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Microfiltration of high purity deionised water
Microfiltration of high purity deionised water by B. Carbonel t
Results are presented of experimental studies conducted on a new type of filtration cartridge which is used for colloidal matter removal from the deionised water used for silicon wafer rinsing, in the microelectronics industry. This new filtration cartridge is made of classical pleated cartridges around which has been injected a thin layer of cation and anion microresins, so-called macroreticular resins. This association of microresins and filters, in the same cartridge allows the user to obtain filtration throughputs and water qualities never reached by classical filters.
1. Introduction The manufacturing technology of semiconductors, and particularly of integrated circuits, has been, these past years, forced to include into production lines more and more sophisticated equipment to try to solve all the numerous problems of ultra purification of fluids, liquids and gases. Most of those fluids can be classified in 3 distinct categories: (i) acids, bases, alcohols, hydrocarbons, solvents, etc., (ii) gases, (iii) deionised water. For categories (i) and (ii), it is true to say that the problems raised by their chemical purification are, at present, solved by classical techniques, except may be for some highly concentrated acids or some photoresists. In the case of deionised water, one can easily see that this fluid is not only poisoned by a lot of contaminants, but also that the ratio of these contaminants changes, either through a slow degradation process due to environment pollution, or through very quick variations.
2. Typical contaminants in water The various contaminants which can be encountered in process water can be classified in five categories: (i) ionic contaminants (ii) suspended particles (iii) microorganisms (iv) organics (v) colloids Ionic contaminants can be removed easily by classical ion exchange techniques. Suspended particles and micro-organisms can also be removed using traditional microfiltration membranes, and choosing correctly the pore size and the filtration area. tA.D.F. Co., Strasbourg, France.
Organics can be fixed on activated carbons or on specialised resins. The only remaining problem is to detect when those materials are exhausted and need to be regenerated. Category (v) includes only the colloidal matter and it appears now that it is the most difficult problem to solve for high purity water production in the semiconductor industry. 3. Colloidal matter structure Colloids, which are aIways present in surface water, are ultra fine and dispersed particles, essentially composed of SiO2, Fe203, A12 03, and such organics as humic and fulvic acids, in varying ratios. The ratios depend not only upon the nature of the soil, but also upon the time of the year, a factor of extreme importance. What happens is the following : as a result of micro biological activity in the soil, CO 2 and above mentioned organic acids form and react with the various silicates present in the soil. The ratios of these constituents depend upon the nature of the silicates and the concentration of organic acids. The iron, aluminium and silicic acid mutually interact to form colloids which absorb some of the organic matter. Depending upon various conditions, the colloid may coagulate or disperse. In the presence of organic matter, the colloids are stabilised as highly dispersed suspensions which are encountered in water treatment. These colloids have variable isoelectric points but they are normally such that the colloids are negatively charged at the pH 0f most waters. Two consequences come from the structure of these colloidal particles: (i) the non-ionic particles go easily through deionisation plants, and (ii) electrically charged particles will create on filtration membranes a polarised layer which will accelerate the clogging of these membranes, and thus increase the filtration costs.
MICROELECTRONICS JOURNAL, Vol. 10 No. 2 © 1979 Mackintosh Publications Ltd., Luton.
13
Microfiltration of high purity deionised water c o n t i n u e d f r o m page 13
4 The Maerotube cartridge (Fig. 1) The experimental study, the results of which are described here, considered the following characteristics: colloidal matter removal, suspended particles removal, microorganisms removal, downstream resistivity, downstream filters life time increase, cartridge rinsing time, organics, ionic contamination.
"nal pleated cartridge. ~roreticular on -Anion roresins.
ernal micromesh.
4. 1.2 Behaviour as an ion exchange resin Conditioning these microresins as a mixed bed obviously produces a better water quality, resistivity-wise, an effect which is well documented.
