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Practical period in Windhoek

Practical period in Windhoek. General (plant) information Data analysis Pilot plant research Risk assessment. General. Water in Windhoek. Rainwater: limited and evaporates Rivers: >500km away Reservoirs: subjected to irregular rains (>70km) Ground water: wells >50km deep

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Practical period in Windhoek

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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. Water quantity figures

  7. Resource for NGWRP • City of Windhoek sets demand for individual WTP

  8. 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)

  9. 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

  10. 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

  11. Results

  12. Scenario’s • Mixing in distribution 1:4

  13. 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

  14. 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

  15. Results (1)

  16. Results (2)

  17. Results (3)

  18. 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%)

  19. Pilot plant research

  20. Schematic

  21. Pilot plant research • Testing 40m2 membrane • Comparing with 35m2 membrane module • Water quality effects?

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

  23. Results (days of detailed research)

  24. Results (2)

  25. Results (3)

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

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

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