| United States Patent Application |
20040026657
|
| Kind Code
|
A1
|
|
Souter, Philip Frank
; et al.
|
February 12, 2004
|
Water treatment compositions
Abstract
Compositions, methods and kits for purifying and clarifying and/or
nutrifying contaminated drinking water and which comprise a primary
coagulant material and a bridging flocculent material, the levels and
ratios of coagulant to flocculent preferably falling within certain
ranges. Highly preferred compositions also contain one or more of a
cationic coagulant aid, especially chitosan, a microbiocidal
disinfectant, a water-soluble alkali, a water-insoluble silicate, and a
food additive or nutrient source.
| Inventors: |
Souter, Philip Frank; (Morpeth, GB)
; Ure, Colin; (Wallsend, GB)
|
| Correspondence Name and Address:
|
THE PROCTER & GAMBLE COMPANY
INTELLECTUAL PROPERTY DIVISION
WINTON HILL TECHNICAL CENTER - BOX 161
6110 CENTER HILL AVENUE
CINCINNATI
OH
45224
US
|
| Serial No.:
|
324358 |
| Series Code:
|
10
|
| Filed:
|
December 20, 2002 |
| U.S. Current Class: |
252/181 |
| U.S. Class at Publication: |
252/181 |
| Intern'l Class: |
C02F 005/10 |
Foreign Application Data
| Date | Code | Application Number |
|---|
| Jun 27, 2000 | GB | 0015571.3 |
| Jun 27, 2000 | GB | 0015569.7 |
| Nov 8, 2000 | GB | 0027214.6 |
Claims
What is claimed is:
1. A composition for purifying and clarifying contaminated drinking water
and which comprises: (i) a primary coagulant selected from the group
consisting of water-soluble, multivalent inorganic salts and mixtures
thereof; (ii) a bridging flocculent selected from the group consisting of
water-soluble and water-dispersible anionic and nonionic polymers having
a weight average molecular weight of at least about 2,000,000, and
mixtures thereof; (iii) a coagulant aid selected from the group
consisting of water-soluble and water-dispersible cationic polymers
having a weight average molecular weight of less than about 1,500,000,
and mixtures thereof; and optionally one or more of (iv) a microbiocidal
disinfectant; (v) a water-soluble alkali; (vi) a water-insoluble silicate
selected from clays, zeolites and mixtures thereof; and (vii) a food
additive or nutrient source.
2. A composition according to claim 1 wherein the weight ratio of primary
coagulant to bridging flocculant is- from about 10:1 to about 200:1,
preferably from about 20:1 to about 100:1, and more preferably from about
25:1 to about 75:1.
3. A composition for purifying and clarifying contaminated drinking water
and which comprises: (i) a primary coagulant selected from the group
consisting of water-soluble, multivalent inorganic salts and mixtures
thereof; (ii) a water-soluble or water-dispersible polymeric bridging
flocculant preferably selected from the group consisting of water-soluble
and water-dispersible anionic and nonionic polymers, the polymeric
bridging flocculant having a weight average molecular weight of at least
about 2,000,000, and wherein the weight ratio of primary coagulant to
bridging flocculent is from about 10:1 to about 150:1, preferably from
about 20:1 to about 100:1, and more preferably from about 25:1 to about
75:1; and optionally one or more of (iii) a water-soluble or
water-dispersible polymeric coagulant aid preferably selected from the
group consisting of water-soluble and water-dispersible cationic
polymers, the polymeric coagulant aid having a weight average molecular
weight of less than about 1,500,000; (iv) a microbiocidal disinfectant;
(v) a water-soluble alkali; (vi) a water-insoluble silicate selected from
clays, zeolites and mixtures thereof; and (vii) a food additive or
nutrient source.
4. A composition according to any preceding claim wherein the weight ratio
of primary coagulant to coagulant aid is from about 8:1 to about 100:1,
preferably from about 12:1 to about 30:1, and more preferably from about
15:1 to about 25:1.
5. A composition according to any preceding claim wherein the weight ratio
of coagulant aid to bridging flocculant is in the range from about 10:1
to about 1:6, preferably from about 5:1 to about 1:3, more preferably
from about 3:1 to about 1:1.
6. A composition according to any preceding claim wherein the weight ratio
of primary coagulant to microbiocidal disinfectant is from about 10:1 to
about 100:1, preferably from about 12:1 to about 60:1, and more
preferably from about 15:1 to about 40:1.
7. A composition according to any preceding claim wherein the weight ratio
of primary coagulant to water-soluble alkali is from about 0.8:1 to about
3:1, preferably from about 0.9:1 to about 2.4:1, and more preferably from
about 1:1 to about 2:1.
8. A composition according to any preceding claim wherein the weight ratio
of primary coagulant to water-insoluble silicate is from about 0.3:1 to
about 5:1, preferably from about 0.7:1 to about 2:1, and more preferably
from about 0.8:1 to about 1.2:1.
9. A composition according to any preceding claim comprising from about
10% to about 99%, preferably from about 15% to about 50%, more preferably
from about 25% to about 40% by weight of the primary coagulant.
10. A composition according to any preceding claim comprising from about
0.1% to about 10%, preferably from about 0.2% to about 5%, more
preferably from about 0.4% to about 3% by weight of the bridging
flocculent.
11. A composition according to any preceding claim comprising from about
0.1% to about 10%, preferably from about 0.5% to about 5%, more
preferably from about 1% to about 4% by weight of the coagulant aid.
12. A composition according to any preceding claim comprising from about
0.2% to about 10%, preferably from about 0.5% to about 4%, more
preferably from about 0.7% to about 2.5% by weight of the microbiocidal
disinfectant.
13. A composition according to any preceding claim comprising from about
10% to about 45%, preferably from about 15% to about 40%, more preferably
from about 18% to about 35% by weight of the water-soluble alkali.
14. A composition according to any preceding claim comprising from about
10% to about 80%, preferably from about 20% to about 50%, more preferably
from about 25% to about 40% by weight of the water-insoluble silicate.
15. A composition according to any preceding claim in unit dosage form for
the batchwise purification and clarification of a relatively small
predetermined volume of contaminated drinking water
16. A composition according to any preceding claim in unit dosage form for
treating a volume of contaminated drinking water in the range from about
0.1 to about 100, preferably from about 0.5 to about 40, more preferably
from about 5 to about 20, and especially from about 8 to about 13 iitres,
and wherein the unit dosage amount of the composition is in the range
from about 50 to about 2000, preferably 250 to about 1000, more
preferably from about 300 to about 750 mg/litre of contaminated drinking
water.
17. A composition according to any preceding claim in unit dosage form
comprising: (i) from about 15% to about 50%, preferably from about 25% to
about 40% by weight of the primary coagulant; (ii) from about 0.5% to
about 5%, more preferably from about 0.7% to about 3% by weight of the
bridging flocculent; and (iii) from about 0.5% to about 5%, more
preferably from about 1% to about 4% by weight of the coagulant aid.
18. A composition according to any preceding claim comprising the primary
coagulant, bridging flocculant and coagulant aid in amounts sufficient to
provide by weight of the contaminated drinking water from about 50 to
about 500, preferably from about 75 to about 300, more preferably from
about 100 to about 250 ppm of primary coagulant, from about 1 to about
15, preferably from about 2 to about 10, more preferably from about 2.5
to about 7.5 ppm of bridging flocculant, and from about 1 to about 25,
preferably from about 5 to about 20, more preferably from about 8 to
about 12 ppm of coagulant aid.
19. A composition according to any preceding claim wherein the
microbiocidal disinfectant is in controlled, delayed, sustained or slow
release form whereby the composition has a t.sub.max corresponding to the
time for achieving maximum disinfectant concentration after addition to
deionized water at 20.degree. C. of at least 1 minute, preferably at
least 2 minutes, more preferably at least 4 minutes, and especially at
least 8 minutes.
20. A composition according to any preceding claim having an 80%-ile
soluble organic matter flocculation rate (t.sub.80) and preferably a
90%-ile soluble organic matter flocculation rate (t.sub.90) as herein
defined of less than 2 minutes, preferably less than 1 minute, more
preferably in less than 30 seconds.
21. A composition for purifying and clarifying contaminated drinking water
and which comprises: (i) a primary coagulant selected from the group
consisting of water-soluble, multivalent inorganic salts and mixtures
thereof; (ii) a water-soluble or water-dispersible polymeric bridging
flocculant; and (iii) a microbiocidal disinfectant; and wherein the
microbiocidal disinfectant is in controlled, delayed, sustained or slow
release form whereby the composition has a t.sub.max corresponding to the
time for achieving maximum disinfectant concentration after addition to
deionized water at 20.degree. C. which is greater than the 80%-ile
soluble organic matter flocculation rate (t.sub.80) and preferably
greater than the 90%-ile soluble organic flocculation rate (t.sub.90) of
the composition.
22. A composition according to claim 21 wherein t.sub.max is at least 1
minute, preferably at least 2 minute, more preferably at least 4 minutes
and especially at least 8 minutes greater than t.sub.80 and preferably
greater than t.sub.90.
23. A composition for purifying, clarifying and nutrifying contaminated
drinking water and which comprises: (i) a primary coagulant selected from
the group consisting of water-soluble, multivalent inorganic salts and
mixtures thereof; (ii) a water-soluble or water-dispersible polymeric
bridging flocculant; and (iii) a food additive or nutrient source.
24. A composition according to claim 24 wherein the food additive or
nutrient source is selected from (i) food additives and nutrient sources
which are non-coagulable or which at least partially survive the
coagulation and flocculation process, for example fluoridating agents,
iodinating agents, and essential minerals such as zinc and iron, and (ii)
food additives and nutrient sources in controlled, delayed, sustained or
slow release form whereby the composition has a t.sub.max corresponding
to the time for achieving maximum nutrient concentration after addition
to deionized water at 20.degree. C. which is greater than the 80%-ile
soluble organic matter flocculation rate (t.sub.80) and preferably
greater than the 90%-ile soluble organic flocculation rate (t.sub.90) of
the composition.
25. A composition according to any preceding claim wherein the coagulant
aid is a substantially water-insoluble cationic polysaccharide,
preferably chitosan.
