namwater report-epukiro pos 3
TRANSCRIPT
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Namibia Water Corporation Ltd
March 2012
DT-RO Pilot Plant Operation at Epukiro Pos 3:
Namibia Sub-standard Water Quality
Improvement
Namibia Water Corporation
Private Bag 13389
Windhoek
Namibia
Water Quality Services
NAMWATER
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EXECUTIVE SUMMARY:
(i) Introduction and Background Information
At present water in Namibia is regulated by the Water Act of 1956. However, in 2004,
Namibia introduced a new Water Resource Management Act, but this has yet to be
made operational. This will be accompanied by new water quality standards that will
replace the current water quality guidelines. These standards are more stringent and
when implemented many of the NamWater schemes will not comply with the standards.
Subsequently, NamWater decided to take a pro-active stand regarding the proposed
standards. This pro-active stand deemed it necessary for NamWater to investigate
schemes that would not comply with these standards and thereafter propose mitigating
actions to ensure that the water produced from such schemes would comply with thenew standards. Such mitigating actions resulted in a desk study and pilot plant
operations. The pilot plant operations were executed at Epukiro Pos 3 and Bethanie
schemes.
(ii) Objective
The objective of this report is to mainly reveal and discuss results obtained from Epukiro
Pos 3 with regard to water quality improvement and system operation. Finally, the
report proposes a full scale plant for the Epukiro Pos 3 scheme.
(iii) Epukiro Pos 3 Scheme
The Epukiro Pos 3 village is situated about 137 km NNE of Gobabis. From the water
sales figures the demand for the village is 110 m3/day. This demand figure is projected
in the Planning Report to reach 150 m3/day. The quality of water supplied to Epukiro
Pos 3 is classified as group C as exceeded by nitrates, sulphates, total hardness and
conductivity. When the new standards would become operational sodium and chlorides
will have to be added to this list. Given this extensive list of parameters that do not
comply with the required standards, Epukiro Pos 3 was therefore a prime candidate for
operating the pilot plant.
(iv) Pilot Operation and Findings
The pilot system that was chosen for Epukiro Pos 3 was the DT-RO module, a low
pressure (15.5 bar) reverse osmosis system. It was operated with and without anti-
scalant to investigate the robustness of the system under various conditions. During the
time when the plant was operated without anti-scalant, the running hours was only for
12 hours/day, while the membrane system was soaked in permeate water for the
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remaining hours of the day. With anti-scalant the plant was operated for 24 hours
continuously.
Under both conditions the system was able to reduce all parameters of concern to
below the required standards (when compared to the current guidelines or the
anticipated standards). The rejection for both conditions was similar, hovering wellabove 90% except for nitrate which averaged at 88% for both conditions. Such results
demonstrate that the DT-RO can be operated without chemicals if it is soaked in the
permeate to avoid excessive membrane scaling.
Another aspect that is worth mentioning, from the results, is the low mineral content of
the permeate water; the calcium carbonate precipitation potential averaged at -209.6
mg/l. That suggests that the final water must be remineralised through blending with
borehole water or chemical stabilisation.
When the plant was operated 24 hrs, continuously, the recovery averaged at 53%. Suchrecovery is low for any part of Namibia. Therefore, to improve the system recovery this
paper proposes the blending of borehole water with permeate water at a ratio of 1.7 to
1.0. Such blending would also improve the overall water stability as well as the system
recovery. The report indicates the system recovery to reach figures well above 70%,
and that is acceptable.
For such blending ratios (indicated above) the capital investment for the DT-RO is
estimated at N$ 1.7 million, which is about 14.3 % less than when the system is
operated without blending.
(v) Cost Estimation
A summary of the Unit Costs for the Epukiro Treatment plant is given in the Table
below. The costs include the annual fixed and variable costs estimated for the Capital
Project. The unit cost of the treated water will amount to N$ 26.75 per m 3 water treated.
The unit cost of the plant will amount to N$ 2,205,000.00 per annum.
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(vi) Conclusion
All parameters of concern (nitrate, sulphate, sodium, chloride, total hardness and
conductivity) were reduced to well below the required levels when compared to the
Namibia proposed standards or Namibia Water Quality Guidelines.
The DT-RO system recovery is about 53% and that could be improved to above
70% through blending (and improved feed water to the system due to the addition of
two other borehole waters).
Blending option can also reduce DT-RO capital investment by 14.3 %.
(vii) Recommendations
NamWater should share this report with the Ministry of Agriculture, Forestry and Water
Affairs as well as the relevant Regional Council for a decision regarding the
implementation of a water treatment plant to improve the water quality at NamWater
schemes with substandard water quality.
Cost Component Amount Amount
N$/m3 N$/a
Fixed Costs
Capital & interest 6.55 540,000
Energy 0.42 34,387
Personnel 5.51 454,250Materials 0.76 62,750
Water quality 0.19 15,500
Maintenance 0.44 36,200
Overheads 11.27 929,074
Variable Costs
Energy 1.58 130,615
Water Chlorination 0.03 2,084
Total Unit Costs 26.75 2,205,000
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Table of Contents
EXECUTIVE SUMMARY: .......................................................................................................................... i
1. Introduction:......................................................................................................................................... 1
1.1 Namibia Water Regulation: ....................................................................................................... 1
1.2 Namibia New Water Quality Standards .................................................................................. 1
1.3 Impact of Proposed Standards on the Quality of Water Supplied: A NamWater
Concern Mitigation ................................................................................................................................. 1
2. Objective of this Report ..................................................................................................................... 5
3. Epukiro Pos 3 Water Scheme .......................................................................................................... 6
3.1 Background Information ............................................................................................................ 6
3.2 Epukiro Pos 3 Water Quality .................................................................................................... 6
4. The DT-RO System Process Description: ...................................................................................... 8
4.1 Case for DT-RO System and Process Overview: ................................................................. 8
4.2 Detailed Process Description: .................................................................................................. 8
4.2.1 DT-RO Module:................................................................................................................... 8
4.2.2 High Pressure Pump:....................................................................................................... 13
4.2.3 Cartridge Filter (10 micron):........................................................................................... 13
4.2.4 Permeate Tank: ................................................................................................................ 13
4.3 DT-RO footprint: ....................................................................................................................... 13
5. Pilot Operation and Data Collection: ............................................................................................. 15
5.1 Pilot System Configuration...................................................................................................... 15
5.2 Plant Recovery: ........................................................................................................................ 15
5.3 Operation without anti-sealant................................................................................................ 16
5.4 Operations with Anti-Sealant (continuous 24 hours operations)....................................... 16
5.5 Data Collection and Analysis.................................................................................................. 16
5.5.1 Flow Measurements......................................................................................................... 16
5.5.2 Onsite Chemical Analysis and Measurements ............................................................ 17
5.5.3 Windhoek Laboratory Analysis (Data collaboration) ................................................... 18
6. Results and Discussions: ................................................................................................................ 19
6.1 Water Quality: ........................................................................................................................... 19
6.2 Plant Recovery ......................................................................................................................... 20
6.3 Community Satisfaction:.......................................................................................................... 21
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7. Conceptual Process Design: .......................................................................................................... 23
7.1 Alternative 1: DT-RO Throughput only ................................................................................ 23
7.2 Alternative 2: DT-RO permeate blend with borehole water............................................... 25
8. Conclusion:........................................................................................................................................ 29
8.1 Water Quality ............................................................................................................................ 31
8.2 DT-RO Recovery ...................................................................................................................... 31
8.3 Most Viable Alternative............................................................................................................ 31
9. Recommendations ........................................................................................................................... 32
10. References .................................................................................................................................... 32
APPENDIX: ............................................................................................................................................... 34
A. Pilot Plant Operational Procedure: ............................................................................................... 34
B. Operations Spreadsheet: ............................................................................................................... 35
C. Water Quality Standards ................................................................................................................ 47
D. Sample Calculations: ...................................................................................................................... 48
E. Cost Estimations:............................................................................................................................. 50
List of Tables:
Table 1: Thomas Area (Water Supply Central)-NamWater 2010.................................................................. 2
Table 2: Cuvelai Area (Water Supply North)-NamWater 2010 ..................................................................... 2Table 3: Karas Area (Water Supply South)-NamWater 2010 ........................................................................ 3
Table 4: Namib Area (Water Supply West)-NamWater 2010 ....................................................................... 3
Table 5: Epukiro Pos 3 water compared to Standards of Drinking Water Quality in Namibia ..................... 6
Table 6: Risks of High Level Contaminants ................................................................................................... 7
Table 7: Chemical Analysis of Permeate (NamWater Laboratory) ............................................................. 19
Table 8: Chemical Analysis from NamWater Laboratory in Windhoek ...................................................... 20
Table 9: Relationship between Feedwater salinity, Brine salinity and Recovery ....................................... 24
Table 10: Relationship between expected permeate and the proposed new standrads ........................... 25
List of Figures:
Figure 1: Inside of DT Module. Source-PALL ROCHEM ................................................................................. 8
Figure 2: Detailed cutaway DT Module diagram (NamWater 2011-AutoCad 2012) .................................. 10
Figure 3: A Membrane Cushion (AutoCad 2012) ........................................................................................ 11
Figure 4: Hydraulic disc; Feed flow path through and across discs (courtesy of Pall-Rochem) ................. 12
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Figure 5: Picture of Pilot Plant inside borehole station (NamWater 2010) ................................................ 14
Figure 6: Flow Measurement Diagram ....................................................................................................... 17
Figure 7: Recovery and Permeability versus Cumulative Operating Hour.................................................. 21
Figure 8: Feed Pressure and Recovery versus Cumulative Operating Hours .............................................. 21
Figure 9: Locals collecting drinking water; Councillor, Brave Tjivera tasting product water ...................... 22
Figure 10: Proposed Full Scale Plant with RO system only ......................................................................... 27
Figure 11: Proposed Full Scale Plant with RO system & Blending .............................................................. 28
Terms and Glossary
Acronym/Symbol: Definition:
ppm parts per million
TDS total dissolved solids
MF micro filtration
UF ultra filtration
NF nano filtration
RO reverse osmosis
P hydraulic pressure difference
osmotic pressure difference
Jw Water Flux
Aw pure water permeability
CF concentration factor
R recovery
SR salt rejectionci concentration of i
SDI silt-density index
MFI modified fouling index
MPFI mini plugging factor index
CP concentration polarization
BH borehole
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1. Introduction:
1.1 Namibia Water Regulation:
Water is essential for life and it is regulated in many countries to protect the user. In
Namibia, over the years, water has been regulated by the Water Act of 1956. However,
the Republic of Namibia has found the need to introduce a new Act after the countrys
Independence. This new Act is known as the Water Resource Management Act of
2004. If properly regulated, it is this new Act that will guide the use of water regarding
quality and other aspects through proper water quality standards implementations.