4.2 Pleated m e m b r a n e cartridge filter Microresins are conditioned around one, or several stacked classical cartridges, using a rather delicate technology, in which important parameters are mainly size distribution, ratios between anion and cation resins, mixture stirring and transfer speeds, and floe expansion. Internal cartridge filters, having a pleated membrane, have two functions: (i) They are used as a mechanical support for microresins; and, (ii) they retain particles, bacteria and resin fines, which would get through the resin precoating. Our choice was pleated cartridges, having a filtration area up to 5000cm 2, a length of 25cm and a pore size of 0.45 micron, this value being currently encountered in the microelectronics industry. It is obvious that it is always possible to select another value, between 0.2 and 5 microns. 5. Experimental study and results 5.1 Experimental apparatus Figure 2 shows the experimental apparatus which has been used for measurements. Deionised water enters a circuit with two lines in parallel, each line having: one or several filters in series, a flow meter, a water counter, sampling ports, for fouling indices, resistivity and pressure measurements.
Ftowmeter. ~ ~__PVC coater counter.
Pleated cartridge. Fig. 1 Structure of a Macrotube cartridge. The Macrotube cartridge concept is as follows: "knowing that 'macroreticular' resins are able to adsorb the colloids present in process water, the idea was to inject, around a classical pleated cartridge filter, a thin layer of cation and anion mixed bed of macroreticular resins, to obtain a composite filter.
4.1
Macroreticularresmscharacteristics
4. 1. 1 B e h a v i o u r as a filter
Macroreticular resin.s .are powder resins, having dimensions between 20 and 100 microns for cation resins, and between 5 and 90 microns for anion resins. The regeneration level in the H* and OH- is close to 100%. The mean pore size is about 7 micron, and it might appear that this pore size would be out of proportion to the colloidal particle dimensions. In fact, due to resin size (average 50 microns), electric interaction forces are enormous, and moreover the mixture of cation and anion microresins produces a 'floe', the expansion of which can go up to 800%. This floe is then behaving exactly as an electrostatic filter, adsorbing colloidal particles with the help of their free electric charge. 14
I
S
v
S
Inlet DI water
DI water
[
P
P
P
SS
T S "~" S \ -PVC coater / Pleated \ counter. Macrotube. cartridge. Flowmeter. Fig. 2 Experimental arrangement. 5.2 Measured parameters were: cartridge rinsing time and volume of water, pressure drops versus filtered volumes, pressure drops of a pleated cartridge protected by a maerotube, fouling indices versus filtered volumes, resistivity versus filtered volumes, microbiological contamination, organics, residual ionic contamination, suspended particle contamination (tentative).
5.3 Macrotube rinsing time It is well known that a new filter, whatever it may be, is a source of ionic contamination, as soon as it is installed on a high resistivity water line. But, after a certain volume of water is filtered through the cartridge, it is returned to the resistivity value measured upstream. It is obvious that this parameter is important because it corresponds to a period of time wasted in production. Two macrotubes have been tested, equipped with two 10 inch pleated internal cartridges. Figure 3 shows the resistivity recovery of macrotubes No. 1 and 2, giving rinse volume figures of 310 and 40 litres respectively. It should be noted that 2000 litres would normally have been necessary to rinse the two pleated cartridges contained in each macrotube.
M f ~ cm / Compens;htion I Temper~ture /
-ZI I'
~
22ii
5.4 Pressure drops v e r s u s filtered v o l u m e s Figure 4 shows that, the available pressure having been higher, volumes bigger than 1000m 3 could have been filtered without major problems. The curves are given for a macrotube equipped with two 10 inch pleated cartridges. 5.5 Pressure drops of a pleated cartridge protected by a macrotube Figure 5 shows the pressure drops of a simple pleated cartridge protected by a macrotube. The pleated cartridge had a 0.45 micron pore size, a 10 inch length, and it was placed immediately downstream of the macrotube. It can be seen that practically no pressure drop increase shows up during the whole macrotube life time (0.2 bar per 1000m3). 5.6 Fouling indices v e r s u s filtered v o l u m e s The method used to determine fouling indices consists of measuring the times to filter two 100 ml water samples, at a 15 minutes interval of time. Then a simple formula allows the operator to calculate the fouling index value of the water. This method does not require the complete clogging of a membrane filter.
