1. Urban Water Department of Hydro Sciences, Institute for Urban Water Management Peter Krebs Dresden, 2010 0 Global water aspects 1 Introduction to urban water management 2 Basics for systems description 3 Water transport 4 Matter transport 5 Introduction to water supply 6 Water extraction 7 Water purification 8 Water distribution 9 Introduction to wastewater disposal 10 Urban drainage 11 Wastewater treatment 12 Sludge treatment

2. Urban Water Chapter 7 Water purification © PK, 2010 – page 2 7 Water purification 7.1 Concept, overview 7.2 Gas exchange 7.3 Removal of particles 7.4 Removal of colloids and solubles 7.5 Chemical stabilisation 7.6 Disinfection and network protection 7.7 Sludge disposal Department of Hydro Sciences, Institute for Urban Water Management Peter Krebs Urban Water

3. Urban Water Chapter 7 Water purification © PK, 2010 – page 3 7 Water purification 7.1 Concept, overview 7.2 Gas exchange 7.3 Removal of particles 7.4 Removal of colloids and solubles 7.5 Chemical stabilisation 7.6 Disinfection and network protection 7.7 Sludge disposal Department of Hydro Sciences, Institute for Urban Water Management Peter Krebs Urban Water

4. Urban Water Chapter 7 Water purification © PK, 2010 – page 4 Turbid raw water Pre-treated water Drinking water Removal of particles Enhanced treatment, stabilisation, disinfection Two major steps of water purification

5. Urban Water Chapter 7 Water purification © PK, 2010 – page 5 (DVGW Handbook of water supply, Vol. 6) TaskConventional ProcessNew approaches (partly in development) Removal of particlesFlocculation, sedimentation, flotation, filtration, bank filtration, groundwater enrichment Micro-filtration, ultra- filtration, ultrasonic Plankton Removal of dissolved inorganic substances Decarbonisation, flocculation/precipitation, ion exchange, Gas exchange Reverse osmosis, nano- filtration, special ion exchange processes, specific adsorption technologies Removal / destruction of organic substances Flocculation, ozonisation, active carbon filtration, biological filtration, sub surface passage, gas exchange Nano- and ultra-filtration, enhanced oxidation processes Removal / inactivation / destruction of micro- organisms Disinfection with ozone, chlorine, chlorine dioxide; sub surface passage and particle removal UV-radiation, Micro-filtration, ultra-filtration Tasks and processes; overview

6. Urban Water Chapter 7 Water purification © PK, 2010 – page 6 7 Water purification 7.1 Concept, overview 7.2 Gas exchange 7.3 Removal of particles 7.4 Removal of colloids and solubles 7.5 Chemical stabilisation 7.6 Disinfection and network protection 7.7 Sludge disposal Department of Hydro Sciences, Institute for Urban Water Management Peter Krebs Urban Water

7. Urban Water Chapter 7 Water purification © PK, 2010 – page 7 Export of CO 2, for de-acidification Export (purging) of volatile substances, such as H 2 S, CH 4 Stripping of volatile organic compounds Import of oxygen for oxidation of dissolved compounds (e.g. ferric substances, manganese, ammonia) and to improve taste and development of protection layers Introduction of ozone Goals of gas transfer

8. Urban Water Chapter 7 Water purification © PK, 2010 – page 8 HENRY-DALTON law c S =  · c G c S Gas saturation concentration in water c G Gas concentration in air  Solubility coefficient = f (t, p G ) Import flux Export flux Transfer process description

9. Urban Water Chapter 7 Water purification © PK, 2010 – page 9 (® Aquadosil) Aeration with free surface

10. Urban Water Chapter 7 Water purification © PK, 2010 – page 10

11. Urban Water Chapter 7 Water purification © PK, 2010 – page 11 7 Water purification 7.1 Concept, overview 7.2 Gas exchange 7.3 Removal of particles 7.4 Removal of colloids and solubles 7.5 Chemical stabilisation 7.6 Disinfection and network protection 7.7 Sludge disposal Department of Hydro Sciences, Institute for Urban Water Management Peter Krebs Urban Water

