WO2012042531A1

WO2012042531A1 - Device for purification of water

Info

Publication number: WO2012042531A1
Application number: PCT/IN2011/000581
Authority: WO
Inventors: Dilshad Ahmad; Vivek Ganvir
Original assignee: Tata Consultancy Services Limited
Priority date: 2010-09-27
Filing date: 2011-08-26
Publication date: 2012-04-05

Abstract

Devices and methods for purification of water are described herein. The device (100) for purification of water includes a doser (305) to provide a chemical substance to the water for formation of flocs, wherein the flocs include a portion of ions removed from the water. The device (100) further includes an adsorption media (510) in fluid communication with the doser (305), wherein the adsorption media (510) facilitates rising up of the water and selectively adsorbs a substantial portion of remaining ions from the water during the rising.

Description

TECHNICAL FIELD

[0001] The present subject matter relates, in general, to a device for purification of water and, in particular, to a device for selective removal of ions from water.

BACKGROUND

[0002] Water available from natural sources, such as groundwater sources, or surface water sources, has impurities and is not safe to drink. The impurities may include chemical impurities, such -as fluoride and arsenic, and biological impurities, such as Escherichia coli, and can 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 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 (WHO) 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 depending on 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 a device for 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. 1

[ΘΘ06] Devices and methods for purification of water are described herein. In an embodiment, the device for purification of water includes a doser to provide a chemical substance to the water for formation of floes. The floes include a portion of ions removed from the water. The device further includes an adsorption media in fluid communication with the doser. The adsorption media facilitates rising up of the water and selectively adsorbs a substantial portion of remaining ions from the water during the rising. The adsorbed ions include fluorine ions. The removal of ions with the floes and subsequent adsorption of the remaining ions by the adsorption media provide water, which is substantially free frcm contaminants, such as, fluorine ions.

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 exemplary device for purification of water, according to an embodiment of the present subject matter.

[0009] Fig. 2 illustrates an exploded view of the device, according to an embodiment of the present subject matter.

[0010] Fig. 3 illustrates an exemplary purifier unit of the device, in accordance with an embodiment of the present subject matter.

[0011] Fig. 4 shows an exploded view of an exemplary doser of the device, in accordance with an embodiment of the present subject matter.

[0012] Fig. 5 illustrates an exploded view of a sump and an adsorption column, in accordance with an embodiment of the present subject matter.

[0013] Fig. 6 illustrates a scatter plot showing performance of an exemplary device for purification of water when used for removal of fluorine ions from water, in accordance with an embodiment of the present subject matter.

DETAILED DESCRIPTION

[0014] Devices and methods for purification of water are described herein. The devices and methods facilitate removal of ions, for example, fluoride, from water. [0015] Fluorine ions (F^~) occur in both surface water, having concentrations ranging from 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. It is well known that excessive exposure to fluoride can lead to a number of adverse effects, such as dental fluorosis and skeletal fluorosis. Various health organizations have prescribed safe limits for fluoride concentration in drinking water. For example, World Health Organization (WHO) prescribes a value of 1.5 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, directly consumes contaminated water. 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 put them beyond the reach of many households.

[0017] Conventionally, techniques such as reverse osmosis and membrane technology are implemented to reduce fluoride concentration in water. However, both the techniques require electrical energy input, which may either be unavailable or be in short supply in rural areas of developing or underdeveloped countries. Furthermore, systems implementing such techniques are usually costly and, thus, beyond the 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 require skilled installation of fittings and careful adjustment of flow rates. Furthermore, such systems have limited durability and the fluorine ions break through after saturation of the bed. This defluoridation method is unreliable and unsafe to be used in households. [0019] Another conventional defluoridation technique, which uses alum and lime, releases fluorine ions back to purified water. Further, in such a technique, aluminium and sulphate concentrations are relatively high in the purified water and disposal of waste containing fluorine ions poses environmental considerations. Additionally, mechanisms based on adsorption of fluoride using activated alumina, are often difficult to maintain. Such mechanisms often produce wastes containing fluorine ions.