1.2 Namibia New Water Quality Standards
To accompany the Act (mentioned above), the Government of the Republic of Namibiaproposed new water quality standards during 2008, to replace the water quality
guidelines from the old Water Act of 1956. The proposed standards are more stringent
when compared to the prevailing guidelines (see Appendix D). Thus, at the time when
these standards are promulgated, through the said Act (WRMA), NamWater would be
required to retrofit process systems in order to comply with these new standards; as
such, the impact of the new standards (from systems procurement or otherwise) may
have adverse unknown consequences on the water supply systems in Namibia, and
that is a concern to NamWater.
1.3 Impact of Proposed Standards on the Quality of Water Supplied: ANamWater Concern Mitigation
Owing to the potential impact, by the proposed standards, on the quality of water
supplied by various NamWater schemes, NamWater took a decision to manage the
situation pro-actively, which would mitigate the concern mentioned above. This pro-
active decision resulted in two tasks, namely:
(i) Task 1: Conduct a desk study that will identify water supply schemes in Namibia
which will not conform to the newly proposed standards.(ii) Task 2: Where possible, operate pilot plants to identify process systems that will
allow the non-conforming schemes (in (i) above) to conform to the proposed
standards.
The desk study (Task 1) was completed in 2010 and the results for the four areas in
Namibia are shown in the tables below. These tables reveal the 95-percentile for each
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parameter, at a given scheme, for the period 2005 to 2010. The Epukiro Pos 3 data is
available in Table 1.
Table 1: Thomas Area (Water Supply Central)-NamWater 2010
Table 2: Cuvelai Area (Water Supply North)-NamWater 2010
Khomas A rea pH Clr
NTU-
GW
NTU-
SW Cond Na Ca Mg TH SO4 NO3 NO2 F Cl Fe Mn Parameters /SchemeGroup B 5.5-9.5 20 5 300 400 500 420 650 600 20 0 2 600 1 1
New Std 6 - 9 15 2 0.5 300 300 375 292 400 300 11 0.5 2 300 0.3 0.1 Grp B New
Aminuis 13.6 0 1
Buitepos 13.3 0 1
Dordabis 15.8 0 1
Epukiro Pos 3 376 303 779 479 1258 604 35.9 590 6 8
Gobabis 23.0 2.6 1 2
Gross Barmen 1.1 0 1
Hochveld 15.9 0 1
Lister 17.2 0 1
Oamites 453 0 1
Onderombapa 11.6 0 1
Osire 16.6 14.2 0 2
Osona 1.1 0 1
Otjihase 0.9 0 1
Otjinene 395 390 17.7 0 3
Otjivero 21.2 8.6 0.2 2 3
Plessis Plaas 401 0 1Rehoboth 18.0 1.8 0 2
Talismanis 27.0 2.1 13.4 1 3
VB Tourism Resort 16.0 1.4 0 2
Whk Airport 2.2 0 1
Witvlei 2.5 395 730 327 11.5 1 5
City of Whk 0.9 0 1
Schemes /Parameter
Grp B 3 0 1 1 0 1 1 2 1 1 0 05 22
New 6 2 9 1 2 1 2 4 3 11 1 1
Cuvelai Area pH Clr NTU-GW
NTU-SW
Cond Na Ca Mg TH SO4 NO3 NO2 F Cl Fe Mn Parameters /Scheme
Group B 5.5-9.5 20 5 300 400 500 420 650 600 20 0 2 600 1 1
New Std 6 - 9 15 2 0.5 300 300 375 292 400 300 11 0.5 2 300 0.3 0.1 Grp B New
Alpha Base 300 559 0 2
Eenhana 2.6 0 1
Elim 4.6 0 1
Ogongo 6.5 1 1
Ohangwena 3.4 0 1
Okahao 9.05 4.9 0 2
Okatope 2.3 0 1
Olushandja 7.6 1 1
Omafo 2.2 0 1
Okmakango 6.5 1 1
Omapale 5.0 1 1
Ombalantu 56.0 19.5 0.8 2 3
Omungwelume 18.2 5.0 1 2
Omuthiya 1.6 0 1
Onambutu 0.6 0 1
Onandjokwe 6.0 1 1
Onayena 2.6 0 1
Ondangwa 2.7 0 1
Ongha 3.0 0 1
Ongwediva 5.4 1 1
Opuwo 875 1231 639 3 3
Oshakati 5.0 1 1
Oshali 2.4 0 1Oshigambo 4.8 0 1
Oshikango 6.5 1 1
Oshikuku 1.7 0.3 0 2
Oshitayi 4.3 0 1
Ruacana 4.7 0 1
sandi 6.2 1 1
Schemes /Parameter
Grp B 0 1 11 1 1 1 012 29New 1 2 27 2 2 1 2
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Table 3: Karas Area (Water Supply South)-NamWater 2010
Table 4: Namib Area (Water Supply West)-NamWater 2010
To execute Task 2, NamWater needed to obtain pilot treatment plants and operate them
at specific schemes of concern. The operation of such a treatment plant was made
possible when NamWater procured two RO plants during 2010, on rental basis, from
Pall International Company, in the UK, at a cost of US$ 100 000. The agreement was
to pilot these plants for a period of 3 months at specifically identified water supply
schemes.
Karas Area pH Clr NTU-
GW
NTU-
SWCond Na Ca Mg TH SO4 NO3 NO2 F Cl Fe Mn Parameters /
SchemeGroup B 5.5-9.5 20 5 300 400 500 420 650 600 20 0 2 600 1 1
New Std 6 - 9 15 2 0.5 300 300 375 292 400 300 11 0.5 2 300 0.3 0.1 Grp B New
Ai-Ais 2.3 303 392 513 437 308 0 6
Ariamsvlei 469 757 13.3 360 1 4
Aroab 405 647 21.9 1 3
Aus 13.3 0 1
Bethanie 3.1 1 1
Gabis 2.4 1 1
Grnau 393 600 26.0 2.3 2 4
Karasburg 11.3 0 1
Keetmanshoop 0.86 0 1
Kosis 543 715 25.4 3 3
Mariental 15.5 4.29 0 2
Noordoewer 15 2.59 0 2
Rosh Pinah 17.4 6.9 1 2
Tses 440 359 21.6 2 3
Warmbad 353 471 539 432 2.5 437 1 6
Schemes /Parameter
Grp B 0 0 1 1 1 2 0 4 4 0 9 15New 3 1 4 3 6 6 3 7 4 3
Namib Area pH Clr NTU-
GW
NTU-
SWCond Na Ca Mg TH SO4 NO3 NO2 F Cl Fe Mn Parameters /
Scheme
Group B 5.5-9.5 20 5 300 400 500 420 650 600 20 0 2 600 1 1
New Std 6 - 9 15 2 0.5 300 300 375 292 400 300 11 0.5 2 300 0.3 0.1 Grp B New
Anichab 2.7 1 1
Gobabeb 16.7 360 505 535 816 410 1.6 710 5 8
Henties Bay 411 0 1
Karibib 34.0 2.2 0.1 1 3
Otjimbingwe 433 0 1
Rssing Mine 372 0 1
Swakopmund 370 0 1
Terrrace Bay 363 11.1 304 0 3
Tubisis 328 611 2.5 1 3
Uis 449 629 456 0 3
Usakos 422 0 1
Schemes /
Parameter
Grp B 1 0 1 1 1 0 1 0 0 0 2 1 0
4 11New 2 1 1 2 2 1 5 1 1 1 2 6 1
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The two schemes that NamWater identified for piloting were Epukiro Pos 3 and
Bethanie.
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2. Objective of this Report
Although this report will concentrate mainly on the Epukiro Pos 3 scheme, its objective
is twofold:
(1) Firstly, to reveal and discuss the Epukiro Pos 3 pilot system operation, and
thereby evaluates the Pall Pilot System at Epukiro Pos 3 against the following
issues:
(i) Product water nitrate levels versus proposed standards
(ii) Product water total hardness levels versus proposed standards
(iii) Product water chloride levels versus proposed standards
(iv) Product water sodium levels versus proposed standards
(v) Product water sulphate levels versus proposed standards
(vi) Optimum system recovery rate
(2) Secondly, it is also the objective of this report to propose a conceptual process
design, based on the DT-RO system, with a high level cost estimate.
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3. Epukiro Pos 3 Water Scheme
3.1 Background Information
Epukiro Pos 3 is a rural settlement near the eastern border of Namibia, directly north of
the town of Gobabis in the Omaheke region (137km north east of Gobabis). The latest
Namibian survey of 2003 puts the population of Epukiro Pos 3 at approximately 7135people (National Planning Commission, Central Bureau of Statistics, 2001). Using the
sales figures of between 2005 and 2010, the demand of Epukiro Pos 3 can be
estimated at about 110 m3/day. The water supply to the village is through three
boreholes (BH-467, BH-30533, BH-21542) that are pumped into a reservoir and
thereafter distributed by gravitation through the community distribution system. Over
the years the quality of this water has been objectionable to the end-user, mainly due to
taste which is caused by excessive hardness. However, as will be shown later in this
document (regarding water quality), chlorides, nitrates, sulphates and sodium levels are
also too high and could pose health and other risks to the consumers.3.2 Epukiro Pos 3 Water Quality
The Epukiro Pos 3 water quality, as shown in Table 5 below, indicates six (6)
parameters that do not conform to the new proposed standards. It is these parameters
that were evaluated, against the proposed standards, during the pilot operations.
Table 5: Epukiro Pos 3 water compared to Standards of Drinking Water Quality in Namibia
Epukiro Pos 3
2004 - 2009
Group B
(good)
Group C
(low risk)
Group D
(high risk)
Ideal
Guidelines
Acceptable
Standards
95 Percentile
Nitrates mg/l (as N) 35.9 10 20 20 40 > 40 < 6 < 11
Sulphates mg/l 604.0 200 600 600 1200 > 1200 < 100 < 300
Sodium mg/l 304.0 100 400 400 800 > 800 < 100 < 300
Total Hardness mg/L as CaCO3 1286.7 300 650 650 1300 > 1300 < 323.5 < 663
Chloride mg/l 592.0 250 600 600 1200 > 1200 < 100 < 300
Conductivi ty mS/m 377.6 150 300 300 400 > 400 < 80 < 300
Actual Namibian Guidelines Proposed New Standards
95 Percentile Requirement
Determinant Units
The risks associated with these parameters are indicated in Table 6. The main health
risk is associated with the nitrates (which level is about 230% above the limit when
compared to the Namibian standards or the WHO guidelines, 2011). Research done by
the Pall Company, claims successful use of membrane processes to reduce nitrates to
within required levels, especially the DT-RO membrane system.