26. A composition according to any preceding claim wherein the
microbiocidal disinfectant is a chlorine-based disinfectant, especially
calcium hypochlorite.
27. A composition according to any preceding claim additionally comprising
a moisture sink and having a free-moisture content of less than about 6%,
preferably less than about 4%, mnore preferably less than about 2.5%, the
moisture sinik preferably having a free moisture content of less than
about 4%, more preferably less than about 3%, especially less than about
2.5% and more especially less than about 1.5% by weight and preferably
being selected from pre-dried clays and aluininosilicates, anhydrous
sodium carbonate and mixtures thereof.
28. A composition for purifying and clarifying contaminated drinking water
and which comprises: (i) a primary coagulant selected from the group
consisting of water-soluble, multivalent inorganic salts and mixtures
thereof; (ii) a water-soluble or water-dispersible polymeric bridging
flocculent; (iii) calcium hypochlorite as microbiocidal disinfectant; and
optionally (iv) a moisture sink, and wherein the composition has a
free-moisture content of less than about 6%, preferably less than about
4% and more especially less than about 2.5% by weight thereof.
29. A composition according to any preceding claim having filtration
characteristics such that at least one litre of model surface water
treated with 620 mg/litre of the composition passes a Whatman 1.2 .mu.m
GF/C grade filter in less than 1 hour, preferably less than 45 minutes,
and more preferably less than 30 minutes under ambient temperature
conditions (20.degree. C.) and such that at least 1 litre, preferably at
least 2 litres, more preferably at least 3 litres of the treated water
will pass the filter without blocking.
30. A composition according to any preceding claim wherein the final
turbidity achieved using the composition on model surface water is less
than 5 NTU, preferably less than 2 NTU and especially less than 1 NTU,
turbidity being measured using a Jenway 6035 turbidity meter calibrated
daily against a 5.0 NTU standard.
31. A composition for purifying contaminated drinking water comprising:
(i) a first polymeric material which comprises an amine group; and (ii) a
second different polymeric material which is substantially water-soluble
and has a weight average molecular weight of at least 2000000; and
optionally (iii) an inorganic metal salt selected from the group
consisting of iron sulphate, iron chloride, aluminium chloride, aluminium
sulphate, manganese sulphate, manganese chloride, copper sulphate, copper
chloride, poly- variations thereof, or a combination thereof.
32. A composition for purifying contaminated drinking water comprising:
(i) a first polymeric material which is a polysaccharide which comprises
an amine group; and (ii) a second different polymeric material which is
substantially water-soluble and has a weight average molecular weight of
at least 100000; and optionally (iii) an inorganic metal salt selected
from the group consisting of iron sulphate, iron chloride, aluminium
chloride, aluminium sulphate, manganese sulphate, manganese chloride,
copper sulphate, copper chloride, poly- variations thereof, or a
combination thereof.
33. A composition according to claim 31 or 32 whereby said first polymeric
material comprises a polysaccharide, preferably chitosan, modified
chitosan, salts thereof or a combination thereof.
34. A composition according to any of claims 31 to 33 whereby said
inorganic metal salt comprises a member selected from the group
consisting of iron sulphate, aluminium sulphate, iron chloride,
poly-variations thereof, or a combination thereof.
35. A composition according to any of claims 31 to 34 whereby said
composition comprises a disinfecting agent.
36. A composition according to any of claims 31 to 35 whereby said
composition comprises clay, preferably smectite clay.
37. A composition according to any claims 31 to 36 whereby said
composition comprises aluminosilicate.
38. A composition according to any of claims 31 to 37 whereby said
composition comprises an alkali agent, preferably said alkali agent
comprises sodium carbonate, sodium bicarbonate, sodium hydroxide, sodium
oxide, calcium carbonate, calcium oxide, calcium hydroxide, potassium
carbonate, potassium bicarbonate, potassium hydroxide, potassium oxide or
a combination thereof.
39. A combination of a composition of any of claims 31 to 38 and a
disinfecting agent, for simultaneous or sequential use in the
purification of water.
40. A method for purifying and clarifying contaminated drinking water and
which comprises contacting the contaminated water with: (i) a primary
coagulant selected from the group consisting of water-soluble,
multivalent inorganic salts and mixtures thereof; (ii) a bridging
flocculant selected from the group consisting of water-soluble and
water-dispersible anionic and nonionic polymers having a weight average
molecular weight of at least about 2,000,000, and mixtures thereof; (iii)
a coagulant aid selected from the group consisting of water-soluble and
water-dispersible cationic polymers having a weight average molecular
weight of less than about 1,500,000, and mixtures thereof; and optionally
one or more of (iv) a microbiocidal disinfectant; (v) a disinfectant
neutralization agent; (vi) a water-soluble alkali; (vii) a
water-insoluble silicate selected from clays, zeolites and mixtures
thereof; and (viii) food additive or nutrient source.
41. A method for purifying and clarifying contaminated drinking water and
which comprises contacting the contaminated water with: (i) a primary
coagulant selected from the group consisting of water-soluble,
multivalent inorganic salts and mixtures thereof; (ii) a water-soluble or
water-dispersible polymeric bridging flocculent preferably selected from
the group consisting of water-soluble and water-dispersible anionic and
nonionic polymers, the polymeric bridging flocculant having a weight
average molecular weight of at least about 2,000,000, and wherein the
weight ratio of primary coagulant to bridging flocculant is from about
10:1 to about 150:1, preferably from about 20:1 to about 100:1, and more
preferably from about 25:1 to about 75:1; and optionally one or more of
(iii) a water-soluble or water-dispersible polymeric coagulant aid
preferably selected from the group consisting of water-soluble and
water-dispersible cationic polymers, the polymeric coagulant aid having a
weight average molecular weight of less than about 1,500,000; (iv) a
microbiocidal disinfectant; (v) a disinfectant neutralization agent; (vi)
a water-soluble alkali; (vii) a water-insoluble silicate selected from
clays, zeolites and mixtures thereof; and (viii) a food additive or
nutrient source.
42. A method for purifying, clarifying and nutrifying contaminated
drinking water and which comprises contacting the contaminated water
with: (i) a primary coagulant selected from the group consisting of
water-soluble, multivalent inorganic salts and mixtures thereof; (ii) a
water-soluble or water-dispersible polymeric bridging flocculent; (iii) a
food additive or nutrient source; and optionally one or more of (iv) a
water-soluble or water-dispersible polymeric coagulant aid; (v) a
microbiocidal disinfectant; (vi) a disinfectant neutralization agent;
(vii) a water-soluble alkali; and (viii) a water-insoluble silicate
selected from clays, zeolites and mixtures thereof.
43. A method according to any of claims 40 to 42 comprising: (i) a
coagulation and flocculation stage in which the contaminated drinking
water is brought into mixing contact with the coagulant, bridging
flocculant and, if present, the coagulant aid so as to coagulate and
flocculate the water impurities in the form of solid matter; (ii) a
disinfectant stage in which the drinking water is brought into
microbiocidal contact with the disinfectant during or after substantial
completion of the coagulation and flocculation stage; (iii) a separation
stage prior or subsequent to the disinfectant stage in which the solid
matter is physically separated from the drinking water; and optionally
one or more of (iv) a neutralization stage in which the drinking water is
brought into contact with a disinfectant neutralization agent subsequent
to said separation stage in order to reduce or remove excess
disinfectant; and (v) a nutrifying stage in which the drinking water is
brought into contact with the food additive or nutrient source prior or
subsequent to the separation stage.
44. A method for purifying and clarifying contaminated drinking water and
which comprises subjecting the contaminated water to: (i) a coagulation
and flocculation stage in which the contaminated drinking water is
brought into mixing contact with a primary coagulant, a polymeric
bridging flocculant and, optionally a polymeric coagulant aid so as to
coagulate and flocculate the water impurities in the form of solid
matter; (ii) a disinfectant stage in which the drinking water is brought
into microbiocidal contact with a disinfectant during or after
substantial completion of the coagulation and flocculation stage; (iii) a
separation stage prior or subsequent to the disinfectant stage in which
the solid matter is physically separated from the drinking water; and
(iv) a neutralization stage in which the drinking water is brought into
contact with a disinfectant neutralization agent subsequent to said
separation stage in order to reduce or remove excess disinfectant.
45. A method for purifying, clarifying and nutrifying contaminated
drinking water and which comprises subjecting the contaminated water to:
(i) a coagulation and flocculation stage in which the contaminated
drinking water is brought into mixing contact with a primary coagulant, a
polymeric bridging flocculant and, optionally a polymeric coagulant aid
so as to coagulate and flocculate the water impurities in the form of
solid matter; (ii) a disinfectant stage in which the drinking water is
brought into microbiocidal contact with a disinfectant during or after
substantial completion of the coagulation and flocculation stage; (iii) a
separation stage prior or subsequent to the disinfectant stage in which
the solid matter is physically separated from the drinking water; and
(iv) a nutrifying stage in which the drinking water is brought into
contact with a food additive or nutrient source prior or subsequent to
the separation stage.
46. A method according to any of claims 40 to 45 wherein the primary
coagulant is used in an amount of from about 50 to about 500, preferably
from about 75 to about 300, more preferably from about 100 to about 250
ppm by weight of the contaminated drinking water.
47. A method according to any of claims 40 to 46 wherein the bridging
flocculent is used in an amount of from about 1 to about 15, preferably
from about 2 to about 10, more preferably from about 2.5 to about 7.5 ppm
by weight of the contaminated drinking water.
48. A method according to any of claims 40 to 47 wherein the coagulant aid
is used in an amount of from about 1 to about 25, preferably from about 5
to about 20, more preferably from about 8 to about 12 ppm by weight of
the contaminated drinking water.
49. A method according to any of claims 40 to 48 wherein the microbiocidal
disinfectant is used in an amount of from about 2 to about 25, preferably
from about 3 to about 20, more preferably from about 4 to about 15 ppm by
weight of the contaminated drinking water.
50. A method according to any of claims 40 to 49 for purifying water
contaminated with arsenic and/or lead and wherein the purified water has
an arsenic concentration below 5 ppb, preferably below 2 ppb and a lead
concentration below 15 ppb, preferably below 10 ppb.