[0020] The present subject matter describes a device for purification of water.

The device selectively removes fluorine ions from water, for example, water for consumption or further use. In an embodiment, the device includes at least one purifier unit. The purifier unit includes three sections, namely, a doser, a sump, and an adsorption column. The doser adds a predetermined amount of a chemical substance to the water passing through the purifier unit. The added chemical substance reduces fluoride concentration in the water and adjusts the pH level of the water to about neutral pH, for example, in a range of -s&out pH 6.5 to about pH 7.5. The adjusted pH value of the water makes the adsorption column selective to fluorine ions.

[0021] The water from the doser passes into the sump. The water reaching the sump has a pH value adjusted to about neutral pH. In an embodiment, the chemical substance is a flocculent, such as aluminium sulphate, which is capable of forming a complex compound with fluorides in the water. The complex compound settles down as agglomerates, also referred to as floes, thereby, settling the fluorine ions along with the floe. Thereafter, the floes can be removed on a regular basis. The sump provides space for settling of sediments and floes formed in the water due to the addition of chemical substance by the doser. The settling of floes in the sump reduces the concentration of fluorine ions to about 30% to 50% of the concentration in contaminated water.

[0022] The water from the sump passes into the adsorption column for further purification. A bottom section of the adsorption column is made perforated to delay choking of the adsorption column due to the floes in the sump. The adsorption column selectively adsorbs a substantial portion of remaining fluorine ions from the water, which further reduces fluoride, and other ions, from the water collected in the sump. For example, the adsorption column, may also reduce the concentration of arsenic, both As⁺³ and As ⁺⁵.

[0023] The device, as described herein, keeps fluoride concentrations in water below the prescribed safe limits throughout its rated life, within wide ranges of input fluoride concentration and water pH level, and total dissolved solids (TDS) conditions. The device 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.

[0024] These, and other, features of the present subject matter are explained hereinafter with reference to embodiments illustrated in the drawings. It would be appreciated that no limitation of the scope of the subject matter is thereby intended and it would be understood by those skilled in the art that the foregoing description is exemplary and explanatory of the specific embodiments and are not intended to be restrictive thereof.

[0025] Fig. 1 illustrates an exemplary device 100 for purification of water, according to an embodiment of the present subject matter. The device 100 includes a source container 105 and a collection container 1 10. A pre- filter (not shown in the figure) may be provided to remove turbidity and suspended particles from the water. The water may be available from any source, such as ground water and other surface water sources, and therefore may have chemical and microbial contaminants. In an embodiment, the pre-filter is disposed before the source container 105. The source container 105 contains water received from the pre-filter, i.e., filtered water, and is covered with a cover 1 15. The collection container 1 10 collects purified water, which may be used for consumption, or further use.

[0026] The source container 105 can be of any suitable capacity, volumetric or any other measure, depending upon the need, say with a capacity to hold 10 litres of water. Similarly, the collection container 1 10 can be of any suitable capacity, say 10 litres. In an embodiment, the source container 105 and the collection container 1 10 may be of different capacity. Filtered water may be supplied to the source container 105 either in batches of a suitable quantity, say 5 litres, at regular intervals, say every 5 hours, or in a continuous manner with the influx rate adjusted, depending upon purification needs. [0027] The device 100 further includes a spacer 120 disposed in between the source container 105 and the collection container 1 10. The collection container 1 10 is provided with a tap 125 and rests on one or more sumps 130-1, 130-2, 130-N, collectively referred to as sumps 130, of one or more purifier units 135-1, 135-2, 135-N, collectively referred to as purifier units 135. The collection container 110 is made in a shape to accommodate the purifier units 135. In an embodiment, the device 100 includes four sumps 130 and four purifier units 135, which together form four pillar-like sections of the device" 100. However, it will be understood that the purification device 100 can include any number of sumps and purifier units. The spacer 120 includes one or more openings (not shown in the figure) to hold the purifier units 135 in position and helps keep the device 100 stable.