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Table 6: Risks of High Level Contaminants
Parameter High Level Risks
nitrates
Methoglobinemia or 'blue baby' syndrome in
infants below six months old and pregnant
womensulphates diarrhea; dehydration; bitter tase
sodium No health risk; hypertension; salty taste
chlorideUnpleasant taste; hypertension; Cause corrosion
of some metals in pumps, pipes etc
total hardness
No health risks; Nuisance due to mineral build-
up in plumbing systems and anti-foaming
tendency; Alkali taste
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4. The DT-RO System Process Description:
4.1 Case for DT-RO System and Process Overview:
One of the membrane systems proposed by the Pall Company was the DT-RO system,
which was also the system that was piloted at Epukiro Pos 3. The unique design of the
DT module has a lot of advantages (as alleged by PALL). It minimizes concentrationpolarization on the surfaces of the membrane discs because of the short flow path
lengths (6cm) of the feed water along the membrane cushions, which enhance the
mixing of the thin feed water film present in the open channels.
The module can be easily assembled and dismantled to replace and/or inspect
individual membrane discs.
It is further alleged by Pall that due to high velocity flux across the membranes the DT-
RO can withstand water with high total hardness the Epukiro Pos 3 was a classic case
to prove such a claim. The process overview (as shown in Figure 1.0) consists of thefollowing process units:
(i) DT-RO Module
(ii) High Pressure Pump
(iii) Cartridge Filter (10 micron)
(iv) Permeate Tank
4.2 Detailed Process Description:
4.2.1 DT-RO Module:
Two pictures of the inside of the DT-RO Module are shown in Figure 1.
Figure 1: Inside of DT Module. Source-PALL ROCHEM
As shown in Figure 1, a standard 1 meter DT Module consists of a tubular pressure
vessel that houses 170 circular hydraulic discs with octagonal-shaped membrane
Octagonal
Membrane Cushion
Hydraulic Disc
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cushions positioned between every two discs (except for the bottom-most disc). The
hydraulic discs are held in place inside the pressure vessel by a central tension rod.
The discs together with the membrane cushions create a membrane stack. The
pressure vessel is sealed by stainless steel end-flanges with rubber seal lining. The
top-end flange or joining flange has openings for the feed input, the brine outlet and the
permeate outlet. An open feed channel (gap) is formed between the outside of the
membrane stack and the inside of the pressure vessel. The flow configuration, for the
DT-Module is as described below.
4.2.1.1 Flow Path thr oug h DT-Modu le:
A detailed cutaway schematic diagram shows the actual path of the feed, permeate and
concentrate through the module (Fig. 2). Feed water is introduced at the bottom end of
the module. It moves up through the raw water channel (gap) between the inside of the
pressure vessel and the hydraulic disc stacking. It enters the top of the membrane
stack via the ring gap in the rubber lining of the top-end flange. The feed water flows
through the first hydraulic discs feed water flow slots into the first open channel and
where it makes contact with the first membrane. The feed water flows over the top side
of the membrane and makes a 180 turn at the octagonal welded edge of the
membrane cushions; flowing in the reverse direction toward the feed water flow slots of
the second hydraulic disc. As the water flows over the top side and bottom side of the
membrane cushion the water molecules are continuously being permeated through the
membrane surfaces into the membrane cushion. The feed water flows through the slots
and make another 180 turn and flow over the top-side of the second membrane sheet
and the bottom side of the disc. The feed water gradually becomes concentrated until it
leaves the last membrane at the bottom of the vessel where it is discharges as thebrine/concentrate.
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Figure 2: Detailed cutaway DT Module diagram (NamWater 2011-AutoCad 2012)
After permeating through the membrane surfaces, the pure water flows between the
fleece sheet and the inside of a membrane sheet toward the permeate channel. The O-
rings from two alternate hydraulic discs pin the two membrane sheets of one membranecushion between them and as pure water is permeated into the membra ne cushion it
flows into the open permeate flow channels down the middle of the module, adjacent to
the central tension rod. The permeate exits the module at the bottom of the pressure
vessel at atmospheric pressure.
The hydraulic disc and the membrane cushion, the two main components of the DT-RO
Module, are briefly described below.
4.2.1.2 Memb rane Cus hio n:
Each membrane cushion consists of a porous spacer (fleece sheet) that is sandwichedbetween two individual membrane sheets. The three components of the membrane
cushion are sealed at the outer ends by ultrasonic welding. The spacer separates the
two membranes and produces flow channels for the permeate to be drained.
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Figure 3: A Membrane Cushion (AutoCad 2012)
Figure 3 shows a typical membrane cushion with its flow channel opening on the inside
of the cushion. The bottom-most hydraulic disc forms a ring gap with the rubber sealing
of the bottom-end flange. This allows the feed water to enter the membrane stacking
from the bottom.
4.2.1.3 Hydrau lic Disc:
The main function of the hydraulic disc is to give support to the membranes. Figure 4
details a descriptive diagram of the top and bottom sides of a hydraulic disc that also
indicates the feed flow path through flow slots. The 170 circular hydraulic discs are
tightly fitted and aligned with alignment pins, on top of each other. A single membranecushion is arranged between the every two alternative discs. Each hydraulic disc is
further designed with flat topped nodules to support the membrane cushion and allow
feed water flow across the surface of each membrane. The nodules generate additional
feed water turbulence that reduces possible concentration polarization on the
membrane surfaces.
Top
MembraneBottom
Membrane
FleeceSheet
UltrasonicallyWelded
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Figure 4: Hydraulic disc; Feed f low path through and across discs (courtesy of Pall-Rochem)
Feed water flow slots on the inner side of the discs permit feed waters to flow from onedisc-channel to the next. O-rings are mounted on both sides of each disc; is to prevent
feed water to come in contact with the product water (permeate). Each hydraulic disc is
designed with manifolds along its inside that create the permeate open channel along
the central tension rod.
Feed flow through
flow slotsand over the
Feed flow over top
side of disc
TOP BOTTOM
Nodules tosupport
Holes
to
Alignme
Feed
Water
Permeat
e flow
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4.2.2 High Pressure Pump:
A high pressure centrifugal pump is used to generate the pressure required by the
reverse osmosis process [up to a pressure of 16.5 bar].
4.2.3 Cartridge Filter (10 micron):
The DT-Module system includes a 10 micron cartridge filter which removes suspendedparticles that may cause damage and/or clogging of the membranes.
4.2.4 Permeate Tank:
A 200 liter permeate tank is connected to the DT Module pilot rig which is used to
collect permeate used for rinsing the membranes during plant shut-down.
4.3 DT-RO footprint:
Figure 5 shows the relative foot print of the DT-RO rig. The system is 1.5 m x 2.5 m x
1m and can easily fit on a pickup and it is therefore easy to transport anywhere.
At Epukiro Pos 3 the plant was assembled by the NamWater maintenance team. Thetraining and commissioning was done on-site and it was conducted by a Pall specialist
from Senegal, Mr. Diop. The one week training which focused on system assembly
also included system recovery optimisation before pilot operation kicked off/started.
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Figure 5: Picture of Pilot Plant inside borehole station (NamWater 2010)
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5. Pilot Operation and Data Collection:
5.1 Pilot System Configuration
The pilot configuration was as shown in Figure 6, below. As seen in Figure 6 the
system was connected to the borehole with the worst water quality (averaging a total
hardness of 1985 mg/l as CaCO3). The brine was connected to the sewerage drain toprevent cattle from drinking the high nitrate water. Initially the plant was operated only
during the day and overnight the membranes was soaked in permeate. At a later
stage, after 48 days of operation, the plant was operated for 24hr/day (continuously) to
have a feel for scale formation as well as investigating the need for chemical cleaning.
However, before the actual process was started there was a need to determine a
recovery mode where scale formation was not going to do irreversible damage to the
membrane system.
5.2 Plant Recovery:As was mentioned earlier, given the high levels of hardness in the feed water, it was
deemed necessary (by Pall Company) to determine the maximum recovery at which the
plant could operate with minimum scaling/fouling on the membranes. The chronology of
events regarding recovery optimisation was as follows:
On the first day, because of the poor water quality, the specialist commissioned
the plant at a recovery of only 26%.
On the second day, the recovery was increased to 31.6% and recording of data
was started. This recovery was maintained for 2 hours while the feed and brine
pressures were continuously monitored for possible scaling and/or fouling. The recovery was thereafter increased to 36% for another 2 hours of monitoring.
The feed and brine pressures remained constant and there was therefore no
danger of immediate fouling and/or scaling of the membranes.
The recovery was consequently increased to 42.7% for another 2 hours and
another hour the next day. A slight increase in both the brine and feed pressures
was observed; indicating that fouling/scaling took place and the plant was
therefore shut-down.
This prompted the specialist to recommend an initial 2 week operation at a
recovery of 35%.
The recovery was thereafter increased by 5% every 2 weeks while closely to
monitoring the plant for possible fouling and/or scaling.
The most suitable recovery for the system could thus be achieved by increasing the
recovery from 35% in increments of 5% until, in the absence of scaling, the maximum
allowable pressure is reached. The recovery was determined using the drop test
method on both the permeate and brine streams.
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5.3 Operation without anti-sealant
As was alluded to, earlier, in the initial stages, the plant was operated only during the
day to establish the most suitable recovery for the system. Operations typically started
early in the morning and ceased in the late afternoon. At this stage fouling of the
membranes were not expected yet and chemical addition was consequently not
necessary. The daily plant shut-down was followed by rinsing/flushing of the membrane
and soaking it overnight in permeate water. This allowed for lime scaling that could
have occurred during the day operation, to be dissolved into the soaking permeate
water. The system was operated with this mode for 48 days and the necessary data
were collected for evaluation.
5.4 Operations with Anti-Sealant (continuous 24 hours operations)
As will be discussed in the next section, upon reaching the most suitable recovery, anti-
sealant was introduced as a form of pre-treatment to avoid excessive fouling and
scaling. At this stage (after 415 cumulative operating hours) the daily operating time
was also increased from 12 hours daily to 24 hours per day continuous operations. The
harshest conditions possible were therefore created to enable observation and
monitoring of the pilot system at the worst case scenario. The continuous operation did
not allow for membrane rinsing and flushing, except when the permeate tank became
full after conducting numerous drop tests.
The feed pressure was kept constant at 15.5 bar. This pressure corresponded to the
manufacturers (Pall Company) maximum recommended pressure that the piping
system could handle. The other parameters were monitored and noted on a 2 hourly
basis.
