WO1998052874A2

WO1998052874A2 - Water treatment system having dosing control

Info

Publication number: WO1998052874A2
Application number: PCT/US1998/010568
Authority: WO
Inventors: Frederick C. Wilkins; Arthur F. Williams; Li-Shiang Liang; Herbert Bendlin; Stephane Dupont; Achim Brust; Bikram Yonjan
Original assignee: United States Filter Corporation
Priority date: 1997-05-20
Filing date: 1998-05-20
Publication date: 1998-11-26
Also published as: EP1017628B1; EP1017628A2; DE69809079T2; DE69809079D1; WO1998052874A3; ATE226921T1; JP2002502307A; US5925240A

Abstract

A water treatment system (10) having dosing control for providing treated water having very low organic and ionic contamination, that can be accurately dispensed. The water treatment system (10) having dosing control includes a water inlet (11) hydraulically connected to a pump (16) having a variable speed motor. At least one water treatment device (18, 22, 26) is hydraulically connected downstream of the pump, at least one outlet valve (30) is hydraulically connected downstream of the water treatment unit, and a recirculation line (32) is hydraulically connected from the outlet valve to the pump. The output of the pump is controlled by a regulating device (44) connected to the variable speed motor. The system provides for lower electrical current usage and reduced acoustical disturbances.

Description

WATER TREATMENT SYSTEM HAVING DOSING CONTROL

BACKGROUND OF THE INVENTION

1. Field of the Invention:

The invention relates to a water treatment system and method and, more particularly, a

water treatment system and method having improved dosing control for accurate distribution of

treated water.

2. Description of the Related Art:

High purity water is required for many applications including, for example, in chemical

and biological analytical laboratories. Water for these applications is purified by a number of

well-known techniques, including filtration, single or multiple distillation, sorption, and ion

exchange. Water initially treated by distillation or reverse osmosis filtration is often further

purified (polished) by passage through activated carbon beds to adsorb residual contaminants,

principally organics. The pretreated water may also be treated by passage through layered or

mixed beds of ion exchange resins to remove residual ionic impurities. Often, these water

streams are also filtered through microporous filters to remove further residual contaminants

prior to the system outlet.

When purified water is not required, conventional water treatment systems typically

recirculate the water in a continuous or periodic operation through the various water treatment

devices included in the system, for example UV lamps, ion exchangers and ultrafilters, to prevent

the water quality from deteriorating while standing. Because of the high energy costs incurred

during continuous operation of a recirculation pump or the like, and the associated high noise

levels which can be disturbing to nearby workers, water treatment systems are often operated in a

periodic mode of, for example, about 50 minutes standstill and 10 minutes of recirculation through the system. When purified water is required, therefore, it is sometimes necessary to

circulate the water through the system for a period of time before the water can be used.

In addition, control of the purified water flow rate from the system is typically performed

by adjusting an outlet valve. However, because the conventional system pump operates at a

single high speed and output rate, to achieve the highest flow rate at the outlet valve, it can be

difficult for users to dose small and/or accurate quantities of purified water from these systems.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a water treatment system having dosing

control, wherein water can be treated such that it has very low organic and ionic contamination,

and can be accurately dispensed from the system. The water treatment system having dosing

control includes a water inlet hydraulically connected to a pump having a variable speed motor.

At least one water treatment device is hydraulically connected downstream of the pump, at least

one outlet valve is hydraulically connected downstream of the water treatment unit, and a

recirculation line is hydraulically connected from the outlet valve to the pump. The output of the

pump is controlled by a regulating device connected to the variable speed motor.

In another embodiment of the present invention, a water treatment system having dosing

control includes a water inlet hydraulically connected to a pump. At least one water treatment

device is hydraulically connected downstream of the pump, and at least one outlet valve is

hydraulically connected downstream of the water treatment device, and a recirculation line is

hydraulically connected from the outlet valve to the pump. A proportional valve is hydraulically

connected downstream of said outlet valve, and the system output is controlled by a regulating

device connected to the proportional valve.

In another aspect of the present invention, a method for treating water includes providing

a water inlet hydraulically connected to a pump having a variable speed motor, and hydraulically connecting at least one water treatment device downstream of the pump, at least one outlet valve

downstream of the water treatment unit, and a recirculation line from the outlet valve to the

pump.

N water stream is then directed to the water inlet, and it is pumped into the water treatment

device to produce a purified water stream. When the outlet valve is closed the purified water

stream is recirculated to the water inlet. When the outlet valve is opened the purified water can

be removed by controlling the pump output with a regulating device connected to the variable

speed motor.

In another aspect of the present invention, a filter cartridge assembly is provided with a

ventilation system to remove entrapped air from the water treatment system. The cartridge

assembly includes at least one filter cartridge having a housing with two ends. The housing

typically includes a filter media. A first end cap is disposed on one end of the housing, which

includes a fluid inlet port, a fluid outlet port, a first fluid distributor, and a vent device secured to

the first end cap. A second end cap is disposed on a second end of the housing, and includes a

product collection plenum, and a second fluid distributor that separates the filter media from the

product collection plenum. Lastly, a liquid transfer tube is disposed within the housing, and

extends from the product collection plenum to the fluid outlet port.

