Water resources in China

1. Sustainable Development in China Water resources in China WANG Hongtao, Ph.D., Associate Professor College of Environmental Science and Engineering, Tongji University hongtao@tongji.edu.cn

2. Outline • Drinking water treatment • Conventional treatment process • Advanced treatment process • Wastewater treatment • Wastewater situation in China • Wastewater treatment process • Case Study of wastewater treatment plant • Algae separation • Reuse of wastewater Question: Which technology is “sustainable?” Why?

3. Drinking water treatment

4. Conventional scheme of water cycle Production of drinking water To protect the quality of the environment reject Effluents Assume a safe water WW treatment plant Adequate sanitation Sludges Open system-closed system

5. Conventional treatment process of drinking water Coagulant Cl2 Disinfection Source Water Clean water Coagulation Sedimentation Filtration Distribution Pump Customer Source: US EPA

6. Coagulation

7. Physical-chemical process involved in Coagulation-Flocculation Coagulation-flocculation: The use of chemical reagents to destabilise and increase the size of the particles; mixing; increasing of flocs size. Source: SNF FLOERGER (2003)

8. Coagulationdestabilises the particles’ charges. Coagulants with charges opposite to those of the suspended solids are added to the water to neutralise the negative charges on dispersed non-settable solids such as clay and organic substances. Once the charge is neutralised, the small-suspended particles are capable of sticking together.

9. flocculation Following coagulation, flocculation, a gentle mixing stage, increases the particle size from submicroscopic microfloc to visible suspended particles.

10. Coagulation

11. Coagulation agitator Jar tester, Nairobi, 1938

12. Coagulation

13. Poly Aluminum Chloride for Drinking Water Heavy metal in the coagulant! Ore: calcium aluminate

14. Drinking water treatment in Ethiopia • Jartest • Raw water turbidity: >500 NTU • Treated water turbidity:1-2 NTU

15. Drinking water treatment in Kenya

16. Questions: • Do you think COAGULATION is a “sustainable?” technology? • What do you think of the advantages and disadvantages of COAGULATION? • Chemical consumption: coagulant • Energy consumption: agitator • Residual coagulant dissolved in water: Al • Safety issue: heavy metals

17. Sedimentation/Settling Sludge • What is the problem of sedimentation/settling? • Pollutants separated from water to sludge(not degraded); • Sludge is a problem. • Residual coagulant in sludge (Al, Fe, PAM);

18. Filtration Rapid Sand Filter (Conventional US Treatment) Depth (cm) 30 45 45 Specific Gravity 1.6 2.65 2.65 Size (mm) 0.70 0.45 - 0.55 5 - 60 Anthracite Influent Sand Gravel Drain Wash water Effluent

19. Filtration Backwash • Wash water is treated water! Anthracite Pollution? Sand Influent Gravel Drain Effluent Wash water

20. Disinfection Chlorine Disinfection (Cl2): one of the most commonly used disinfectants for water disinfection. can be applied for the deactivation of most microorganisms and it is relatively cheap.Advantages: efficient oxidant and disinfectant effectively eliminates unpleasant taste and odors featured with aftereffect (Free chlorine residual of 0.2-0.5 mg/L) prevents and controls growth of algae, biological slimes and microbes decomposes organic contaminants (phenols, etc.) oxidizes iron and magnesium decomposes hydrogen sulfide, cyanides, ammonium and other nitrogen compounds.Disadvantages: strict requirements for transportation and storage ; potential risk to health in case of leakage; formation of disinfection by-products, such as trihalomethanes.

21. Disinfection Sodium hypochlorite (NaClO):Advantages: effective against most of pathogenic microorganisms relatively safe during storage and use when produced on site does not require transportation and storage of hazardous chemicals Disadvantages:looses its activity during long-term storage ineffective against cysts (Giardia, Cryptosporidium) produces disinfection by-products, such as trihalomethanes generated on-site requires immediate useOther disinfectants:Chlorine dioxide; Chloramine; Ozone; Ultraviolet Solar Disinfection(SODIS) Heating water to 65°C (149°F) in a solar cooker will pasteurize the water and kill disease causing microbes.

23. What is the problem of disinfection? Disinfection Byproducts(DBPs) Cl2+natural organic matter——trihalomethanes（THMs, carcinogenic）

24. Advanced treatment process of drinking water Coagulant O3 Source Water Coagulation Sedimentation Oxidation Filtration Chlorine Activated carbon Clean water Pump Customer Ozone biological activated carbon technology

25. Oxidation Oxidation and Reduction • Oxidation- complete or partial loss of electrons or the gain of oxygen. • Reduction- complete or partial gain of electrons or loss of oxygen

26. Oxidation F2 F2(g)+ 2H++2e-=2HF Half reactions Standard-State Reduction Potentials, Eo 3.06 Oxidizing agent MnO2 MnO2(s)+4H++2e- =Mn2++2H2O2 1.23 Cl2 Cl(g)+2e-=2Cl- 1.36 ClO2 ClO2+2e-= Cl-+ O2 1.50 H2O2 H2O2+ 2H++2e-=2 H2O 1.77 O3+2H++2e-= H2O+ O2 2.07 O3 ·OH ·OH+ H++2 e-= H2O 2.80 Oxidizing Strength of ·OH ·OH oxidizing properties are comparable to Fluorine (F2) the most electronegative element in the periodic table hydroxyl radical