~ ridge No. ~-
tridge I~o.i
t7
Litres 12
~,o
I()O
2()o
3£~0 =
Fig. 3 Macrotube cartridge rinsing. Figure 6 shows variations of relative fouling indices (FIi,l~t - Floutt~t)/Flinlct, versus filtered volumes. Averaging these ratios, one has following values: macrotube 0.45 micron 0.61 pleated cartridge No. 1, 0.45 micron 0.37 pleated cartridge No. 2, 0.22 micron 0.28 The conclusion is that the good filtration efficiency and the life time of a macrotube are due mainly to microresin precoating and not to the pore size of the internal pleated cartridge. 5.7 Resistivity v e r s u s filtered v o l u m e s Figure 7 shows the average resistivity increase, through
Ap bars
+,,~/ j.jf '
ff
f
f ff
f
1//, . ... *" ""~"~. ..~~.~, i-s~
÷
te=2g
~m
Flowrate= 5gpm
J
f,_......_-.-----Filter Volume 24 o
6q ~0
8~ '0
m3 1030=
Fig. 4 Pressure drops of a Macrotube 0.45/.tm versus filtered volume. 15
Microfiltration of high purity deionised water continued from page 15
AP bars 2.C
:lowrate= 2 gpn
/
1.0
Flowrate= 4gpm
__2
_2____---
/
Off
Filtered Volumelm 3
0
2()0
im
4£0
6(O
8~ tO
1£ 3O
Fig. 5 Pressure drops of a pleated cartridge, w/o microresins, downstream ofa 0.45/zm Macrotube cartridge.
I
Relative _ ~ c o ~ xngA FI/ F__~] O91 ~
Average ('~
--
.
........ 7,
0
Macrotube
.
.
~
-
--0-61
.
...... 7.1~0
41)0
- -0-37 --0.28
I,,,ooVo,umem3
6(10
8q)O
lC
Fig. 6 Relative fouling index (FX) versus filtered volume.
the macrotube to be 1.25 megohm cm. This important characteristic is due to the fact that microresins are conditioned in a H + and O H - mixed bed form, which produces a secondary deionisation effect. T h e macrotube is then able to maintain water resistivity at its higher value, for 1 or 2 hours, in the case of any accident occurring in the central deionisation plant. This m e a n s that production areas will be protected against any resistivity drop on line. 5.8 Bacteriological c o n t a m i n a t i o n T h e analysis done upstream and downstream of the m a c r o t u b e shows clearly (Table I) that although a high v o l u m e o f water has been filtered by the same cartridge, t h e r e is no bacterial growth inside mieroresins. Incubations have been done at 37°C for 24 hours and 22°C for 72 hours. 16
Table I
Bacteriological contamination anal,,sis Inlet
Inlet
Outlet
Outlet
37"C
22"C
37~C
22°C
Filter Volume (cubicmetres)
17.05.78
3-3
0.0
100-17
04)
3
23.05.78
1-34
04)
12-75
3-1
110
29.05.78
0.0
0.0
0.0
0-0
232
27.06.78
1-11
12-12
11-6
2-8
443
14.06.78
6-0
0.0
5-0
0.0
588
Dates
MY[
cm Compensat ion Temperature
--. D~,wJ~trea~ Rp--~isti ~~Upstrean
,ity
Resistivity
-25
m3
Filtered Volume m
2( )0
4( )0 Fig. 7
Table II V = 120m 3
61 t0
V=562m 3
V=960m a
Up.
Down-
Up-
Down:.
Up-
Down-
up.