51. A method according to any of claims 40 to 50 for purifying water
contaminated with soluble organic impurities such as humic acid and
wherein the purified water has a total organic content below 10 ppm,
preferably below 7 ppm and more preferably below 4 ppm and a
trihalomethane (THM) level below 100 ppb, preferably below 70 ppb, more
preferably below 40 ppb.
52. A method according to any of claims 40 to 51 for purifying water
contaminated with cysts such as Cryptosporidium parvum and wherein the
cyst concentration is reduced by a factor of at least about log2,
preferably at least about log 3, and more preferably at least about log
3.5.
53. A method according to any of claims 40 to 52 in which the volume of
contaminated drinking water treated according to the method is in the
range from about 0.1 to about 100, preferably from about 0.5 to about 20,
more preferably from about 5 to about 15, and especially from about 8 to
about 12 litres.
54. A method according to any of claims 40 to 53 comprising a separation
stage using a paper, non-woven or cloth filtration element and wherein
preferably separation is accomplished in a single filtration step without
change of the filtration element.
55. A method for purifying and clarifying contaminated drinking water so
as to render it potable and which comprises contacting the contaminated
drinking water with a composition according to any of claims 1 to 38.
56. A method of purifying contaminated water comprising the steps of: (a)
contacting the contaminated water with a composition according to any of
claims 31 to 38 to obtain partially purified water comprising solid
matter; and (b) removing at least part of said solid matter from said
partially purified water by (i) filtration; or (ii) decanting; or (iii)
sedimentation; or (iv) flotation; or (v) a combination thereof; to obtain
purified water.
57. A method according to claim 56 comprising the step of adding a
disinfectant agent to water prior to, during or after step (b),
preferably after step (b).
58. A kit for purifying and clarifying contaminated drinking water and
which comprises (i) one or more-unit doses of a composition according to
any of claims 1 to 38, and (ii) means for physically separating solid
matter from drinking water.
59. A kit according to claim 58 which additionally comprises one or more
unit doses of a microbiocidal disinfectant composition.
60. A kit according to claim 58 or 59 which additionally comprises one or
more unit doses of a food additive or nutrient composition.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to compositions, methods and kits for
use in the purification of contaminated drinking water for purposes of
rendering it potable. The compositions and kits are especially designed
for personal or domestic use in the batchwise purification and
clarification of relatively small predetermined volumes of contaminated
drinking water. The compositions and kits are also designed for personal
or domestic use in the purification and nutrification of contaminated
drinking water.
BACKGROUND TO THE INVENTION
[0002] There is a need for potable water in all areas of the world. In
developed countries, water is purified and potable water is supplied on a
large scale, typically by large national or multinational water
management companies. This water is typically supplied directly to the
consumers homes in a potable form. However, in some parts of the world,
for example in some rural areas of developing countries, many people
either do not have a direct water supply to their homes and only have
access to a non-potable communal water supply such as a village well, or
cannot be guaranteed that the water they do receive is potable. As a
result, considerable numbers of people die each year as the direct result
of drinking contaminated drinking water. Thus, there is a need for water
purification kits and compositions that allow the consumer to purify
their own water, which produces potable water in a fast and efficient
manner.
[0003] Current water purification compositions available on the market to
date, consist mainly of disinfectants, e.g. sources of chlorine and/or
iodine, and do not adequately purify water. Water which is obtained after
treatment by these water purification kits, may still comprise amounts of
water impurities, e.g. heavy metal ions such as arsenic, which, when
continually consumed for a prolonged period of time, may lead to health
problems. Thus, there is a need to provide a water purification
composition which removes water-impurities like heavy metal ions
including arsenic and lead, more efficiently and effectively than current
water purification kits.
[0004] It has now been found that water purification compositions based on
certain combinations of inorganic coagulants and water-soluble or
water-dispersible polymers remove greater amounts of water impurities,
such as heavy metals, from water compared to current water purification
compositions.
[0005] Also, current water purification compositions do not adequately
remove, kill or inactive micro-organisms such as bacteria, viruses and
cysts, which are present in the water. Thus, there remains a need to
provide a water purification composition which does adequately remove,
kill or inactive these micro-organisms.
[0006] It has now been found that when the composition of the present
invention comprises a disinfecting agent, the composition removes, kills
or inactivates a surprisingly larger amount of micro-organisms such as
bacteria, viruses and cysts compared to water purification compositions
known in the art.
[0007] In addition, the water which is to be purified by a water
purification composition typically comprises a large amount of
water-soluble organic content such as humic acid. With current water
purification compositions, bleach, especially chlorine based bleach, can
react with the water-soluble organic content and produce by-products in
the water, including chlorine derivatives such as chloroacetic acid or
chloroform, which are harmful to human and animal health. Thus, there is
a need to provide water purification compositions, methods and kits which
produce purified water comprising a low amount of disinfection
by-products.
[0008] Another problem associated with the use of certain chlorine-based
disinfectants such as calcium hypochlorite is that of product stability.
In particular, it has been found that known compositions based on calcium
hypochlorite can lose substantial disinfection efficacy under regular
conditions of storage and use. Thus, there is a need for purification and
disinfection compositions having improved storage stability.
[0009] After purification and disinfection of contaminated drinking water,
there raises the further problem of maintaining the purity of the water
until such time as it is required for drinking, whilst at the same time
providing drinking water of satisfactory taste. Thus there is a need for
compositions, methods and kits for purifying contaminated drinking water
and which provides purified water having both longer life and improved
taste attributes.
[0010] In addition to the need for purifying and clarifying contaminated
drinking water, there is also a huge need in many parts of the world to
improve standards of nutrition and health. The effective provision of
both clean water and essential minerals and vitamins would clearly be of
universal benefit but especially so in those parts of the world where
potable water is in short supply. Thus there is a need for compositions,
methods and kits for purifying and at the same time nutrifying
contaminated drinking water.
SUMMARY OF THE INVENTION
[0011] The present invention relates to compositions, methods and kits for
purifying and/or clarifying contaminated drinking water, as well as to
compositions, methods and kits for purifying and nutrifying contaminated
drinking water. In general terms, the compositions herein comprise at
least a primary coagulant material and a so-called bridging flocculent
material, the levels and ratios of coagulant to flocculent preferably
falling within certain ranges. Highly preferred compositions also contain
one or more of a coagulant aid, a microbiocidal disinfectant, a
water-soluble alkali, a water-insoluble silicate (for example a clay,
zeolite or mixture thereof), and a food additive or nutrient source.
[0012] According to a first aspect of the invention, there is provided a
composition for purifying and clarifying contaminated drinking water and
which comprises a primary coagulant, a bridging flocculent and a
coagulant aid.
[0013] In preferred embodiments, the primary coagulant is selected from
the group consisting of water-soluble, multivalent inorganic salts and
mixtures thereof, for example, iron sulphate, iron chloride, aluminium
chloride, aluminium sulphate, manganese sulphate, manganese chloride,
copper sulphate, copper chloride, poly- variations thereof, and mixtures
thereof. Generally, the compositions herein comprise from about 10% to
about 99%, preferably from about 15% to about 50%, more preferably from
about 25% to about 40% by weight of the primary coagulant.
[0014] The bridging flocculent on the other hand is preferably a high
molecular weight water-soluble or water-dispersible polymer or mixture of
polymers having a weight average molecular weight of at least about
2,000,000, more preferably at least about 5,000,000 and especially at
least about 15,000,000. Bridging flocculents preferred for use herein are
selected from the group consisting of water-soluble and water-dispersible
anionic and nonionic polymers and mixtures thereof. Generally, the
compositions herein comprise from about 0.1% to about 10%, preferably
from about 0.2% to about 5%, more preferably from about 0.5% to about 3%
by weight of the bridging flocculent
[0015] The term `coagulant aid` herein refers to a water-soluble or
water-dispersible polymer of lower molecular weight than that of the
bridging flocculent and which aids the overall aggregation and
flocculation process. The coagulant aid preferred for use herein is a low
molecular weight, water-soluble or water-dispersible polymer which
generally has a weight average molecular weight of less than about
1,500,000, preferably less than about 750,000 and especially less than
about 300,000 and mixtures thereof. Generally the compositions herein
comprise from about 0.1% to about 10%, preferably from about 0.5% to
about 5%, more preferably from about 1% to about 4% by weight of the
coagulant aid.
[0016] Although suitable coagulant aids include anionic polymeric
hydrophilic colloids such as the carboxymethylcelluloses, highly
preferred from the viewpoint of delivering excellent heavy metal, total
soluble organic and cyst reduction perfonnance are coagulant aids
selected from the group consisting of water-soluble and water-dispersible
cationic polymers and mixtures thereof, for example cationic
polysaccharides of which chitosan is especially preferred. Preferred
coagulant aids herein are substantially water-insoluble, having at least
10% by dry total weight of undissolved material as determined by the test
described herein below, this being preferred from the viewpoint of
providing compositions and methods delivering low total water-soluble
organic content.
[0017] The weight ratio of primary coagulant to bridging flocculant herein
is preferably from about 10:1 to about 200:1, more preferably from about
10:1 to about 150:1, yet more preferably from about 20:1 to about 100:1,
and especially from about 25:1 to about 75:1, these ratios being valuable
especially in conjunction with the levels of coagulant and flocculant
described herein above for providing optimum purification performance in
highly contaminated water conditions and for providing significantly
improved rates of filtration and `non-blocking` filter characteristics as
well as excellent final product purity and clarity using paper and
non-woven filters. Although the reasons for this improvement in
filtration rate, non-blocking characteristics and product clarity are not
fully understood, it is believed that higher levels and ratios of the
bridging flocculant relative to the coagulant increases the `stickiness`
of the floes with a consequent reduction in colloidal particulates. Such
compositions are also highly suitable for use herein in conjunction with
cloth filters.
[0018] Thus, according to another aspect of the invention, there is
provided a composition for purifying and clarifying contaminated drinking
water and which comprises a primary coagulant selected from the group
consisting of water-soluble, multivalent inorganic salts and mixtures
thereof; a water-soluble or water-dispersible polymeric bridging
flocculent wherein the weight ratio of primary coagulant to bridging
flocculant is from about 10:1 to about 150:1, preferably from about 20:1
to about 100:1, and more preferably from about 25:1 to about 75:1; and
optionally a water-soluble or water-dispersible polymeric coagulant aid.