12. Urban Water Chapter 7 Water purification © PK, 2010 – page 12 Sieves Removal of coarse particles Sedimentation Removal of easy-to-settle and flocculated particles quiescent, undisturbed flow conditions Filtration sand layer passage Removal of particles: overview

13. Urban Water Chapter 7 Water purification © PK, 2010 – page 13 Rack only with surface waters wide and narrow slots Micro sieves Steel or textile grid size < 0,1 mm, continuous back rinsing  Raw water  Clear water tank  Effluent  Micro sieve  Rotating cylinder  Rinsing  Driver, controlled Removal of coarse particles

14. Urban Water Chapter 7 Water purification © PK, 2010 – page 14 Source: Bodenseewasserversorgung Micro sieve

15. Urban Water Chapter 7 Water purification © PK, 2010 – page 15 0.1 10 1000 10 -5 10 -3 10 -1 10 Particle concentration (g TSS /m 3 ) Particle size (mm) Flocculation Filtration Sedimentation Sieves Rack VirusesBacteriaAlgae Processes to remove particles

16. Urban Water Chapter 7 Water purification © PK, 2010 – page 16 MixingFlocculationSeparation Sludge Treatment Flocculant De-stabilisation, generation of micro-flocs Aggregation and generation of macro-flocs Sedimentation, flotation, filtration Enhanced treatment Filtration ev. flocculation aid Flocculation

17. Urban Water Chapter 7 Water purification © PK, 2010 – page 17 QQ  Inlet region  Effluent region  Sediments  Sedimentation region Length of tank Sedimentation Length L S Sedimentation

18. Urban Water Chapter 7 Water purification © PK, 2010 – page 18 · often layered (two or more layers) top: coarse, light material (e.g. pumice stone 1,4 – 2,5 mm) bottom: fine, heavy material (e.g. sand, 0,71 – 1,25 mm) · hydraulic load 4 – 30 m/h · Pressure head 2 – 5 m · Quick increase of resistance an pressure head decrease; clogging of fine material is faster, · Back rinsing with water, air, and water/air · Pressure filtration for smaller filter areas Fast filtration

19. Urban Water Chapter 7 Water purification © PK, 2010 – page 19 Open fast filter

20. Urban Water Chapter 7 Water purification © PK, 2010 – page 20  Filtrate concentration  Filter resistance Threshold values  p cr (h F,cr ) critical filtrate conc. c cr Filtrate concentration c in TE/F or mg/l Filter resistance  p (h F in m)   Filter operation time t t1t1 t2t2 Filtration effect and resistance

21. Urban Water Chapter 7 Water purification © PK, 2010 – page 21 Back rinsing

22. Urban Water Chapter 7 Water purification © PK, 2010 – page 22  Removal of particles microbial load bio-degradable substances Sieve effect Adsorptive effect over entire filter depth „Mud cover“, a few cm, biologically active Organic compounds are degraded Ammonia is nitrified Prerequisite O 2 -concentration is sufficient small TSS-concentration Surface overflow rate 0,1 – 0,2 m/h, pressure head ca. 1 m 3 – 24 months removal of „mud cover“ large area necessary Slow filtration (i)

23. Urban Water Chapter 7 Water purification © PK, 2010 – page 23 Raw water Filtration Mud layer, bio-active ! Sand filter,   0.6 mm, H > 0.5 m Drainage bottom Sand filter, layered with increasing diameter towards bottom Slow filtration (ii)

24. Urban Water Chapter 7 Water purification © PK, 2010 – page 24 7 Water purification 7.1 Concept, overview 7.2 Gas exchange 7.3 Removal of particles 7.4 Removal of colloids and solubles 7.5 Chemical stabilisation 7.6 Disinfection and network protection 7.7 Sludge disposal Department of Hydro Sciences, Institute for Urban Water Management Peter Krebs Urban Water

25. Urban Water Chapter 7 Water purification © PK, 2010 – page 25 Removal of Ferric and Manganese Fe 2+ Fe 3+ Contact with O 2 High solubility Low solubility Rosty precipitation  Filtration Manganese Similar to ferric substances, Oxidation through micro-organisms or catalytic reaction