Down.
streartl
stream
$tr¢arn
$1r~ara
stream
$tream
$trcartl
Stream
B
<3
3'
4
<3
3
3
3
3
Si
--<1
<1
_-<1
ND
E1
ND
ND
ND
Mg
2
2
2
2
2
2
2
2
Fe
ND
ND
ND
ND
ND
ND
ND
ND
AI
ND
ND
ND
<1
--~1
ND
ND
ND
Sn
ND
ND
ND
ND
ND
ND
ND
ND
Cu
ND
ND
ND
ND
2
ND
ND
ND
Ca
8
6
5
5
7
6
4
4
Na
<1
<1
<1
<1
<1
<1
<1
<1
Other detectable elements: Pb - Ni - A g - M n - C r - Sb
5.9 Organics Analysis of the organic matter content upstream and downstream of the macrotube shows that this cartridge does not improve or degrade the wate.r quality. The average values of total organic carbon (TOC) were,"
upstream downstream
, oo
Upstream and downstream resistivity.
Ionic contamination V=347m a
8?0
335ppb
337ppb
5.10 Residual ionic contaminants All elements have been analysed with emission spectroscopy, except for sodium, which was detected using atomic absorption spectroscopy.
Table II expresses all results, in ppb, on 4 series of samples, taken after the filtration of 120, 347, 562 and 960m 3 of water. 5.11 Suspended particle contamination Particle count is difficult on microporous membrane filters, because of the very low level of particles downstream. An approximate count was done, with the help of HIAC counters, measuring simultaneously upstream and downstream of the macrotube. upstream average particle count 5600 downstream average particle count 5 Though it is certainly possible to discuss the validity of such measurements knowing the difficulties in obtaining a complete degassing of water, it must be noted that these figures are always pessimistic because of the constant presence of air microbubbles. 6. Conclusions To summarise the results obtained on the Macrotube, it was found that the most important characteristics of this cartridge were the following: rinsing: 310 and 40 litres (1000 litres for a standard pleated cartridge), 1000m 3, throughput: a v e r a g e r e t e n t i o n 61% (37% and 28% for efficiency of standard pleated cartridges), colIoidal particles: resistivity: 1.25 megohm cm increase, bacteria: no bacterial growth inside resins, organics: no improvement or degradation of water quality, ionic contaminants: improvement of water quality, particles: virtually no particles downstream, protection of a excellent, pleated cartridge: resistivity level 1-2 hours. maintenance: 17
Results are presented of experimental studies conducted on a new type of filtration cartridge which is used for colloidal matter removal from the deionised water used for silicon wafer rinsing, in the microelectronics industry. This new filtration cartridge is made of classical pleated cartridges around which has been injected a thin layer of cation and anion microresins, so-called macroreticular resins. This association of microresins and filters, in the same cartridge allows the user to obtain filtration throughputs and water qualities never reached by classical filters.
1. Introduction The manufacturing technology of semiconductors, and particularly of integrated circuits, has been, these past years, forced to include into production lines more and more sophisticated equipment to try to solve all the numerous problems of ultra purification of fluids, liquids and gases. Most of those fluids can be classified in 3 distinct categories: (i) acids, bases, alcohols, hydrocarbons, solvents, etc., (ii) gases, (iii) deionised water. For categories (i) and (ii), it is true to say that the problems raised by their chemical purification are, at present, solved by classical techniques, except may be for some highly concentrated acids or some photoresists. In the case of deionised water, one can easily see that this fluid is not only poisoned by a lot of contaminants, but also that the ratio of these contaminants changes, either through a slow degradation process due to environment pollution, or through very quick variations.
2. Typical contaminants in water The various contaminants which can be encountered in process water can be classified in five categories: (i) ionic contaminants (ii) suspended particles (iii) microorganisms (iv) organics (v) colloids Ionic contaminants can be removed easily by classical ion exchange techniques. Suspended particles and micro-organisms can also be removed using traditional microfiltration membranes, and choosing correctly the pore size and the filtration area. tA.D.F. Co., Strasbourg, France.
