Note: Descriptions are shown in the official language in which they were submitted.
CA 02753144 2011-08-19
WO 2010/096521 PCT/US2010/024531
WATER PURIFICATION AND ENHANCEMENT SYSTEMS
[0001] The present invention relates to a low-cost potable water
purification system and a sensor to alert the user when the water is no longer
safe to drink. This low-cost water purification system incorporates additional
functionality that enables beneficial impurities and molecules to be added to
the water,
BACKGROUND OF THE INVENTION
[0002] Water purification systems can be comprised of many different
components using various mechanisms for removing impurities from water,
One class of prior water purification systems is commonly referred to as
`point-of-use' (POU) water purification systems. Such POU systems are
composed of components that remove water impurities on a relatively small
scale, e.g. a table-top or dwelling-oriented system as opposed to a large
central facility, like a municipal water treatment facility.
[0003] POU systems in general have been constructed for high-end
marketplaces, i.e., markets where higher costs in POU systems can be
tolerated. POU systems have not effectively penetrated large but lower-end
marketplaces due to the lack of inventive design in low-cost environments.
[0004] A typical POU system may have a pre-filter to remove sediment,
followed by mechanisms that ensure pathogen and sometimes inorganic
material removal. One of the most important aspects of a POU system which
contains consumables, such as filters, is an `end-point' detection system that
warns user or service personnel that the time to change the filter has
arrived.
Most POU systems use a time-based system where, after a certain amount of
time has passed, a light turns on (or some other indicator) which signals that
it
is time to change the filter. This relatively low cost sensor is not adequate.
If
the water purification system is deployed in different environments, the
CA 02753144 2011-08-19
WO 2010/096521 PCT/US2010/024531
required length of time between filter changes to avoid contamination can vary
greatly, thus possibly exposing individuals to contaminated water.
[0005] The main method of determining water composition (and safety)
is to periodically take samples of the water and ship these samples to a
laboratory where relatively large equipment is used to analyze the water
composition. This information supplies feedback to the user or service
personnel of what is in the water. In addition, there are field-kits which can
test for particular contaminates, e.g. chlorine. Generally, neither of these
standardized test methods is either universal enough or compatible with a
POU water system. Likewise, neither of these test methods is consumer
friendly.
[0006] Current POU water purification systems do not add beneficial
ingredients to the water. Typical systems that impart molecules or
compounds into water are found in the confectionary or restaurant
businesses. A soda fountain, for example, adds molecules and compounds
that add flavor to carbonated water by simply mixing streams of liquids, but
not ingredients beneficial to the consumer's health.
[0007] A need exists for an improved system for purifying water and/or
adding beneficial ingredients to the water. The present invention seeks to
satisfy this need.
SUMMARY OF THE INVENTION
[0008) In one aspect there is provided a water purification system
comprising at least two filtration media sized with respect to each other to
allow a first contaminate to be saturated first with a delay before a second
contaminate is saturated. In another aspect, there is provided a method of
purifying water comprising passing water through a system comprising at
least two filtration media sized with respect to each other to allow a first
2
CA 02753144 2011-08-19
WO 2010/096521 PCT/US2010/024531
contaminate in the water to be saturated first with a delay before a second
contaminate is saturated.
[0009] An important aspect of the present system is to employ the user
of the system as the end-point detector of pathogens or other dangerous
elements. This aspect of the system allows for the ultimate in low-cost water
purification and water safety. The present inventive system employs the user
as a detector through the user's sight or taste. A mechanism in the water
purification system releases a color element when the water filter has reached
or is beginning to reach the end of its life. Additionally the system also has
the ability to release a different taste in the water which also can alert the
user
that the filter has reached its end of life. In addition, since these
detection
mechanisms are introduced in a low-cost manner, the same mechanisms can
be utilized to impart desired molecules or compounds into purified water, thus
creating healthy beverages and/or therapeutic drinks.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Figure 1 is a schematic of a first embodiment of the present
invention showing a low-cost arsenic purification system;
[0011] Figure 2 illustrates how taste removal media breaks through first
and the water will possess an undesirable musty or earthy taste for some time
period of delay before the water begins to be contaminated with arsenic;
[0012] Figure 3 illustrates how time release capsules can release taste
substances at a constant rate which is absorbed by a downstream media and
saturates the media at the right time;
[0013] Figure 4 illustrates how time release capsules are engineered into
abrupt-release form which are located in this case at the end of the
purification system;
3
CA 02753144 2011-08-19
WO 2010/096521 PCT/US2010/024531
[0014] Figure 5 illustrates time-release capsules designed to inject an
even dose of flavor over time;
[0015] Figure 6 illustrates a time-release capsule designed so that the
outer shell dissolves at a rate such that the flavor is released as abruptly
as
possible when the arsenic media is about to expire; and
[0016] Figures 7 and 8 show arsenic removal results of the combination
AC/GFO filter on Chapala water over the lifetime of the filter.
