Presentation on theme: "Water resources in China WANG Hongtao, Ph.D., Associate Professor College of Environmental Science and Engineering, Tongji University"— Presentation transcript:
Water resources in China WANG Hongtao, Ph.D., Associate Professor College of Environmental Science and Engineering, Tongji University firstname.lastname@example.org Sustainable Development in China
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?
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 Source Water Coagulation Filtration Pump Customer Coagulant Sedimentation Clean water Cl 2 Conventional treatment process of drinking water Disinfection Distribution Source: US EPA
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.
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.
Following coagulation, flocculation, a gentle mixing stage, increases the particle size from submicroscopic microfloc to visible suspended particles. flocculation
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
Jar test Raw water turbidity: >500 NTU Treated water turbidity:1-2 NTU Drinking water treatment in Ethiopia
WTPPAC-SDDPAC-CFIIALUM NG’ETHU97.7%98%89.8% SASUMUA81.9%84%75% KABETE91.8%92%89% Drinking water treatment in Kenya
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
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);
Sand Gravel Influent Drain Effluent Wash water Anthracite Backwash Wash water is treated water! Filtration Pollution?
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
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
What is the problem of disinfection? Disinfection Byproducts(DBPs) Cl 2 +natural organic matter——trihalomethanes （ THMs, carcinogenic ）
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 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
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
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
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
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
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
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
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
Wetland wastewater treatment system in Nanhui District, Shanghai
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.
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
Introduction of Tai Lake China's famous scenic spot
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
Algae collection Algae separation Algae Separation from Tai Lake
2,000 m 3 /d Designed by Tongji University Solid content: 0.5-1% 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 Algae Separation from Tai Lake ABCED A1 C1B1D1 A1:algae slurry B1:+absorbent modified with chitosan C1: +poly aluminum chloride (PACl) D1: +alum
(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
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
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
Project profile Sirte City Wastewater reuse-Desalination in Libya
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
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