5.5 Data Collection and Analysis
5.5.1 Flow Measurements
To calculate the system recovery, both the permeate and feed flow are required. To
measure the permeate flow Tap 1 was closed and Tap 2 was opened (Figure 6) and the
volume timed in a 2 L measuring cylinder. Similarly, the brine flow was measured by
closing Tap 3 and opening Tap 4 (also in Figure 6) and the feed flow was calculated by
adding the brine flow to the permeate flow. These measurements were performed 2
hourly for most part of the project duration.
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Pressure
Pressure200LPermeate
Tank
Disc Tube Module
Feed from theborehole
Brine
Permate directed to community ouside station
fv
Tap1Tap3
Anti-ScalantContainer
Flow Meter
Flo
wM
eter
PositiveDisplacement Pump
SamplingTap
Sam
plin
g
Tap
fav
bav
tov
LEGEND:
fv feed valvebov brine outlet valvepov permeate outlet valvebav brine adjustment valvefav feed adjustment valvetov tank outlet valve
High PressurePump
10 Filter
Tap2
Tap4
SamplingTap
Figure 6: Flow Measurement Diagram
5.5.2 Onsite Chemical Analysis and Measurements
Data were collected, on-site, every 2 hours to analyse for conductivity, temperature,
total hardness, nitrates and pH. Due to the expensive reagent associated with nitrate
analysis, nitrates were only analysed every 7 days.
The nitrates, conductivities and temperatures were measured using the portable HACH
instruments. On-site volumetric analysis by the common titration methods was used to
determine the total hardness concentrations. The conventional drop-test was used to
determine the different flow-rates after it was suspected that parallax errors could be
introduced when using the rota meter type flow meters of the plant.
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5.5.3 Windhoek Laboratory Analysis (Data collaboration)
In addition to do on-site chemical analysis, samples were collected once a week and
sent to the Windhoek laboratory for full chemical analysis. In all instances the
Windhoek laboratory results collaborated with the on-site measurements.
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6. Results and Discussions:
6.1 Water Quality:
As was previously mentioned (in this report) water quality analysis was done on-site
every 2 hours and at the Windhoek Laboratory, once a week.
The quality of water produced from the DT-RO plant and analysed once per week at the
Windhoek Laboratory is shown in Table 7. Table 7 is also comparing the various
parameters of concern with the proposed new water quality standards and all the
parameters are well below these Standards. The quality of water produced by the DT-
RO plant further strengthen the notion of blending as was alluded to earlier.
Table 7: Chemical Analysis of Permeate (NamWater Laboratory)
Operation PermeateTotal
Hardness
(mg/l)
Nitrates(mg/l)
Sodium(mg/l)
Sulphate(mg/l)
Chloride(mg/l)
Conductivity(Sm/m)
New Standard < 663 < 11 < 300 < 300 < 300 < 3002-Jun-10 47.5 3.6 26.0 9.0 42.0 26.37-Jun-10 37.5 0.5 30.0 17.0 56.0 23.629-Jun-10 77.5 3.2 27.0 12.0 40.0 33.515-Jul-10 33.3 4.6 30.0 9.0 41.0 24.628-Jul-10 28.3 4.7 32.0 8.0 40.0 24.227-Aug-10 58.3 5.9 40.0 14.0 54.0 37.4
Average 47.1 3.8 30.8 11.5 45.5 28.38-Sep-10 145.8 4.2 30.0 11.0 43.0 43.616-Oct-10 28.3 3.9 27.0 10.0 38.0 23.220-Oct-10 113.3 4.5 31.0 12.0 45.0 43.321-Oct-10 28.3 3.9 27.0 12.0 37.0 23.6
15-Nov-10 87.5 3.9 29.0 7.0 36.0 31.821-Nov-10 32.5 4.1 32.0 9.0 41.0 24.6Average 72.6 4.1 29.3 10.2 40.0 31.7
withoutant-scalant
withanti-scalant
&24
hours
The percentage rejection was also calculated for the data analysed once a week at the
Windhoek laboratory, see Table 8. Table 8 is split in two to reflect the time when the
plant was operated with and without anti-sealant so as to evaluate the degree of
rejection for both conditions.
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Table 8: Chemical Analysis from NamWater Laboratory in Windhoek
Date
Total
Hardness
Rejection
Nitrate
Rejection
Sodium
Rejection
Sulphate
Rejection
Chloride
Rejection
Conductivity
Rejection
Calcium
Rejection
Magnesium
Rejection
Alkalinity
Rejection
Flouride
Rejection
2-Jun 97.5% 91.0% 93.2% 98.8% 95.7% 95.2% 98.2% 98.1% 94.4% 75.0%
7-Jun 97.8% 92.5% 92.7% 97.8% 94.3% 95.6% 93.8% 98.0% 77.4% 75.0%29-Jun 95.9% 87.9% 93.4% 98.4% 96.3% 94.0% 98.5% 98.6% 95.4% 75.0%
15-Jul 98.1% 88.4% 92.3% 98.9% 96.0% 95.6% 93.1% 96.4% 68.2% 75.0%
28-Jul 98.4% 86.5% 92.7% 98.9% 95.7% 95.7% 98.5% 98.6% 94.8% 75.0%
27-Aug 96.6% 83.5% 91.5% 98.4% 94.4% 93.3% 91.3% 92.8% 62.0% 66.7%
Averages 97.4% 88.3% 92.6% 98.5% 95.4% 94.9% 95.6% 97.1% 82.0% 73.6%
8-Sep 91.8% 89.3% 93.0% 98.8% 95.7% 92.2% 95.6% 98.6% 88.5% 81.3%
16-Oct 98.6% 88.1% 92.7% 99.0% 96.4% 95.8% 98.2% 98.6% 95.9% 75.0%
20-Oct 94.1% 86.2% 92.6% 98.8% 95.7% 92.2% 97.8% 98.7% 94.7% 75.0%
21-Oct 98.5% 89.5% 93.7% 98.8% 96.5% 95.9% 94.7% 98.1% 81.0% 66.7%
15-Nov 95.2% 87.8% 94.1% 99.3% 96.3% 93.5% 97.2% 98.0% 92.7% 75.0%
21-Nov 98.1% 89.7% 93.3% 99.1% 95.9% 95.2% 97.8% 97.9% 95.9% 66.7%
Average 96.1% 88.5% 93.2% 99.0% 96.1% 94.1% 96.9% 98.3% 91.5% 73.3%
6.2 Plant Recovery
NamWater started plant operations on the 1st of June 2010 at a recovery of 36.1%
which corresponds with a feed pressure of 12.3 bar. Operations were thereafter varied
(by gradually increasing the inlet flow) to obtain the most optimum recovery point. The
recovery was kept constant for a period of 2 weeks after which incremental increases of
5% recovery were done for every succeeding 2 weeks until the end of August,
representing 403 cumulative operating hours. At the end of this period the inlet
pressure was at 15.5 bar and that was the maximum allowable pressure, as per supplier
specification.
Recovery is a function of membrane permeability. It can be seen, from Figure 7, that
permeability dropped by about 30% from the time when the DT-RO was operated for 12
hours/day to the time the DT-RO was operated for 24 hours/day. Since permeability is
a function of both flux and net driving pressure (which in turn is a function of both
osmotic pressure and inlet pressure), such significant drop in permeability is a clear
indication of Epukiro hardness in affecting membrane performance.
At the maximum pressure, the recovery ranged between 60 and 70%. It was during this
time that the anti-scalant was introduced to prevent permanent membrane scaling.From Figure 8 it is clear that at a feed pressure of 15.5 bar, the DT-RO system
averages about a 53% recovery rate, when it is operated 24 hours continuously. Again,
since the water quality output from the DT-RO system, is far superior from the proposed
water quality standards, this low recovery rate can be increased to well beyond 60%
through blending of RO water with borehole water.
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The pilot results therefore demonstrate that the membrane life cycle could be
lengthened more by overnight soaking in the permeate as opposed to operating 24
hours/day continuously. Hence, the DT-RO Module system could be more suitable for
schemes with low demand that could afford membrane soaking during the night.
Figure 7: Recovery and Permeability versus Cumulative Operating Hour
Figure 8: Feed Pressure and Recovery versus Cumulative Operating Hours
6.3 Community Satisfaction:
As was indicated in Figure 6 (earlier in this document) that the permeate water was
directly supplied to the towns inhabitants for the period the pilot study was conducted.
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.0
5.0
10.015.0
20.0
25.0
30.0
35.0
40.0
45.0
50.0
55.0
60.0
65.0
70.0
75.0
0 100 200 300 400 500 600 700 800 900 1000
Recovery(%)
cumulative operating hours
Permeability(L/mi
n.bar.m^2)
Permeability(L/mi
n.bar.m^2)
30.00
40.00
50.00
60.00
70.00
80.00
90.00
100.00
0
2
4
6
8
10
12
14
16
18
0 100 200 300 400 500 600 700 800 900 1000
Pressure(bar)
Cumulative Operating Time(hrs)
Recovery(%)
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Many of the community members expressed their satisfaction and joy regarding the
taste of the water: tea was tasting differently; for many inhabitants the first taste of the
Omauozonjanda taste of the water was something special and there was a total new
expectation of what the future could hold, regarding this water.
However, although the palatability of the water was excellent, permeate quality was toocorrosive (due to low CCPP) and cannot be supplied as is. It is envisaged that the
CCPP correction can be easily achieved with permeate and borehole water blending.
Such a blending scenario is highlighted in the conceptual design, which is the focus of
the next section.
Figure 9: Locals collecting drinking water; Councillor, Brave Tjivera tasting product water
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7. Conceptual Process Design:As was indicated earlier, in the objective, it is the aim of this document to propose a full
scale plant for Epukiro that will produce acceptable quality water to the community in a
sustainable manner. This section therefore presents the treatment process (conceptual
process design) for the proposed Epukiro Water Supply Scheme, taking into
consideration the newly proposed water quality standards. Two alternatives are
discussed.
7.1 Alternative 1: DT-RO Throughput only
The current thought process is that the plant will be located adjacent to the existing
reservoir (Figure 10). Water will be pumped from the 3 boreholes to the RO feed tank.
It is assumed that the quality of water in the RO feed tank will be the same as the
current water quality from the Epukiro Pos 3 distribution reservoir (see Table 1 as
previously shown in this document).
Table 1 indicates that the current total hardness, based on the three boreholes(combined) operation, averages at 1258 mg/l, which is approximately 40% lower than
the figure of 1985 mg/l (the average for BH-467) on which the pilot plant was evaluated.
These two figures (of 1258 mg/l and 1985 mg/l) correspond to TDS values of 2858 mg/l
and 4194 mg/l, respectively.