BRIEF DESCRIPTION OF THE DRAWINGS

It is to be understood that the following drawings are for the purpose of illustration only

and are not intended as a definition of the limits of the invention. Objects and advantages of the

present invention will become apparent with reference to the following detailed description when

taken in conjunction with the following drawings, which disclose multiple embodiments of the

invention, wherein the same reference numerals identify the same feature, in which:

FIG. 1 is a schematic flow diagram of one embodiment of a water treatment system of the present invention;

FIG. 2 is a schematic flow diagram of another embodiment of a water treatment system of

the present invention;

FIG. 3 is a schematic flow diagram of another embodiment of a water treatment system of

the present invention;

FIG. 4 is a schematic flow diagram of another embodiment of a water treatment system of

the present invention;

FIG. 5 is a schematic flow diagram of another embodiment of a water treatment system of

the present invention;

FIG. 6 is a graphic representation of the outflow rates of a conventional system and that

of the present invention, with increasing opening and closing movements of a regulating device;

FIG. 7 is a top plan view of an illustrative embodiment of four filter cartridges arranged

in a U-shaped configuration;

FIG. 8 is a side elevational view of the filter cartridge assembly shown in FIG. 7;

FIG. 9 is a top plan view of an illustrative embodiment of a top end cap of one filter

cartridge;

FIG. 10 is a cross-sectional side view, taken along section line 10-10, of the filter

cartridge shown in FIG 9;

FIG. 1 1 is an exploded assembly view of an illustrative embodiment of a top end cap and

a filter cartridge vent system of the filter cartridge shown in FIG 9;

FIG. 12 is a partial section view of an illustrative embodiment of a top end cap and the

filter cartridge vent system of the filter cartridge shown in FIG 9;

FIG. 13 is a partial section view of an illustrative embodiment of a top end cap and an

alternative filter cartridge vent system; FIG. 14 is a section view of an alternative embodiment of a filter cartridge vent system

positioned in a filter cartridge top end cap; and

FIG. 15 is a schematic view of a filter cartridge assembly having an alternative filter

cartridge vent system. DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to a water treatment system having dosing control. As

shown in FIG. 1, one embodiment of a water treatment system 10 having dosing control of the

present invention includes a water inlet having an inlet valve 11 , for example in the form of a

solenoid valve, connected to an untreated or retreated water line 12. This line can be

hydraulically connected to a storage tank 14 downstream from inlet valve 11 , to which the

aspirating side of a pump 16 having a variable speed motor M is connected. The pump 16 passes

the untreated or retreated water to at least one water treatment device that is hydraulically

connected downstream of the pump. For example, an ultraviolet (UV) lamp unit 18, a filter

cartridge 22 having a plurality of series connected cartridges, for example, having at least one

cartridge having at least one layer of an activated carbon and/or at least one layer of a mixture of

ion exchange resins, and/or an ultrafilter (UF) unit 26, and combinations thereof can be used in

the present system 10. Alternative embodiments of system 10 are shown in FIG. 2, wherein filter

cartridge 22 is the only water treatment device; FIG. 3, wherein UV lamp unit 18 is connected

upstream of filter cartridge 22; and FIG. 4, wherein UF unit 26 is connected downstream of filter

cartridge 22. A disinfection unit 42 can also be hydraulically connected in system 10, positioned

parallel with filter cartridge 22. A three-way valve 20 and a check valve 24 can be used to

prevent disinfectant from unit 42 from entering filter cartridge 22. At the end of the system 10,

at least one outlet valve 30, for example, in the form of a three-way solenoid valve, is

hydraulically connected downstream of the water treatment units. A conductivity measuring cell 28, which typically includes an integrated temperature sensor, can also be used in the system to

monitor the water quality.

N first recirculation line 32 is hydraulically connected from the outlet valve 30 to storage

tank 14 through check valve 34, or directly to the aspirating side of pump 16. As shown in

FIGS. 1 and 4, if UF unit 26 is used, the portion of the water which does not flow through unit 26

is directed to valve 38 at wastewater outlet 40, or it is directed to the aspirating side of pump 16

through outlet line 36 and a second recirculation line 31, having a throttle 33 and a check valve

35 upstream of solenoid valve 38. Recirculation line 32 is connected with outlet line 36 and

circulation line 31 via connecting line 37 having a check valve 39.