[0028] In operation, the filtered water from the source container 105 passes at a suitable flow rate, say 5 litres per hour, into the purifier units 135 for purification. The flow rate may be adjusted using any known flow regulating mechanism, such as a valve or a nozzle. The purifier units 135 include means to provide a chemical substance into the filtered water to form a complex chemical compound with the fluorine ions present in the filtered water. The means can include any chemical delivery system, for example, a doser, that can provide the chemical substance at a predetermined rate. The chemical substance is also capable of forming agglomerates, i.e., floes, which are insoluble in water. The floes form a complex chemical compound with the fluorine ions, which settle down along with the floes: The sumps 130 also facilitate settling of other impurities, such as sediments and suspended particles, which can be removed at regular intervals. The device 100 also includes a pre-filter lid 140, which encloses the pre- filter.

[0029] The source container 105, the collection container 110, the cover 1 15, the spacer 120, the tap 125, the sumps 130, the purifier units 135 and the pre-filter lid 140 can be made of a material including, but not limited to, polyethylene, polypropylene, acrylonitrile butadiene styrene, polycarbonate, polyethylene terephthalate, low density polyethylene, high density polyethylene, polystyrene, polyvinyl chloride, polytetrafluoroethylene, nylon, polyester, acrylic, polyolefin, polyurethane, polyamide, polycarboxyamide, phenolic and polylactic acids, rubber and any combination thereof. [0030] The device 100 is further described in detail with respect to fig. 2 to fig.

5.

[0031] Fig. 2 illustrates an exploded view of the device 100, according to an embodiment of the present subject matter. As described above, contaminated water from a source maybe supplied to the device 100. In an embodiment, the contaminated water is poured into the device 100 through a pre-filter 205, which fits into an opening 210 provided in the cover 115. The pre-filter 205 substantially removes turbidity and suspended particles from the contaminated water. The pre-filter 205 can be enclosed by the pre-filter lid 140.

[0032] The pre-filter 205 may be made of a material, such as cotton, canvas, felt, nylon, polypropylene, polyamide polyester, polyvinyl alcohol, and any combination thereof. The material may be formed in a woven or a non-woven manner. Non-woven material is produced using any known process, such as spun bound, melt blown, and needle punched process.

[0033] The contaminated water, which passes through the pre-filter 205, collects in the source container 105. Filtered water emerges from the source container 105 through one or more openings, collectively referred to as openings 215, with at least one opening 215 provided in each semi-cylindrical vertical recess. The openings 215 are located near the bottom of the source container 105, as shown in the Fig. 2. In an embodiment, the openings 215 are four in number, one in each semi-cylindrical vertical recess. The openings 215 align with and fit into corresponding inlets (shown in Fig. 3) provided in the purifier units 135. Thus, the filtered water flows from the source container 105 through the openings 215 and enters directly into the purifier units 135 through the inlets.

[0034] In an embodiment, each of the purifier units 135 works independently.

The purifier units 135 adjust pH level of the filtered water and reduce the fluoride concentration in the filtered water before discharging purified water into the collection container 110. The purifier units 135, as will be explained in detail with reference to description of figure 3, substantially remove the fluoride content from the filtered water. In addition, the purifier units 135 also reduce concentration of other ions, such as arsenic, both As⁺³ and As⁺⁵, from the filtered water. [003S] Further, to hold the purifier units 135 in place, the spacer 120 includes one or more adaptors, collectively referred to as adaptors 220. Each of the adaptors 220 holds one of the purifier units 135, thereby preventing any unwanted movement of the purifier units 135. In an embodiment, the spacer 120 includes four adaptors 220. The purified water, i.e., water obtained after substantial removal of impurities such as fluorine ions and turbidity, can be withdrawn from the collection container 1 10 for consumption or further use through the tap 125.