Organics can be fixed on activated carbons or on specialised resins. The only remaining problem is to detect when those materials are exhausted and need to be regenerated. Category (v) includes only the colloidal matter and it appears now that it is the most difficult problem to solve for high purity water production in the semiconductor industry. 3. Colloidal matter structure Colloids, which are aIways present in surface water, are ultra fine and dispersed particles, essentially composed of SiO2, Fe203, A12 03, and such organics as humic and fulvic acids, in varying ratios. The ratios depend not only upon the nature of the soil, but also upon the time of the year, a factor of extreme importance. What happens is the following : as a result of micro biological activity in the soil, CO 2 and above mentioned organic acids form and react with the various silicates present in the soil. The ratios of these constituents depend upon the nature of the silicates and the concentration of organic acids. The iron, aluminium and silicic acid mutually interact to form colloids which absorb some of the organic matter. Depending upon various conditions, the colloid may coagulate or disperse. In the presence of organic matter, the colloids are stabilised as highly dispersed suspensions which are encountered in water treatment. These colloids have variable isoelectric points but they are normally such that the colloids are negatively charged at the pH 0f most waters. Two consequences come from the structure of these colloidal particles: (i) the non-ionic particles go easily through deionisation plants, and (ii) electrically charged particles will create on filtration membranes a polarised layer which will accelerate the clogging of these membranes, and thus increase the filtration costs.
MICROELECTRONICS JOURNAL, Vol. 10 No. 2 © 1979 Mackintosh Publications Ltd., Luton.
13
Microfiltration of high purity deionised water c o n t i n u e d f r o m page 13
4 The Maerotube cartridge (Fig. 1) The experimental study, the results of which are described here, considered the following characteristics: colloidal matter removal, suspended particles removal, microorganisms removal, downstream resistivity, downstream filters life time increase, cartridge rinsing time, organics, ionic contamination.
"nal pleated cartridge. ~roreticular on -Anion roresins.
ernal micromesh.
4. 1.2 Behaviour as an ion exchange resin Conditioning these microresins as a mixed bed obviously produces a better water quality, resistivity-wise, an effect which is well documented.
4.2 Pleated m e m b r a n e cartridge filter Microresins are conditioned around one, or several stacked classical cartridges, using a rather delicate technology, in which important parameters are mainly size distribution, ratios between anion and cation resins, mixture stirring and transfer speeds, and floe expansion. Internal cartridge filters, having a pleated membrane, have two functions: (i) They are used as a mechanical support for microresins; and, (ii) they retain particles, bacteria and resin fines, which would get through the resin precoating. Our choice was pleated cartridges, having a filtration area up to 5000cm 2, a length of 25cm and a pore size of 0.45 micron, this value being currently encountered in the microelectronics industry. It is obvious that it is always possible to select another value, between 0.2 and 5 microns. 5. Experimental study and results 5.1 Experimental apparatus Figure 2 shows the experimental apparatus which has been used for measurements. Deionised water enters a circuit with two lines in parallel, each line having: one or several filters in series, a flow meter, a water counter, sampling ports, for fouling indices, resistivity and pressure measurements.
Ftowmeter. ~ ~__PVC coater counter.
Pleated cartridge. Fig. 1 Structure of a Macrotube cartridge. The Macrotube cartridge concept is as follows: "knowing that 'macroreticular' resins are able to adsorb the colloids present in process water, the idea was to inject, around a classical pleated cartridge filter, a thin layer of cation and anion mixed bed of macroreticular resins, to obtain a composite filter.
4.1
Macroreticularresmscharacteristics
4. 1. 1 B e h a v i o u r as a filter
Macroreticular resin.s .are powder resins, having dimensions between 20 and 100 microns for cation resins, and between 5 and 90 microns for anion resins. The regeneration level in the H* and OH- is close to 100%. The mean pore size is about 7 micron, and it might appear that this pore size would be out of proportion to the colloidal particle dimensions. In fact, due to resin size (average 50 microns), electric interaction forces are enormous, and moreover the mixture of cation and anion microresins produces a 'floe', the expansion of which can go up to 800%. This floe is then behaving exactly as an electrostatic filter, adsorbing colloidal particles with the help of their free electric charge. 14
I
S
v
S
Inlet DI water
DI water
[
P
P
P
SS
T S "~" S \ -PVC coater / Pleated \ counter. Macrotube. cartridge. Flowmeter. Fig. 2 Experimental arrangement. 5.2 Measured parameters were: cartridge rinsing time and volume of water, pressure drops versus filtered volumes, pressure drops of a pleated cartridge protected by a maerotube, fouling indices versus filtered volumes, resistivity versus filtered volumes, microbiological contamination, organics, residual ionic contamination, suspended particle contamination (tentative).
