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Urban Water

Department of Hydro Sciences, Institute for Urban Water Management. Global water aspects Introduction to urban water management Basics for systems description Water transport Matter transport Introduction to water supply Water extraction Water purification Water distribution

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Urban Water

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  1. Department of Hydro Sciences, Institute for Urban Water Management • Global water aspects • Introduction to urban water management • Basics for systems description • Water transport • Matter transport • Introduction to water supply • Water extraction • Water purification • Water distribution • Introduction to wastewater disposal • Urban drainage • Wastewater treatment • Sludge treatment Urban Water Peter Krebs Dresden, 2010

  2. Peter Krebs Department of Hydro Sciences, Institute for Urban Water Management Urban Water 2 Basics for system description 2.1 Water consumption 2.2 Wastewater fluxes 2.3 Parameters to characterise water quality

  3. Peter Krebs Department of Hydro Sciences, Institute for Urban Water Management Urban Water 2 Basics for system description 2.1 Water consumption 2.2 Wastewater fluxes 2.3 Parameters to characterise water quality

  4. Type of water supply Typical consumptionl/(Ca·d) Rangel/(Ca·d) Communal water point distance > 1000 m distance 500 – 1000 m 7 12 5 – 10 10 – 15 Village well distance < 250 m 20 15 – 25 Communal standpipe distance < 250 m 30 20 – 50 Yard connection 40 20 – 80 House connection single tap multiple tap 50 150 30 – 60 70 – 250 Typical domestic water demand

  5. Average domestic water demand in Germany „Western Germany“ DE

  6. German drinking water consumption 2007

  7. 80 60 Drinking water supply (Mio m³/a) 40 20 0 1875 1900 1920 1960 1980 2000 1940 Water supply in Dresden 1875 – 1999 (Source: DREWAG GmbH (2002))

  8. 28% WC 34% bath/shower 2% 2% 4% 6% 12% washing cloths 28% 6% 6% personal hygiene 6% 6% wash dishes 6% cleaning 4% watering 12% 2% cooking/drinking 34% 2% cleaning cars Composition of water consumption

  9. Water use of household appliances

  10. 2,5 City Town Village 2 Daily average 1,5 m Q / Q 1 0,5 0 0 4 8 12 16 20 24 Daytime (h) Diurnal variation of water consumption

  11. Extreme events of water consumption Water consumption in Dortmund, football world championship Italy-Germany, 11 July 1982

  12. Peak factors: peak day, peak hour Peak hour factor fh Peak factor Peak day factor fd (DVGW-W 400-1) Inhabitants

  13. Definition and application of peak factors

  14. Africa 214 km³ Asia 2156 km³ Europe 512 km³ World 3760 km³ North America 680,8 km³ South America 166 km³ Oceania 33,6 km³ Agriculture Industry Domestic Others Water use (Source: WRI (2001))

  15. Peter Krebs Department of Hydro Sciences, Institute for Urban Water Management Urban Water 2 Basics for system description 2.1 Water consumption 2.2 Wastewater fluxes 2.3 Parameters to characterise water quality

  16. Wastewater fluxes: dry-weather conditions Qdw Dry-weather flow Qs Sewage flow Qew Extraneous water flow Qdw = Qs + Qew QdomDomestic sewage flow Qind Industrial sewage water flow Qs = Qdom + Qind  all parameters are subject to distinct variations!

  17. Extraneous water flow Qew • Groundwater infiltration • Drainage water • Spring and brook water • Fountain water • Cooling water • Excess water from reservoirs  Extraneous water flow is variable Rule of thumb

  18. Sewage storage Overflow structure CSO WWTP Treated wastewater Combined water storage Urban drainage at wet-weather conditions (i) Receiving water

  19. Urban drainage at wet-weather conditions (ii) Significance of rain events • Rain runoff  decisive for sewer dimension • Rainwater is contaminated after runoff • Rain water causes overflow of sewage • Sewer sediments are eroded • WWTP operation is disturbed for a longer time period than rain event

  20. Peter Krebs Department of Hydro Sciences, Institute for Urban Water Management Urban Water 2 Basics for system description 2.1 Water consumption 2.2 Wastewater fluxes 2.3 Parameters to characterise water quality

  21. Particulate compounds TSS Total Suspended Solids • Filter with pore width 0.45 m • Sedimentation VSSVolatile Suspended Solids • Glow of TSS at 650°C • volatile fraction is organic substance incl. biomass • important for oxygen depletion TSS – VSSNon-organic solids

  22. Parameters indicating oxygen consumption BOD5biochemical oxygen demand in 5 days • 5 days, 20°C, dark  reduction of O2-concentration • bio-degradable organic substances • dilution with O2-rich water, inoculation of biomass CODchemical oxygen demand • Complete oxidation of org. substances to CO2 and H2O • Oxidation means potassium-di-chromate (K2Cr2O7) in high temperature and acid environment • all org. substances, not only bio-degradable • COD can be balanced

  23. Nitrogen compounds NH4+Ammonium and NH3ammonia • the total is measured • equilibrium is depending on temperature and pH-value  Temp. and pH high  NH3-fraction higher • Degradation of organic compounds  NH4+is released • Nitrification to nitrate  oxygen depletion NO3-Nitrate and NO2-nitrite • (NH4+ + NH3)  NO2- NO3- • Nitrite is toxic to fish • Nitrate is a problem in groundwater

  24. Nitrogen TKNtotal Kjeldahl Nitrogen • Sum of organic N + ammonia-N) • org. N in proteins • Chemical oxidation of org. N  the released ammonia is measured N2nitrogen gas • N2 main fraction of atmosphere • Hydrophobic • Denitrification NO3- N2

  25. Organic carbon and phosphorous TOCtotal organic carbon DOC dissolved organic carbon • Includes all organic compounds • Measurement ( CO2) expensive, accurate TP, Ptottotal phosphorous DP dissolved phosphorous PO4–P ortho-phosphate • org. P part of DNA, RNA • Analytics: org. P is mineralised, the product ortho-phosphate is measured

  26. Population equivalents in g/(Ca∙d) Raw sewage After primary sedimentation Parameter Residence time in primary clarifier 0.5 – 1.0 h 1.0 – 1.5 h > 1.5 h BOD5 60 50 45 40 COD 120 100 90 80 TSS 70 40 35 30 TKN 11 10 10 10 Ptot 1,7 1,5 1,5 1,5

  27. 70 7 60 6 NH -load 4 50 5 COD-load 40 4 -load (kg/h) COD-load (kg/h) 30 3 4 COD NH Daily average of and NH 20 2 4 10 1 0 0 00:00 04:00 08:00 12:00 16:00 20:00 00:00 Clock time (hh:mm) Diurnal variation of dry-weather loads

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