Practical period in Windhoek

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Practical period in Windhoek

• General (plant) information
• Data analysis
• Pilot plant research
• Risk assessment

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General
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Water in Windhoek

• Rainwater limited and evaporates
• Rivers gt500km away
• Reservoirs subjected to irregular rains (gt70km)
• Ground water wells gt50km 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

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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

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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

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Water quantity figures
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Resource for NGWRP

• City of Windhoek sets demand for individual WTP

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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)

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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 a0.2 b33

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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
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Scenarios

• Mixing in distribution 14

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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

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Data Analysis

• Performance of UF
• 5 racks (A-E)
• Piles of data
• Selection temperature adjusted permeability
• K(Fluxviscosity)/TMP
• 360 (L Pa s)/(m2 h Bar) 110-12 m
• 3 continues periods of operation
• Excluding Ks below 100
• Daily average, p10 and p90

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Results (1)
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Results (2)
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Results (3)
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Data analysis, conclusions

• No clear decrease in permeability
• Decrease of feed flow (flux) -gt 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)

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Pilot plant research
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Schematic
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Pilot plant research

• Testing 40m2 membrane
• Comparing with 35m2 membrane module
• Water quality effects?

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Problems

• Chemical pumps
• New chemical pump
• Algae brake through
• Carbon bag fibers?
• Many stops

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Results (days of detailed research)
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Results (2)
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Results (3)
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Remarks

• Many stops, irregular chemical cleans
• Little to now effects in water quality
• BW after chemical clean

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Conclusions

• 40m2 membrane seems to perform better then 35m2
• Effect of flux on (prevailing) fouling mechanisms

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