DETAILED DESCRIPTION OF THE INVENTION
[0017] Referring to the drawings, Figure 1 is a schematic of a first
embodiment of the present invention of a low-cost arsenic purification system.
The system 2 comprises a reservoir 4 for containing water to be purified
connected via a valve 8 to a filter region 10 having a series of remediation
medics 12,14,16. Water passing through the filter region 10 exits through
nozzle 18 via valve 20 into receiving vessel 22.
[0018] The prefilter 12 is designed to eliminate large particles and
sediment from the water. The pre-filter 12 is followed by a series filter
medias
which are designed to remove targeted atoms, molecules, or compounds from
the water and/or may be employed to impart either a color or taste change to
the water when the media are saturated with contaminates and the media is
no longer purifying the water (i.e. the invention indicates that the water
will
soon be unsafe). In the particular embodiment illustrated in Figure 1, the
prefilter media 12 is followed by a taste removal media 14, and an arsenic
removal media 16.
[0019] Similar mechanisms can be employed to inject other beneficial
compounds into the water. Beneficial compounds can be, for example,
vitamins, amino acids, minerals, and/or herbal extracts. Some examples
include vitamin A, vitamin C, vitamin D, and vitamin E, vitamin K, vitamin Be,
4
CA 02753144 2011-08-19
WO 2010/096521 PCT/US2010/024531
vitamin B12, thiamin, riboflavin, niacin, folic acid, biotin, pantothenic
acid,
calcium, iron, phosphorus, iodine, magnesium, zinc, selenium, copper,
manganese, chromium, molybdenum, potassium, boron, nickel, silicon, tin,
vanadium, lutein, and lycopene.
[0020] The system of the invention is primarily designed for treatment of
water which has been disinfected with chlorine. As noted above, one of the
remediation medias 14 may be designed to remove undesirable tastes, and
the other 16 may be chosen to remove arsenic.
[0021] Different geographical areas may have different water problems
and, hence, may require adjustment of the media types, number of medias, or
media ratios to properly remove contaminants. The filter system is designed
with an appropriate empty bed contact time (EBCT) for each of the medias to
allow sufficient removal of the target contaminants. Typical EBCTs are on the
order of 1 to 10 minutes, and these guidelines determine water flow rates
through the media filter volume.
[0022] The purification system may include additional filter stages after
the remediation medias described above (not shown). For example, a filter to
remove media fines (such as a fiber wound filter) and or a filter to remove
microbial contaminants may be implemented after the remediation media
stages. Common causes of water taste problems are algal metabolites such
as geosmin, or 2 methylisoborneol (M1B) which impart musty or earthy tastes
to the water. (See for example, chapter 26 in Adsorption by Carbon, edited by
Bottani and Tascon). Although the order of the media in the present system is
not critical, in the embodiment illustrated in Figure 1, the taste removal
filter
media 14 is positioned immediately following the prefilter media 12, followed
by the arsenic removal media 16.
[0023] In other embodiments, the medics may be intermixed, alternating,
or stacked. Additionally, although there are other potential media that can
CA 02753144 2011-08-19
WO 2010/096521 PCT/US2010/024531
perform both tasks described above, activated carbon (also referred to as
activated charcoal) is typically selected as the taste removal filter media
14,
and one or more of granular ferric hydroxide, activated alumina, granular
ferric
oxide, titanium oxide, zirconium oxide, or another metal oxide or mixture of
metal oxides may be selected as the arsenic removal media 16.
[0024] The design of the system of the invention is very low cost for two
principal reasons. First, the system is targeted at the two primary problems
arising with the water, namely the toxic arsenic concentration and the
undesirable taste. Secondly, the method of end-point-detection is either time,
or more importantly, taste. The system is able to employ user taste as an
end-point detection mechanism by sizing the taste-removal media and the
arsenic-removal media such that the taste-removal media is saturated before
the arsenic-removal media is saturated. When these media volumes are
sized as described, the taste removal media breaks through first, and the
water will possess an undesirable musty or earthy taste for some time period
of delay before the water begins to be contaminated with arsenic.