5.3 Macrotube rinsing time It is well known that a new filter, whatever it may be, is a source of ionic contamination, as soon as it is installed on a high resistivity water line. But, after a certain volume of water is filtered through the cartridge, it is returned to the resistivity value measured upstream. It is obvious that this parameter is important because it corresponds to a period of time wasted in production. Two macrotubes have been tested, equipped with two 10 inch pleated internal cartridges. Figure 3 shows the resistivity recovery of macrotubes No. 1 and 2, giving rinse volume figures of 310 and 40 litres respectively. It should be noted that 2000 litres would normally have been necessary to rinse the two pleated cartridges contained in each macrotube.
M f ~ cm / Compens;htion I Temper~ture /
-ZI I'
~
22ii
5.4 Pressure drops v e r s u s filtered v o l u m e s Figure 4 shows that, the available pressure having been higher, volumes bigger than 1000m 3 could have been filtered without major problems. The curves are given for a macrotube equipped with two 10 inch pleated cartridges. 5.5 Pressure drops of a pleated cartridge protected by a macrotube Figure 5 shows the pressure drops of a simple pleated cartridge protected by a macrotube. The pleated cartridge had a 0.45 micron pore size, a 10 inch length, and it was placed immediately downstream of the macrotube. It can be seen that practically no pressure drop increase shows up during the whole macrotube life time (0.2 bar per 1000m3). 5.6 Fouling indices v e r s u s filtered v o l u m e s The method used to determine fouling indices consists of measuring the times to filter two 100 ml water samples, at a 15 minutes interval of time. Then a simple formula allows the operator to calculate the fouling index value of the water. This method does not require the complete clogging of a membrane filter.
~ ridge No. ~-
tridge I~o.i
t7
Litres 12
~,o
I()O
2()o
3£~0 =
Fig. 3 Macrotube cartridge rinsing. Figure 6 shows variations of relative fouling indices (FIi,l~t - Floutt~t)/Flinlct, versus filtered volumes. Averaging these ratios, one has following values: macrotube 0.45 micron 0.61 pleated cartridge No. 1, 0.45 micron 0.37 pleated cartridge No. 2, 0.22 micron 0.28 The conclusion is that the good filtration efficiency and the life time of a macrotube are due mainly to microresin precoating and not to the pore size of the internal pleated cartridge. 5.7 Resistivity v e r s u s filtered v o l u m e s Figure 7 shows the average resistivity increase, through
Ap bars
+,,~/ j.jf '
ff
f
f ff
f
1//, . ... *" ""~"~. ..~~.~, i-s~
÷
te=2g
~m
Flowrate= 5gpm
J
f,_......_-.-----Filter Volume 24 o
6q ~0
8~ '0
m3 1030=
Fig. 4 Pressure drops of a Macrotube 0.45/.tm versus filtered volume. 15
Microfiltration of high purity deionised water continued from page 15
AP bars 2.C
:lowrate= 2 gpn
/
1.0
Flowrate= 4gpm
__2
_2____---
/
Off
Filtered Volumelm 3
0
2()0
im
4£0
6(O
8~ tO
1£ 3O
Fig. 5 Pressure drops of a pleated cartridge, w/o microresins, downstream ofa 0.45/zm Macrotube cartridge.
I
Relative _ ~ c o ~ xngA FI/ F__~] O91 ~
Average ('~
--
.
........ 7,
0
Macrotube
.
.
~
-
--0-61
.