During the pilot operation, as was demonstrated earlier in this report, at equilibrium the
pilot plant yielded a recovery of about 53%. However, given the lower TDS value (of
2858 mg/l) a higher recovery is expected as will be demonstrated below, using
information from Table 9.
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Table 9: Relationship between Feedwater salinity, Brine salinity and Recovery
%Recovery 80 75 70 65.88 65 60 55 50.59 50 45 40 35 30
Conce ntration Factor 5.00 4.00 3.33 2.93 2.86 2.50 2.22 2.02 2.00 1.82 1.67 1.54 1.43
Fe ed TDS = 10,000 mg/l 50000 40000 33333 29308 28571 25000 22222 20237 20000 18182 16667 15385 14286Fe ed TDS = 9, 000 mg/l 45000 36000 30000 26377 25714 22500 20000 18213 18000 16364 15000 13846 12857
Fe ed TDS = 8, 000 mg/l 40000 32000 26667 23446 22857 20000 17778 16190 16000 14545 13333 12308 11429
Fe ed TDS = 7, 000 mg/l 35000 28000 23333 20516 20000 17500 15556 14166 14000 12727 11667 10769 10000
Fe ed TDS = 6, 000 mg/l 30000 24000 20000 17585 17143 15000 13333 12142 12000 10909 10000 9231 8571
Fe ed TDS = 5,000 mg/l 25000 20000 16667 14654 14286 12500 11111 10119 10000 9091 8333 7692 7143
Feed TDS = 4,139 mg/l 20695 16556 13797 12131 11826 10348 9198 8376 8278 7525 6898 6368 5913
Feed TDS = 4,000 mg/l 20000 16000 13333 11723 11429 10000 8889 8095 8000 7273 6667 6154 5714
Feed TDS = 3,000 mg/l 15000 12000 10000 8792 8571 7500 6667 6071 6000 5455 5000 4615 4286
Feed TDS = 2,858 mg/l 14290 11432 9527 8376 8166 7145 6351 5784 5716 5196 4763 4397 4083
Feed TDS = 2,000 mg/l 10000 8000 6667 5862 5714 5000 4444 4047 4000 3636 3333 3077 2857
Feed TDS = 1,000 mg/l 5000 4000 3333 2931 2857 2500 2222 2024 2000 1818 1667 1538 1429
Feed TDS = 500 mg/l 2500 2000 1667 1465 1429 1250 1111 1012 1000 909 833 769 714
Brine TDS(mg/l) at different Recoveries
NOTE: The shaded figures (15000 mg/l) will cause rapid fouling/scaling in the DT-RO Module.
Table 9 (courtesy of El-Manharawy and Hafez, 2001) illustrates the effects of feed water
TDS, for given recovery rates, on corresponding brine TDS. During the pilot plant
operation the average brine TDS was 8376 mg/l at a feed TDS of 4139 mg/l. From this
table the corresponding recovery is 51% and it confirms the actual value obtained from
the pilot operation (53%). For this alternative, the brine TDS value (of 8376 mg/l) is
taken as the maximum; therefore, at a feed TDS of 2858 mg/l the corresponding
recovery (from Table 9.0) is 65.88%.
Based on the new feed water quality (for this alternative) the expected permeate is
calculated using the rejection values obtained from the pilot work; the results are shown
in Table 10. From Table 10 the parameters of concern are all below the proposed
Namibian standards except for the CCPP a value of -259.6 mg/l makes the water too
aggressive.
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Table 10: Relationship between expected permeate and the proposed new standrads
pH Conductivity Na in mg/l Ca Mg SO4 NO3 Cl Alkalinity Temperature CCPP
mS/m mg/l mg/l as CaCO3 mg/l as CaCO3 mg/l as N in mg/l mg/l as CaCO3 C mg/l
Average Feed water quality 7.60 354.07 283.23 733.37 447.12 535.19 24.81 553.46 339.45 20 92.53
Rejection ( as fraction) 0.95 0.93 0.96 0.98 0.99 0.88 0.96 0.87
Expected Permeate quality 5.7 19.44 20.00 27.69 10.24 6.70 2.88 23.53 45.01 20 -259.6
Proposed New Standards 6 to 9
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For this alternative the overall recovery is 75.57% - an improvement of 9.69% when
compared to Alternative 1. The capital cost for Alternative 2 has been given by Pall
Company to be N$ 1.8 million.
A comparison of the two alternatives reveals that Alternative 2 requires less chemical
addition; it also has a higher recovery rate as well as a lower capital investment.Therefore, the DT-RO system is effective in improving the water quality at Epukiro Pos
3 (or perhaps at many plants with similar water quality), but the system can only be cost
effective if blending with borehole water is incorporated.
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Borehole 2
Borehole 1
Borehole 3
10 m^3
Raw Water
Mixing Tank
High Pressure Pump
10 Filter
P-12
RO DT Module
R = 65%
P-15
10 m^3
Permeate
Holding Tank
Epukiro Pos 3
Reservior
Permeate Stream mg/l
NO3-
4
Cl-
41
T ot al H ar dn es s 3 3
B ri ne S tr ea m m g/ l
NO3-
63.6
Cl-
1940
T ot al H ar dn es s 3 41 7
RO F e ed S t re am m g /l
NO3-
36
Cl-
590
T o ta l H ar dn e ss 1258
5.6 m3/h
8.0 m3/h
2.4 m3/h
8.0 m3/h
P-29
P-30
P-31
Figure 10: Proposed Full Scale Plant with RO system only
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Borehole 2
Borehole 1
Borehole 3
10 m^3Raw Water
Mixing Tank
High Pressure Pump
10 Filter
P-12
RO DT Module
R = 65.88%
Bypass
10 m^3Permeate
Holding Tank
Epukiro Pos 3Reservior
Raw Water Stream mg/l
NO3-
36
Cl-
590
T otal Har dn es s 1 25 8
P e rm e at e S t re a m m g /l
NO3-
4
Cl-
41
T o ta l H ar dn es s 3 3
B le nd e d S tr e am m g/ l
NO3-
11
Cl-
250
T ot al H ar dn es s 3 00
B ri ne S tr ea m m g/ l
NO3-
63.6
Cl-
1940
T ot al H ar dn es s 3 41 7
1.2 m3/h
4.4 m3/h
5.6 m3/h
1.9 m3/h
6.3 m3/h
RO Feed Stream mg/l
NO3-
36
Cl-
590
Total Hardness 125 8
7.5 m3/h
P-15
P-29 P-30
P-31
P-32
Figure 11: Proposed Full Scale Plant with RO system & Blending
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8. Cost Estimations:A summary of the Unit Costs for the Epukiro Treatment plant is given in the Table
below. The costs include the annual fixed and variable costs estimated for the Capital
Project. The unit cost of the treated water will amount to N$ 26.75 per m 3 water treated.
The unit cost of the plant will amount to N$ 2,205,000.00 per annum.
8.1 Design and Costing of Evaporation Ponds
The proposed plant at Epukiro Pos 3 will produce brine at an approximate flow rate of
2.5 m3/hr. This brine will be routed to two evaporation ponds situated appropriatelyclose to the plant. The two ponds will be used interchangeably to allow for maximum
evaporation during the year. The required area of one of the ponds can be calculated
using the general material balance equation below. The calculations will include the
brine flowing into the ponds, the portion of water evaporated as well as the assumed
annual rain downfall.
Material Balance:
The generation term will equal zero as there will be no generation of material inside the
ponds. The above generalized equation will yield the following:
Cost Component Amount Amount
N$/m3 N$/a
Fixed Costs
Capital & interest 6.55 540,000
Energy 0.42 34,387
Personnel 5.51 454,250
Materials 0.76 62,750
Water quality 0.19 15,500
Maintenance 0.44 36,200
Overheads 11.27 929,074
Variable Costs
Energy 1.58 130,615
Water Chlorination 0.03 2,084
Total Unit Costs 26.75 2,205,000
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( ) Rearranging, * +
Assuming a PAN evaporation rate of 2900 mm/year for the Epukiro Pos 3 area and a
maximum pond depth of 1.5 meters, gives the following pond area calculations:
NOTE: seepage will be assumed to be negligible, due to salt crusts created in the
ponds, preventing seepage. Salt deposits on the bottom of each pond will occur rapidly
due to the extremely high concentration of salts (super saturation) in the brine.
A mean annual rainfall of 400 mm is also assumed for the Epukiro Pos 3 area. Since
there will be two identical ponds adjacent to each other, their surface areas will both be
1825 m2.
8.2 Cost of Civil Works for Evaporation Ponds
Assumptions:
Cost of Civil Works is N$ 75/m3
Method of construction is landfill
Number of ponds = 2
Distance between ponds = 3 m
Assuming rectangular block type ponds
Volume of earth to be removed:
The depth of the two ponds is 1.5 m and the calculated total surface area is 3 650 m2.
This means that a total of 2 737.5 m3 volume of earth should be removed for one pond
and 5 475 m3 volume of earth for both the ponds. The cost estimate for constructing the
two ponds will therefore be in the order of N$ 75/m3 x 5 475 m3 = N$ 410 625.
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9. Conclusion:From this DT-RO Pilot operation the following issues can be concluded:
9.1 Water Quality
(i) Nitrate can be reduced by 88.4% from levels of 36.5 mg/l to levels as low as 4
mg/l which is well below the 11 mg/l acceptable limit of the Namibian proposedstandards.
(ii) Sulphate can be reduced by 98.7% from levels of 880 mg/l to levels as low as
10.2 mg/l which is well below the 300 mg/l acceptable limit of the Namibian
proposed standards.
(iii) Sodium can be reduced by 92.9% from levels of 426.7 mg/l to levels as low as
29.3 mg/l which is well below the 300 mg/l acceptable limit of the Namibian
proposed standards.
(iv) Chloride can be reduced by 95.7% from levels of 1009.2 mg/l to levels as low as
45.5 mg/l which is well below the 300 mg/l acceptable limit of the Namibian
proposed standards.
(v) Total Hardness can be reduced by 96.7% from levels of 1827.1 mg/l to levels as
low as 72.6 mg/l which is well below the 663 mg/l acceptable limit of the
Namibian proposed standards.
(vi) Conductivity can be reduced by 94.5% from levels of 546.7 mS/m to levels as
low as 28.3 mg/l which is well below the 300 mS/m acceptable limit of the
Namibian proposed standards.
9.2 DT-RO Recovery
(i) When the system is operated during daytime and soaked in permeate during the
night, higher recoveries of between 60 and 70% can be obtained. However, to
make a reliable decision (regarding maximum achievable recovery) a longer
operating period is required for recoveries of between 60 and 70% the pilot
was only operated for a period of 28 days.