As shown in FIGS. 1-4, system 10 further includes a regulating device including an input

device 44, to allow a user to set a flow rate, and a controller 46 (most typically, a CPU with

memory). The input device 44 is in the form of, for example, a potentiometer, a key pad, an

angle encoder, and the like. These devices typically include a rotating handle or key pad that is

used to provide an input signal, for example the angle of rotation position, to controller 46 that

represents a desired flow rate of water at outlet valve 30. The controller 46 converts the input

signal to a motor control signal that causes the motor M to operate at a speed which drives pump

16 and causes the flow of water at outlet valve 30 to correspond to the desired flow rate. It is

noted that, although shown near outlet valve 30, input device 44 can be positioned at any

location throughout system 10 that is easily accessible for a user dispensing water. In another

embodiment of the invention, input device 44, for example a potentiometer, may directly send an

input signal to motor M which causes the flow of water at the system outlet to correspond to the

desired flow rate. Therefore, the output of pump 16 is controlled by the user making, for

example, rotating movements of an input device 44. The motor control signal causes the speed

of motor M to vary between zero and a predetermined maximum speed, at which the highest output of pump 16 can be reached. The pump 16 is preferably a magnetically coupled positive

displacement gear pump that is driven by motor M. As noted above, motor M is preferably a

variable speed motor, such as a 3 -phase, brushless, electronically commutated direct current

motor in a small power, low-voltage range, having an electronic drive, for example a

VARIOTRONIC™ compact drive electronic assembly (available from Papst-Motoren GmbH &

Co. KG, Germany).

In a further embodiment of the present invention, the regulating device can include a

device that can function as a timer to turn off motor M at a first predetermined time, and/or turn

on motor M at a second predetermined time. This operation would allow, for example, pump 16

to be preprogrammed to start up prior to normal hours of operation of water treatment system 10,

and to shut down during extended periods of nonuse. Typically, a user would provide desired

times of operation and shut down to the regulating device directly through an input device such

as a key pad. In another aspect of the invention, the predetermined times, for example, for

starting up and shutting down motor M, are provided directly by the regulating device as a

function of operational data. In this embodiment, controller 46 of the regulating device is

adaptable, and can be programmed to monitor usage characteristics and trends to predict use.

For example, operational data, such as water volumes, flow rates, times and dates, and periods of

operation can be gathered by controller 46 to draw inferences as to the motors operational

schedule. It is possible, therefore, to run pump 16 at short time intervals or, preferably,

continuously during standby mode with less noise, and lower operating cost, and provide high

purity water that is readily available for use when outlet valve 30 is opened. When pump 16 is

switched from the standby mode to a water dispensing mode by input device 44 of regulating

device, the pump output rate can be adjusted in a stepwise manner or, preferably, essentially

continuously up to a predetermined maximum output. This feature allows small quantities of water to be easily and accurately metered with a low pump output.

The control of the output of pump 16 by the regulating device allows for better control of

the pump output in the recirculation (or standby) mode when outlet valve 30 is closed, and

maintains the treated water quality during the standby mode by circulating the water through the

units 18, 22 and 26 for water treatment at a comparatively slow rate. As is known, water

treatment by a UV lamp unit is effective at a 185 nm wavelength to reduce the TOC to levels of

about 5 ppb, as well as at 254 nm wavelength to reduce bacteria levels. Water treatment by a

filter cartridge having a plurality of series connected cartridges, for example having at least one

cartridge having at least one layer of an activated carbon, and at least one layer of a mixture of

ion exchange resins, is known to be effective to adsorb residual organic contaminant materials as

well as to remove residual ionic impurities. Water treatment by UF units is known to remove

suspended small particles and pyrogens.

In a preferred embodiment of the present invention, outlet valve 30 can be switched

between a completely closed and a completely open position. For example, outlet valve 30 can

be a solenoid valve which, starting from the closed position, is switched into the opened position

during the initial phase of the movement of input device 44. As noted above, however, the

outflow rate of treated

water from system 10 is determined by the output of pump 16 and not by the cross section of

outlet valve 30.

In the preferred embodiment of the present invention, when outlet valve 30 is closed,

pump 16 is operated in the standby mode, at least in time intervals, at a comparatively low

output. When outlet valve 30 is open, pump 16 is operated with an output whose lowest value is

less than, and whose greatest value is higher than, the output in the standby mode. In the water

dispensing mode, the water in system 10 is initially brought to an approximate standstill, and can then be easily and accurately metered in small or large quantities by the user providing an input

signal with input device 44. For example, in standby operation pump 16 can run at an output of

about 0.5 liter/min; this output can be reduced or increased to about 1.5 liters/min when the

system is dispensing water and outlet valve 30 is opened. When the system is returned to

standby mode, by the input signal provided by the user, the controller 46 provides a motor

control signal that causes the motor M to initially stop and then operate at a speed which causes

pump 16 to recirculate water through the system.

As noted above, system 10 can include an inlet valve 11 , for example a solenoid valve,

that is either directly connected to an untreated public water supply system, or a retreated (for

example, by reverse osmosis) water line 12. System 10 can also include storage tank 14,

positioned between inlet valve 11 and pump 16, into which recirculation line 32 is hydraulically

connected. If used, inlet valve 11 is opened simultaneously with outlet valve 30. Alternatively,

inlet valve 11 can be used to control the liquid level of storage tank 14.

