|Title of Invention||
WATER PURIFICATION COMPOSITION
|Abstract||The invention relates to a water purification composition. The invention particularly relates to a water purification composition that is especially useful for removal of trace quantities of harmful contaminant like Arsenic in addition to removal of microorganisms like virus, bacteria and cyst to make the water suitable for human consumption.|
|Full Text||FORM - 2
THE PATENTS ACT, 1970
(39 of 1970)
The Patents Rules, 2006
(See Section 10 and Rule 13)
WATER PURIFICATION COMPOSITION
HINDUSTAN LEVER LIMITED, a company incorporated under the Indian Companies Act, 1913 and having its registered office at Hindustan Lever House, 165/166, Backbay Reclamation, Mumbai -400 020, Maharashtra, India
The following specification describes the invention
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FIELD OF THE INVENTION
The invention relates to a water purification composition. The invention particularly relates to a water purification composition that is especially useful for removal of trace
5 quantities of harmful contaminant like Arsenic in addition to removal of microorganisms like virus, bacteria and cyst to make the water suitable for human consumption.
BACKGROUND AND PRIOR ART
10 A large population of people in the world live in developing and under-developed countries where there is a severe shortage of hygienic potable water. A high percentage of these people live in rural areas where there are no water purification systems like the ones provided by urban municipal drinking water treatment plants. Many people have to depend directly on ground and/or underground water sources like wells, tube-wells,
15 ponds and rivers. Often these water sources are contaminated by sewage, industrial and agricultural wastes.
The various types of water purification systems available like those that utilize UV radiation, halogenated resins, reverse osmosis etc are not very convenient to use in
20 these rural areas since they either require running water and / or electricity or are too expensive for the consumers. Hence many people in the rural areas resort to boiling of water to kill the pathogenic microorganisms in their drinking water. This is also often not feasible since boiling requires large amount of fuel which is increasing becoming scarce. Further there are many areas in the world which are naturally contaminated with high
25 amounts of inorganic impurities like Arsenic. Arsenic is an extremely harmful contaminant. People continue to ingest water with these high levels of microorganisms and impurties like Arsenic which are responsible for the high mortality and morbidity in these areas.
30 Arsenic is one of the most toxic contaminants found in the environment. Arsenic is found in soils, rocks, natural waters and organisms. Arsenic is the twentieth most abundant
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element in earth's crust. The most common oxidation states of arsenic are +3 and +5. Among all the arsenic compounds present in the environment, of particular interest is arsenite (which is arsenic in the As (III) form, which is 25-50 times more toxic than arsenate (which is arsenic in As (V) form) and 70 times more toxic than the methylated
5 species, dimethylarsinate (DMA) and monomethylarsonate(MMA). These facts indicate why it would be of priority interest to develop technologies for the removal of As (III), from drinking water.
Inorganic arsenic is identified as a group-l carcinogen for humans. More than 100 million people are affected worldwide due to arsenic contaminated drinking water. Drinking water
10 in many of these areas have arsenic content as high as 300 parts per billion (ppb). The WHO and USEPA recommended MCL (maximum contaminant limit) of arsenic in drinking water is 10 ppb. Available arsenic removal technologies are membrane separation, ion exchange and adsorption. These technologies either require expensive equipments which are not affordable in many parts of the world or are not successful in removing
15 arsenic, especially arsenic in the As (III) to the WHO recommended specification. Further, boiling of water, which many people resort to for purification of water, does not remove arsenic. Thus, one of the major challenges in this field is poor removal of arsenic (III). Additionally, while arsenic in the purified water has to meet these stringent requirements, the technology should also ensure removal of harmful micro organisms like cysts,
20 bacteria and virus to a level which is safe for people to consume. According to EPA, water from any unknown origin can be rendered microbiologically safe to drink if removal of log 6 of bacteria, log 4 of virus and log 3 of cysts is attained. Thus a generally accepted removal criteria for bacteria, virus and cysts are log 6, log 4 and log 3 removal respectively.
A large number of chemical methods of purifying water have been known and used at municipal, local and domestic levels. The chemicals include coagulants and flocculants to precipitate the suspended and dissolved impurities and biocides for killing microorganisms.
WO02/00557 (Proctor and Gamble) describes a water purification composition along with a nutrient additive as apart from purifying and clarifying drinking water, a need was felt in
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many parts of the world to improve standards of nutrition and health. The composition
disclosed comprises essentially a primary coagulant, a bridging flocculent and a coagulant aid. Although this publication claims to remove arsenic, the present inventors have found that further improvement in the technology is required to meet the stringent
5 WHO standards for safe drinking water.
Titanium dioxide has been used for removal of Arsenic from water. US6919029 (2005) by Stevens Institute of Technology teaches use of specific form of titanium dioxide for improved Arsenic removal. The present inventors have found that mere use of titanium
10 dioxide alone does not provide for the near complete removal of arsenic.