[0036] Fig. 3 illustrates an exemplary purifier unit, such as the purifier unit

135-1, in accordance with an embodiment of the present subject matter. The purifier unit 135-1 includes a doser 305, the sump 130-1, and an adsorption column 310. Filtered water from the source container 105 enters into the purifier unit 135-1 through an inlet 315. The filtered water then passes into the doser 305, in which the chemical substance is dissolved in the filtered water in a predetermined amount, for example, in a range of 50 ppm to 500 ppm, to the filtered water. The water after treatment with the chemical substance is referred to as treated water hereinafter. The doser 305 may include any chemical delivery system, such as a chemical candle, which can dissolve the chemical substance in the predetermined amount.

[0037] The chemical substance can be an aluminium salt, for example, aluminium acetate, aluminium chloride, aluminium hydroxide, aluminium sulphate, aluminium nitrate, and aluminium- carbonate, or an iron salt, for example, ferric bromide, ferrous carbonate, ferrous chloride, ferrous hydroxide, ferrous sulphate, ferrous oxalate, ferric sulphate, and ferric chloride. In an embodiment, the chemical substance is mixed with an additive, such as calcium hydroxide, calcium oxalate, calcium phosphate, calcium sulphate, D-galactose, magnesium carbonate, magnesium hydroxide, magnesium phosphate, and magnesium oxalate, to lower a dissolution rate of the chemical substance in the water. The chemical substance adjusts the pH of the water to about neutral pH, i.e., near a pH value of 7, for example, between 6.5 and 7.5.

[0038] The treated water from the doser 305 flows down to the sump 130-1 through a tube (not shown in the figure) centrally located in the adsorption column 310. The chemical substance forms hydroxides in the water. The hydroxides form floes in the sump 130-1. The hydroxide forms a complex chemical compound with the fluorine ions, which settles along with the floes in the sump 130-1. The floes remove about 30% to 50% of the fluorine ions from the treated water. Further, the sump 130-1 is made such that it collects the floes for its rated life and needs to be cleaned only after the rated life is over, thereby, eliminating the need for regular cleaning.

[0039] The treated water rises up, because of head difference, the adsorption column 310, in which remaining fluoride, and other ₅ ions get adsorbed. The adsorption column 310 contains an adsorption media (not shown in this figure), such as activated alumina, bone char, aluminium hydroxide coated rice husk ash, ferric hydroxide coated rice husk ash, and any combination thereof. The adsorption media becomes selective to fluorine ions around neutral pH levels, for example, in the range of pH 6.5 and 7.5. Purified water emerges from the purifiei unit 135-1 through an outlet 320 proximate to an adsorption column top 325. In an embodiment, the adsorption column top 325 receives the treated water from the doser 305 and passes it to the sump 130-1 through the centrally located tube.

[0040] The sumps 130, and thereby the purifier units 135, are held in place with the help of a tongue 330 and a groove 335 provided in each of the sumps 130. such as the sump 130-1. The tongue 330 and the groove 335 of the sump 130-1 fit into a groove and a tongue, respectively, of adjacent sumps, i.e., the sumps 130-2 and 130-N. Although the description of Fig. 3 is with reference to the purifier unit 135-1 , it will be understood that it can be extended to other purifier units, for example, the purifier unit 135-2,.., 135-N, as well.

[0041] Fig. 4 shows an exploded view of the doser 305, in accordance with an embodiment of the present subject matter. Pre-treated water from the source container 105 enters into the doser 305 through the inlet 315 comprising an inlet tube 405, which is connected to a base 410, and a nozzle 415. The pre-treated water collects in a metering container 420. The nozzle 415 meters the flow rate through the inlet tube 405. A chemical candle 425 rests on the base 410 and is held in position by an indicator 430 located within an indicator guide 435. The indicator 430 keeps pressing against chemical candle 425, thereby keeping it under constant compression. The indicator guide 435 is provided with grooves (not shown in the figure) on its inner surface, which guide the indicator 430 within it.

