluminum hydroxide coated RHA is obtained by adding a basic solution to an aluminum salt, wherein the base is selected from a group consisting of potassium hydroxide, barium hydroxide, cesium hydroxide, sodium hydroxide, strontium hydroxide, calcium hydroxide, magnesium hydroxide, lithium hydroxide, rubidium hydroxide, sodium carbonate, ammonium chloride, ammonium hydroxide, and any combination thereof.

13. The water purification device (104) as claimed in claim 12, wherein the aluminum salt is selected from a group consisting of poly-aluminum chloride, aluminum sulfate, potash alum, aluminum chloride, and any combination thereof.
14. The water purification device (104) as claimed in claim 1, wherein the pH conditioner (116) is configured to release a predetermined amount of the pH conditioning agent in the untreated water, and wherein the predetermined amount of the pH conditioning agent dosed in the untreated water is based in part on flow rate of the untreated water entering the pH conditioner (116).
15. The water purification device (104) as claimed in claim 14, wherein the pH conditioner (116) comprises a doser (404) provided with a slanting tip (418) to release the predetermined amount of the pH conditioning agent in the untreated water.
16. The water purification device (104) as claimed in claim 15, wherein the predetermined amount of the pH conditioning agent dosed in the untreated water is based at least in part on area of the slanting tip (418) in contact with the untreated water entering the pH conditioner (116) and length of the doser (404).
17. The water purification device (104) as claimed in claim 1 further comprising:
a bottom chamber (312) provided below the primary purification unit (118), wherein the bottom chamber (312) is configured to receive the conditioned water from the pH conditioner (116) and provide the conditioned water to the primary purification unit (118) in an upward direction to maintain a uniform flow of the conditioned water through the primary purification unit (118); and
a central tube (310) for transferring the conditioned water from the pH conditioner (116) to the bottom chamber (312), wherein the central tube (310) includes a first end connected to the pH conditioner (116) to receive the conditioned water and a second end connected to the bottom chamber (312) to provide the conditioned water.
18. The water purification device (104) as claimed in claim 1 further comprising:
a middle chamber (320) provided below the secondary purification unit (120), wherein the middle chamber (320) is configured to receive the defluoridated water from

the primary purification unit (118) and provide the defluoridated water to the secondary purification unit (120) in an upward direction to maintain a uniform flow of the defluoridated water through the secondary purification unit (120); and
a top chamber (328) provided above the secondary purification unit (120) to receive purified water from the secondary purification unit (120).
19. A method for purification of water for consumption comprising:
adjusting pH level of the water to provide conditioned water;
adsorbing a first portion of fluoride ions present in the conditioned water using a primary adsorption media (316) to provide defluoridated water; and
adsorbing a second portion of the fluoride ions present in the defluoridated water using a secondary adsorption media (324) to provide purified water.
20. The method as claimed in claim 19, wherein the primary adsorption media (316) is formed using aluminum hydroxide granules.
21. The method as claimed in claim 19, wherein the secondary adsorption media (324) is fabricated by heating an aluminum hydroxide coated RHA in a temperature range of about 50 °C to 200 °C.