...... 7.1~0
41)0
- -0-37 --0.28
I,,,ooVo,umem3
6(10
8q)O
lC
Fig. 6 Relative fouling index (FX) versus filtered volume.
the macrotube to be 1.25 megohm cm. This important characteristic is due to the fact that microresins are conditioned in a H + and O H - mixed bed form, which produces a secondary deionisation effect. T h e macrotube is then able to maintain water resistivity at its higher value, for 1 or 2 hours, in the case of any accident occurring in the central deionisation plant. This m e a n s that production areas will be protected against any resistivity drop on line. 5.8 Bacteriological c o n t a m i n a t i o n T h e analysis done upstream and downstream of the m a c r o t u b e shows clearly (Table I) that although a high v o l u m e o f water has been filtered by the same cartridge, t h e r e is no bacterial growth inside mieroresins. Incubations have been done at 37°C for 24 hours and 22°C for 72 hours. 16
Table I
Bacteriological contamination anal,,sis Inlet
Inlet
Outlet
Outlet
37"C
22"C
37~C
22°C
Filter Volume (cubicmetres)
17.05.78
3-3
0.0
100-17
04)
3
23.05.78
1-34
04)
12-75
3-1
110
29.05.78
0.0
0.0
0.0
0-0
232
27.06.78
1-11
12-12
11-6
2-8
443
14.06.78
6-0
0.0
5-0
0.0
588
Dates
MY[
cm Compensat ion Temperature
--. D~,wJ~trea~ Rp--~isti ~~Upstrean
,ity
Resistivity
-25
m3
Filtered Volume m
2( )0
4( )0 Fig. 7
Table II V = 120m 3
61 t0
V=562m 3
V=960m a
Up.
Down-
Up-
Down:.
Up-
Down-
up.
Down.
streartl
stream
$tr¢arn
$1r~ara
stream
$tream
$trcartl
Stream
B
<3
3'
4
<3
3
3
3
3
Si
--<1
<1
_-<1
ND
E1
ND
ND
ND
Mg
2
2
2
2
2
2
2
2
Fe
ND
ND
ND
ND
ND
ND
ND
ND
AI
ND
ND
ND
<1
--~1
ND
ND
ND
Sn
ND
ND
ND
ND
ND
ND
ND
ND
Cu
ND
ND
ND
ND
2
ND
ND
ND
Ca
8
6
5
5
7
6
4
4
Na
<1
<1
<1
<1
<1
<1
<1
<1
Other detectable elements: Pb - Ni - A g - M n - C r - Sb
5.9 Organics Analysis of the organic matter content upstream and downstream of the macrotube shows that this cartridge does not improve or degrade the wate.r quality. The average values of total organic carbon (TOC) were,"
upstream downstream
, oo
Upstream and downstream resistivity.
Ionic contamination V=347m a
8?0
335ppb
337ppb
5.10 Residual ionic contaminants All elements have been analysed with emission spectroscopy, except for sodium, which was detected using atomic absorption spectroscopy.
Table II expresses all results, in ppb, on 4 series of samples, taken after the filtration of 120, 347, 562 and 960m 3 of water. 5.11 Suspended particle contamination Particle count is difficult on microporous membrane filters, because of the very low level of particles downstream. An approximate count was done, with the help of HIAC counters, measuring simultaneously upstream and downstream of the macrotube. upstream average particle count 5600 downstream average particle count 5 Though it is certainly possible to discuss the validity of such measurements knowing the difficulties in obtaining a complete degassing of water, it must be noted that these figures are always pessimistic because of the constant presence of air microbubbles. 6. Conclusions To summarise the results obtained on the Macrotube, it was found that the most important characteristics of this cartridge were the following: rinsing: 310 and 40 litres (1000 litres for a standard pleated cartridge), 1000m 3, throughput: a v e r a g e r e t e n t i o n 61% (37% and 28% for efficiency of standard pleated cartridges), colIoidal particles: resistivity: 1.25 megohm cm increase, bacteria: no bacterial growth inside resins, organics: no improvement or degradation of water quality, ionic contaminants: improvement of water quality, particles: virtually no particles downstream, protection of a excellent, pleated cartridge: resistivity level 1-2 hours. maintenance: 17