[0042] When water level in the metering container 420 is near a threshold level, for example, within 90% to 100% of the maximum water level in the metering container 420, the pre-treated water touches the chemical candle 425 at its bottom end. While the chemical candle 425 touches the pre-treated water, a predetermined amount, for example, in a range of 50 ppm to 500 ppm, of a chemical substance present in the chemical candle 425 dissolves in the pre-treated water contained in the metering container 420, thereby providing treated water. The dissolution of the chemical substance from the chemical candle 425 reduces a height of the chemical candle 425.

[0043] As the chemical candle 425 dissolves in the treated water contained in the metering container 420, the indicator 430 slides downwards within the indicator guide 435 due to its own weight. The indicator 430 is made visible from outside, for example, by making the indicator guide 435 transparent, or translucent. Thus, a visual indication of a portion of a rated life of the chemical candle 425 is available to the user. Further, the amount of the chemical substance dissolved is related to the amount of the treated water passed through the metering container 420, thus making the metering container 420 act as a flow totalizer of the amount of the treated water passed through the doser 305, and thereby, the purifier unit 135-1.

[0044] In an implementation, the chemical candle 425 is made in such a way that the amount of water required to dissolve the entire chemical candle 425 is nearly equal to the adsorption capacity of the adsorption column 310. By the time the chemical candle 425 dissolves completely, i.e., upon expiration of the rated life of the chemical candle 425, the indicator 430 slides down the length of the indicator guide 435 and sits on the base 410, thus shutting water flow through the purifier unit 135-1. It would be appreciated that any other means, for example, a chemical ball, a chemical powder, a chemical solution, etc., of delivering the chemical substance in the predetermined amount is also within the scope of the present subject matter.

[0045] The chemical candle 425 can be made of a defluoridating agent, such as aluminium acetate, aluminium chloride, aluminium hydroxide, aluminium sulphate, aluminium nitrate, aluminium carbonate, ferric bromide, ferrous carbonate, ferrous chloride, ferrous hydroxide, ferrous sulphate, ferrous oxalate, ferric sulphate, ferric chloride and any combination thereof. In an embodiment, the chemical candle 425 is composed of a defluoridating agent, such as aluminium sulphate, mixed with an additive, such as calcium sulphate. The additive may be any other chemical substance that lowers the dissolution rate of the defluoridating agent in water, such as calcium hydroxide, calcium oxalate, calcium phosphate, D-galactose, magnesium carbonate, magnesium hydroxide, magnesium phosphate, magnesium oxalate or any combination thereof.

[0046] Aluminium sulphate, being acidic in nature, adjusts the pH of water, for example, between pH levels of 8 and 9.5, to near neutral pH, for example, between pH levels of 6.5 and 7.5, and forms aluminium hydroxide. Aluminium hydroxide is a flocculent and forms floes, which settle in the sumps 130 at the bottom of the purifier units 135. The fluorine ions in the treated water form a complex compound with the aluminium hydroxide floes and settle along with the floes in the sumps 130. The settling of the fluorine ions removes about 30% to 50% of the fluorine ions from the treated water.

[0047] At the neutral pH levels, for example, between pH levels of 6.5 and 7.5, the adsorption column 310 becomes selective to fluorine ions. Hence, the functioning of the adsorption column 310 is net affected by the presence of other ions, such as sulphate, nitrate, chloride, carbonates, and bicarbonates, which are usually present in high concentrations in water, for example; drinking water, available from ground and surface water sources.