(ii) Soaking the system overnight in permeate can permit operations without the
application of anti-scaling treatment.
(iii) Operating the system continuously on a 24 hours/day basis, and with anti-
scalant, yields recoveries averaging at 51% only (feed water Total Hardness of
1827.1 mg/l).
(iv) However, higher recoveries in the order of 66% can be achieved with a better
feed water quality (i.e mixed borehole Total Hardness of 1180.49 mg/l).
9.3 Most Viable Alternative
The results from the pilot operation indicate that the most viable option/alternative is to
blend the DT-RO permeate with untreated borehole water, when considering a full scale
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treatment plant. Such a scenario improves the resultant water stability as well as
improving the overall system recovery, to as much as 75.55%. Blending also reduces
the cost, associated with DT-RO system capital investment, by as much as 14.3% (N$
1,744,689.00 for Blending and N$ 2,036,554.00 for RO-only).
10. Recommendations(i) NamWater should share this report with the Ministry of Agriculture, Forestry and
Water Affairs as well as the Omaheke Regional Council for a decision regarding
the implementation of a DT-RO water treatment plant at Epukiro Pos 3.
(ii) If a decision is taken to implement a DT-RO water treatment plant, the system
must utilise the option of blending with borehole water to achieve higher recovery
rates.
(iii) It is important for NamWater to confirm the recovery figures of between 60 and70% that were obtained when the pilot was operated during daytime and soaked
in permeate during the night; therefore, it is recommended that this pilot plant be
tested at substandard water schemes such as Warmbad, Grunau, Ai-Ais,
Ariamsvlei, Aruab, Mpunguvlei etc.
11. ReferencesFetter, C. W (1994).Applied Hydrogeology. 3
rdEdition, Prentice Hall
Peters, T. A (2001). High Advanced Open Channel Membrane Desalination (Disc Tube Module). ELSEVIER
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Peters, T. A (1999). Desalination of Seawater and Brackish Water with Reverse Osmosis and the Disc
Tube Module DT. ELSEVIER
M. Afonso, J. Jaber, M. S. Mohsen (2004). Brackish Groundwater Treatment by Reverse Osmosis in
Jordan. ELSEVIER
J.D.Seader, E. J. Henley (2006). Separation Process Principles. 2nd
Edition, John Wiley & Sons, Inc
Jol Mallevialle, P. E. Odendaal, M. R. Wiesner (1996). Water Treatment Membrane Processes. American
Water Works Association Research Foundation, Lyonnaise des Eaux, Water Research Commission of
South Africa.
Belkacem. M, Bekhti. S, Bensadok (2007). Groundwater treatment by reverse osmosis. ELSEVIER
Alawadhi. A. A (1997). Pretreatment plant design- Key to successful reverse osmosis desalination plant.
ELSEVIER
Schoeman. J. J (2009). Nitrate-nitrogen removal with small-scale reverse osmosis, electrodialysis and io-
exchange units in rural areas. Water SA Vol. 35 No 5
Kim. S. L, Chen.J. P, Ting. Y. P (2002). Study on feed pretreatment for membrane filtration of secondary
effluent. ELSEVIER
Schoeman. J. J, Steyn. A (2003). Nitrate removal with reverse osmosis in a rural are in South Africa.
ELSEVIER
Bilidt. H (1985). THE USE OF REVERSE OSMOSIS FOR REMOVAL OF NITRATE IN DRINKING WATER.
Elsevier Science Publishers
Bohdziewicz. J, Bodzek. M, Wasik. E (1999). The application of reverse osmosis and nanofiltration to the
removal of nitrates from groundwater. ELSEVIER
Salvestrin. H, Hagare. P (2009). Removal of nitrates from groundwater in remote indigenous settings in
arid Central Australia. Desalination Publications (www.deswater.com)
Shrestha. P.R, Engle. O, Karlsson. M (2009). Water Hardness Removal For Potable Water. VVAN01, Lund
WHO, (2004). Chapter 6, Water treatment process for reducing nitrate concentrations.
Bilidt. H (1985). THE USE OF REVERSE OSMOSIS FOR REMOVAL OF NITRATE IN DRINKING WATER.
Elsevier Science Publishers
http://www.deswater.com/http://www.deswater.com/http://www.deswater.com/http://www.deswater.com/ -
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APPENDIX:
A. Pilot Plant Operational Procedure:
The Pilot Plant is very easy to operate and maintain. The start-up and shut-down
procedures is also operator friendly and is summarized below:
Start-Up:
1. Keeping the pump off, let the feed water run through the system for at least 10
minutes. To achieve this, the permeate outlet valve (pov), the brine outlet valve
(bov), the brine adjustment valve (bav), the feed adjustment (fav) as well as the
feed valve(fv) must be completely open.
2. After flushing the system for 10 minutes, the fav and bav must be completely closed
and thereafter re-opening bav with half a turn.
3. Keep pov and bov valves open.4. Turn the pump on and progressively open the fav valve to obtain the desired feed
pressure reading on the feed pressure gauge or alternatively to obtain the desired
feed flowrate.
5. Adjust the brine flow or pressure by adjusting the bav valve.
6. After achieving the desired flowrates and/or pressures start filling the permeate tank
up to the total volume, to later use in the rinsing of the membrane before shut-
down.
Shut-Down:
1. Open the tov, while simultaneously closing the fv. This should be done as quickly
as possible as the pressure from the borehole will cause particulates to enter the
tank.
2. Allow the water from the tank to run through the system to rinse the module.
3. When the tank is nearly empty, turn the pump off.
4. Immediately close all valves, starting downstream at the outlet valves moving
systematically back toward the borehole feed valve.
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B. Operations Spreadsheet:
The following spreadsheet was drawn up to monitor plant operations on an hourly basis.
Feed Permeate Br ine
DT M odule A rea 7. 65 m2 TD S F ac t or s 0 .7 84 0 .5 98 0 .8 3
Pf 1.01325 bar
Permeate permeability Feed
D at e Ti meTest Cumulated
Duration (hours)
Temperature
(C)
Pressure
(bar)
Flowrate
(L/min)
Pressure
(bar)
Flowrate
(L/min)
Flowrate
(L/min)Feed Permeate Br ine Feed Permeate Br i ne
Recovery
(%)
Total
Hardness
Rejection
(%)
Conductivity
Rejection (%)CF flux P
Aw(L/min.bar.m 2)
TDS (mg/l)Cumulative
Duration (hrs)
2/6/2010 9h50 60 24.1 10.6 1 2.74 7.5 8.71 4.03 2300 90 3800 5.45 0 .276 7.65 31.63 9 6.09 94.94 1.46 0.53 9.59 4.75 0.10891 4273 1
2/6/2010 10h50 120 24.2 10.6 12.74 7.5 8.71 4.03 2300 90 3800 5.45 0 .264 7.6 31.63 9 6.09 95.16 1.46 0.53 9.59 4.75 0.10891 4273 22/6/2010 13h50 60 24.3 12.3 1 3.47 9 8.61 4.86 2600 65 4100 5.43 0 .245 8.04 36.08 9 7.50 95.49 1.56 0.64 1 1.29 5.06 0.10205 4257 3
2/6/2010 14h50 120 24.4 12.5 13.47 9 8.61 4.86 2600 65 4100 5.44 0 .241 8.09 36.08 9 7.50 95.57 1.56 0.64 11.49 5.07 0.09902 4265 4
2/6/2010 17h45 60 24 13 1 2.37 10.3 7.17 5.2 2500 90 4500 5.43 0 .244 8.7 42.04 9 6.40 95.51 1.73 0.68 1 1.99 5.58 0.10613 4257 5
