Namwater Report-Epukiro Pos 3

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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


proposed standards.

(iv) Chloride can be reduced by 95.7% from levels of 1009.2 mg/l to levels as low as


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

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Namwater Report-Epukiro Pos 3

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