[0048] In one embodiment, the inlet tube 405, the base 410, the nozzle 415, the metering container 420, the chemical candle 425, the indicator 430, and the indicator guide 435 are enclosed within a doser cap 440. Inside the metering container 420, a siphon tube 445 is placed in such a way that an inner end of the siphon tube 445 opens inside the metering container 420, while an outer end of the siphon tube 445 opens outside the metering container 420. The outei end of the siphon tube 445 is, however, still inside the doser cap 440 and opens above the adsorption column top 325. The siphon tube 445 allows pre-treated water, i.e., the water coming from the source container 105, to collect inside the metering container 420 up to the threshold level. During collection of the pre-treated water inside the metering container 420, the chemical substance dissolves in the pre-treated water, thereby giving treated water.

[0049] Once the threshold level is reached, the treated water starts escaping through the outer end of the siphon tube 445 and passes into the adsorption column top 325, either directly or through a channel (not shown in the figure). The efflux of the water, i.e., the treated water, from the siphon tube 445 continues until the water level inside the metering container 420 reaches the level of the inner end of the siphon tube 445,^' after which pre-treated water starts to collect in the metering container 420 again. This process of falling and rising of the water level within the metering container 420 repeats continuously and, thereby, regulates water flow through the metering container 420.

[0050] The inlet tube 405, the base 410, the metering container 420, the indicator 430, the indicator guide 435, the doser cap 440, and the siphon tube 445 may be made of one, or a combination of two or more, of polyethylene, polypropylene, acrylonitrile butadiene styrene, polycarbonate, polyethylene terephthalate, low density polyethylene, high density polyethylene, polystyrene, polyvinyl chloride, polytetrafluoroethylene, nylon, polyester, acrylic, polyolefin, polyurethane, polyamide, polycarboxyamide, phenolic and polylactic acids or rubber.

[0051] Fig. 5 shows an exploded view of the sump 130-1 and the adsorption column 310, according to an embodiment of the present subject matter. The adsorption column 310 includes an adsorption cartridge 505 filled with an adsorption media 510, such as, activated alumina, bone c a-, aluminium hydroxide coated rice husk ash, ferric hydroxide coated rice husk ash, and aiv</ combination thereof. The adsorption cartridge 505 facilitates selective adsorption of ions from water. The adsorption cartridge 505 has a cover (not shown in the figure), which can be made in a cylindrical shape. In an embodiment, the adsorption media 510 may be aluminium hydroxide coated rice husk ash. The adsorption cartridge 505 is provided with a central tube 515 for carrying treated water received from the siphon tube 445 to the sump 130- 1.

[0052] In the adjusted pH range, the adsorption media 510 becomes selective to fluorine ions. While passing through the adsorption cartridge 505, the fluoride and other ions remaining in the treated water get adsorbed in the adsorption media 510 and the water coming from the outlet 320, i.e., purified water, is substantially free from fluorine ions. For example, the adsorption media 510 also adsorbs arsenic, such as As⁺³ and As⁺⁵ ions, from the floc-free water. ·

[0053] The adsorption media 510 comprising aluminium hydroxide coated rice husk ash may be made using any known method. In one method, rice husk is cleaned and sieved to a size in a range of about 425 microns to 800 microns. The rice husk ash is then coated with aluminium hydroxide. In one implementation, the aluminium hydroxide coated rice husk ash is dried at a temperature in a range of about 80 °C to 120 °C for a period of about 5 to 8 hours. Other adsorbent media may be prepared using known methods.

[0054J The adsorption cartridge 505 is provided with a top lip 520 proximate its top end and a bottom lip 525 proximate its bottom end. A bottom section 530 of the adsorption cartridge 505 is made perforated for ingress of water in the adsorption cartridge 505 and to delay the choking of the adsorption cartridge 505 due to the floes. The bottom section 530 is inserted inside the sump 130-1, through an opening 535 up to the bottom lip 525. The bottom section 530 is tightened in place with the help of a casing 540 in order to make the opening 535 leak proof. A cap 545 is tightened onto the casing 540 and pressed onto the top lip 520 to make a leak proof joint between the casing 540, the adsorption cartridge 505 and the cap 545. A top portion 550 of the cap 545 is made, for example, cup-shaped and connects to the central tube 515 in a leak proof manner.

