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1
Practical period in Windhoek
General (plant) information Data analysis Pilot plant research Risk assessment
2
General
3
Water in Windhoek
Rainwater: limited and evaporates Rivers: >500km away Reservoirs: subjected to irregular rains (>70km) Ground water: wells >50km deep Windhoek: 250.000 inhabitants Water demand: 221 liter per person per day
Reuse since 1960s: Irrigation city parks and sports fields Drinking water supply
4
Water treatment plants
Owned by City of Windhoek, privately operated
Drinking water treatment plants: Von Bach treatment plants New Goreangab Water reclamation plant Ground water boreholes
Waste water treatment plants: Gammams water care works Otjomuize water care works
5
Gammams & NGWRP
Gammams water care works: Bar screens, sedimentation Part stream: trickling filters / humus tanks Activated sludge, sedimentation Maturation ponds: 3 – 4 days
New Goreangab Water Reclamation Plant Storage, pre-ozone, coagulation, DAF Rapid Sand filtration, ozone, BACF, GAC, GAC Ultra Filtration, chlorination
6
Sand
fil
tratio
nC
hlor
inat
ion
Coa
gula
tion
& se
dim
enta
tion
Von
Bach
wat
er tr
eatm
ent p
lant
wat
erst
orag
eFe
Cl3
Was
te
wat
er
Mix
ing
Pre
ozon
e &
Floc
cula
tion
Flot
atio
nSa
nd
filtra
tionO
zona
tion
Activ
ated
ca
rbon
Ultr
a fil
tratio
n Chl
orin
atio
n
New
Gor
eang
ab w
ater
recl
amat
ion
plan
tW
ater
stor
age
Was
te
wat
er
ScreensPrim
ary settling
Activated sludge
Secondary settling
Solid waste,
sand & grit
Sludge
Effluent
Otjom
uize waste w
ater treatment plant
ScreensPrim
ary settling
Digesters
Activated sludge
Trickling filters
Hum
us tanks
Secondary settling
Maturation ponds
Dry
sludge
Solid waste,
sand & grit
Gam
mam
s Water C
are Works
Northern industrial Area
City area 1
City area 2
City area 3
City area 4
City reservoir
City irrigation
Ground water
Goreangab dam
Von Bach dam
Gammans river
Nat
ural
wat
er s
yste
m
7
Water quantity figures
Treatment plant Amount
Production Von Bach water treatment plant (2003) 11.3
Production Goreangab water Reclamation plant (2003) 5.2
- Share of waste water effluent (Gammams MP 8) 3.6
- Share of water from Gorangab dam 1.6
Production from the boreholes (2003) 3.7
Supply of city irrigation water (2003) 1.3
Inflow in Gammams Water Care Works (2004) 11.2
8
Resource for NGWRP
City of Windhoek sets demand for individual WTP
0
5,000
10,000
15,000
20,000
25,000
1-7-2002
1-10-2002
1-1-2003
1-4-2003
1-7-2003
1-10-2003
1-1-2004
1-4-2004
1-7-2004
1-10-2004
1-1-2005
1-4-2005
1-7-2005
1-10-2005
Goreangab m3/d Gammans m3/d Production loss m3/d
9
Risk Assessment
Monte-Carlo analysis (equal MSc Thesis) Cryptosporidium DOC Data from resource Expert guess with people from WINGOC
(conservative approach based on US EPA / literature)
10
Resource concentration
Twice a week measuring Since 1996 Microscopic count Recovery 30-70%
(proven other labs) Gammams MP8 dataset of
165, 41 possitive Highest measured = 20
oocysts / liter (recovery
50%) Gamma: a=0.2; b=33
11
Removal in treatment plant
average/p90 Pre-ozonation nothing Coagulation/flocculation/DAF 0.5Log/0.4Log RSF 0.7Log/0.5Log Ozonation 2Log/1.5Log BACF/GAC/GAC 0.5Log/0.3Log UF 3Log/2.5Log Chlorination nothing
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Results
13
Scenario’s
Mixing in distribution 1:4
Scenario Average # of infections
# of illnesses
Basic situation 3.2*10-7 oocysts/litre
0.03 per year 0.01 per year
Failure of the UF 1.3*10-3 oocysts/litre
29.7 per year 9.9 per year
Failure of the ozonation 3.3*10-5 oocysts/litre
3 per year 1 per year
Peak concentration 0.05 oocysts/litre 12 per day 4 per day
Peak concentration + Ozone 4.95 oocysts/litre 1238 per day 413 per day
14
Traffic accidents (2004)
5 fatal traffic accidents in Windhoek 57 marked serious About 1 in 4 alcohol related
What is a risk? Comments on Monte-Carlo
15
Data Analysis