JP2005058987 discloses compositions for waste water purification containing nine components viz. calcium sulphate, aluminium sulphate, silica, soda, polymeric flocculant, talc, zeolite, activated carbon and titanium oxide. This patent application describes
15 detoxification of waste sludge water using titanium oxide as a photocatalyst. The present inventors have found that this composition is not suitable for purification of raw water to meet the criteria for potable water set by WHO and other health agencies.
The present inventors have worked diligently on solving this problem. They found that
20 use of adsorbents like titanium dioxide in a flocculation formulation, although provides improvement in the removal of Arsenic (V) compounds from water, this prior art composition is not able to meet the removal requirement of the more toxic and more difficult to remove Arsenic (III) compounds. They then worked on several fronts to solve this problem and found that use of certain selective biocides solve the problem of removal
25 of all arsenic compounds to meet the stringent WHO standards. In addition, the selective biocides ensure sufficient removal of microorganisms.
It is thus an object of the present invention to provide for a water purification composition that solves most of the problems encountered when using compositions reported in the
30 past. It is another object of the present invention to provide for a water purification composition that provides purified water with low Arsenic content that meets the WHO standards of less than 10 ppb, especially Arsenic (III) compounds. It is yet another object
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of the present invention to provide for a water purification composition that also meets the high microbiological removal standards of 6 log bacteria, 4 log virus and 3 log cysts.
SUMMARY OF THE INVENTION
5 According to one aspect of the present invention there is provided a water purification composition comprising
(a) a coagulating agent which is a water soluble inorganic metal salt having
(b) a flocculating agent which is a high molecular weight water soluble polymer;
10 (c) an adsorbent which is a water insoluble oxide, hydroxide or oxo-hydroxides
of titanium, zirconium, iron, copper or zinc; and (d) a biocide which is a halogen compound.
It is particularly preferred that the absorbent is titanium dioxide or iron oxo-hydroxide.
According to a preferred aspect of the invention there is provided a water purification composition comprising two portions which are spatially separated wherein the first portion comprises the biocide and the second portion comprises the flocculating agent and the coagulating agent.
DETAILED DESCRIPTION OF THE INVENTION
All parts herein are by weight unless otherwise specified.
The water purification composition of the present invention comprises a coagulating agent, a flocculating agent, a selective adsorbent and a selective biocide.
The coagulating agent is a compound which is a water-soluble inorganic metal salt having trivalent cation. Suitable trivalent cations are Al3+ and Fe3+. The coagulant is generally free from carbon atoms. Examples of coagulating agents are ferric sulfate, aluminium sulfate and polyaluminium chloride. Without being limited by theory, it is believed that
30 these coagulating agents when added to water form gelatinous hydroxide compounds at
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pH greater than or equal to 6. The mechanism of coagulation via the formation of
gelatinous hydroxide is optimum when pH is adjusted between 6 and 8.5. The gelatinous precipitate entrains fine suspended particles and microbes as it settles or coagulates. The coagulating agent is preferably present in an amount in the range of from 5 to 50%,
5 more preferably from 15 to 40% by weight of the composition.
The flocculating agent as per this invention is a compound which is a high molecular weight water soluble polymer. Examples of flocculating agents are polysaccharides (dextane celluloses), proteins, modified celluloses (hydroxyethyl/hydroxypropyl or
10 carboxymethyl), and polyacrylamides preferably high molecular weight polyacrylamide. It is especially preferred that the polyacrylamide is either anionic or non-ionically modified, more preferably anionically modified. Suitable molecular weights of these polyacrylamides are in the range of 105 to 107. Preferred flocculating agent is Superfloc (from Cytec). Preferred amounts of the flocculating agent is from 0.5 to 15%, more
15 preferably from 1 to 10% and most preferably from 2 to 8% by weight of the composition.
The water purification composition of the invention comprises an adsorbent uniquely selected to give the desired properties. The adsorbent is a water insoluble oxide, hydroxide or oxo-hydroxide of titanium, zirconium, iron, copper or zinc. Especially
20 preferred adsorbents are water insoluble oxide, hydroxie or oxo-hydroxide of titanium, and iron. Suitable adsorbents are titanium dioxide, zirconium oxide, iron oxide, copper
oxide, zinc oxide, iron oxo-hydroxides, titanium oxo-hydroxides, zirconium oxo-hydroxides or combinations of these adsorbents. The more preferred adsorbents are titanium di oxide, titanium oxo-hydroxide, iron oxide, iron hydroxide or iron oxo-hydroxide, most
25 preferred adsorbent being titanium dioxide and iron oxo-hydroxide. Preferred amounts of adsorbent is in the range of 5 to 70%, more preferably 10 to 50%, most preferably 15 to 30% by weight of the composition.