[0055] In operation, the treated water comes from the metering container 420 into the top portion 550 of the cap 545 through the siphon tube 445. The treated water passes from the top portion 550 into the bottom sump 130-1 through the central tube 515. The sump 130-1 provides sufficient .pace and time for the formation of aluminium hydroxide floes and settling of the aluminium hydroxide floes. The aluminium hydroxide floes form a complex chemical compound with the fluorine ions in the treated water. The fluorine ions settle along with the aluminium hydroxide floes in the sump 130-1.

[0056] The treated water from the sump 130-1 enters the adsorption cartridge

505 through its bottom section 530, rises up the adsorption media 510 and emerges through the outlet 320 provided in the cap 545. The adsorption media facilitates adsorption of remaining fluoride resulting into further reduction of fluoride from the treated water. It would be understood that the treated water rises up due to head difference in the adsorption media 510 from a region of a high concentration of fluoride in the sump 130-1 to a region of its low concentration near the outlet 320.

[0057] The cover of the adsorption cartridge 505, the central tube 515, the top lip 520, the bottom lip 525, the casing 540, and the cap 545 may be made of one, or a combination of two or more, of polyethylene, polypropylene, acrylonitrile butadiene styrene, polycarbonate, polyethylene terephthalate, low density polyethylene, high density polyethylene, polystyrene, polyvinyl chloride, polytetrafluoroethylene, nylon, polyester, acrylic, polyolefin, polyurethane, polyamide, polycarboxyamide, phenolic and polylactic acids, rubber, and any combination thereof.

[0058] The performance of the exemplary device of the present subject matter, described with reference to figures 1 through 5, is described below with the help of a few examples.

[0059] Fig. 6 illustrates a scatter plot 600 showing performance of an exemplary device, such as the device 100, wheri used for removal of fluorine ions from water, in accordance with an embodiment of the present subject matter. The device included only one purifier unit, such as the purifier unit 135-1, and was supplied with 600 litres of water contaminated with 10 ppm of fluorine ions. The performance was measured using known methods of measuring ionic concentration. ^β

[0060] In the scatter plot 600, an axis 605 designates a total amount of water, in litres, purified using the device. An axis 610 depicts a concentration of fluorine ions in the water in ppm. Circular points, marked as 615, illustrate a concentration of fluorine ions in the contaminated water. Triangular points marked 620 depict a concentration of fluorine ions in the purified water. As seen in Fig. 6, the fluoride content in the purified water is less than 0.02 ppm for consumption of up to about 500 litres of water, which was the detection limit of the instrument used for measuring. The fluoride concentration was well below the permissible limit of 2 ppm set forth by the United States Environmental Protection Agency (USEP A).

[0061] The concentration was also within the permissible limit set forth by similar standards in India and by the WHO, which is 1.5 ppm. Hence, it can be concluded that a single purifier unit, such as the purifier unit 135-1 , is capable of substantially reducing fluoride ion concentration in water, for example, from a concentration of 10 ppm in 600 litres of water to about 0.5 ppm, as shown in the scatter plot 600. Accordingly, a set of purifier units, such as the set of four purifier units 135, is capable of removing the same concentration of fluoride from approximately 2400 litres of water.

[0062] In another example, the performance of the exemplary device was also tested for removal of arsenic from water. Water was mixed with 250 parts-per-billion (ppb) of arsenic and then purified using the device 100 comprising only one purifier unit, such as the purifier unit 135-1. The purified water was analyzed for concentration of arsenic ions using known methods of measuring ionic concentration. The arsenic ion concentration in the purified water was found to be below 50 ppb, which was the detection limit of the method. Thus, it can be concluded that, in addition to removing fluorine ions from water, a single purifier unit, such as the purifier unit 135-1 , is also capable of removing arsenic, both As⁺³ and As⁺⁵ from water.