[0025] This effect is represented schematically in the graph shown in
Fig. 2, The sizing of the volume media to arrive at this functional effect, in
which the user is the sensor since the user is signaled to replace the media
when an earthy or musty taste is sensed in the water, is accomplished in a
series of steps as described below.
[0026] First, the local water is measured to determine the level of taste
imparting compounds such as geosmin or MIB and the level of arsenic in the
water. Secondly, the taste and arsenic removal media is tested to determine
how long it will take a volume of media to be saturated with geosmin and/or
MIB or arsenic. Once this second step is complete, volumes of the media in
the system can b chosen to achieve the effect shown in Fig. 2.
6
CA 02753144 2011-08-19
WO 2010/096521 PCT/US2010/024531
[0027] For example, a two component POU filter can be constructed with
activated carbon for taste improvement and granular ferric oxide (GFO) for
arsenic removal. By appropriately sizing the medics, the taste improvement
serves the function of an early warning system for the user that it is time to
replace the filter. The relevant parameters are the media adsorption
capacities for target contaminants, typically listed in mg contaminant
adsorbed
per gram of media. The adsorption capacity of MIB on activated carbon is in
the range of 1 to 3 mg/g, depending on activated carbon structure (carbon
containing source material, pore size distribution, and surface area), and
water chemistry. (See for example, Chapter 26 in Adsorption by Carbon,
edited by Bottani and Tascon, p.683, (2008)). Similarly, the adsorption
capacity of arsenic (V) on GFO is in the range of 0.5 to 1 mg/g depending on
water chemistry. (Reference, Adsorption Treatment Technologies for Arsenic
Removal,AWWA publishing, Chapter 6, (2005)).
[0028] A suitable activated carbon can be obtained from Calgon Carbon
Corporation
(http://www.calgoncarbon.com/solutions/?view=ChallengeProducts&Industry=
10&Application=7&Challenge=7). Similarly GFO can be obtained from
Severnt Trent
Corporation.(http://severntrentservices.com/Water Wastewater-Treatment/
Arsenic_Removal_prod_52.aspx).
[0029] For example, it is assumed that, in the input water, MIB and
arsenic(V) concentrations are both 0.05mg/L, and further it is assumed that
the adsorption capacity of both contaminants on their respective removal
medics is 1 mg/g. Neither GFO nor AC has appreciable adsorption capacity
for the other contaminant. Thus, to design a filter where MIB breaks through
the activated carbon prior to arsenic break through in the GFO requires a
GFO to carbon ratio greater than 1. Suitable ratios could be 2:1 = mass
GFO:mass activated carbon. Such a ratio would result in an undesirable taste
notification to the user that it is time to replace the filter prior to the
user being
7
CA 02753144 2011-08-19
WO 2010/096521 PCT/US2010/024531
exposed to elevated levels of arsenic. Of course, the overall media masses
(and hence filter volume) must be chosen appropriately for the intended water
flowrate and filter lifetime. If the concentration of geosmin or MIB is not
large
enough, the saturation is not abrupt enough, or another suitable taste
imparting compound is not present in the water, the method described above
cannot be used as an end-point-detection sensor.
[0030] If a constant rate of a taste compound is added outside the POU
system, the invention has a similar design as shown in Fig.1 since the
geosmin or MIB taste removal media is replaced with a media that removes
the intentionally introduced taste compound. Alternatively, the taste
substance or compound may be added within the POU system by employing
time-release capsules.
[0031] Figure 3 shows a system similar to that shown in Figure 1 except
that a region 24 is provided downstream of the taste removal media 14
containing capsules adding constant rate release of taste substances. These
time release capsules can either release taste substances at a constant rate
which is absorbed by a downstream media and saturates the media at the
right time (as seen in Fig. 3), or the capsules may be engineered into abrupt-
release form 26 which are located in this case at the end of the purification
system as the last stage (see Fig. 4). In the first case (continuous), the
time-
release capsules (see Fig. 5) are designed to inject an even dose of flavor
over time. In the capsule shown in Fig. 6, this is designed so that the outer
shell dissolves at a rate such that the flavor is released as abruptly as
possible when the arsenic media is about to expire.
