Water purifier abstract
A domestic nanofiltration membrane based water purifier without
a storage tank. The water purifier according to the present invention
uses a nanofiltration membrane filter as a main filtering section
and does not have a storage tank for containment of purified water.
Although conventional reverse osmosis membrane based water purification
systems provide good quality water, they have problems in that installation
of the storage tanks due to insufficient flow rate results in the
increased volumes of water purifiers, and at the same time, secondary
pollution may be caused by microorganism propagation upon prolonged
storage. In this regard, the present invention provides a domestic
nanofiltration membrane based water purifier without a storage tank,
in which a nanofiltration membrane filter with a pore size of approximately
0.1 to 10 nm is used as a main filtering section.
Water purifier claims
1. A domestic nanofiltration membrane based water purifier without
a storage lank, said purifier comprising: a pretreatment filter,
a pretreatment carbon filter, a main filtering section, a backflow
prevention valve and a post treatment filter; wherein purified water
is directly drained from a purified water discharge valve without
storage; and wherein a nanofiltration membrane filter of pore size
of 0.1 to 10 nm is used as the main filtering section in order to
provide an intake water volume ranging from 1.0 to 3.5 liters/min.
2. The domestic nanofiltration membrane based water purifier without
a storage tank as set fort in claim 1 wherein a nanofiltration
membrane filter module of 8 to 50 ft.sup.2 effective membrane area,
1.5 to 4.5 inches outer diameter, and 8 to 18 inches length is used
as the nanofiltration membrane filter.
3. The domestic nanofiltration membrane based water purifier without
a storage tank as set forth in claim 1 wherein the nanofiltration
membrane filter is prepared by interfacial polymerization of piperazine
or methaphenylendiamine with trimesoylchloride on a microporous
4. The domestic nanofiltration membrane based water purifier without
a storage tank as set forth in claim 1 wherein the nanofiltration
membrane filter is comprised of a spiral wound type nanofiltration
membrane filter or a hollow fiber type nanofiltration membrane filter.
5. The domestic nanofiltration membrane based water purifier without
a storage tank as set forth in claim 1 further comprising a pressure
pump is coupled between the pretreatment filter and the pretreatment
Water purifier description
RELATED U.S. APPLICATIONS
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
REFERENCE TO MICROFICHE APPENDIX
FIELD OF THE INVENTION
The present invention relates to a domestic nanofiltration membrane
based water purifier without a storage tank, and more particularly
to a domestic nanofiltration membrane based water purifier, which
does not use a storage tank for containment of purified water, contrary
to conventional water purification systems in which purified water
is stored in their storage tanks for use when a demand occurs.
BACKGROUND OF THE INVENTION
In step with industrial progress, water pollution and water resources
scarcity are emerging as severe problems. Because of industrial
advancement, population growth, and increased standards of living,
the demand to good quality water is increasing rapidly. However,
water pollution due to domestic waste or industrial sewage has become
a serious problem and therefore, available water has become scarce.
In order to utilize limited water resources efficiently, purification
treatment is absolutely necessary before drinking natural water
is to be consumed, in addition to the removal of sources of water
Conventional water purifiers take forms of different kinds of purification
systems depending on filter type. At present, the purification system
using a filtration membrane is considered to be the most effective
because it can eliminate impurities including minute substances
such as bacteria and heavy metals.
As representative filtration membranes for use in water purifiers,
there exist an ultrafiltration membrane, a nanofiltration membrane
and a reverse osmosis membrane. Among them, the ultrafiltration
membrane is used to remove mainly colloid-sized substances. Although
it can provide a high flow rate due to larger pore size than those
of the nanofiltration and reverse osmosis membranes, there is a
limit to elimination of minute substances such as bacteria and heavy
Meanwhile, the reverse osmosis membrane can eliminate almost all
minute substances such as bacteria and heavy metals and thus has
been widely used recently. Such reverse osmosis membrane based water
purification systems are disclosed in several documents including
U.S. Pat. Nos. 4626346 and 6190558. However, most such reverse
osmosis membrane based water purifiers are provided with storage
tanks for containment of purified water, due to insufficient flow
rate. Therefore, there are problems in that the volumes of the purifiers
are increased due to installation of the storage tanks, and microorganisms
are propagated due to prolonged storage, thereby causing secondary
BRIEF SUMMARY OF THE INVENTION
Therefore, the present invention has been made in view of the above
problems, and it is an object of the present invention to provide
a domestic nanofiltration membrane based water purifier, which can
eliminate almost all impurities including bacteria and heavy metals,
and which does not require the installation of a storage tank for
containment of purified water.
In accordance with the present invention, the above and other objects
can be accomplished by the provision of a domestic nanofiltration
membrane based water purifier without a storage tank, comprising
of a pretreatment filtering section including a pretreatment filter
and a pretreatment carbon filter, a main filtering section, and
a post-treatment filtering section, characterized in that a nanofiltration
membrane filter providing an adequate flow rate is used for the
main filtering section.
Preferably, the nanofiltration membrane used in the present invention
has a pore size ranging from about 0.1 to 10 nm, corresponding to
a mean pore size between the reverse osmosis membrane and the ultrafiltration
membrane. Advantageously, such nanofiltration membrane based water
purifiers can selectively pass some monovalent ions that do not
affect the human body and eliminate almost all multivalent ions,
low molecular weight organic substances, and bacteria. In detail,
as the nanofiltration membrane has a larger pore size than the reverse
osmosis membrane, a desirable quantity of purified water can be
immediately obtained from a purified water discharge valve by way
of modulation of a pump pressure or an effective membrane area.