In another aspect of the invention, disinfecting unit 42 through which at least one

disinfectant can be introduced into the water flowing through system 10, is hydraulically

connected between pump 16 and outlet valve 30. Disinfecting unit 42 can be used to disinfect

water-contacting elements of system 10. As shown in FIGS. 1-4, certain water treatment units,

for example filter cartridge 22 including at least one layer of a mixture of ion exchange resins,

can be isolated from the system, by operation of valve 20 and check valve 24, prior to the start of

a disinfecting process. As is known to those skilled in the art, disinfectants typically include

oxidants which can adversely affect cation and anion exchange resins, resulting in a loss of the

ion exchange resins capacity.

An alternative embodiment of the water treatment system of the present invention is

shown in FIG. 5. This system is similar to that shown in FIG. 1 and described above. As shown, an input device 44, which can be in the form of , for example, a potentiometer, a keypad, an

angle encoder, and the like, is used to provide an input signal to controller 46 that represents a

desired flow rate of water. The controller 46 converts the input signal from input device 44 to a

valve control signal, which controls the outflow cross-section of valve 48 and causes the flow of

water at the valve to correspond to the desired flow rate. As noted above, although shown near

valve 48, input device 44 can be positioned in any location throughout the system that is easily

accessible for a user dispensing water. The valve control signal causes the valve 48 cross-section

to vary between 0 and a predetermined maximum opening, at which the highest output of the

system can be achieved. Valve 48 is preferably a proportional valve which opens proportionally

in response to a particular applied voltage. Preferably, the valve's internal structure is lined with

an inert plastic material to prevent water contamination at the system outlet. Such proportional

valves are commercially available, for example, from South Bend Controls, Inc. (South Bend,

IN); or Skinner Valve, Honeywell, Inc. (New Britain, CT). The output of system 10, therefore,

can be controlled by the user making, for example, rotating movements of an input device 44 to

control outflow cross-section of valve 48 and/or the speed of motor M.

As an example of the improved dosing control of the present system, FIG. 6 graphically

illustrates the outflow rates of a conventional system and that of the present invention. As

shown, line 50 is a curve of the outflow rate of a conventional system over the opening and

closing angle of the outlet valve. Line 52 represents the outflow rate of the present system as a

function of the angle of rotation position of input device 44. As shown, line 50 indicates that a

circulating pump is operated continuously, or at intervals, to achieve a maximum outflow rate

when the outlet valve is completely opened. Thus, a high water pressure is initially present at the

outlet valve, as shown by the steep rise of line 50, which indicates that small amounts of water

can be difficult to easily and accurately meter. The outflow rates of the present system, however, can be controlled, as represented by

line 52. Increasing movement of input device 44 corresponds to a proportional rise of the

outflow rate. Moreover, it is noted that it is also possible in the present system to select and

program the shape of the line 52, for example as a sine curve with an initially flat and

subsequently steeper rise, in controller 46. As shown, the outflow rate begins to rise only after

an angle of rotation of input device 44 of about 10% of the entire opening angle. As noted

above, the initial output of pump 16 is lowered to zero from the level of the standby mode, outlet

valve 30 is then completely opened, and the output of pump 16 is subsequently increased during

further adjustment of input device 44.

It has been found in the present system that, during the periods when the output of pump

16 is adjusted from the standby mode to the water dispensing mode, it is sometimes not possible

to completely ventilate the system. As the pump is started up, air may get pulled into the system

resulting in air bubbles in the system lines and water treatment units. To address this possibility,

another aspect of the present invention includes incorporating a ventilation system on filter

cartridge assembly 22.

As noted above, the filter cartridge assembly 22 can include a plurality of series

connected cartridges. Each of the cartridges typically include an outer housing, a top end cap, a

bottom end cap, and a central return tube. The top and bottom end caps are secured to opposite

ends of the housing, while the return tube extends between, and is connected to, the top and

bottom end caps. The housing is typically filled with filtering media, which includes, for

example, at least one layer of an activated carbon and/or at least one layer of a mixture of ion

exchange resins, which is placed around the return tube and is retained within the housing by the

top and bottom end caps. Water to be treated enters the filter cartridge through an inlet port and

an inlet plenum located in the top end cap. The water is then directed into the housing through an upper flow distributor in the top end cap which uniformly distributes the water into the filter

media. The water permeates down through the filtering media to the bottom of the housing

where it passes through a lower flow distributor and collects in a product collection plenum in

the bottom end cap. The water is then directed upwardly from the product collection plenum

through the return tube into the top end cap from which the purified water is discharged through

an outlet port. The construction and fluid flow scheme of a filter cartridge that can be used in the

present invention is more specifically described in pending U.S. Patent Application Serial No.