The filtration characteristics of the composition can be assessed using a
standard filtration test and are preferably such that at least one litre
of treated model surface water after treatment with 620 mg/litre of
purification composition passes a Whatman 1.21 .mu.m GF/C grade filter in
less than 1 hour, preferably less than 45 minutes, and more preferably
less than 30 minutes under ambient temperature conditions (20.degree. C.)
and that at least 1 litre, preferably at least 2 litres, more preferably
at least 3 litres of the treated water will pass the filter without
blocking.
[0019] The model surface water described comprises:
[0020] (i) 24 mg/l humic acid--source of soluble natural organic matter;
[0021] (ii) 20 mg/l fine test dust(1-3 .mu.m)--designed to add turbidity;
[0022] (iii) 1500 mg/l salt--to give stress conditions of high total
dissolved solids.
[0023] The resultant water has a high organic content (>10 mg/l total
organic content (TOC)), high colour (>300 platinum cobalt units
(PCU)), high turbidity (>15 nephelometric turbidity units (NTU)) and
high total dissolved solids (TDS). The pH of the water is near neutral
but can also be adjusted to pH 5 or 9 using HCl or NaOH respectively for
stress testing. This water is referred to herein as `model surface
water`.
[0024] Compositions having optimum purification and clarification
performance can also be defined by reference to the weight ratio of the
primary coagulant and coagulant aid to the bridging flocculant. Thus, in
preferred embodiments, the weight ratio of primary coagulant to coagulant
aid is from about 8:1 to about 100:1, preferably from about 12:1 to about
30:1, and more preferably from about 15:1 to about 25:1. The weight ratio
of coagulant aid to bridging flocculant, on the other hand, is preferably
in the range from about 10:1 to about 1:6, preferably from about 5:1 to
about 1:3, more preferably from about 3:1 to about 1:1.
[0025] The compositions, methods and kits of the invention also preferably
comprise a microbiocidal disinfectant. Although a broad range of
microbiocidal disinfectants are envisaged for use herein, preferred is a
chlorine-based disinfectant. Calcium hypochlorite is especially
preferred. Preferably, the compositions herein comprise primary coagulant
and microbiocidal disinfectant in a weight ratio of from about 10:1 to
about 100:1, more preferably from about 12:1 to about 60:1, and
especially from about 15:1 to about 40:1. Generally, the compositions
herein comprise from about 0.2% to about 10%, preferably from about 0.5%
to about 4%, more preferably from about 0.7% to about 2.5% by weight of
the microbiocidal disinfectant.
[0026] The compositions, methods and kits of the invention will also
generally comprise a water-soluble alkali, this being valuable from the
viewpoint of delivering an optimum in-use pH profile. In general terms,
the levels of primary coagulant and alkali should be adjusted so as to
provide a pH at in-use concentration (generally about 620 ppm of total
composition) in the range from about 6.0 to 8.5, but preferably in the
range from about 6.0 to 7.0, this being preferred from the viewpoint of
providing performance robustness to contaminated waters of differing
contamination levels and types. To achieve the requisite pH levels, the
weight ratio of primary coagulant to water-soluble alkali will generally
be in the range from about 0.8:1 to about 3:1, preferably from about
0.9:1 to about 2.4:1, and more preferably from about 1:1 to about 2:1.
Generally, the compositions comprise from about 10% to about 45%,
preferably from about 15% to about 40%, more preferably from about 20% to
about 35% by weight of the water-soluble alkali.
[0027] The compositions, methods and kits of the invention can also
include a water-insoluble silicate material such as a clay or zeolite
which acts to aid the flocculation process by acting as a seed particle
or by promoting absorption or cation exchange of metal ions. In preferred
embodiments, the weight ratio of primary coagulant to water-insoluble
silicate herein is from about 0.3:1 to about 5:1, preferably from about
0.7:1 to about 2:1, and more preferably from about 0.8:1 to about 1.2:1.
Generally, the compositions herein comprise from about 10% to about 80%,
preferably from about 20% to about 50%, more preferably from about 25% to
about 35% by weight of the water-insoluble silicate.
[0028] The compositions and kits herein can utilized in a variety of forms
and process types including batch and continuous, but preferably the
composition is in unit dosage form and is used in the batchwise
purification and clarification of a relatively small predetermined volume
of contaminated drinking water. By relatively small volume is meant a
volume of water typically required for immediate consumption in domestic
or personal use, or which is required for short term storage and
consumption. Typically, the compositions herein will be used for treating
a volume of contaminated drinking water in the range from about 0.1 to
about 100, preferably from about 0.5 to about 40, more preferably from
about 5 to about 20 and especially from about 8 to about 13 litres. Unit
dosage amounts of the composition, on the other hand, will generally
range from about 50 to about 2000, preferably from about 100 to about
1000, more preferably from about 250 to about 750 mg per litre of
contaminated drinking water. Unit dosage forms suitable for use herein
include tablets, compacts, extrudates, water-soluble single and
multi-compartment pouches etc but preferred unit dosage forms are single
and multi-compartment sachets comprising a unit dose of granular or
powdered composition which is opened prior to use and the contents
emptied into a predetermined quantity of contaminated drinking water.
[0029] For the above purposes, highly preferred herein is a composition in
unit dosage form comprising;
[0030] (i) from about 15% to about 50%, preferably from about 25% to about
40% by weight of the primary coagulant;
[0031] (ii) from about 0.2% to about 5%, more preferably from about 0.5%
to about 3% by weight of the bridging flocculent; and
[0032] (iii) from about 0.5% to about 5%, more preferably from about 1% to
about 4% by weight of the coagulant aid.
[0033] It is also important to ensure that in-use of the compositions,
effective levels of the formulation ingredients are delivered to the
sample of contaminated water to be purified. Thus the levels of primary
coagulant, bridging flocculant and coagulant aid in composition should
preferably be sufficient to provide by weight of the contaminated
drinking water from about 50 to about 500, preferably from about 75 to
about 300, more preferably from about 100 to about 250 ppm of primary
coagulant, from about 1 to about 15, preferably from about 2 to about 10,
more preferably from about 2.5 to about 7.5 ppm of bridging flocculent,
and from about 1 to about 25, preferably from about 5 to about 20, more
preferably from about 8 to about 12 ppm of coagulant aid.
[0034] In preferred embodiments, the microbiocidal disinfectant is
incorporated in the compositions of the invention in a controlled,
delayed, sustained or slow release form whereby the disinfectant is
released into the drinking water and allowed to react with soluble
organic impurities therein only after substantial completion of the
coagulation and flocculation stage, this being valuable from the
viewpoint of controlling and minimising the level of trihalomethanes
(THM) generated during the purification process. A measure of the rate of
release of disinfectant herein is t.sub.max,, this being the time taken
to achieve maximum residual disinfectant concentration after addition of
the composition to deionized water at 20.degree. C. with gentle stirring.
Preferably the compositions herein have a t.sub.max, of at least about 1
minute, preferably at least about 2 minutes, more preferably at least
about 4 minutes, and especially at least about 8 minutes. The rate of
coagulation and flocculation of organic impurities, on the other hand, is
measured by the n %-ile soluble organic matter flocculation rate
(t.sub.n). The n %-ile soluble organic matter flocculation rate is
defined herein as the time taken for n % reduction in the concentration
of humic acid as measured according to the procedure described
hereinbelow. Preferably, t.sub.80 for the compositions herein is less
than about 2 minutes, preferably less than about 1 minute, more
preferably less than about 30 seconds. In preferred embodiments,
moreover, t.sub.90 for the compositions herein is less than about 2
minutes, preferably less than about 1 minute, more preferably less than
about 30 seconds.
[0035] Thus according to another aspect of the invention, there is
provided a composition for purifying and clarifying contaminated drinking
water and which comprises:
[0036] (i) a primary coagulant selected from the group consisting of
water-soluble, multivalent inorganic salts and mixtures thereof;
[0037] (ii) a water-soluble or water-dispersible polymeric bridging
flocculant; and
[0038] (iii) a microbiocidal disinfectant; and wherein the microbiocidal
disinfectant is in controlled, delayed, sustained or slow release form
whereby the composition has a t.sub.max corresponding to the time for
achieving maximum disinfectant concentration after addition to deionized
water at 20.degree. C. which is greater than the 80%-ile soluble organic
flocculation rate (t.sub.80) of the composition and more preferably
greater than the 90%-ile soluble organic flocculation rate (t.sub.90) of
the composition.
[0039] Preferably t.sub.max is at least about 1 minute, more preferably at
least about 2 minute, even more preferably at least about 4 minutes and
especially at least about 8 minutes greater than t.sub.80 and preferably
greater than t.sub.90.
[0040] The n%-ile organic matter flocculation rate is measured on the
model surface water described herein above. 620 mg of the
water-purification composition is added to a 1 litre sample of the model
surface water with stirring. Aliquots of the liquid are then taken at 30
second intervals, each aliquot being filtered through a 0.45 .mu.m
filter. The colour of the aliquot is then measured using for example a
Hanna H193727 colour meter and compared with a set of standards of known
humic acid concentration and colour reading. The n %-ile soluble organic
matter flocculation rate is the time taken to achieve a colour reading
corresponding to a humic acid level which is (100-n) % of that of the
initial level (24 ppm).
[0041] Preferably the final colour achieved (for example post-filtration
at 30 minutes) using the purification compositions of the invention
either in-vivo or on model surface water is less than 20 PCU, more
preferably less than 15 PCU and especially less than 10 PCU. The final
turbidity achieved using the purification compositions of the invention
either in-vivo or on model surface water, on the other hand, is
preferably less than 5 NTU, more preferably less than 2 NTU and
especially less than 1 NTU, turbidity being measured using a Jenway
603.5turbidity meter calibrated daily against a 5.0 NTU standard.
[0042] In an alternative embodiment, the disinfectant and
water-purification composition can be used in separate treatment steps,
either simultaneously or sequentially with one another.
[0043] Preferably, the weight ratio of water-purification composition to
disinfectant when used separately is from 10000:1, or preferably from
5000:1 or preferably from 1000:1, or preferably from 500:1, and
preferably to 2:1, or preferably to 10:1, or preferably to 25:1, or
preferably to 50:1, or preferably to 100:1.