26. Urban Water Chapter 7 Water purification © PK, 2010 – page 26 Active carbon adsorption  Removal of dissolved organic compounds microscopic pores through glowing of coal at 650°C, as a significant part is oxidised and volatilised as CO 2 huge internal surface: 1000 – 2000 (m 2 /g active carbon) active carbon is sensitive on mechanical stress rinsing as seldom as possible via pre-treatment and separation of particles before the activated carbon process microorganisms on the surface  bio-degradation of organic compounds

27. Urban Water Chapter 7 Water purification © PK, 2010 – page 27 7 Water purification 7.1 Concept, overview 7.2 Gas exchange 7.3 Removal of particles 7.4 Removal of colloids and solubles 7.5 Chemical stabilisation 7.6 Disinfection and network protection 7.7 Sludge disposal Department of Hydro Sciences, Institute for Urban Water Management Peter Krebs Urban Water

28. Urban Water Chapter 7 Water purification © PK, 2010 – page 28 De-acidification CO 2 CaCO 3 Drinking water treatment Neutralisation AcidLime, calcium carbonate Aggressive, corrosive  Aeration  Filtration through lime  Adding hydroxides, soda Precipitation, encrusting  Precipitation  Reduction of solubility  Ion exchange

29. Urban Water Chapter 7 Water purification © PK, 2010 – page 29 K S4,3 K B8,2 lime – carbonic – acid – system

30. Urban Water Chapter 7 Water purification © PK, 2010 – page 30 7 Water purification 7.1 Concept, overview 7.2 Gas exchange 7.3 Removal of particles 7.4 Removal of colloids and solubles 7.5 Chemical stabilisation 7.6 Disinfection and network protection 7.7 Sludge disposal Department of Hydro Sciences, Institute for Urban Water Management Peter Krebs Urban Water

31. Urban Water Chapter 7 Water purification © PK, 2010 – page 31 Disinfection  Inactivation of pathogenic germs Chemical oxidation UV-radiation O 3 fast decay, no by-products, Oxidation Cl 2 cheap, Network safety, reactive ClO 2 Network protection, local production In 1 cm layer, for some seconds No by-products No network protection Only for small plants, expensive  possibly production of by-products

32. Urban Water Chapter 7 Water purification © PK, 2010 – page 32 Effect of disinfection means OxidationDisinfectionlong term effect ChlorineSatisfactorygood Chlorine dioxideBadsatisfactory OzoneGoodgoodnegative UV-RadiationBadsatisfactorynegative

33. Urban Water Chapter 7 Water purification © PK, 2010 – page 33 7 Water purification 7.1 Concept, overview 7.2 Gas exchange 7.3 Removal of particles 7.4 Removal of colloids and solubles 7.5 Chemical stabilisation 7.6 Disinfection and network protection 7.7 Sludge disposal Department of Hydro Sciences, Institute for Urban Water Management Peter Krebs Urban Water

34. Urban Water Chapter 7 Water purification © PK, 2010 – page 34 Sludge production ProcessResidues Sieves, grills, coarse filters Rinsing water with gross solids Flocculation and sedimentation, filters Sludge-water mixture with content of e.g. Fe, Mn, organics and Flocculation aids, e.g. Al, Fe CaCO 3 Dosing stationsDosing chemicals

35. Urban Water Chapter 7 Water purification © PK, 2010 – page 35 Mass in Germany (Source: Wichmann and Akkiparambath 2001)  ca. 4 % of annual WWTP sludge production (related to DM) Others (13.000 t, 11 %) Fe and Mn Sludges (13.000 t, 11 %) Flocculation sludges (42.000 t, 34 %) CaCO 3 residues (55.000 t, 44 %)

36. Urban Water Chapter 7 Water purification © PK, 2010 – page 36 Disposal in Germany (Source: Wichmann and Akkiparambath 2001) Disposal (35 %) WWTP treatment (31 %) Industrial use (7 %) Land and forestry management (9 %) Receiving water (7 %) Environmental Technology (6 %) WWTP application (5 %)