[0063] In another example, the performance of the exemplary device was also tested for the removal of bacteria from water. Water was spiked with 4.7 ^χ 10⁶ colony forming unit per millilitre (CFU/ml) of Escherichia coli (E. Coli; ATCC 1 1229) and then purified using the exemplary device having only one purifier unit, such as the purifier unit 135-1. The purified water was analyzed for the presence of E. coli. The output E. coli count was enumerated to be about zero CFU/ml. The exemplary device had reduced the E. coli count by 6 + log (4.7) on the logarithmic scale, i.e., by 99.9999 %. Thus, it can be concluded that, in addition to reducing fluoride and arsenic concentration in water, a single purifier unit, such as the purifier unit 135-1 , of the exemplary device is also capable of substantially removing E. Coli content present in water.

[0064] The device, as described herein, keeps fluoride concentrations in water below the safe limits throughout its rated life and within wide ranges of input fluoride concentration, water pH level and total dissolved solids (TDS) conditions. The device 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. Hence, the device is affordable for households with low income level, such as rural households in developing and underdeveloped countries. Besides, the device is also capable of reducing concentration of arsenic, both As⁺³ and As⁺⁵, and bacteria, such as E. Coli.

[0065] Although embodiments for a device have been described in language specific to structural features and methods, it is to be understood that the invention is not necessarily limited to the specific features or methods described. Rather, the specific features and methods are disclosed as exemplary implementations for the device.

Claims

I/We Claim:

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

a doser (305) to provide a chemical substance to the water for formation of floes, wherein the floes include a portion of ions removed from the water; and

an adsorption media (510) in fluid communication with the doser (305), wherein the adsorption media (510) facilitates rising up of the water and selectively adsorbs a substantial portion of remaining ions from the water during the rising.

2. The device (100) as claimed in claim 1, wherein the device (100) further comprises a sump (130), disposed in a fluid communication path between the doser (305) and the adsorption media (510), to allow the floes to settle.

3. The device (100) as claimed in claim 1, wherein the doser (305) comprises a chemical candle (425) to provide the chemical substance.

4. The device (100) as claimed in claim 3, wherein the doser (305) further provides a visual indication of a remaining portion of a rated life of the chemical candle (425).

5. The device (100) as claimed in claim 3, wherein the doser (305) further stops flow of the water passing through the device (100) after expiration of a rated lite of the chemical candle (425).

6. The device (100) as claimed in claim 1, wherein the doser (305) further provides an additive to the water, wherein the additive lowers a dissolution rate of the chemical substance in the water.

7. The device (100) as claimed «:v claim i,¹ wherein the adsorption media (510) comprises aluminum hydroxide coated rice husk ash.

8. The device (100) as claimed in claim 1, wherein the chemical substance adjusts pH of the water to about 6.5 to 7.5.

9. The device (100) as claimed in claim 1 , wherein the floes include at least one of fluorine ions and arsenic ions.

10. The device (100) as claimed in claim 1, wherein the chemical substance removes microbial contaminants from the water.

11. The device (100) as claimed in claim 1, wherein the device (100) further comprises at least one pre-filter (205) to remove turbidit and suspended particles from the water, and wherein contaminated water passes through the pre-filter (205) to the doser (305).

12. A method for purification of water, the method comprising:

providing a chemical substance to the water in a predetermined amount to form agglomerates, wherein the agglomerates include a portion of ions in the water;

separating the agglomerates from the water; and

adsorbing selectively a substantial portion of remaining ions from the water to provide purified water.

13. The method of purification of water as claimed in claim 1 1, wherein the separating further comprises collecting the water having the chemical substance in a sump (130) such that the agglomerates settle down in the sump (130).

14. The method of purification of water as claimed in claim 1 1, wherein the providing the chemical substance further comprises providing an additive to control a dissolution rate of the chemical substance in the water.