[0044] The compositions, methods and kits of the invention also preferably
comprise a food additive or nutrient source, this being valuable from the
viewpoint of providing drinking water which is not only pure but which
also contains essential minerals and other food additives necessary for
good health and nutrition. The food additive or nutrient source can be
included in the kits of the invention as one or more separate
compositions in unit dosage form, or they can be incorporated directly
into the water-purification composition itself.
[0045] Thus, according to a further aspect of the invention, there is
provided a composition for purifying, clarifying and nutrifying
contaminated drinking water and which comprises:
[0046] (i) a primary coagulant selected from the group consisting of
water-soluble, multivalent inorganic salts and mixtures thereof;
[0047] (ii) a water-soluble or water-dispersible polymeric bridging
flocculant; and
[0048] (iii) a food additive or nutrient source.
[0049] In the case of food additives and nutrient sources which are
non-coagulable or which at least partially survive the coagulation and
flocculation process, for example fluoridating agents, iodinating agents,
and essential minerals such as zinc and iron, the food additive or
flocculent can be incorporated without special measures into the water
purification composition. Otherwise, the food additive or nutrient
sources can also be incorporated in controlled, delayed, sustained or
slow release form as described herein with respect to the disinfectant.
In this instance, the composition should have has a t.sub.max
corresponding to the time for achieving maximum nutrient concentration
after addition to deionized water at 20.degree. C. which is greater than
the 80%-ile soluble organic flocculation rate (t.sub.80) and preferably
greater than the 90%-ile soluble organic flocculation rate (t.sub.90) of
the composition.
[0050] It is also desirable herein to control the free moisture content of
the water-purification compositions, especially in those compositions of
the invention comprising calcium hypochlorite as microbiocidal
disinfectant. It should be understood that many of the ingredients of the
compositions herein such as the bentonite clays, alum based coagulants,
etc contain a natural amount of free moisture and this has been found to
be especially detrimental to calcium hypochlorite stability. In preferred
embodiments, therefore, the compositions of the invention should have a
free-moisture content of less than about 6%, preferably less than about
4% and more especially less than about 2.5% by weight thereof. It is also
highly desirable to incorporate one or more ingredients which are capable
of acting as a moisture sink, for example, low-moisture, pre-dried clays
and hydratable salts in anhydrous or partly hydrated form whereby the
free moisture content of the composition is maintained below the
theoretical amount necessary for 100% hydration of the components of the
composition. Particularly preferred moisture sinks include pre-dried
clays and aluminosilicates, anhydrous sodium carbonate, and mixtures
thereof. Preferably the moisture silks have a free moisture content of
less than about 4%, more preferably less than about 3%, especially less
than about 2.5% and more especially less than about 1.5% by weight. Free
moisture content of the product or moisture sink is determined as
follows. A 2 g sample of the product or moisture sink is extracted into
50 mls of dry methanol at room temperature for 20 mins. A 1 ml aliquot of
this solution is then taken and the free moisture determined by a
standard Karl Fischer titration. The free moisture is expressed as the
percentage weight of water relative to the sample weight (in this case 2
g).
[0051] Thus according to another aspect of the invention, there is
provided a composition for purifying and clarifying contaminated drinking
water and which comprises:
[0052] (i) a primary coagulant selected from the group consisting of
water-soluble, multivalent inorganic salts and mixtures thereof;
[0053] (ii) a water-soluble or water-dispersible polymeric bridging
flocculent;
[0054] (iii) calcium hypochlorite as microbiocidal disinfectant; and
optionally
[0055] (iv) a moisture sink, and wherein the composition has a
free-moisture content of less than about 6%, preferably less than about
4% and more especially less than about 2.5% by weight thereof.
[0056] The present invention also relates to methods for purifying
contaminated drinking water comprising contacting the water with at least
a primary coagulant material and a bridging flocculent material wherein
the levels and ratios of coagulant to flocculent preferably fall within
certain ranges. Highly preferred methods also comprise contacting the
drinking water with one or more of a coagulant aid, a microbiocidal
disinfectant, a disinfectant neutralization agent; a water-soluble
alkali, a water-insoluble silicate (for example a clay, zeolite or
mixture thereof), and a food additive or nutrient source.
[0057] Thus in a method aspect, the invention relates to a method for
purifying and clarifying contaminated drinking water and which comprises
contacting the contaminated water with:
[0058] (i) a primary coagulant selected from the group consisting of
water-soluble, multivalent inorganic salts and mixtures thereof;
[0059] (ii) a bridging flocculent selected from the group consisting of
water-soluble and water-dispersible anionic and nonionic polymers having
a weight average molecular weight of at least about 2,000,000, and
mixtures thereof; and
[0060] (iii) a coagulant aid selected from the group consisting of
water-soluble and water-dispersible cationic polymers having a weight
average molecular weight of less than about 1,500,000, and mixtures
thereof.
[0061] In a another method aspect, the invention relates to a method for
purifying and clarifying contaminated drinking water and which comprises
contacting the contaminated water with:
[0062] (i) a primary coagulant selected from the group consisting of
water-soluble, multivalent inorganic salts and mixtures thereof;
[0063] (ii) a water-soluble or water-dispersible polymeric bridging
flocculant preferably selected from the group consisting of water-soluble
and water-dispersible anionic and nonionic polymers, the polymeric
bridging flocculent having a weight average molecular weight of at least
about 2,000,000, and wherein the weight ratio of primary coagulant to
bridging flocculant is from about 10:1 to about 150:1, preferably from
about 20:1 to about 100:1, and more preferably from about 25:1 to about
75:1; and optionally
[0064] (iii) a water-soluble or water-dispersible polymeric coagulant aid
preferably selected from the group consisting of water-soluble and
water-dispersible cationic polymers, the polymeric coagulant aid having a
weight average molecular weight of less than about 1,500,000.
[0065] The present invention further relates to a method for purifying,
clarifying and nutrifying contaminated drinking water and which comprises
contacting the contaminated water with:
[0066] (i) a primary coagulant selected from the group consisting of
water-soluble, multivalent inorganic salts and mixtures thereof;
[0067] (ii) a water-soluble or water-dispersible polymeric bridging
flocculant; and
[0068] (iii) a food additive or nutrient source.
[0069] The methods of the invention comprise a number of distinct chemical
and physical stages which can run either concurrently or in sequence. In
broad terms, these stages include
[0070] (i) a coagulation and flocculation stage in which the contaminated
drinking water is brought into mixing contact with the coagulant,
bridging flocculant and, if present, the coagulant aid so as to coagulate
and flocculate the water impurities in the form of solid matter;
[0071] (ii) a disinfectant stage in which the drinking water is brought
into microbiocidal contact with the disinfectant during or after
substantial completion of the coagulation and flocculation stage;
[0072] (iii) a separation stage prior or subsequent to the disinfectant
stage in which the solid matter is physically separated from the drinking
water.
[0073] Preferably, the drinking water is brought into microbiocidal
contact with the disinfectant after substantial completion of the
coagulation and flocculation stage whereby t.sub.max as hereinabove
defined is greater than the 80%-ile soluble organic flocculation rate
(t.sub.80) and preferably greater than the 90%-ile soluble organic
flocculation rate (t.sub.90) of the composition.
[0074] In addition, the methods of the invention also preferably include a
neutralization stage in which the drinking water is brought into contact
with a disinfectant neutralization agent subsequent to said separation
stage in order in order to maintain drinking water purity during storage
of the drinking water but to reduce or remove excess disinfectant prior
to use. In the case of chlorine-based disinfectants, suitable
disinfectant neutralization agents include activated carbon and reducing
agents such as sodium thiosulfate, sodium sulphite, hydrogen peroxide and
sodium percarbonate.
[0075] Thus, according to a further aspect of the invention, there is
provided a method for purifying and clarifying contaminated drinking
water and which comprises subjecting the contaminated water to:
[0076] (i) a coagulation and flocculation stage in which the contaminated
drinking water is brought into mixing contact with a primary coagulant, a
polymeric bridging flocculant and, optionally a polymeric coagulant aid
so as to coagulate and flocculate the water impurities in the form of
solid matter;
[0077] (ii) a disinfectant stage in which the drinking water is brought
into microbiocidal contact with a disinfectant during or after
substantial completion of the coagulation and flocculation stage;
[0078] (iii) a separation stage prior or subsequent to the disinfectant
stage in which the solid matter is physically separated from the drinking
water; and (iv) a neutralization stage in which the drinking water is
brought into contact with a disinfectant neutralization agent subsequent
to said separation stage in order to reduce or remove excess
disinfectant.
[0079] In addition, the methods of the invention also preferably include a
nutrifying stage in which the drinking water is brought into contact with
the food additive or nutrient source prior or subsequent to the
separation stage.
[0080] Thus in a further method aspect, there is provided a method for
purifying, clarifying and nutrifying contaminated drinking water and
which comprises subjecting the contaminated water to:
[0081] (i) a coagulation and flocculation stage in which the contaminated
drinking water is brought into mixing contact with a primary coagulant, a
polymeric bridging flocculant and, optionally a polymeric coagulant aid
so as to coagulate and flocculate the water impurities in the form of
solid matter;
[0082] (ii) a disinfectant stage in which the drinking water is brought
into microbiocidal contact with a disinfectant during or after
substantial completion of the coagulation and flocculation stage;
[0083] (iii) a separation stage prior or subsequent to the disinfectant
stage in which the solid matter is physically separated from the drinking
water; and
[0084] (iv) a nutrifying stage in which the drinking water is brought into
contact with a food additive or nutrient source prior or subsequent to
the separation stage.
[0085] In the method aspects of the invention, the primary coagulant is
generally added in an amount of from about 50 to about 500, preferably
from about 75 to about 300, more preferably from about 100 to about 250
ppm by weight of the contaminated drinking water; the bridging flocculant
is generally added in an amount of from about 1 to about 15, preferably
from about 2 to about 10, more preferably from about 2.5 to about 7.5 ppm
by weight of the contaminated drinking water; the coagulant aid is
generally added in an amount of from about 1 to about 25, preferably from
about 5 to about 20, more preferably from about 8 to about 12 ppm by
weight of the contaminated drinking water; and the microbiocidal
disinfectant is added in an amount of from about 2 to about 25,
preferably from about 3 to about 20, more preferably from about 4 to
about 15 ppm by weight of the contaminated drinking water. The volume of
contaminated drinking water treated according to the methods of the
invention is preferably in the range from about 0.1 to about 100, more
preferably from about 0.5 to about 40, yet more preferably from about 5
to about 20, and especially from about 8 to about 13 litres.