3/6/2010 9h15 60 24 12.9 1 2.05 10.2 6.9 5.15 2300 75 4400 5.43 0 .254 8.77 42.74 96.74 95.32 1.75 0.67 1 1.89 5.65 0.10795 4257 6
3/6/2010 10h15 120 23.5 12.9 12.05 10.2 6.9 5.15 2300 75 4400 5.44 0.249 8.78 42.74 96.74 95.42 1.75 0.67 11.89 5.66 0.10813 4265 7
3/6/2010 14h35 60 24.5 11.4 12.5 8.2 8.32 4.18 2200 85 4500 5.37 0 .249 7.96 33.44 9 6.14 95.36 1.50 0.55 10.39 4.81 0.09793 4210 6
3/6/2010 15h35 120 24.6 11.4 12.5 8.2 8.32 4.18 2200 85 4500 5.37 0 .253 7.9 33.44 9 6.14 95.29 1.50 0.55 10.39 4.81 0.09793 4210 7
3/6/2010 16h35 180 24.2 11.4 12.5 8.2 8.32 4.18 2200 85 4500 5.57 0.254 8.24 33.44 96.14 95.44 1.50 0.55 10.39 4.99 0.10118 4367 8
4/6/2010 9h15 60 24.1 11.5 12.94 8.1 8.52 4.42 2300 95 4600 5.43 0 .247 7.56 34.16 9 5.87 95.45 1.52 0.58 10.49 4.91 0.10368 4257 9
4/6/2010 10h15 120 24.3 11.5 1 2.94 8.1 8.52 4.42 2300 95 4600 5.43 0 .255 7.85 34.16 9 5.87 95.30 1.52 0.58 1 0.49 4.91 0.10368 4257 10
4/6/2010 11h15 180 24.7 11.5 12.94 8.1 8.52 4.42 2200 100 4400 5.31 0 .246 7.68 34.16 9 5.45 95.37 1.52 0.58 10.49 4.81 0.10170 4163 11
4/6/2010 12h15 240 24.5 11.5 12.94 8.1 8.52 4.42 2200 100 4400 5.43 0 .237 7.73 34.16 9 5.45 95.64 1.52 0.58 10.49 4.91 0.10368 4257 12
4/6/2010 13h15 300 24.2 11.5 12.94 8.1 8.52 4.42 2300 95 4600 5.33 0.26 7.75 34.16 95.87 95.12 1.52 0.58 10.49 4.82 0.10202 4179 13
4/6/2010 14h15 360 24.3 11.5 1 2.94 8.1 8.52 4.42 2300 95 4600 5.35 0 .261 7.73 34.16 9 5.87 95.12 1.52 0.58 1 0.49 4.84 0.10235 4194 14
4/6/2010 15h15 420 24.7 11.5 1 2.94 8.1 8.52 4.42 2300 85 4500 5.38 0 .263 7.75 34.16 9 6.30 95.11 1.52 0.58 1 0.49 4.87 0.10284 4218 15
4/6/2010 16h15 480 24.9 11.5 12.94 8.1 8.52 4.42 2300 85 4500 5.36 0.26 7.72 34.16 96.30 95.15 1.52 0.58 10.49 4.85 0.10251 4202 16
4/6/2010 17h15 540 25.2 11.5 12.94 8.1 8.52 4.42 2400 65 4400 5.41 0.267 7.8 34.16 97.29 95.06 1.52 0.58 10.49 4.90 0.10334 4241 17
5/6/2010 9h20 60 24.4 11.3 12.9 8.3 8.44 4.46 2950 85 3900 5.43 0 .261 7.79 34.57 9 7.12 95.19 1.53 0.58 10.29 4.95 0.10914 4257 18
5/6/2010 10h20 120 24.5 11.3 12.9 8.3 8.44 4.46 2950 85 3900 5.42 0.252 7.88 34.57 97.12 95.35 1.53 0.58 10.29 4.94 0.10896 4249 19
5/6/2010 11h20 180 24.7 11.3 12.9 8.3 8.44 4.46 2600 95 4000 5.33 0.241 7.75 34.57 96.35 95.48 1.53 0.58 10.29 4.85 0.10731 4179 20
5/6/2010 12h20 240 24.3 11.3 12.9 8.3 8.44 4.46 2600 95 4000 5.31 0.243 7.77 34.57 96.35 95.42 1.53 0.58 10.29 4.84 0.10696 4163 21
5/6/2010 13h20 300 24.9 11.3 12.9 8.3 8.44 4.46 2500 90 3900 5.35 0.247 7.76 34.57 96.40 95.38 1.53 0.58 10.29 4.87 0.10768 4194 22
5/6/2010 14h20 360 24.8 11.3 12.9 8.3 8.44 4.46 2500 85 4000 5.48 0.26 7.94 34.57 96.60 95.26 1.53 0.58 10.29 4.99 0.11008 4296 23
5/6/2010 15h20 420 24.7 11.3 12.9 8.3 8.44 4.46 2500 85 4000 5.53 0 .253 8 34.57 9 6.60 95.42 1.53 0.58 1 0.29 5.04 0.11104 4336 24
5/6/2010 16h20 480 24.8 11.3 12.9 8.3 8.44 4.46 2600 80 4000 5.53 0 .256 8 34.57 9 6.92 95.37 1.53 0.58 1 0.29 5.04 0.11104 4336 25
5/6/2010 17h20 540 25 11.3 12.9 8.3 8.44 4.46 2600 80 4000 5.49 0 .259 7.88 34.57 9 6.92 95.28 1.53 0.58 10.29 5.00 0.11027 4304 26
6/6/2010 9h00 60 24.3 11.1 12.7 8.1 8.39 4.31 2500 85 3900 5.45 0 .259 7.81 33.94 9 6.60 95.25 1.51 0.56 10.09 4.92 0.10895 4273 27
6/6/2010 10h00 120 24.7 11.1 12.7 8.1 8.39 4.31 2500 85 3900 5.48 0.259 7.78 33.94 96.60 95.27 1.51 0.56 10.09 4.94 0.10952 4296 28
6/6/2010 11h00 180 24.9 11.1 12.7 8.1 8.39 4.31 2200 65 3300 5.43 0.259 7.78 33.94 97.05 95.23 1.51 0.56 10.09 4.90 0.10857 4257 29
6/6/2010 12h00 240 24.8 11.1 12.7 8.1 8.39 4.31 2200 65 3300 5.4 0 .255 7.8 33.94 9 7.05 95.28 1.51 0.56 10.09 4.87 0.10801 4234 30
6/6/2010 13h00 300 24.9 11.1 12.7 8.1 8.39 4.31 2300 70 4000 5.58 0.259 8.03 33.94 96.96 95.36 1.51 0.56 10.09 5.03 0.11148 4375 316/6/2010 14h00 360 24.9 11.1 12.7 8.1 8.39 4.31 2300 70 4000 5.41 0.25 7.82 33.94 96.96 95.38 1.51 0.56 10.09 4.88 0.10819 4241 32
6/6/2010 15h00 420 24.8 11.1 12.7 8.1 8.39 4.31 2350 85 3900 5.56 0.25 8.15 33.94 96.38 95.50 1.51 0.56 10.09 5.01 0.11108 4359 33
6/6/2010 16h00 480 24.6 11.1 12.7 8.1 8.39 4.31 2350 85 3900 5.5 0.244 7.95 33.94 96.38 95.56 1.51 0.56 10.09 4.96 0.10991 4312 34
6/6/2010 17h00 540 24.3 11.1 12.7 8.1 8.39 4.31 2300 95 4000 5.5 0.244 7.95 33.94 95.87 95.56 1.51 0.56 10.09 4.96 0.10991 4312 35
7/6/2010 9H00 60 24 11.3 1 2.85 8.1 8.49 4.36 2550 75 4300 5.48 0 .247 7.78 33.93 9 7.06 95.49 1.51 0.57 1 0.29 4.94 0.10664 4296 36
7/6/2010 10H00 120 24.7 11.3 12.85 8.1 8.49 4.36 2550 75 4300 5.45 0.258 7.9 33.93 97.06 95.27 1.51 0.57 10.29 4.91 0.10610 4273 37
7/6/2010 11H00 180 24.9 11.3 1 2.85 8.1 8.49 4.36 2600 75 4300 5.46 0 .254 7.88 33.93 9 7.12 95.35 1.51 0.57 1 0.29 4.92 0.10628 4281 38
7/6/2010 12H00 240 24.8 11.3 12.85 8.1 8.49 4.36 2600 75 4300 5.44 0.247 7.9 33.93 97.12 95.46 1.51 0.57 10.29 4.91 0.10592 4265 39
7/6/2010 13H00 300 24.9 11.3 1 2.85 8.1 8.49 4.36 2600 80 4400 5.43 0 .249 7.92 33.93 9 6.92 95.41 1.51 0.57 1 0.29 4.90 0.10574 4257 40
7/6/2010 14H00 360 25.2 11.3 12.85 8.1 8.49 4.36 2600 80 4400 5.5 0.251 7.99 33.93 96.92 95.44 1.51 0.57 10.29 4.96 0.10700 4312 41
7/6/2010 15H00 420 25.4 11.3 1 2.85 8.1 8.49 4.36 2400 75 4100 5.48 0 .249 7.93 33.93 9 6.88 95.46 1.51 0.57 1 0.29 4.94 0.10664 4296 42
7/6/2010 16H00 480 25.1 11.3 1 2.85 8.1 8.49 4.36 2400 75 4100 5.45 0 .252 7.88 33.93 9 6.88 95.38 1.51 0.57 1 0.29 4.91 0.10610 4273 43
7/6/2010 17H00 540 24.6 11.3 12.85 8.1 8.49 4.36 2400 80 4200 5.45 0.24 7.89 33.93 96.67 95.60 1.51 0.57 10.29 4.91 0.10610 4273 44
7/6/2010 18H00 600 23.4 11.3 1 2.85 8.1 8.49 4.36 2400 80 4200 5.44 0 .239 7.87 33.93 9 6.67 95.61 1.51 0.57 1 0.29 4.91 0.10592 4265 45
7/6/2010 19H00 660 23.4 11.3 1 2.85 8.1 8.49 4.36 2400 80 3800 5.45 0 .238 7.84 33.93 9 6.67 95.63 1.51 0.57 1 0.29 4.91 0.10610 4273 46
7/6/2010 20H00 720 24.1 11.3 1 2.85 8.1 8.49 4.36 2400 80 3800 5.43 0 .239 7.87 33.93 9 6.67 95.60 1.51 0.57 1 0.29 4.90 0.10574 4257 47
7/6/2010 21H00 780 23.7 11.3 1 2.85 8.1 8.49 4.36 2300 75 3900 5.43 0 .249 7.78 33.93 9 6.74 95.41 1.51 0.57 1 0.29 4.90 0.10574 4257 48
7/6/2010 22H00 840 23.5 11.3 1 2.85 8.1 8.49 4.36 2300 75 3900 5.47 0 .242 7.83 33.93 9 6.74 95.58 1.51 0.57 1 0.29 4.93 0.10646 4288 49
7/6/2010 23H00 900 23.1 11.3 1 2.85 8.1 8.49 4.36 2300 75 3900 5.47 0 .252 7.72 33.93 9 6.74 95.39 1.51 0.57 1 0.29 4.93 0.10646 4288 50
Permeate Pressure = 1 atm = 1.01325 bar
Feed Brine Total Hardness (mg/l) Conductivity (mS/m)
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Permeate permeability Feed
D at e Ti meTest Cumulated
Duration (hours)
Temperature
(C)
Pressure
(bar)
Flowrate
(L/min)
Pressure
(bar)
Flowrate
(L/min)
Flowrate
(L/min)Feed Permeate Br ine Feed Permeate Br i ne
Recovery
(%)
Total
Hardness
Rejection
(%)
Conductivity
Rejection (%)CF flux P
Aw(L/min.bar.m 2)
TDS (mg/l)Cumulative
Duration (hrs)
7/6/2010 24H00 960 22.8 11.3 1 2.85 8.1 8.49 4.36 2300 75 3900 5.52 0 .249 7.76 33.93 9 6.74 95.49 1.51 0.57 1 0.29 4.98 0.10736 4328 51