08/598,818, entitled "WATER PURIFICATION CARTRIDGE ASSEMBLY WITH

UNIDIRECTIONAL FLOW THROUGH FILTER MEDIA," filed February 9, 1996, and such

disclosure is incorporated herein by reference. Moreover, it is noted that the individual filter

cartridges can be hydraulically connected in series by coupling the outlet port of a first cartridge

to an inlet port of a second cartridge, wherein the water flows through each cartridge as described

above. The filter cartridges can be connected with additional mechanical devices, for example

filter clips, to provide further stability. For example, the connection between filter cartridge units

is more specifically described in pending U.S. Patent Application Serial No. 08/599,259, entitled

"MODULAR FILTERING SYSTEM AND METHOD OF ASSEMBLY," filed February 9,

1996, and such disclosure is incorporated herein by reference.

As noted, the filter cartridge assembly 22 of the present system incorporates a ventilation

system to allow entrapped air to readily leave the system to the atmosphere. One embodiment of

the filter assembly 22 utilizing a combination of individual filter cartridges is shown in FIGS. 7

and 8. The filter assembly 22 includes four filter cartridges hydraulically connected in series to

achieve a flow through each filter cartridge as described above. In particular, the filter cartridge

assembly 22 includes a first filter cartridge 60, a second filter cartridge 62, a third filter cartridge

64 and a fourth filter cartridge 66. Each of the filter cartridges is hydraulically connected to another of the filter cartridges such that fluid which enters the filter cartridge assembly through

inlet port 68 subsequently flows through each cartridge as described above and is discharged

from the outlet port 70 of the fourth filter cartridge 66. The inlet and outlet ports, 68, 70 are

positioned on the top of the filter cartridge assembly 22 so that the assembly can be easily

mounted in a console (not shown) housing system 10.

As further shown in FIG. 7, the top end caps of each filter cartridge are hydraulically

connected to establish a flow circuit. Water to be treated enters the first filter cartridge 60

through inlet port 68. The water is discharged from the first filter cartridge 60 through its outlet

port 72 which is hydraulically connected to the inlet port 74 of the second filter cartridge 62.

The water then flows through the second filter cartridge 62 and is discharged through its outlet

port 76 which is hydraulically connected to the inlet port 78 of the third filter cartridge 64. The

outlet port 80 of the third filter cartridge 64 is hydraulically connected to the inlet port 82 of the

fourth filter cartridge 66 so that water discharged from the third filter cartridge 64 enters the

fourth filter cartridge 66, and the water is subsequently discharged from the filter cartridge

assembly 22 through the outlet port 70 of the fourth cartridge 66. As shown, the configuration of

the filter cartridge assembly 22 shown in FIG. 7 is achieved using top end caps having various

configurations of inlet and outlet ports which can be selectively attached to filter cartridges to

achieve a desired arrangement. Also, as shown in FIG. 7, the individual filter cartridges are

mechanically secured to each other using a center clip 84 and side clips 86 (as shown in FIG. 8).

FIG. 8 is a side elevational view of the filter cartridge assembly shown in FIG. 7.

Referring again to FIG. 7, the ventilation system of the present invention includes the

incorporation of an individual vent device 88 positioned on the filter cartridge top caps to allow

entrapped air in the system and, more particularly, in filter cartridge assembly 22 to escape, while

preventing water or filter media to leave a filter cartridge. Preferably, vents 88 also prevent air from entering the filter cartridge. As shown in FIG. 7, vent 88 is positioned on filter cartridge

top caps 90, 92, 94 and 96. A preferred embodiment of vent 88 is shown on top cap 90 that is

secured to filter cartridge 60 in FIGS. 9-12. FIG. 10 illustrates a side elevational cross-sectional

view, taken along section line 10-10 of FIG. 9 through vent 88 and filter cartridge 60. As shown

in FIG. 10, the water enters filter cartridge 60 through inlet port 68 in top end cap 90. The fluid

is directed into housing 98 through an upper flow distributor 100 in the top end cap 90 which

uniformly distributes the water into the housing. The fluid permeates down through a screen 104

having a spider ring 106 into the filtering media. The media, for example, may consist of at least

one layer of an activated carbon 102 and at least one layer of a mixture of ion exchange resins

102', which are separated by a media separation screen 104. The fluid permeates down through

the filter media to the bottom of housing 98 where it passes through screen and spider ring 106

and a lower flow distributor 108 and collects in a product collection plenum 110 in the bottom

end cap 112. The fluid is then directed upwardly from the plenum 110 through a return tube 114

into the top cap 90 from which the fluid is discharged through an outlet port.

An exploded assembly view of the filter cartridge vent device 88, and a cutaway section

view of the vent device assembled in top cap 90, are respectively shown in FIGS. 11 and 12. As

shown, a preferred embodiment of vent 88 is positioned in a channel 116 formed in top cap 90.

The vent components include, for example, an O-ring seal 118, a porous membrane 120, a

porous support disc 122 and a compression ring 124. FIG. 12 shows the vent components

installed in top cap 90 to provide a means for entrapped air in the filter cartridge to escape to the

atmosphere.