[0086] Although any convenient method of separating the solid matter from
the partially purified drinking water can be utilized, for example, by
decanting, sedimentation, flotation, etc, preferably separation is
accomplished by filtration in a separation stage using a paper, non-woven
or cloth filtration element. Moreover, separation of the solid matter is
preferably accomplished in a single filtration step without the need for
change of the filtration element. It is a feature of the invention that
the compositions and methods have superior filtration characteristics
through disposable paper and non-woven filters and such filtration means
may be preferred for optimum performance in removing cysts and bacterial
contamination. The compositions and methods of the invention also provide
superior filtration characteristics through cloth filtration elements
made of a hydrophilic substrate such as cotton and such systems may be
preferred from the viewpoint of cost and environmental considerations
whilst at the same time providing highly effective filtration
performance.
[0087] The compositions, methods and kits of the invention are
particularly valuable in the purification of water which has been
contaminated with heavy metals such as arsenic and/or lead and are
effective in purifying water to an arsenic concentration below about 5
ppb, preferably below about 2 ppb and to a lead concentration below about
15 ppb, preferably below about 10 ppb.
[0088] The compositions, methods and kits of the invention are also
valuable in the purification of water which has been contaminated with
soluble organic impurities such as humic acid and are effective in
purifying water to a total organic content below about 10 ppm, preferably
below about 7 ppm and more preferably below about 4 ppm and to a
trihalomethane (THM) level below about 100 ppb, preferably below about 70
ppb, more preferably below about 40 ppb.
[0089] The compositions, methods and kits of the invention are also
valuable in the purification of water which has been contaminated with
cysts such as Giardia and Cryptosporidium parvum and wherein the cyst
concentration is reduced by a factor of at least about log 2, preferably
at least about log 3, and more preferably by a factor of at least about
log 3.5.
[0090] In a kit aspect, the present invention relates to a kit for
purifying and clarifying contaminated drinking water and which comprises
[0091] (i) one or more unit doses of the water-purification composition
herein, and
[0092] (ii) means for physically separating solid matter from drinking
water.
[0093] The means for physically separating solid matter from drinking
water includes cloth, paper and non-woven filters as described
hereinabove.
[0094] The kits of the invention can additionally comprise one or more
unit doses of a microbiocidal disinfectant composition and/or one or more
unit doses of a food additive or nutrient composition. The microbiocidal
disinfectant composition can be used with the water-purification
composition either simultaneously or sequentially. Also the food additive
or nutrient composition can be used with the water-purification
composition either simultaneously or sequentially.
DETAILED DESCRIPTION OF THE INVENTION
[0095] Primary Coagulant
[0096] Primary coagulants suitable for use herein include water-soluble
inorganic salts and mixtures thereof. In highly preferred embodiments,
the composition herein comprises an inorganic metal salt selected from
the group consisting of iron sulphate, iron chloride, manganese sulphate,
manganese chloride, copper sulphate, copper chloride, aluminium sulphate,
aluminium chloride, poly- variations thereof, and combinations thereof.
The inorganic metal salt of the composition of the present invention is
selected on the basis that it can act as a coagulant and can interact
with charged water-soluble impurities in such a manner so as to
neutralise the charge of said water-soluble impurity to form a
water-insoluble impurity, usually to form a water-insoluble salt of said
impurity, which precipitates out of solution. The inorganic salt of the
composition of the invention can also lower the turbidity of the water by
increasing the particle size of the water-insoluble impurities possibly
causing sedimentation or facilitating the removal of these
water-insoluble impurities by filtration or other water-insoluble matter
removal techniques such as flotation or decanting. The inorganic salts
selected herein, can also co-precipitate heavy metal ions out of water,
and can also lower the total organic content present in the water by
coagulating or adsorption of this organic content onto the
water-insoluble impurities which have been formed in the water.
[0097] Preferably the inorganic metal salt of the composition of the
invention is a multivalent, preferably a di- or tri-valent, inorganic
metal salt such as, aluminium III sulphate, iron II (ferrous) sulphate or
iron III (ferric) sulphate. A most preferred inorganic metal salt for use
herein is iron III sulphate. The term "inorganic metal salt" includes all
poly-variations thereof such as polyaluminum chloride and polyferric
material, but does not include compounds comprising methyl or ethyl
groups. The inorganic metal salt is preferably free of carbon atoms. The
term "inorganic metal salts which are free of carbon atoms" includes
sources of inorganic metal salts winch comprise minor amounts of carbon
impurity such as often found in naturally occurring inorganic metal salt
sources. For example, preferred inorganic metal salts of the composition
of the invention comprise (by weight of said salt) less than 5%, more
preferably less than 3%, more preferably less than 1%, even more
preferably less than 0.1%, even more preferably less than 0.01% carbon
atoms.
[0098] Particularly preferred are those inorganic metal salts which are a
source of acid, such as aluminium III sulphate or iron sulphate. This is
especially true when the composition herein also comprises a source of
carbonate such as sodium carbonate, since the acid source, and carbonate
source, may react together to form a gas. This process is known as
effervescence and helps to disperse the composition herein, especially
when the composition herein is in the form of a tablet.
[0099] The composition herein preferably comprises (by weight) from 1%, or
preferably from 5%, or preferably from 10%, or preferably from 15%, or
preferably from 20%, or preferably from 25%, and preferably to 50%, or
preferably to 40%, or preferably to 30% inorganic salt selected fiom the
group consisting of iron sulphate, iron chloride, manganese sulphate,
manganese chloride, copper sulphate, copper chloride, aluminium sulphate,
aluminium chloride, poly- variations thereof, and combinations thereof.
[0100] Coagulant Aid
[0101] The water purification composition herein preferably comprises a
coagulant aid (sometimes referred to herein as `first polymeric
material`). Highly preferred are polymeric materials which comprises an
amine group and which are therefore cationic in nature. The first
polymeric material is selected on the basis that it can aid the
coagulation and flocculation process and in particular can in conjunction
with the primary coagulant aid particle adherence and the aggregation of
water-insoluble particles into larger water-insoluble aggregated
complexes known as flocs. The first polymeric material may also adsorb or
coagulate oils, fats and other organic or inorganic matter, and may
sequester heavy metal ions.
[0102] The term "amine group" is defined herein as including primary amine
groups, secondary amine groups, tertiary amine groups, quaternary amine
groups such as quaternary ammonium groups, but the term "amine group"
does not include amide groups. Said amine group can be the group linking
the monomeric units of the backbone of the polymeric material, or may be
present as a side group of the polymeric material, for example as an
amine side group of a polysaccharide. Preferably the amine group is
present as a side group.
[0103] Preferably, the polymeric material is substantially
water-insoluble. "Substantially water-insoluble" is defined herein as
having at least 10% by dry total weight of undissolved material present
as determined by the following method:
[0104] 1 g material is added to 1 litre of distilled water at a pH of
between 6.0 and 8.0, at 20.degree. C. and stirred vigorously for 24
hours. The water is then filtered through a 3 micrometer filter, and the
undissolved material which is collected by the filter step is dried at
80.degree. C. until constant weight, typically for 24 to 48 hours. The
weight of this undissolved material is then determined and the % dry
weight of this undissolved material can be calculated.
[0105] The amine group of the first polymeric material is preferably at
least partly protonated when the first polymeric material comes into
contact with water, typically this protonation reaction occurs at a pH of
below 9.0, and preferably at a pH of from 3 to 8. Thus, preferably the
first polymeric material is cationic when in a solution of water at a pH
of below 9. Alternatively, the amine group of the first polymeric
material may already be in a charged state, for example a substituted or
protonated state. The amine group of the first polymeric material may be
a cationic quaternary ammonium group.
[0106] The first polymeric material preferably comprises a polysaccharide
comprising an amine group. The first polymeric material may comprise a
cationic starch, for example, cationic starch obtained from potato
starch, waxy maize starch, corn starch, wheat starch and rice starch.
More preferably, the first polymeric material comprises a polysaccharide
which comprises an amine group which is bound directly to the monomer
saccharide backbone unit of said polysaccharide. More preferably the
first polymeric material comprises a polymer of glucosamine where all the
monomer saccharide backbone units are connected in a linear conformation
via beta-1-4-glycosidic bonds. More preferably, the first polymeric
material comprises a modified chitin, such as chitosan, modified
chitosan, or salts thereof. Most preferably the first polymeric material
comprises chitosan or modified chitosan. The first polymeric material may
be an impurity of chitin, and therefore, chitin may be a preferred source
of first polymeric material for use herein.
[0107] Chitosan suitable for use herein is typically derived from the
chitin of crustacea such as crabs, lobsters and shrimps. Chitosan derived
from the chitin of fungi can also be used herein. The chitosan for use
herein is typically found in the shells of crustacea and can be extracted
by any technique known in the art, for example by using the extraction
techniques described in U.S. Pat. No. 3,533,940, U.S. Pat. No.3,862,122,
U.S. Pat. No. 3,922,260 and U.S. Pat. No. 4,195,175.
[0108] The first polymeric material for use herein typically has an amine
modification degree of at least 0.1, more preferably at least 0.2, or
preferably at least 0.3, or preferably at least 0.4, or preferably at
least 0.5, or preferably at least 0.6, or preferably at least 0.7, or
preferably at least 0.8, or preferably at least 0.9, or preferably at
least 1.0. Said modification degree is an indication of the amount of
amine groups present in the polymeric material and is defined as the
number ratio of the number of amine groups present in the polymeric
material per monomer unit of the polymeric material.
[0109] Preferably, the first polymeric material has a weight average
molecular weight of at least 10000, or preferably at least 25000, or
preferably at least 50000, or preferably at least 75000, or preferably at
least 100000.