The composition of the invention comprises a biocide which is a halogen compound.
30 More preferred halogens compounds are those of chlorine or iodine, more preferably
those of chlorine. Suitable chlorine compounds are inorganic compounds like sodium
hypochlorite, calcium hypochlorites, chlorine dioxide, or chloramines, or organic chlorine
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compounds like sodium dichloro-isocyanurates, or trichloroisocyanuric acid. The biocide
is preferably present in an amount in the range of from 1 to 20%, more preferably from about 2 to 12% by weight of the composition. Most preferred biocide is calcium hypochlorite. The present inventors have found that not all biocides are effective in
5 meeting the objects of the present invention. Several conventional biocides like quarternary ammonium compounds, triazine, glutaraldehyde, isothiazoline, organo tin compounds, carbamates, methylene thio cyanate were used and although they were useful for microbiological removal they had poor efficacy with respect to meeting arsenic removal. Thus the invention is especially suitable for removal of Arsenic, especially when
10 the water is heavily contaminated with arsenic compounds which are in the As(lll) form,
which has always been difficult to achieve using prior art methods.
The water purification composition works best when it is packed to have a moisture content of not more than 5%, more preferably not more than 3%, and most preferably not
15 more than 2% by weight of the composition.
The purification action of the composition of the invention can be attained at the pH of the
raw water available. As a preferred aspect, the pH of the composition may be adjusted to the desired range by including a buffering agent in the composition. Suitable buffering
20 agents are calcium oxide, sodium carbonate or sodium bicarbonate. The buffering agent when present is included in an amount in the range of 0.5 to 10% by weight of the composition.
The water purification composition may optionally comprise a co-adsorbent. The co-
25 adsorbent is preferably a material which is capable of adsorbing high levels of water and organic or inorganic compounds. Suitable co-adsorbent is a clay. Examples of clay include Montmorillonite clay (dioctheydral smectite clay), Laponite, Hectorite, Nontronite, Saponite, Volkonsite, Sauconite, Beidellite, Allevarlite, lllite, Halloysite, Attapulgite, Mordenite, Kaolines, and Bentonite. A highly preferred clay as per this invention is
30 Bentonite clay. When included, co-adsorbents are present in an amount in the range of 5 to 75%, more preferably from about 10 to 60% by weight of the composition.
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According to a preferred aspect of the invention the water purification composition is delivered as a two-component system. The two-component system comprises a first portion and a second portion which are kept spatially separated. The first portion comprises the biocide and the second portion comprises the flocculating agent and the
5 coagulating agent. A further preferred aspect has the adsorbent present in the second portion of the two-component system. When delivered as a two-component system, it is preferred that the first portion comprises less than 5 % moisture by weight of said first portion. In the two component system, the co-adsorbent, if present, may be included in both the first portion and the second portion or may be present in any one of the portions.
A further preferred aspect of the invention provides for the second portion to comprise a biocide quencher which is capable of reacting with the biocide to render it safe and aesthetically acceptable for human consumption. Suitable quenchers are sodium thiosulphate and ascorbic acid. The quencher is preferably present in an amount in the
15 range of 1 to 20% by weight of the second portion, more preferably from about 2 to 12% by weight of the second portion.
The solid form is the most suitable form of the composition of the invention. Suitable solid forms
Include the powder, granule and tablet forms, most preferred form being the
20 powder form. When delivered as a two-component system, the most preferred form is the powder form in both the first portion and the second portion.
The water purification composition of the invention is preferably delivered in amounts in the range of 0.5 to 10 grams more preferably in the range of 1 to 5 grams. These are
25 usually added to 5 to 20 litres of water. When delivered as a two component system, suitable weight of the first portion is 0.01 to 5 grams, more preferably 0.1 to 1 gram and suitable weights of the second portion is 0.5 to 10 grams.
The water purification composition of the invention may be delivered to the consumer in
30 any known suitable packaging form. When formed as tablets, the packaging may be
metallised laminate or blister packing. When formed as powders, suitable packaging is
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metallised laminate. However the metallised laminate packaging has to be such that the halogenated compounds that usually react with metals are kept separated from the metal part of the laminate by use of suitable polymeric layers on the metal layer.