Performance of UF 5 racks (A-E) Piles of data Selection: temperature adjusted permeability K=(Flux*viscosity)/TMP 360 (L Pa s)/(m2 h Bar) = 1*10-12 m 3 continues periods of operation Excluding K’s below 100 Daily average, p10 and p90
16
Results (1)
Membrane Stacks total (01-04-2003 / 31-05-2003)
0
100
200
300
400
500
600
31 March 2003
07 April 2003
14 April 2003
21 April 2003
28 April 2003
05 May 2
003
12 May 2
003
19 May 2
003
26 May 2
003
02 June 2003
Per
mea
bili
ty, K
(L
Pa
s m
-2 h
-1 B
ar-1
)
0
200
400
600
800
1000
1200
10 percentile average90 percentileQperm [m3/s] QfeedD
Qfe
edD
an
d Q
per
m (
m3/
h)
17
Results (2)
Membrane Stacks total (01-08-2003 / 25-01-2004)
0
100
200
300
400
500
600
28 July 2003
25 August 2003
22 September 2003
20 October 2
003
17 November 2003
15 December 2003
12 January 2004
Per
mea
bili
ty, K
(L
Pa
s m
-2 h
-1 B
ar-1
)
0
200
400
600
800
1000
1200
10 percentile average90 percentileQperm [m3/h] QfeedD [m3/h]
Qfe
edD
an
d Q
per
m (
m3/
h)
18
Results (3)
Membrane Stacks total (01-05-2005 / 30-09-2005)
0
100
200
300
400
500
600
25 April 2005
23 May 2
005
20 June 2005
18 July 2005
15 August 2005
12 September 2005
10 October 2
005
Per
mea
bili
ty, K
(L
Pa
s m
-2 h
-1 B
ar-1
)
0
200
400
600
800
1000
1200
10 percentile average90 percentileQperm [m3/h] QfeedD [m3/h]
Qfe
edD
an
d Q
per
m (
m3/
h)
19
Data analysis, conclusions
No clear decrease in permeability Decrease of feed flow (flux) -> increase permeability Suspected effect of integrity checks Improve storage and handling of data Not just in retrospect Prediction method Often changes of settings Rack A = worse, B = best (10%)
20
Pilot plant research
21
Schematic
Drain
Feed Water
Feed water tank
Permeate water tank
Membrane module
Permeate
Backwash
Concentrate
HClNaOH & NaOCl
1 2
p10
p40 p50
p20
AV27
AV25
AV12AV11
AV23
AV30 AV31
AV33
22
Pilot plant research
Testing 40m2 membrane Comparing with 35m2 membrane module Water quality effects?
Parameter Experiment 1 Experiment 2 Experiment 3
Pilot plant – feed flow 4 m3/h 4.5 m3/h 5 m3/h
Pilot plant – flux 100 L/m2h 112.5 L/m2h 125 L/m2h
Start date 21-10-2005 9-11-2005 14-12-2005
End date 9-11-2005 14-12-2005 21-12-2005
Days of detailed research 26-10-20052-11-20059-11-2005
9-11-200516-11-200515-12-2005
16-12-200520-12-2005
23
Problems
Chemical pumps New chemical pump Algae brake through Carbon bag fibers? Many stops
24
Results (days of detailed research)
Results membrane performance
0
100
200
300
400
500
600
700
2-11-2005 11:00
2-11-2005 12:30
2-11-2005 14:00
2-11-2005 15:30
2-11-2005 17:00
2-11-2005 18:30
TM
P,
Flu
x an
d p
erm
eab
ilit
y
10
15
20
25
30
35
40
45
TMP [mBar]Flux [L m-2 h-1]Permeability (not adjusted for temperature) [L m-2 h-1 Bar-1 @ 20 °C]Permeability (adjusted for temperature) [L Pa s m-2 h-1 Bar-1]Temperature [°C]
Te
mp
era
ture
25
Results (2)
Results membrane performance
0
100
200
300
400
500
600
700
15-12-2005 8:00
15-12-2005 9:30
15-12-2005 11:00
15-12-2005 12:30
15-12-2005 14:00
15-12-2005 15:30
TM
P, F
lux
an
d p
erm
ea
bili
ty
10
15
20
25
30
35
40
45
TMP [mBar]Flux [L m-2 h-1]Permeability (not adjusted for temperature) [L m-2 h-1 Bar-1 @ 20 °C]Permeability (adjusted for temperature) [L Pa s m-2 h-1 Bar-1]Temperature [°C]
26
Results (3)
Results membrane performance
0
100
200
300
400
500
600
700
16-12-2005 9:00
16-12-2005 10:30
16-12-2005 12:00
16-12-2005 13:30
16-12-2005 15:00
16-12-2005 16:30
TM
P,
Flu
x an
d p
erm
eab
ilit
y
10
15
20
25
30
35
40
45
TMP [mBar]Flux [L m-2 h-1]Permeability (not adjusted for temperature) [L m-2 h-1 Bar-1 @ 20 °C]Permeability (adjusted for temperature) [L Pa s m-2 h-1 Bar-1]Temperature [°C]
27
Remarks
Many stops, irregular chemical cleans Little to now effects in water quality BW after chemical clean
0
2
4
6
8
0:00:00 0:05:00 0:10:00 0:15:00 0:20:00
pH
28
0
100
200
300
400
500
600
80 100 120 140
Flux (L/m2h)
TM
P (
mB
ar)
Rack D real plant (35m2) pilot plant (40m2)
Linear (Rack D real plant (35m2)) Linear (pilot plant (40m2))
29
Conclusions
40m2 membrane seems to perform better then 35m2 Effect of flux on (prevailing) fouling mechanisms
30
31
32
33
34