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Water resources in China WANG Hongtao, Ph.D., Associate Professor College of Environmental Science and Engineering, Tongji University

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Presentation on theme: "Water resources in China WANG Hongtao, Ph.D., Associate Professor College of Environmental Science and Engineering, Tongji University"— Presentation transcript:

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

2  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 Outline Question: Which technology is “sustainable?” Why?

3 Drinking water treatment

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

5 5 Source Water Coagulation Filtration Pump Customer Coagulant Sedimentation Clean water Cl 2 Conventional treatment process of drinking water Disinfection Distribution Source: US EPA

6 Coagulation

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

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

10 Coagulation

11 agitator Jar tester, Nairobi, 1938

12 Coagulation

13 Poly Aluminum Chloride for Drinking Water Index LiquidSolid High-class product First-class product High-class productFirst-class product Al 2 O 3 Content %≥10.0 30.028.0 Basicity %40-8540-8040-90 Density (20%)/(g/cm 3 ) ≥1.15 -- Non-dissolved Substances /%≤0.10.3 1.0 pH(1% aqueous suspension) 3.5-5.0 As /%≤ 0.00010.0002 Pb /%≤ 0.00050.001 Cd /%≤ 0.00010.0002 Hg /%≤ 0.00001 Cr 6+ /%≤ 0.0005 Heavy metal in the coagulant! Ore: calcium aluminate

14 Jar test Raw water turbidity: >500 NTU Treated water turbidity:1-2 NTU Drinking water treatment in Ethiopia

15 WTPPAC-SDDPAC-CFIIALUM NG’ETHU97.7%98%89.8% SASUMUA81.9%84%75% KABETE91.8%92%89% 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 Sand Gravel Influent Drain Effluent Wash water Anthracite Size (mm) 0.70 0.45 - 0.55 5 - 60 Specific Gravity 1.6 2.65 Depth (cm) 30 45 Rapid Sand Filter (Conventional US Treatment)

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

20 Chlorine Disinfection (Cl 2 ): 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. Disinfection

21 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 use Other 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. Disinfection


23 What is the problem of disinfection? Disinfection Byproducts(DBPs) Cl 2 +natural organic matter——trihalomethanes ( THMs, carcinogenic )

24 24 Source Water Coagulation Oxidation Pump Customer O 3 Coagulant Sedimentation Activated carbon Clean water Advanced treatment process of drinking water Filtration Ozone biological activated carbon technology Chlorine

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

26 Oxidizing Strength of ·OH · OH oxidizing properties are comparable to Fluorine (F 2 ) the most electronegative element in the periodic table 26 Oxidizing agent Half reactions Standard-State Reduction Potentials, E o MnO 2 MnO 2 MnO 2 (s)+4H + +2e - =Mn 2+ +2H 2 O 2 1.23 Cl 2 Cl 2 Cl(g)+2e - =2Cl - 1.36 ClO 2 ClO 2 ClO 2 +2e - = Cl - + O 2 1.50 H 2 O 2 H 2 O 2 H 2 O 2 + 2H + +2e - =2 H 2 O 1.77 O 3 O 3 O 3 +2H + +2e - = H 2 O+ O 2 2.07 ·OH ·OH ·OH+ H + +2 e - = H 2 O 2.80 F 2 F 2 F 2 (g)+ 2H++2e-=2HF 3.06 Oxidation hydroxyl radical

27 Taihu Lake algae crisis(2007): Oxidant: potassium permanganate (KMnO 4 ) Oxidation What is the problem of KMnO 4 addition?  Erosion to the pipelines (Fe)  Hazardous to human health

28 Adsorption

29 Increasing magnification Adsorption

30 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. Adsorbent: activated carbon

31 Adsorption (Fixed Bed Absorber). Effluent Concentration CoCo CECE CBCB Volume of Effluent VBVB VEVE Breakpoint Exhaustion point Breakthrough Curve Breakthrough of Adsorbent

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

33 Wastewater treatment

34 Wastewater treatment ratio in Shanghai wastewater treatment in Shanghai

35 Wastewater treatment plants in Shanghai

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

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

38 Case study: Shidongkou WWTP,Shanghai,China 项 目 COD BOD 5 SS NH 3 -N TP Influent(mg/L)400200250304.5 Effluent(mg/L)6020208(15)1.5

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

40 Effluent:  Discharged to Yangtze River;  Reclaimed and reused for road flushing, firefighting, irrigation Effluent discharge Reclaimed water Case study: Shidongkou WWTP,Shanghai,China 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 km Shanghai is located in the downstream of Yangtze River Huangpu River and entrance of Yangtze River provide raw water for Shanghai. Tai Lake is in the upstream of Huangpu River Shanghai Tai Lake

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 Blooming algae fills large areas of the Tai LakeDucks swim in the algae-rich Tai Lake Tai Lake turns green after an algae bloom

48 Algae collection Algae separation Algae Separation from Tai Lake

49 2,000 m 3 /d Designed by Tongji University Solid content: 0.5-1% Algae Separation from Tai Lake

50 Coagulant:150 ppm A:algae slurry B:+absorbent modified with chitosan C:+poly aluminum chloride (PACl) D:+poly ferric sulfate E: +alum Algae Separation from Tai Lake ABCED A1 C1B1D1 A1:algae slurry B1:+absorbent modified with chitosan C1: +poly aluminum chloride (PACl) D1: +alum

51 (a)SEM of modified fly ash coagulant(10 um) (b)SEM of modified fly ash coagulant(2 um) (c) SEM of the algae cell after treatment(5 um) (d) SEM of the algae cell after treatment(2 um) Algae Separation from Tai Lake

52 Energy producing and carbon sequestration

53 1ton algae(dry)=600 m 3 methane +100 kg N +10 kg P Carbon sequestration=0.85~3.39 ton carbon/d Energy producing and carbon sequestration elementCHN SP content ( % ) 37.633.4533.0500.940.57 Table 1. Elementary analysis table of algae sludge

54 Energy producing and carbon sequestration

55  Algae bloom is a serious problem in Tai Lake  Algae can be separated from water by coagulation/adsorption and dewatering  Algae can produce energy and fertilizer  Significant for carbon sequestration Algae Separation from Tai Lake

56 Reuse of Wastewater: Desalination

57 Example: wastewater reuse in Tongji University Source: Prof. XIA Siqing

58 Wastewater reuse-Desalination in Libya

59 Project profile Sirte City Wastewater reuse-Desalination in Libya

60 Sirte Wastewater Treatment Pant: Constructed in 2001 Capacity: 30000m 3 /d Treatment Process: activated sludge Existing Problem: TDS (Total Dissolved Solid) is too high! Acceptable TDS for irrigation: 600~1000 mg/L Current TDS in S WWTP: 2500 mg/L Desalination is needed! Wastewater reuse-Desalination in Libya

61 Reuse of Waste Water for Forest Plantation Irrigation project in Libya Sampling in Sirte City, Libya Preliminary scheme of tertiary treatment and reuse of wastewater in Sirte City, Libya

62 Libya-Desalination

63 What is your opinion on the wastewater reuse?  Save water  Cost-effective? Too expensive!  Reliability (power system; infrastructure; solar power?)

64 thanks for your attention

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