22/6/2010 15H10 60 24.5 11.5 12.804 8.4 8.199 4.605 2707.25 93.925 5525 5.33 0.242 7.73 35.97 96.53 95.46 1.56 0.60 10.49 4.96 0.10891 4179 52
22/6/2010 16H10 120 24.5 11.5 12.804 8.4 8.199 4.605 2707.25 93.925 5525 5.3 0.239 7.83 35.97 96.53 95.49 1.56 0.60 10.49 4.93 0.10836 4155 53
22/6/2010 17H10 180 24.6 11.5 12.804 8.4 8.199 4.605 2707.25 93.925 5525 5.33 0.242 7.81 35.97 96.53 95.46 1.56 0.60 10.49 4.96 0.10891 4179 54
23/6/2010 9H19 60 23.7 11.55 12.39 8.55 7.9 4.49 2707.25 88.4 4751.5 5.5 0.252 8.02 36.24 96.73 95.42 1.57 0.59 10.54 5.14 0.10875 4312 55
23/6/2010 10H19 120 24 11.4 12.39 8.5 7.9 4.49 2707.25 88.4 4751.5 5.49 0.257 8.11 36.24 96.73 95.32 1.57 0.59 10.39 5.13 0.11166 4304 56
23/6/2010 11H19 180 24.4 11.4 12.39 8.5 7.9 4.49 2596.75 82.875 4972.5 5.47 0.26 8.13 36.24 96.81 95.25 1.57 0.59 10.39 5.11 0.11126 4288 57
23/6/2010 12H19 240 24.5 11.4 12.39 8.5 7.9 4.49 2596.75 82.875 4972.5 5.48 0.252 8.17 36.24 96.81 95.40 1.57 0.59 10.39 5.12 0.11146 4296 58
23/6/2010 13H19 300 24.5 11.4 12.39 8.5 7.9 4.49 2596.75 82.875 4972.5 5.47 0.252 8.18 36.24 96.81 95.39 1.57 0.59 10.39 5.11 0.11126 4288 59
23/6/2010 14H19 360 24.6 11.4 12.39 8.5 7.9 4.49 2596.75 93.925 4641 5.5 0.248 8.14 36.24 96.38 95.49 1.57 0.59 10.39 5.14 0.11186 4312 60
23/6/2010 15H19 420 24.6 11.4 12.39 8.5 7.9 4.49 2596.75 93.925 4641 5.47 0.246 8.15 36.24 96.38 95.50 1.57 0.59 10.39 5.11 0.11126 4288 6123/6/2010 16H19 480 24.4 11.4 12.39 8.5 7.9 4.49 2652 99.45 4751.5 5.45 0.253 8.01 36.24 96.25 95.36 1.57 0.59 10.39 5.09 0.11087 4273 62
23/6/2010 17H19 540 24.4 11.4 12.39 8.5 7.9 4.49 2652 99.45 4751.5 5.47 0.249 8.13 36.24 96.25 95.45 1.57 0.59 10.39 5.11 0.11126 4288 63
24/6/2010 9H20 60 23.5 11.6 12.255 8.6 7.829 4.426 2817.75 93.925 4751.5 5.49 0.25 8.01 36.12 96.67 95.45 1.57 0.58 10.59 5.12 0.10584 4304 64
24/6/2010 10H20 120 24.5 11.6 12.255 8.6 7.829 4.426 2817.75 93.925 4751.5 5.51 0.248 7.97 36.12 96.67 95.50 1.57 0.58 10.59 5.14 0.10620 4320 65
24/6/2010 11H20 180 24.2 11.6 12.255 8.6 7.829 4.426 2652 88.4 4862 5.47 0.249 8.17 36.12 96.67 95.45 1.57 0.58 10.59 5.10 0.10548 4288 66
24/6/2010 12H20 240 24.4 11.6 12.255 8.6 7.829 4.426 2652 88.4 4862 5.45 0.252 8.15 36.12 96.67 95.38 1.57 0.58 10.59 5.08 0.10512 4273 67
24/6/2010 13H20 300 24.7 11.6 12.255 8.6 7.829 4.426 2762.5 93.925 4751 5.47 0.248 7.99 36.12 96.60 95.47 1.57 0.58 10.59 5.10 0.10548 4288 68
24/6/2010 14H20 360 25 11.6 12.255 8.6 7.829 4.426 2817.75 99.45 5414.5 5.52 0.251 8.03 36.12 96.47 95.45 1.57 0.58 10.59 5.15 0.10639 4328 69
24/6/2010 15H20 420 25.2 11.6 12.255 8.6 7.829 4.426 2817.75 99.45 5414.5 5.46 0.247 8.01 36.12 96.47 95.48 1.57 0.58 10.59 5.09 0.10530 4281 70
24/6/2010 16H20 480 24.3 11.6 12.255 8.6 7.829 4.426 2817.75 99.45 5414.5 5.45 0.242 8.1 36.12 96.47 95.56 1.57 0.58 10.59 5.08 0.10512 4273 71
24/6/2010 17H20 540 24.3 11.6 12.255 8.6 7.829 4.426 2817.75 99.45 5414.5 5.43 0.24 8.12 36.12 96.47 95.58 1.57 0.58 10.59 5.06 0.10477 4257 72
26/6/2010 9H05 60 23.8 11.6 12.564 8.6 8.028 4.536 2817.75 93.925 5083 5.39 0.251 7.84 36.10 96.67 95.34 1.57 0.59 10.59 5.03 0.10663 4226 73
26/6/2010 10H05 120 23.1 11.6 12.564 8.6 8.028 4.536 2817.75 93.925 5083 5.57 0.269 8.09 36.10 96.67 95.17 1.57 0.59 10.59 5.19 0.10995 4367 74
26/6/2010 11H05 180 23.6 11.6 12.564 8.6 8.028 4.536 2873 99.45 5414.5 5.57 0.25 8.08 36.10 96.54 95.51 1.57 0.59 10.59 5.19 0.10995 4367 75
26/6/2010 12H05 240 24.6 11.6 12.564 8.6 8.028 4.536 2873 99.45 5414.5 5.42 0.248 8.02 36.10 96.54 95.42 1.57 0.59 10.59 5.05 0.10717 4249 76
26/6/2010 13H05 300 24.5 11.6 12.564 8.6 8.028 4.536 2762.5 93.925 5193.5 5.43 0.269 8.03 36.10 96.60 95.05 1.57 0.59 10.59 5.06 0.10735 4257 77
26/6/2010 14H05 360 24.8 11.6 12.564 8.6 8.028 4.536 2762.5 93.925 5193.5 5.41 0.265 8.1 36.10 96.60 95.10 1.57 0.59 10.59 5.04 0.10699 4241 78
26/6/2010 15H05 420 24.5 11.6 12.564 8.6 8.028 4.536 2817.75 104.975 5525 5.56 0.253 8.19 36.10 96.27 95.45 1.57 0.59 10.59 5.18 0.10976 4359 79
26/6/2010 16H05 480 24.5 11.6 12.564 8.6 8.028 4.536 2817.75 104.975 5525 5.43 0.276 8.02 36.10 96.27 94.92 1.57 0.59 10.59 5.06 0.10735 4257 80
26/6/2010 17H05 540 24.4 11.6 12.564 8.6 8.028 4.536 2817.75 104.975 5525 5.55 0.258 8.15 36.10 96.27 95.35 1.57 0.59 10.59 5.18 0.10957 4351 81
27/6.2010 8H20 60 24.1 11.6 12.509 8.6 8.017 4.492 2928.25 88.4 4862 5.5 0.247 8.07 35.91 96.98 95.51 1.56 0.59 10.59 5.11 0.10728 4312 82
27/6/2010 9H20 120 24 11.6 12.509 8.6 8.017 4.492 2928.25 88.4 4862 5.49 0.251 8.19 35.91 96.98 95.43 1.56 0.59 10.59 5.10 0.10710 4304 84
27/6/2010 10H20 180 24.2 11.6 12.509 8.6 8.017 4.492 2928.25 99.45 5.304 5.5 0.245 8.2 35.91 96.60 95.55 1.56 0.59 10.59 5.11 0.10728 4312 85
27/6/2010 11H20 240 24.5 11.6 12.509 8.6 8.017 4.492 2928.25 99.45 5.304 5.52 0.246 8.19 35.91 96.60 95.54 1.56 0.59 10.59 5.13 0.10765 4328 86
27/6/2010 12H20 300 24.5 11.6 12.509 8.6 8.017 4.492 2762.5 93.925 4.862 5.49 0.248 8.17 35.91 96.60 95.48 1.56 0.59 10.59 5.10 0.10710 4304 87
27/6/2010 13H20 360 24.8 11.6 12.509 8.6 8.017 4.492 2762.5 93.925 4.862 5.42 0.271 8.04 35.91 96.60 95.00 1.56 0.59 10.59 5.04 0.10584 4249 88
27/6/2010 14H20 420 24.7 11.6 12.509 8.6 8.017 4.492 2762.5 93.925 4.862 5.51 0.239 8.17 35.91 96.60 95.66 1.56 0.59 10.59 5.12 0.10746 4320 89
27/6/2010 15H20 480 24.6 11.6 12.509 8.6 8.017 4.492 2762.5 93.925 4.862 5.5 0.243 8.17 35.91 96.60 95.58 1.56 0.59 10.59 5.11 0.10728 4312 90
27/6/2010 16H20 540 24.4 11.6 12.509 8.6 8.017 4.492 2762.5 93.925 4.862 5.49 0.242 8.14 35.91 96.60 95.59 1.56 0.59 10.59 5.10 0.10710 4304 91
28/6/2010 8H15 60 23.3 11.6 12.225 8.6 7.724 4.501 2762.5 93.925 4972.5 5.41 0.249 8.03 36.82 96.60 95.40 1.58 0.59 10.59 5.10 0.10727 4241 92
28/6/2010 9H15 120 23.9 11.6 12.225 8.6 7.724 4.501 2762.5 93.925 4972.5 5.51 0.25 8.26 36.82 96.60 95.46 1.58 0.59 10.59 5.20 0.10915 4320 93
28/6/2010 10H15 180 24.4 11.6 12.225 8.6 7.724 4.501 2817.75 88.4 5304 5.5 0.252 8.21 36.82 96.86 95.42 1.58 0.59 10.59 5.19 0.10896 4312 94
28/6/2010 11H15 240 24.5 11.6 12.225 8.6 7.724 4.501 2817.75 88.4 5304 5.48 0.245 8.22 36.82 96.86 95.53 1.58 0.59 10.59 5.17 0.10858 4296 95
28/6/2010 12H15 300 24.6 11.6 12.225 8.6 7.724 4.501 2707.25 93.925 5193.5 5.5 0.246 8.21 36.82 96.53 95.53 1.58 0.59 10.59 5.19 0.10896 4312 96
28/6/2010 13H15 360 24.6 11.6 12.225 8.6 7.724 4.501 2707.25 93.925 5193.5 5.5 0.239 8.21 36.82 96.53 95.65 1.58 0.59 10.59 5.19 0.10896 4312 97
28/6/2010 14H15 420 24.3 11.6 12.225 8.6 7.724 4.501 2873 93.925 5.525 5.55 0.241 8.22 36.82 96.73 95.66 1.58 0.59 10.59 5.23 0.10992 4351 98
28/6/2010 15H15 480 24.6 11.6 12.225 8.6 7.724 4.501 2873 93.925 5.525 5.5 0.238 8.22 36.82 96.73 95.67 1.58 0.59 10.59 5.19 0.10896 4312 99
28/6/2010 16H15 540 24.6 11.6 12.225 8.6 7.724 4.501 2873 93.925 5.525 5.51 0.24 8.24 36.82 96.73 95.64 1.58 0.59 10.59 5.20 0.10915 4320 100
29/6/2010 8H10 60 22.6 11.6 12.365 8.6 7.854 4.511 2762.5 99.45 5304 5.42 0.248 7.94 36.48 96.40 95.42 1.57 0.59 10.59 5.08 0.10717 4249 101
2