5 According to another aspect of the invention there is provided a process for purifying water comprising the steps of (i) mixing the composition of the invention with the water to be purified and (ii) separating the flocculated mass from the mixture.
When the product is configured as two component system, a suitable process comprises
10 the sequential steps of mixing the composition of the first portion with the water to be purified; followed by the step of mixing the composition of the second portion and then separating the flocculated mass from the mixture. The first portion is usually mixed for a period of time from 0.5 to 5 minutes and the water is then allowed to stand for a time period of 2 to 10 mins, after which the second portion is added. The mixture is then
15 mixed for a period of time from 0.5 to 5 minutes and again allowed to stand for 2 to 10 mins. The flocculated mass is then allowed to settle down and then separated from the mixture usually by filtration or decantation. A simple cloth may be used for filtration.
The process of the invention is especially suited for purifying water which contains
20 arsenic. In contaminated areas, average arsenic concentration in raw water is around 300 ppb by weight. By using the process of the invention, it is possible to get purified water having an arsenic content as low as less than 10 ppb by weight of the purified water.
25 The invention will now be illustrated by the following non-limiting examples.
Preparation of test water: 10 litres of R. O water (reverse osmosis purified water) was
taken and 15 g of sea salt, 0.025 g humic acid and 1.5 g fine dust (Arizona test dust) was
30 added to it. Total dissolved salts was less than 50 ppm. Arsenic compounds either
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sodium arsenate (Na2HAs04.7H20) in which arsenic is in the As (V) form or Sodium
arsenite (NaAs02) in which arsenic is in the As (III) state was added to the test water, as desired.
Determination of arsenic content
5 Inductively coupled plasma-optical emission spectroscopy (ICP-OES) (Varian-Vista-PRO)
was used to measure total arsenic concentration (>50 ppb) in the solution. The total arsenic concentrations lower than 50 ppb were analyzed by inductively coupled plasma-mass spectrometry (ICP-MS) (Eldrin 9000). In both the analytical methods the samples were injected in the machines without any pre-concentration or pre-dilution and the total
10 arsenic concentrations were measured.
Comparative Example - A
A test water containing 300 ppb of arsenic from sodium arsenate (Arsenic (V) form) was used . The process of purification was as follows:
15 Purification process: 10 litres of test water was taken in a bucket and the composition as shown in Table-1 was added to the test water and stirred for one minute after which the water was left to stay for five minutes. The flocculated mass was then filtered through a layered cloth. The arsenic content of the purified water was measured and the result is summarized in Table - 1.
Comparative Example - B
A test water containing 300 ppb of arsenic from sodium arsenite (Arsenic (III) form) was used. The process of purification was as used for Comparative Example - A. The arsenic content of the purified water was measured and the result is summarized in
A water purification composition as shown in Table-1 was used for purification of water. The composition was a two component system with the first component having calcium
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hypochlorite and the second component having polyaluminium chloride, polyacrylamide and titanium dioxide. The process of purification was as follows.
Purification process: 10 litres of the test water was taken in a bucket and the composition
5 as shown in Table-1 was added to the test water and stirred for one minute after which the water was left to stay for five minutes. After this the second component was added and stirred for one minute after which it was allowed to stay for five minutes. The flocculated mass was then filtered through a layered cloth. The arsenic content of the purified water was measured and the result is summarized in Table - 1.
Example - 2
A composition as per Example-1 was used. The test water was similar to that used in Example -1 except that the test water contained 150 ppb of sodium arsenite and 150 ppb of sodium arsenate which is generally encountered in ground water contaminated with
15 arsenic. The arsenic content of the purified water was measured and the result is summarized in Table - 1.
Example - 3
A water purification composition similar to Example-1 was used, as shown in Table-1, except that iron oxide was used instead of titanium dioxide. The composition was
20 prepared as a two component system.
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Example Comparative Example - A Comparative Example - B Example-1 Example- 2 Example-3
Calcium hypochlorite, g - - 0.15 0.15 0.15
Polyaluminium chloride, g 0.60 0.60 0.60 0.60 0.60
Polyacrylamide,g 0.08 0.08 0.08 0.08 0.08
Adsorbent Ti02 Ti02 Ti02 Ti02 Iron oxo-hydroxide
Adsorbent, g 0.50 0.50 0.50 0.50 0.50
Form of arsenic in test water As(V) As(lll) As(lll) As(lll) + As(V) in 1:1 wtratio As(lll)
ppb arsenic in purified water 5 100 5 5 10
The data in Table- 1 indicates that using composition as per prior art (Comparative
5 Example A), the standards of removal of As (V) can be achieved but it is not possible to meet the purification standard for As (III) (Comparative Example - B). However using the compositions as per the present invention (Examples 1 - 3), it is possible to ensure removal of Arsenic in the As (III) form alone or as a mixture of As (III) and As (V) forms.