Furthermore, the nanofiltration membrane can provide a sieving effect
depending on a pore size such as in the ultrafiltration membrane
and eliminate approximately 30 to 60% of monovalent ions and calcium
ions by adsorption of the ions to the membrane surface. In particular,
90% or more of multivalent ions and salts such as sulfate can be
eliminated, thereby providing drinking water containing a suitable
amount of minerals.
The nanofiltration membrane is classified into a spiral wound type
membrane and a hollow fiber type membrane depending on its preparation
method, both of which can be used herein. It can be also classified
into a polyamide based membrane and a polyvinylalcohol based membrane
depending on membrane material. It can be used herein regardless
of the membrane material providing that the pore size of the membrane
ranges from 0.1 to 10 nm. Generally, the polyamide based membrane
can be prepared by interfacial polymerization of a multivalent amine
such as piperazine and methaphenylendiamine with trimesoylchloride
on a microporous support. The polyvinylalcohol based membrane can
be prepared by applying polyvinylalcohol to a microporous support,
followed by curing.
Preferably, a nanofiltration membrane module of about 8 to 50 ft.sup.2
effective membrane area, 1.5 to 4.5 inches outer diameter, and 8
to 18 inches length is used in order to provide an intake water
volume ranging from about 1.0 to 3.5 liters/min. The intake water
volume of less than 1.0 liters/min is insufficient for a water purifier
without a storage tank. On the other hand, if the intake water volume
exceeds 3.5 liters/min, the capacity of a pump must be increased
and the size of the module is thus excessively increased.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
The above object and other objects, features and advantages of
the present invention will be more clearly understood from the following
detailed description taken in conjunction with the accompanying
FIG. 1 is a schematic illustration of the water purification system
of the water purifier according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail
with reference to the accompanying figure.
As shown in FIG. 1 the water purification system according to
the present invention is comprised of a water supply pipe 3 a pretreatment
filter 4 a pretreatment carbon filter 6 a nanofiltration membrane
filter 7 functioning as a main filtering section, a backflow prevention
valve 8 a post-treatment filter 9 and a purified water discharge
valve 10. During water purification, concentrate water from the
nanofiltration membrane filter 7 is drained via a concentrate water
pipe 13 by a flow control valve 11.
The pretreatment filter 4 may be a micro sediment filter of metal
or plastic material, and a carbon filter such as a granulated active
filter, a powdered active carbon filter and a rod active carbon
filter, alone or in combination. The post-treatment filter 9 may
be an ultraviolet sterilizing filter, an active carbon filter, a
ceramic filter, a silver-containing active carbon filter, an ultrafiltration
membrane filter and a magnetization filter, alone or in combination.
The nanofiltration membrane filter 7 which is the main filtering
section in the water purification system according to the present
invention, uses a nanofiltration membrane ranging from about 0.1
to 10 nm in pore size. The pore size of less than 0.1 nm is inadequate
for a water purifier without the use of a storage tank, due to insufficient
flow rate. On the other hand, if the pore size exceeds 10 nm, impurities
such as heavy metals and bacteria cannot be completely eliminated.
The purified water in the main filtering section is pumped to the
post-treatment filter 9 via the backflow prevention valve 8 for
final water purification. The finally purified water is directly
drained from the purified water discharge valve 10 when needed.
A water pressure or a pressure pump 5 according to the present
invention is designed to selectively modulate the input rate of
raw water within a range of about 0.5 to 12 liter/min under an operating
pressure condition within a range of about 15 to 120 psi.
Hereinafter, the present invention will be illustrated detail by
way of the non-limiting examples.
The water purification system shown in FIG. 1 was operated under
30 psi operating pressure of the pressure pump 5 using a nanofiltration
membrane module of 1.5 nm pore size, 23 ft.sup.2 effective membrane
area, 3.5 inches outer diameter, and 12 inches length. The flow
rate and desalination rate were measured and their results are presented
in Table 1 below.
NaCl and MgSO4 were present in raw water at concentrations of 500
ppm and 2000 ppm respectively.
The same procedures were performed as in the example 1 except
for using operating pressures as shown in Table 1. The water purification
efficiency was evaluated and is presented in Table 1 below.
TABLE 1 Operating Flow Flow NaCl MgSO.sub.4 pressure rate rate
elimination elimination Example (psi) (gpd) (ml/min) rate (%) rate
(%) Example 1 30 390 1027 62.0 98.1 Example 2 15 214 564 58.9 97.6
Example 3 45 570 1498 63.8 98.3 Example 4 60 729 1916 64.4 98.5
Example 5 90 1014 2666 64.6 98.7 Example 6 120 1335 3510 64.6 98.7
As apparent from the above examples, the purifiers using the water
purification system according to the present invention can eliminate
monovalent ions by a reasonable level and almost all divalent or
multivalent salts. As a result, the inherent taste of water is maintained
and impurities such as heavy metals and bacteria are eliminated,
thereby providing good quality drinking water. Furthermore, drinking
water can be directly obtained from the water purifier of the present
invention without storage within an intake water volume of about
1.0 to 3.5 liter/min, when needed.
Although the preferred embodiments of the present invention have
been disclosed for illustrative purposes, those skilled in the art
will appreciate that various modifications, additions and substitutions
are possible, without departing from the scope and spirit of the
invention as disclosed in the accompanying claims.