In a preferred embodiment of this aspect of the present invention, the porous membrane

120 is made of a hydrophobic material to allow air to pass through and prevent water from

escaping the filter cartridge. The porosity of the membrane can vary, and is typically between 0.02 micron and 0.2 micron to prevent a water intrusion condition. As noted, the membrane is

preferably made of a hydrophobic material such as polypropylene, TEFLON® resin, and the like.

In an operative embodiment of the present invention, membrane 120 is made from GOR-TEX®

expanded polytetrafluoroethylene having a 0.02 micron pore size (available from W.L. Gore &

Associates, Inc., Elkton, MD). The porous disc support membrane 122 is also preferably

constructed from a hydrophobic material, such as a porous polypropylene material, and has a

porosity of between about 50 and about 350 microns. In an operative embodiment of the present

invention, the porous support disc is constructed from POREX® polypropylene material, having

an average pore size of between about 125 and 350 microns (available from Porex Technologies,

Fairburn, GA). O-ring seal 118 provides vent device 88 with a secure fit and seal into channel

116 of top cap 90 to prevent passage of materials other than entrapped air from escaping through

the vent. Lastly, compression ring 124 is constructed of a material that is compatible with the

top cap 90, and can be secured to top cap, as shown in FIG. 12 by, for example, ultrasonic

welding, to rigidly secure vent components in the cap.

Alternative embodiments of the ventilation system of the present invention, as well as

alternative arrangements of the individual vent device positioned on the filter cartridge top caps

are shown in FIGS. 13, 14 and 15. As shown in FIG. 13, an alternative embodiment of vent 88'

is positioned in channel 116 formed in top cap 90. Top cap 90 is sealed to housing 98 as

described above, and further includes port 68. The alternative vent components are similar to

those shown in the embodiment of FIG. 12, and include, for example, O-ring seal 118, porous

hydrophobic membrane 120, and porous support disk 122. This alternative embodiment further

includes a one-way valve 130, which also functions as a compression ring that seals the vent

components in the top cap channel 116. The one-way valve 130 allows air to exit, but prevents

air from entering, the filter cartridge. The hydrophobic membranes prevent water and/or filter media from escaping the filter cartridge.

FIG. 14 shows another embodiment of the ventilation system of the present invention,

wherein a vent device 88" is assembled in top cap 90 which is secured to housing 98. Vent 88"

includes, for example, O-ring seal 118, retaining ring 124', and one-way valve 130' having a flat

gasket portion 132 which provides a seal for the vent device within the channel. The retaining

ring 124' is constructed of a material that is compatible with top cap 90 such that the ring can be

secured to the top cap, for example, by ultrasonic welding to secure the vent components in the

channel 116. The one-way valve 130' allows for the passage of air from the filter cartridge at a

predetermined pressure while preventing air from entering the cartridge.

Another alternative embodiment of the ventilation system of the present invention is

shown in FIG. 15, wherein cartridge assembly 22, includes a plurality of series-connected

cartridges and each of the cartridges includes a vent device 88 positioned on each filter cartridge

top cap to allow entrapped air in the system to escape and prevent air from entering, while

preventing water or filter media from leaving the filter cartridge. A similar arrangement of filter

cartridges having individual vent devices is shown in FIG. 7. The alternative embodiment of the

ventilation system shown in FIG. 15 includes vent connectors 134 which are attached to vent

devices 88. The vent connectors are then each connected via conduits 136 to a solenoid

connector 138, which is connected to a valve (not shown) which opens periodically to release

entrapped air from the filter cartridge assembly.

The present invention will be further illustrated by the following Example, which is

intended to be illustrative in nature and is not to be construed as limiting the scope of the

invention.

EXAMPLE

A water treatment system having dosing control was evaluated to determine the effectiveness of the system in providing pure water, substantially free of contaminants, which

can be accurately dosed at the system outlet when desired, or recirculated throughout the system

at lower motor speeds and lower noise levels.

Pretreated water (by reverse osmosis) having a conductivity of about 2.0 μS/cm was

introduced to the system through a on/off solenoid valve (lined with an inert material) at a flow

rate of about 1.5 liters per minute. The feed water was then introduced to a magnetically coupled

positive displacement gear pump (available from Tuthill, Inc.) to pressurize the water up to about

4 bars. The pump was driven by a VARIOTRONIC™ variable speed motor and motor

controller. The pump then passed the water through a series of water treatment devices. The

first device was a 185 nm one-pass UV lamp unit (available from Ideal Horizons, Inc., Poultney,

VT). The UV lamp unit was used to oxidize organic contaminants present in the water. The

water was then fed to a second device, which was a filter cartridge assembly (available from

United States Filter Corporation, Lowell, MA) that included four individual filter cartridges

hydraulically connected in series, and contained at least one layer of an activated carbon and/or

at least one layer of a mixture of ion exchange resins. The filter cartridge assembly was used to

remove residual organic and ionic impurities. After passage through the filter cartridge

assembly, the water was then passed through an electrical resistivity sensor which measured the

resistivity of the water to be about 18.3 megohm-cm (0.054 μS/cm). The water was then passed

through a 10,000 molecular weight cutoff polysulfone hollow fiber membrane ultrafilter, wherein

at least about 90 percent of the water passed through, while the reject stream was recycled to the

pump inlet. Lastly, a 0.22 μm membrane final filter made from a cellulose nitrate membrane

(available from Gelman Sciences, Ann Arbor, MI), was used to remove any remaining

microorganisms and/or particles in the water.