10 A test water as used for Example -1 was prepared and in addition micro-organisms viz. cyst, bacteria and virus at the concentration as shown in Table-2 was added to it. The test water was purified as per the process used for Example -1. The amount of microorganisms in the purified water was determined and the result is summarized in Table-2. The method used to measure the amount of the various microorganisms in water is
15 described in detail in the publication "Tropical Medicine and International Health, volume
11 no 9 pp 1399-1405 September 2006, in article titled "'Microbiological performance of a water treatment unit designed for household use in developing countries", by Thomas Clasen, Suresh Nadakatti and Shashikala Menon.
Microbes Input Cone. Output Cone. Log reduction
Bacteria (E-coli) 7x10b/100mL
Polio Virus 104.10 pfu / 100
Cysts (irradiated) 5x104/L 50/L 3.00
The data indicates that the composition as per the invention is capable of purifying water which contains harmful microorganisms to a high degree of purification required for maintenance of good health in people consuming the water viz. the composition ensures at least 6 log removal of bacteria, 4 log removal of virus and 3 log removal of cyst.
10 Several prior art compositions (Comparative Examples C to F) and compositions outside the scope of the invention (Comparative Example G) were tried as shown in Table - 3. The test water was as used for Example - 1.
The water purification composition as shown in Table-3 was prepared as a one 15 component system and the process as per Comparative Example - A was used for purifying the test water.
Comparative Example- D
The composition as shown in Table-3 as a two component system was prepared. The test water was purified as per the process used in Example-1.
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Comparative Example -E
A composition as shown in Table-3 was prepared as a one component system and a process as per comparative Example - A was used for purifying the test water.
Comparative Example - F
5 A composition as shown in Table-3 was prepared as a one component system. The test water was purified as per the process used in Comparative Example - A.
Comparative Example - G
The composition as shown in Table-3 as a two component system was prepared. The test water was purified as per the process used in Example-1.
10 The results of the experiments (Comparative Examples C to G) in terms of the Arsenic content in the purified water are summarized in Table - 3.
Example Comp Ex-C Comp Ex-D Comp Ex-E Comp Ex-F Comp Ex-G
Biocide CaHypo CaHypo CaHypo CaHypo CPB
Biocide, g - 0.15 - - 0.15
Polyaluminium chloride, g 0.60 0.60 - 0.60 0.60
Polyacrylamide,g 0.08 0.08 - 0.08 0.08
Adsorbent - - Ti02 Fe203 Ti02
Adsorbent, g - - 0.50 0.50 0.50
ppb arsenic in purified water 150 50 150 120 100
CaHypo: Calcium hypochlorite CPB: Cetyl pyridinium bromide
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The data in Table-3 indicates that compositions as per the prior art (Comparative Examples C to F) is not able to meet the removal criterion of arsenic. Further use of any conventional biocide (Comparative Example - G) alone is not sufficient to meet the removal criterion of arsenic.
5 Comparative Examples- H to K
Experiments were conducted using compositions as shown in Table-4, where various other commonly known adsorbents were used. The process used was similar to that used for Example-1. The result on the Arsenic content in the purified water is shown in Table-4. The result of Example-1 is reproduced for comparison.
Example Ex-1 Comparative Example - H Comparative Example -1 Comparative Example- J Comparative Example- K
Calcium hypochlorite, g 0.15 0.15 0.15 0.15 0.15
Polyaluminium chloride, g 0.60 0.60 0.60 0.60 0.60
Polyacrylamide, g 0.08 0.08 0.08 0.08 0.08
Adsorbent Titanium di oxide Bentonite Activated Carbon Talc Zeolite
Adsorbent, g 0.50 0.50 0.50 0.50 0.50
ppb arsenic in purified water 5 50 50 50 50
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The data in table-4 indicates that only use of a selective adsorbent in the composition of the invention provides for the synergistic benefit in arsenic removal while use of conventional adsorbents do not provide this benefit.
5 Dated this 1st day of February 2007.
|Indian Patent Application Number||186/MUM/2007|
|PG Journal Number||19/2012|
|Date of Filing||01-Feb-2007|
|Name of Patentee||HINDUSTAN UNILEVER LIMITED|
|Applicant Address||UNILEVER HOUSE, B.D. SAWANT MARG, CHAKALA, ANDHERI EAST, MUMBAI-400 099|
|PCT International Classification Number||C02F1/52, C02F1/28, C02F1/56|
|PCT International Application Number||N/A|
|PCT International Filing date|