[0110] The composition herein preferably comprises (by weight) from 0.1%,
or preferably from 0.5%, or preferably from 1%, or preferably from 1.5%,
or preferably from 2%, or preferably from 2.5%, and preferably to 50%, or
preferably to 40%, or preferably to 30%, or preferably to 20%, or
preferably to 10%, or preferably to 5%, or preferably to 4% first
polymeric material.
[0111] Bridging Flocculant
[0112] The composition also herein comprises a bridging flocculant
(sometimes referred to herein as the second polymeric material).
Preferably the second polymeric material is substantially water-soluble
at in-use concentrations and has a weight average molecular weight of at
least about 100,000, preferably at least about 2000000. The second
polymeric material is selected on the basis that it can act as flocculent
and cause the aggregation of water-insoluble particles into larger
water-insoluble aggregated complexes known as flocs. It is believed that
the ability of the second polymeric material to act as a flocculent, is
due to the combination of its high molecular weight, structure, and
water-solubility properties.
[0113] The second polymeric material is usually of greater molecular
weight than the first polymeric material and preferably does not comprise
an amine group. Preferably the second polymeric material comprises an
amide group. More preferably the second polymeric material is a
polyacrylamide. The second polymeric material is preferably not a
cationic polyacrylanide, and preferably, the second polymeric material is
not cationic.
[0114] Preferably, the second polymeric material for use herein is
nonionic or anionic, preferably anionic, more preferably the second
polymeric material contains at least 0.02, or preferably at least 0.05,
or preferably at least 0.1 anionic groups per monomer unit.
[0115] The second polymeric material for use herein is typically a
polyacrylamide, especially preferred are anionic or nonionic
polyacrylamides. Typical anionic and nonionic polyacrylamides for use
herein are those from the Magnafloc range supplied by Ciba. Of these
polyacrylamides, especially preferred are those known under the trade
name as Magnafloc LT20, Magnafloc LT25, Magnafloc LT25S, Magnafloc LT26,
Magnafloc LT28, Magnafloc 351 and Magnafloc 919.
[0116] It is preferred that a low amount of substantially water-soluble
organic content is present in the composition herein. The term "low
amount of substantially water-soluble content" can be determined by the
following method:
[0117] 500 mg of said composition is added to 1 litre of deionised water
which comprises no detectable amounts of substantially water-soluble
organic content, to form a solution. Said solution is left with
occasional stirring for 30 minutes and is then filtered through Whatman
GF/C paper having an average pore size of 1.2 micrometers to obtain
purified water. The level of total organic content (TOC) of said purified
water is determined using the ISO method 8245:1999. A composition
comprising "a substantially low amount of water-soluble content" is
defined as a composition which gives a TOC of said purified water of less
than 10 ppm, preferably less than 7 ppm, more preferably less than 4 ppm
when determined using this method.
[0118] It is also preferred that a low amount of substantially
water-soluble organic content is obtained on use of the composition
either in-vivo or on model surface water. For this purpose, 620 mg of the
composition is added to 1 litre of in-vivo or model surface water
respectively and the test repeated. Preferably, the TOC of the water
after treatment is less than 10 ppm, more preferably less than 7 ppm, and
especially less than 4 ppm.
[0119] Preferably, the second polymeric material does not comprise a
polysaccharide and more preferably the second polymeric material does not
comprise a carboxymethyl cellulose or derivative thereof.
[0120] Preferably, the weight average molecular weight of the second
polymeric material is at least 2500000, or preferably at least 3000000,
or preferably at least 5000000, or preferably at least 7500000, or
preferably at least 10000000, or preferably at least 15000000.
[0121] Preferably, the composition herein comprises (by weight) from 0.1%,
or preferably from 0.2%, or preferably from 0.5%, or preferably from 1%,
and preferably to 30%, or preferably to 20%, or preferably to 10%, or
preferably to 5%, or preferably to 3% second polymeric material.
[0122] Microbiocidal Disinfectant
[0123] The composition herein preferably comprises a microbiocidal
disinfectant (sometimes referred to herein as the disinfecting agent).
The disinfecting agent may comprise any compound which disinfects or
sanitises water. The disinfecting agent may be inorganic such as silver
salts,
colloidal silver, nanosilver, ozone, chlorine dioxide, chlorine,
sodium hypochlorite or chloramine. The disinfecting agent may also be
organic such as a quaternary ammonium compound. Preferred disinfecting
agents include inorganic chlorine based disinfectants, wherein the
chlorine is in a formal oxidation state that is not minus one, preferably
above minus one. Preferred sources of chlorine comprise hypochlorites
(especially calcium hypochlorite) and organic sources of chlorine such as
isocyanurates. Other preferred disinfecting agents comprise iodine and
sources of iodine such as polyiodide resins.
[0124] As previously discussed, the disinfecting agent is preferably used
in a controlled, delayed, sustained or slow release form. Means for
providing such controlled, delayed, sustained or slow release (hereafter
`means for providing delayed release`) can include blending or coating
the disinfecting agent with, for example, a poorly water-soluble or
hydrophobic material, or providing a coating of sufficient thickness that
the kinetics of dissolution of the coating provide delayed release.
Poorly water-soluble or hydrophobic materials include waxes, paraffins,
silicas, zeolites, clays, polymeric resins, celluloses, cross-linked
polymers, insoluble salts such as calcium carbonate, etc. The coating
material can be applied by agglomeration in, for example, pan, rotary
drum and vertical blenders, or by spray atomization. Other means for
providing delayed release include mechanical means for altering the
physical properties of the disinfecting agent, for example, compaction,
granulation means for altering the particle size distribution of the
disinfecting agent, etc.
[0125] Highly preferred herein from the viewpoint of achieving optimum
flocculation and disinfectancy performance in water contaminated with
high levels of organic impurities is a particulate disinfecting agent,
preferably calcium hypochlorite, having a particle size distribution such
that at least about 50%, preferably at least about 75%, more preferably
at least about 90% by weight is retained on a 210 .mu.m (Tyler 65 mesh)
screen, preferably on a 425 .mu.m (35 mesh) screen, more preferably on a
600 .mu.m (28 mesh) screen, yet more preferably on a 710 .mu.m (24 mesh)
screen, even more preferably on a 850 .mu.m (20 mesh) screen, and
especially on a 1000 .mu.m (16 mesh) screen.
[0126] In order to minimise random sampling variance in the final unit
dose composition, it is also preferred that the particulate disinfecting
agent has a particle size distribution such that at least about 50%,
preferably at least about 75% by weight thereof passes through a 2000
.mu.m (9 mesh) screen and more preferably through a 1400 .mu.m (12 mesh)
screen.
[0127] The composition herein preferably comprises (by weight) from 0.01%,
or preferably from 0.1%, or preferably from 0.2%, or preferably from
0.5%, or preferably from 0.7%, or preferably from 1.0%, or preferably
from 1.2%, or preferably from 1.5%, and preferably to 20%, or preferably
to 10%, or preferably to 5%, or preferably to 4%, or preferably to 2.5%
disinfecting agent.
[0128] Water-Insoluble Silicate
[0129] The composition herein preferably comprises a water-insoluble
silicate selected from clays, zeolites and mixtures thereof.
[0130] Highly preferred silicates for use herein are clays. The clay acts
as a seed particle onto which water-insoluble impurities can aggregate to
form floes. The presence of clay in the composition improves the rate of
floc formation and allows the formation of larger flocs compared to when
clay is absent from the composition herein. The clay may also act as a
swelling agent, and if the composition herein is in the form of a tablet,
the clay improves the rate at which the tablet disintegrates on contact
with water by swelling upon contact with water so that the components of
the tablet are pushed apart by the swollen clay particles. The clay can
also act as a desiccant within the tablet. The clay may also act as a
cationic exchange agent to remove metal ions from the water and the clay
can also remove colour, heavy metals and some organic material from water
by adsorption.
[0131] The clay is preferably a smectite clay, preferably a dioctahedral
smectite clay such as montmorillonite clay or a trioctahedral smectite
clay such as hectorite clay. Those clays found in bentonite clay deposits
are also preferred. Particularly preferred clays for use herein include
laponite clay, hectorite, montmorillonite, nontronite, saponite,
volkonsite, sauconite, beidellite, allevarlite, illite, halloysite and
attapulgite. In compositions containing calcium hypochlorite, the free
moisture content of the clay should be carefully controlled to provide
acceptable disinfectant stability. Preferably the free moisture content
should be less than about 4%, more preferably less than about 3%,
especially less than about 2.5% and more especially less than about 1.5%
by weight. Free moisture content is determined on a 2 g sample of the
test material following the procedure as described hereinabove.
[0132] Highly preferred for use herein from the viewpoint of providing
optimum disinfectant stability are pre-dried clays which in their
dessicated form have the potential to scavenge or pick up moisture. Such
clays can be described in terms of their so-called `water-capacity`,
defined herein as the equilibrium weight percentage of moisture picked up
by a small sample (e.g. 10 mg) of the dessicated material from air at 80%
relative humidity and 20.degree. C. as measured by dynamic vapour
sorption techniques. For example, if 10 mg of the dessicated clay picks
up 2 mg moisture, the dessicated clay has a water capacity of 20%.
Preferred for use herein are dessicated clays having a water capacity of
at least about 10%, preferably at least about 15%, and more preferably at
least about 18%.
[0133] The composition herein preferably comprises (by weight) from 1%, or
preferably from 5%, or preferably from 10%, or preferably from 15%, or
preferably from 20%, or preferably from 25%, and preferably to 80%, or
preferably to 50%, or preferably to 35% clay.
[0134] Aluminosilicates may be used herein in place of, or in addition to,
clay. The aluminosilicate can act as a cationic exchange agent to remove
metal ions from water, and can also act as a seed particle to enhance
floc formation and as dessicant for enhancing disinfectant stability.
Preferred aluminosilicates for use herein include zeolite A, zeolite X,
zeolite Y, zeolite P and zeolite beta. Preferably the free moisture
content of the aluminosilcate should be less than about 4%, more
preferably less than about 3%, especially less than about 2.5% and more
especially less than about 1.5% by weight.
[0135] Highly preferred for use herein from the viewpoint of providing
optimum disinfectant stability are pre-dried aluminosilicates which in
their dessicated form have the potential to scavenge or pick up moisture.