The output of the motor, which drives the pump was controlled by an input device in the form of a potentiometer having a rotating handle that can be adjusted up to 300°. The

potentiometer provided an input signal, which represents a desired flow rate of water at the outlet

of the system, to a microprocessor. The microprocessor converted the input signal from the

potentiometer to a motor control signal, which was sent to the VARIOTRONIC™ motor

controller which caused the VARIOTRONIC™ motor to operate at a speed which caused the

pump to pass the water through the system to the outlet valve at the desired flow rate. This flow

rate was adjustable between a range of 0 to about 1.5 liters per minute at increments as small as a

few drops of water to allow for accurate dosing of purified water. When water was not desired at

the system outlet, the pump was operated in a recirculation mode, and the water was recirculated

at a flow rate of about 0.5 liters per minute through the system to maintain the high level of water

purity.

The system was also provided with a sanitization cycle. The sanitization cycle was

intended to be used to maintain a low microorganism population within the system despite the

fact that the system components (the conduits, valves, and connectors) were made from inert

materials in terms of extractables or leachables. The sanitization cycle was started by

introducing a chlorine sanitization tablet (available from United States Filter Corporation,

Lowell, MA), typically made from a chemical oxidant such as chloroisocyanuric acid, or the like,

into a sanitization chamber which was then dissolved in the flow stream of water. The chemical

oxidant then passed through the system to sanitize the internal tubing, fittings, pump, UV lamp

unit and UF membrane. The filter cartridge assembly was isolated because the chemical oxidant

used in the sanitization cycle is detrimental to the ion exchange resin in the filter cartridges.

The noise level of the system was measured to determine the actual reduced noise level

resulting from the use of a variable speed motor. A Radio Shack™ sound level meter was used

in determining the noise levels, which were measured at 0.5 and 1.0 meter from the front of the water treatment system in both recirculation (0.5 liters per minute) and at full production (1.5

liters per minute). At recirculation, the measured noise level from the system was 63.5 dB at 0.5

meter and 54.0 dB at 1.0 meter. At full production, which is equivalent to the motor speed and

associated noise levels of conventional systems without variable speed motors, the measured

noise level from the system was 68.0 dB at 0.5 meter and 64.0 dB at 1.0 meter. The background

noise for each test was less than about 50 dB at both 0.5 and 1.0 meter.

This Example illustrates the effectiveness of the present system in providing pure water,

substantially free of both organic and ionic contaminants, which can be accurately distributed as

a desired product flow rate. In addition, the Example illustrates that water can be effectively and

continuously purified in a recirculation mode at lower pump outputs (motor speed) resulting in

substantially reduced noise levels.

Although particular embodiments of the invention have been described in detail for

purposes of illustration, various modifications may be made without departing from the spirit and

scope of the invention. For example, it is understood that system 10 can include additional or

alternative water treatment devices such as dialysis units, continuous electrodeionization units,

reverse osmosis units, other types of media filters, and the like. Moreover, the dosing control

feature of the present invention can be applied to larger systems having higher flow rates in a

wide variety of industrial applications such as in pharmaceuticals, electronics, food and beverage

applications, chemical processing, wastewater and municipal water treatment, as well as

analytical applications. Furthermore, a device which is to be supplied with ultra-pure water can

be fixedly connected, for example by means of a hose (not shown), to the outlet valve 30, or

valve 48 (FIG. 5). A dispensing unit (not shown) may also be provided in system 10 to make

accurate water dosing more convenient for the user. Another modification to system 10

contemplated by the present invention is the provision of a remote control of the input device 44 to control the motor M and/or valve 48, or providing an input device at various locations in the

system, for example at a central switchboard. Accordingly, the invention is not to be limited

except as by the appended claims.

What is claimed is:

Claims

1. A water treatment system having dosing control, comprising:

a water inlet hydraulically connected to a pump having a variable speed motor;

at least one water treatment device hydraulically connected downstream of said pump;

at least one outlet valve hydraulically connected downstream of said water treatment

device; and

a recirculation line hydraulically connected from said outlet valve to said pump,

wherein said pump output is controlled by a regulating device connected to said variable

speed motor.

2. The system of claim 1, wherein said at least one water treatment device is selected

from the group consisting of an ultraviolet light lamp unit, a filter cartridge having at least one

layer of an activated carbon and at least one layer of a mixture of ion exchange resins, an

ultrafilter unit, and combinations thereof.

3. The system of claim 2, wherein said water treatment device is an ultraviolet light

lamp unit.

