Department of Hydro Sciences, Institute for Urban Water Management Urban Water 1 Global water aspects 2 Introduction to urban water management 3 Basics for systems description 4 Water transport 5 Matter transport 6 Introduction to water supply 7 Water extraction 8 Water purification 9 Water distribution 10 Introduction to wastewater disposal 11 Urban drainage 12 Wastewater treatment 13 Sludge treatment Peter Krebs Dresden, 2010
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 Urban Water Chapter 2 Basics for system description © PK, 2010 – page 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 Urban Water Chapter 2 Basics for system description © PK, 2010 – page 3
Typical domestic water demand Typical consumption l/(Ca·d) Range l/(Ca·d) Communal water point distance > 1000 m distance 500 – 1000 m 7 12 5 – 10 10 – 15 Village well 20 15 – 25 Communal standpipe distance < 250 m 30 20 – 50 Yard connection 40 20 – 80 50 150 30 – 60 70 – 250 Type of water supply distance < 250 m House connection single tap multiple tap Urban Water Chapter 2 Basics for system description © PK, 2010 – page 4
Average domestic water demand in Germany „Western Germany“ Urban Water Chapter 2 Basics for system description DE © PK, 2010 – page 5
German drinking water consumption 2007 Urban Water Chapter 2 Basics for system description © PK, 2010 – page 6
Drinking water supply (Mio m³/a) Water supply in Dresden 1875 – 1999 80 60 40 20 0 1875 1900 1920 1960 1940 1980 2000 (Source: DREWAG Gmb. H (2002)) Urban Water Chapter 2 Basics for system description © PK, 2010 – page 7
Composition of water consumption 28% WC 6% 6% 6% 34% bath/shower 4% 2%2% 28% 12% washing cloths 6% personal hygiene 6% wash dishes 6% cleaning 4% watering 12% 34% Urban Water Chapter 2 Basics for system description 2% cooking/drinking 2% cleaning cars © PK, 2010 – page 8
Water use of household appliances Washing machine Manufactured (l/cycle) 1980 125 – 175 45 – 55 1985 100 – 125 30 – 40 1990 70 – 125 20 – 30 2000 50 – 60 12 – 15 2010 Urban Water Dish washer 40 – 50 10 – 12 Chapter 2 Basics for system description © PK, 2010 – page 9
Diurnal variation of water consumption 2, 5 City Town Village Daily average Q / Qm 2 1, 5 1 0, 5 0 0 4 8 12 16 20 24 Daytime (h) Urban Water Chapter 2 Basics for system description © PK, 2010 – page 10
Extreme events of water consumption Water consumption in Dortmund, football world championship Italy-Germany, 11 July 1982 Urban Water Chapter 2 Basics for system description © PK, 2010 – page 11
Peak factors: peak day, peak hour Peak hour factor fh Peak day factor fd (DVGW-W 400 -1) Urban Water Inhabitants Chapter 2 Basics for system description © PK, 2010 – page 12
Definition and application of peak factors Symbol Definition For dimensioning of Qd, m Mean daily consumption Water budget, running costs, price Qd, max Maximum daily water consumption Water extraction, water purification, storage Qh, m Mean hourly consumption = mean daily consumption Qh, max Maximum hourly consumption Urban Water Chapter 2 Basics for system description Distribution system, storage © PK, 2010 – page 13
Water use Africa Asia Europe 214 km³ 2156 km³ World 512 km³ 3760 km³ North America 680, 8 km³ Agriculture Urban Water South America 166 km³ Industry Oceania 33, 6 km³ Domestic Chapter 2 Basics for system description (Source: WRI (2001)) Others © PK, 2010 – page 14
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 Urban Water Chapter 2 Basics for system description © PK, 2010 – page 15
Wastewater fluxes: dry-weather conditions Qdw = Qs + Qew Qdw Qs Qew Dry-weather flow Sewage flow Extraneous water flow Qs = Qdom + Qind Qdom Qind Domestic sewage flow Industrial sewage water flow all parameters are subject to distinct variations! Urban Water Chapter 2 Basics for system description © PK, 2010 – page 16
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 Urban Water Chapter 2 Basics for system description © PK, 2010 – page 17
Urban drainage at wet-weather conditions (i) Sewage storage Overflow structure CSO Combined water storage Urban Water WWTP Treated wastewater Receiving water Chapter 2 Basics for system description © PK, 2010 – page 18
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 Urban Water Chapter 2 Basics for system description © PK, 2010 – page 19
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 Urban Water Chapter 2 Basics for system description © PK, 2010 – page 20
Particulate compounds TSS Total Suspended Solids • Filter with pore width 0. 45 m • Sedimentation VSS Volatile Suspended Solids • Glow of TSS at 650°C • volatile fraction is organic substance incl. biomass • important for oxygen depletion TSS – VSS Urban Water Non-organic solids Chapter 2 Basics for system description © PK, 2010 – page 21
Parameters indicating oxygen consumption BOD 5 biochemical oxygen demand in 5 days • 5 days, 20°C, dark reduction of O 2 -concentration • bio-degradable organic substances • dilution with O 2 -rich water, inoculation of biomass COD chemical oxygen demand • Complete oxidation of org. substances to CO 2 and H 2 O • Oxidation means potassium-di-chromate (K 2 Cr 2 O 7) in high temperature and acid environment • all org. substances, not only bio-degradable • COD can be balanced Urban Water Chapter 2 Basics for system description © PK, 2010 – page 22
Nitrogen compounds NH 4+ Ammonium and NH 3 ammonia • the total is measured • equilibrium is depending on temperature and p. H-value Temp. and p. H high NH 3 -fraction higher • Degradation of organic compounds NH 4+ is released • Nitrification to nitrate oxygen depletion NO 3 - Nitrate and NO 2 - nitrite • (NH 4+ + NH 3) NO 2 - NO 3 - • Nitrite is toxic to fish • Nitrate is a problem in groundwater Urban Water Chapter 2 Basics for system description © PK, 2010 – page 23
Nitrogen TKN total Kjeldahl Nitrogen • Sum of organic N + ammonia-N) • org. N in proteins • Chemical oxidation of org. N the released ammonia is measured N 2 nitrogen gas • N 2 main fraction of atmosphere • Hydrophobic • Denitrification NO 3 - N 2 Urban Water Chapter 2 Basics for system description © PK, 2010 – page 24
Organic carbon and phosphorous TOC total organic carbon DOC dissolved organic carbon • Includes all organic compounds • Measurement ( CO 2) expensive, accurate TP, Ptot total phosphorous DP dissolved phosphorous PO 4–P ortho-phosphate • org. P part of DNA, RNA • Analytics: org. P is mineralised, the product orthophosphate is measured Urban Water Chapter 2 Basics for system description © PK, 2010 – page 25
Population equivalents in g/(Ca∙d) Raw sewage Parameter After primary sedimentation Residence time in primary clarifier 0. 5 – 1. 0 h 1. 0 – 1. 5 h > 1. 5 h BOD 5 60 50 45 40 COD 120 100 90 80 TSS 70 40 35 30 TKN 11 10 10 10 Ptot 1, 7 1, 5 Urban Water Chapter 2 Basics for system description © PK, 2010 – page 26
Diurnal variation of dry-weather loads 70 6 NH 4 -load 50 5 COD-load 40 30 3 Daily average of. COD and NH 4 20 2 10 0 00: 00 4 NH 4 -load (kg/h) COD-load (kg/h) 60 7 1 04: 00 08: 00 12: 00 16: 00 20: 00 0 00: 00 Clock time (hh: mm) Urban Water Chapter 2 Basics for system description © PK, 2010 – page 27
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