Such dessicated aluminosilicates can also be described in terms of their
so-called `water-capacity`, as defined hereinabove. Preferred for use
herein are dessicated aluminosilicates having a water capacity of at
least about 10%, preferably at least about 15%, and more preferably at
least about 18%.
[0136] The composition herein preferably comprises (by weight) from 1%, or
preferably from 5%, or preferably from 10%, or preferably from 15%, or
preferably from 20%, or preferably from 25%, and preferably to 80%, or
preferably to 50%, or preferably to 35% aluminosilicate.
[0137] A Third Polymeric Material
[0138] The composition herein may comprise a third polymeric material.
Said third polymeric material does not contain an amine group and is
substantially water insoluble. The term "substantially water insoluble"
is defmed hereinbefore. Thus, the third polymeric material is different
to, and is not, the first polymeric material or the second polymeric
material. The third polymeric material is selected on the basis that it
can act as a seed particle to enhance floc formation. The third polymeric
material can be used in place of, or in addition to, clay or zeolite.
Preferably the free moisture content of the third polymeric material
should be less than about 4%, more preferably less than about 3%,
especially less than about 2.5% and more especially less than about 1.5%
by weight.
[0139] Preferably the third polymeric material comprises cellulose, more
preferably the third polymeric material is an unmodified cellulose. Most
preferably the third polymeric material comprises powdered cellulose.
[0140] The composition herein preferably comprises (by weight) from 1%, or
preferably from 5%, or preferably from 10%, or preferably from 15%, or
preferably from 20%, or preferably from 25%, and preferably to 80%, or
preferably to 50%, or preferably to 35% third polymeric material.
[0141] Alkali Agent
[0142] The composition herein may comprise an alkali agent. The alkali
agent can be any compound which gives alkalinity when contacted to water.
The alkali agent for use herein is not a polymeric material. The
composition herein preferably comprises an amount of alkali agent such
that when the composition herein is contacted to water to form a
solution, said solution has a pH of from 5 to 8, preferably from 6 to 7.
[0143] Preferred alkali agents are selected from the group consisting of
sodium carbonate, sodium bicarbonate, sodium hydroxide, sodium oxide,
calcium carbonate, calcium bicarbonate, calcium hydroxide, calcium oxide,
potassium carbonate, potassium bicarbonate, potassium hydroxide,
potassium oxide and combinations thereof.
[0144] Particular alkali agents which are a source of carbonate when
contacted to water, for example sodium carbonate or sodium bicarbonate
may be preferred for used herein. If the composition herein comprises a
source of acid, for example an inorganic salt of the composition of the
present invention such as iron sulphate, said alkali agent which is a
source of carbonate can interact with said acid source in the presence of
water to produce a gas. This process is known as effervescence, and
improves the rate at which the composition disperses, especially when the
composition herein is in the form of a tablet.
[0145] Highly preferred herein, especially in compositions containing
calcium hypochorite as disinfecting agent, are alkalis which can also act
as moisture sinks, especially anhydrous sodium carbonate.
[0146] The composition herein typically comprises (by weight) from 1% to
50%, preferably from 10%, or preferably from 15%, or preferably from 20%,
or preferably from 25%, and preferably to 45%, or preferably to 40%, or
preferably to 35% alkali agent.
[0147] Composition
[0148] The composition herein is preferably in a solid unit dose form,
most preferably in a tablet or powder form. The composition herein is
preferably packaged so that it is protected from environmental conditions
such as moisture. Preferably the composition herein is packaged in a
water impermeable material such as polypropylene or typical laminates. An
example of one such laminate is a laminate supplied by Akerlund & Raus,
comprising layers of coated paper (outer), LDPE, aluminium foil and an
inner layer Surlyn (an ethylene/methacrylate co-polymer)--an FDA approved
food packaging.
[0149] Method for Use
[0150] The composition herein can be used to purify water using a method
comprising the steps of (a) contacting the composition herein to water to
obtain partially purified water comprising solid matter; and (b) removing
at least part of said solid matter from said partially purified water by;
(i) filtration; or (ii) decanting; or (iii) sedimentation; or (iv)
flotation; or (v) a combination thereof, to obtain purified water.
[0151] The composition herein can be in the form of a tablet or solid
powder which is added to water, typically to form partially purified
water comprising solid matter such as floes. This solid matter can be
removed or separated from the remaining part of the partially purified
water by any technique, typically by filtration but decanting,
sedimentation and flotation may also be used. By filtration it is meant
passing the partially purified water through a filter. Filtration can
occur by pouring means, for example by pouring said partially purified
water through a filter to remove at least part of the solid matter from
said partially purified water. Filtration can also occur by centripetal
force means, for example by total enclosing the partially purified water
by a filter and spinning said partially purified water and said filter so
that said partially purified water passes through said filter and at
least part of said solid matter is separated from said partially purified
water. Filtration can also occur by plunging means, for example by
plunging or moving a filter through said partially purified water so that
at least part of said solid matter is separated from said partially
purified water.
[0152] Filters typically used include cloth filters, non-woven and paper
filters and polishing filters, such as filters comprising activated
carbon, glass fibre, zeolite, ion exchange media, or a combination
thereof, which remove residual water-impurities, e.g. organic matter,
heavy metal ions and residual disinfectant from the water. Filters
suitable for use may be impregnated with silver or other biostatic
components so that bacteria cannot grow on said filter and the filter can
be reused several times without contaminating the water being filtered.
Sand filters can also be used, and more than one filter may be used in
combination herein.
[0153] Preferably, from 10 mg, or preferably from 50 mg, or preferably
from 75 mg, or preferably from 100 mg, or preferably from 150 mg, or
preferably from 200 mg, or preferably from 250 mg, or preferably from 300
mg, and preferably to 2000 mg, or preferably to 1000 mg, or preferably to
750 mg of composition herein is added to 1 litre of water. The amount of
composition herein which is added to the water depends on the impurity of
said water. For example, less composition is needed to adequately purify
water which is not very impure compared to the amount of composition
herein which is needed to purify very impure water.
EXAMPLES
Example 1
[0154] The following compositions are in accord with the present
invention. All percentages are by weight of composition.
1
Composition
Ingredient A B C D E F G H I J K
Chitosan 3.5 4 1.5 3 15 1 2 3 1.5
Cationic modified
3 1
potato starch
Magnafloc LT20 2 5 10 1
Magnafloc LT25 1.5 2 1 3 3
Magnafloc LT28 3 1 5 1.5
Aluminium 32 15 10 30 45 25 10 35
sulphate
Iron III
sulphate 30 22 25
Calcium 2 0.5 1
hypochlorite
Iodine 1
Hectorite clay 40 15 20 40 25
Montmorillonite 30 32 55 5 70
clay
Zeolite X 12 70
20
Sodium carbonate 30 25 15 10 30 10 25
Sodium 22
45 25 35
bicarbonate
Miscellaneous to to to to to to to
to to to to
100 100 100 100 100 100 100 100 100 100 100
Example 2
[0155] 500 mg of the compositions A to K from example 1 were added in
powder or tablet from to 1 litre of water, respectively. The water was
then agitated or stirred briefly. The water was left to stand for 5
minutes, after which said water was stirred or agitated for a further
minute and then left to stand for another 20 minutes. During this time,
water-insoluble floes formed in the water. The was then poured through a
tightly woven cloth filter to remove said water-insoluble floes, and the
remaining part of the water was collected. This remaining part of the
water is purified water.
Example 3
[0156] 500 mg of the compositions A, C, D, F, G, I, J and K were added in
powder or tablet from to 1 litre of water, respectively. The water was
then agitated or stirred briefly. The water was left to stand for 10
minutes, after which said water was stirred or agitated for a further
minute and then left to stand for another 20 minutes. During this time,
water-insoluble flocs formed in the water. The was then poured through a
tightly woven cloth filter to remove said water-insoluble floes, and the
remaining part of the water was collected. 1 mg calcium hypochlorite was
then added to the collected water, and the collected water was agitated
or stirred briefly. This collected water is purified water.
Example 4
[0157] The following are further compositions according to the invention.
All percentages are by weight of composition.
2
Composition
Ingredient L M N O P Q R S T U V
Chitosan 1.7 2 1.5 1.3 3 1 2 1.8 1.5
Cationic
modified 1.5 1
potato starch
Magnafloc LT20 0.2
0.5 1.1 0.3
Magnafloc LT25 1.5 0.8 1 0.3 0.9
Magnafloc LT28 1.3 1 1.5 1.5
Aluminium 34 33 35 29 36
sulphate
Iron III sulphate 33 25 30 37 29 30
Calcium 0.8 1 1.5 1 0.5 0.8 1.2 1 1.5 0.9 1.1
hypochlorite
Hectorite clay 35 28 20 40 26
Montmorillonite 32 34 35 27
45
clay
Zeolite X 12 40 20
Sodium carbonate 31
27 23 26 27 31 32 25 22 25 33
Sodium fluoride 0.9 1.5 0.4 2.2
1
Miscellaneous to to to to to to to to to to to
100 100
100 100 100 100 100 100 100 100 100
[0158] In the above, the calcium hypochlorite was added in granular form
comprising particles of about 1212 .mu.m median particle size with less
than 25% by weight larger than 1400 .mu.m, less than 0.5% by weight
larger than 2000 .mu.m and less than 3% by weight smaller than 150 .mu.m.
The free moisture content of the compositions was in the range from 1% to
4%. The hectorite clay, montmorillonite clay and zeolite X were all
predried to a free moisture content below 1.5% by weight and had a water
capacity in excess of 18%. The compositions have a t.sub.max of at least
about 8 minutes and a t.sub.80 of less than about 30 seconds. 6.2 g of
compositions L to V were added in powder form from unit dose
polypropylene sachets to 10 litres of water. The water was then agitated
or stirred briefly. The water was left to stand for 5 minutes, after
which said water was stirred or agitated for a further minute, left to
stand for a further five minutes, after which said water was stirred or
agitated for a further minute and then left to stand for another 5
minutes. During this time, water-insoluble floes formed in the water. The
liquid was then filtered through a cotton cloth or non-woven filter to
remove said water-insoluble floes, and the filtrate was collected. The
filtrate was left for a further 15 minutes and is purified water.