4. The system of claim 2, wherein said water treatment device is a filter cartridge

having at least one layer of an activated carbon and at least one layer of a mixture of ion

exchange resins.

5. The system of claim 2, wherein said water treatment device is an ultrafilter unit.

6. The system of claim 2, further comprising a disinfection unit hydraulically

connected between said pump and said outlet valve.

7. The system of claim 1, wherein said outlet valve is in a completely closed

position during water recirculation in said system, and is in a completely opened position for

removing purified water from said system.

8. The system of claim 7, wherein said pump has an output of about 0.5 liter/min for

water recirculation in said system when said outlet valve is closed.

9. The system of claim 7, wherein said pump output is controlled by said regulating

device when said outlet valve is opened.

10. The system of claim 1, wherein said regulating device includes a controller and an

input device to provide an input signal, which represents a desired flow rate at said outlet valve,

to said controller, said controller converts said input signal to a motor control signal that causes

said motor to operate at a speed which causes the flow of water at said outlet valve to correspond

to the desired flow rate.

11. The system of claim 10, wherein said input device includes a potentiometer.

12. The system of claim 10, wherein said input device includes a key pad.

13. The system of claim 10, wherein said input device includes an angle encoder.

14. The system of claim 1, wherein said regulating device is a potentiometer.

15. The system of claim 1 , wherein said regulating device includes a device to

perform at least one of turning off said motor at a first predetermined time, and turning on said

motor at a second predetermined time.

16. The system of claim 15, wherein said first and second predetermined times are

provided by a user through an input device.

17. The system of claim 15, wherein said first and second predetermined times are

provided by said regulating device as a function of operational data.

18. The system of claim 1 , further including a proportional valve hydraulically

connected downstream of said outlet valve, wherein said system output is controlled by a

regulating device connected to said proportional valve.

19. The system of claim 18, wherein said regulating device includes a controller and

an input device to provide an input signal, which represents a desired flow rate at said

proportional valve, to said controller, said controller converts said input signal to a valve control

signal that causes said valve to open at a cross-section which causes the flow of water at said

proportional valve to correspond to the desired flow rate.

20. A water treatment system having dosing control, comprising: a water inlet hydraulically connected to a pump;

device;

a recirculation line hydraulically connected from said outlet valve to said pump; and

a proportional valve hydraulically connected downstream of said outlet valve,

wherein said system output is controlled by a regulating device connected to said

proportional valve.

21. The system of claim 20, wherein said at least one water treatment device is

selected from the group consisting of an ultraviolet light lamp unit, a filter cartridge having at

least one layer of an activated carbon and at least one layer of a mixture of ion exchange resins,

an ultrafilter unit, and combinations thereof.

22. The system of claim 20, wherein said outlet valve is in a completely closed

removing purified water from said system.

23. The system of claim 22, wherein said pump has an output of about 0.5 liter/min

for water recirculation in said system when said outlet valve is closed.

24. The system of claim 20, wherein said regulating device includes a controller and

proportional valve, to said controller, said controller converts said input signal to a valve control signal that causes said valve to open at a cross-section which causes the flow of water at said

proportional valve to correspond to the desired flow rate.

25. A method for treating water, comprising:

providing a water inlet hydraulically connected to a pump having a variable speed motor;

hydraulically connecting at least one water treatment device downstream of said pump, at

least one outlet valve downstream of said water treatment unit, and a recirculation line from said

outlet valve to said pump;

directing a water stream to said water inlet;

pumping said water stream into said water treatment device to produce a purified water

stream;

closing said outlet valve;

recirculating said purified water stream to said water inlet;

opening said outlet valve; and

removing said purified water by controlling said pump output with a regulating device

connected to said variable speed motor.

26. The method of claim 25, wherein said at least one water treatment device is

ultrafilter unit, and combinations thereof.

27. The method of claim 26, wherein said water treatment device is an ultraviolet

light lamp unit.

28. The method of claim 26, wherein said water treatment device is a filter cartridge

exchange resins.

29. The method of claim 26, wherein said water treatment device is an ultrafilter unit.

30. The method of claim 25, further comprising hydraulically connecting a

disinfection unit between said pump and said outlet valve.

31. The method of claim 25, wherein said pump has a low output during water

recirculation when said outlet valve is closed.

32. A filter cartridge assembly, comprising:

at least one filter cartridge;

said filter cartridge including a housing having two ends, the housing containing a filter

media;

a first end cap disposed on one end of said housing, said first end cap including a fluid

inlet port, a fluid outlet port, a first fluid distributor, and a vent device that allows entrapped air

to be removed from said cartridge;

a second end cap disposed on a second end of said housing, said second end cap

including a product collection plenum, and a second fluid distributor that separates said filter

media from said product collection plenum; and

a liquid transfer tube disposed within the housing and extending from said product collection plenum to said fluid outlet port.

33. The assembly of claim 32, wherein said vent device includes at least one

hydrophobic membrane.

34. The assembly of claim 32, wherein said vent device includes a one-way valve.