[0032] The inventive time-release capsules used in the water purification
system of the invention can also be used to release color either in addition
to
or instead of taste. For example, both methods described above for flavor
release can be used for color release. In the first case, the constant-rate-
release time capsule can be used. to release a color that is absorbed by one
8
CA 02753144 2011-08-19
WO 2010/096521 PCT/US2010/024531
of the media in a filter system, and the saturation is planned such that the
color compound achieves saturation in the media just before a purification
media becomes saturated with an undesirable atom, molecule, or
compound(s) which is being removed. Thus, the water will change color
when it is time to replace the purification media. A time delay is designed
into
this system as well, so that even though the water changes color, the water is
still safe for some delay time. The delay is designed by understanding the
saturation rate of the color compound concentration released by the time-
release capsule as well as the saturation of the undesirable atom, molecule,
or compound that is being removed.
[0033] An abrupt-time-release time capsule can be used as well to
impart color in the. water to indicate that it is time to replace the
purification
media. In this embodiment, the outer shell of the time release capsule
dissolves at a rate such that color is released abruptly just before the
purification media is saturated with the atom, molecule, or compound that it
is
removing from the water.
[0034] The time-release capsules described herein are also useful in
adding desirable atoms, molecules, or compounds to the water. The
constant-rate time capsules described previously are desirable for this
beneficial release. The capsules are loaded into a media, or separately,
located at the last stage of the water purification system (so that other
media
do not remove the desired beneficial atoms, molecules, or compounds).
Flavors can be released by these capsules, as well as therapeutic substances
such as vitamins.
[0035] A key aspect of the invention is the recognition that local water
conditions must be carefully assessed in order to choose the most
appropriate, lowest cost media for optimum arsenic POU removal with
sufficient longevity to produce potable water in amounts suitable for a
household. For example, in one particular location, testing determined that
9
CA 02753144 2011-08-19
WO 2010/096521 PCT/US2010/024531
the chlorine content, arsenic valence, and pH would need to be primarily
considered when choosing the most appropriate arsenic removal media.
Likewise, the ratios of the media in the filtration system would have to be
adjusted based on the water characteristics and desired longevity and quality
of the water post-filtration. Chlorine neutralization requires activated
carbon
(AC), while arsenic removal requires a metal oxide media such as GFO. In
the example above, GFO media was chosen because it exhibits superior
As(V) removal at the elevated pHs present in the local water supply compared
to other metal oxide medias such as activated alumina. (Reference,
Adsorption Treatment Technologies for Arsenic Removal,AWWA publishing,
Chapter 6, (2005)).
[0036] To minimize plumbing connections and reduce unit assembly
cost, the medias were combined in a single standard filter housing. It was
estimated that 550g of GFO (1.1 dry liters) would give sufficient arsenic
removal capacity under local water conditions to achieve the designed filter
lifetime of 7,000 liters. The overall filter volume was fixed to that of a
standard
130cc filter element in the POU device. It was determined that the element
containing 1.1 L of GFO and 1.1 L of AC, in a 1:1 media ratio by volume
worked best for the conditions present in the example.
[0037] Following the above described process, the media ratios can be
adjusted without undue experimentation once the local water characteristics
have been assessed. The medias formed two distinct layers, and water
flowed through the AC prior to the GFO. Figures 7 and 8 show arsenic
removal results of the combination AC/GFO filter on Chapala water over the
lifetime of the filter. Arsenic is maintained below the 0.01 mg/L limit during
the
test. In addition, chlorine was not detected in the treated water, resulting
in
pleasing taste to local residents. Depending on the local water quality
factors,
POU filter size, and designed operational lifetime the ratios of GFO to AC may
be adjusted as required. For small filter sizes present in POU devices, it is
expected that proper ratios of GFO arsenic removal media to activated carbon
CA 02753144 2011-08-19
WO 2010/096521 PCT/US2010/024531
would be approximately 1:1 = volume of GFO:volume AC or larger such as
2:1. These volumes should be adjusted for the arsenic removal capacities
and densities of different medias appropriate for the local water conditions.
Additional medics may be added to the filter elements to remove other water
contaminants as required resulting in elements with 3, 4, or more media
components. The individual medias may be separated (i.e., layered) as in the
above example, or they may be intermixed.
[0038] While the invention has been described in connection with what is
presently considered to be the most practical and preferred embodiment, it is
to be understood that the invention is not to be limited to the disclosed
embodiment, but on the contrary, is intended to cover various modifications
and equivalent arrangements included within the spirit and scope of the
appended claims.
11