27. Oxidation • Taihu Lake algae crisis(2007): Oxidant: potassium permanganate (KMnO4) What is the problem of KMnO4 addition? • Erosion to the pipelines (Fe) • Hazardous to human health

28. Adsorption

29. Adsorption Increasing magnification

30. Adsorbent: activated carbon Applications in water treatment usually involve adding AC as a media to the filtration unit. In some cases a contactor is added just before the final chlorination step.

31. Breakthrough of Adsorbent Adsorption (Fixed Bed Absorber). Co CE Breakthrough Curve Effluent Concentration Exhaustion point Breakpoint CB VB VE Volume of Effluent

32. What is the problem of Adsorption? • expensive • regeneration • Pollutants transferred, not degraded

33. Wastewater treatment

34. wastewater treatment in Shanghai Wastewater treatment ratio in Shanghai

35. Wastewater treatment plants in Shanghai

36. How to Choose the Process Wastewater treatment process in China 二级处理 Secondarytreatment 三级处理 Tertiary treatment 一级处理 Primary treatment Bar Screen Conventional activated sludge Disinfection Grit chamber Coagulation BNR Filtration Primary sedimentation Biological phosphorus removal MBR Discharge or Reuse Enhanced primary sedimentation Biological nitrogen &phosphorus removal RO Ecological treatment Biofilm BNR: Biological Nutrient Removal MBR: Membrane Bioreactor RO: Reverse Osmosis

37. Exhaust Smell treatment Wastewater Bar screen Secondary treatment Primary treatment Drainage/ reuse Disposal Sludge treatment Advanced treatment How to Choose the Process General concept and process of wastewater treatment plant

38. Case study: ShidongkouWWTP,Shanghai,China

39. 鼓风机房 Aeration station Coarse Screen Lift Pump Fine Screen Grit Chamber Flow meter Chlorination Disinfection Unitank 沉砂池 粗格栅 细格栅 计量槽 一反体应化池 出水泵房 进水泵房 加氯消毒 排放 进水 Effluent Influent 主体工艺 Grid Residue 栅渣 砂 栅渣 剩余污泥 Sand Surplus sludge 砂水分离器 剩余污泥泵 栅渣压干机 栅渣压干机 Presser Presser Separator Sludge Pump 至剩余污泥处理段 栅渣外运 To Sludge treatment Landfill Treatment technologies of ShidongkouWWTP,Shanghai

40. Case study: ShidongkouWWTP,Shanghai,China Reclaimed water Effluent discharge • Effluent: • Discharged to Yangtze River; • Reclaimed and reused for road flushing, firefighting, irrigation • Sludge treatment • Thickening; • Dewatering; • incineration; • Landfill Sludge dewatering Incineration

41. What is your opinion on the technologies adopted in Shidongkou Wastewater Treatment Plant? • Efficient to remove pollutants from water • Energy consumption • Air pollution (incineration) • Landfill leachate pollution

42. Wetland wastewater treatment system in Nanhui District, Shanghai

43. Benefits of Treatment Wetlands Constructed and natural treatment wetlands provide several major benefits compared to more conventional treatment alternatives: • less expensive to construct than traditional secondary and tertiary wastewater treatment systems. • less maintenance and are less expensive to operate than traditional treatment systems. • may provide important wetland wildlife habitat, as well as human recreational opportunities such as birdwatching, hiking, and picnicking. • Treatment wetlands are viewed as an asset by regulatory agencies in many regions and as a potentially effective method for replacing natural wetlands lost through agricultural practices, industrial and municipal development, and groundwater withdrawal.

44. Case study: Separation of Algae from Tai Lake

45. Tai Lake to Shanghai: 130 kmShanghai is located in the downstream of Yangtze RiverHuangpu River and entrance of Yangtze River provide raw water for Shanghai.Tai Lake is in the upstream of Huangpu River Tai Lake Shanghai

46. Introduction of Tai Lake China's famous scenic spot

47. Algae bloom in Tai Lake Blue-green algae is seen on the surface of Tai Lake Tai Lake turns green after an algae bloom Blooming algae fills large areas of the Tai Lake Ducks swim in the algae-rich Tai Lake

48. Algae Separation from Tai Lake • Algae collection • Algae separation

49. Algae Separation from Tai Lake 2,000 m3/d Designed by Tongji University Solid content: 0.5-1%

50. Algae Separation from Tai Lake Coagulant:150 ppm A:algae slurry B:+absorbent modified with chitosan C:+poly aluminum chloride (PACl) D:+poly ferric sulfate E: +alum A B C D E A1:algae slurry B1:+absorbent modified with chitosan C1: +poly aluminum chloride (PACl) D1: +alum B1 C1 D1 A1