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


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?

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

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

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)

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.

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

agitator
Jar tester, Nairobi, 1938

Poly Aluminum Chloride for Drinking Water
Solid
Index
Al
2
O
3
Content %≥
Basicity %
Density (20%)/(g/cm 3 ) ≥
High-class product
10.0
40-85
Liquid
First-class product
10.0
40-80
1.15
1.15
High-class product First-class product
30.0
40-90
28.0
40-90
-
Non-dissolved Substances /%≤ pH(1% aqueous suspension)
As /%≤
Pb /%≤
Cd /%≤
Hg /%≤
Cr 6+ /%≤
0.1
3.5-5.0
0.0001
0.0005
0.0001
0.00001
0.0005
0.3
3.5-5.0
0.0002
0.001
0.0002
0.00001
0.0005
0.3
3.5-5.0
1.0
3.5-5.0
Ore: calcium aluminate

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

WTP
NG’ETHU
SASUMUA
KABETE
PAC-SDD
97.7%
81.9%
91.8%
PAC-CFII
98%
84%
92%
ALUM
89.8%
75%
89%

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

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);

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

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

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.

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.

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

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

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

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

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

Increasing magnification

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.

Adsorption ( Fixed Bed Absorber ) .
C
C o
E
Breakthrough Curve
Exhaustion point
C
B
Breakpoint
Volume of Effluent
V
B
V
E

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

wastewater treatment in Shanghai
Wastewater treatment ratio in Shanghai

Wastewater treatment plants in Shanghai

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

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

Case study: Shidongkou WWTP,Shanghai,China
项 目
Influent
(mg/L)
Effluent
(mg/L)
COD BOD
5
400 200
60 20
SS
250
20
NH
3
-N TP
30 4.5
8(15) 1.5

Treatment technologies of Shidongkou WWTP,Shanghai
鼓风机房 Aeration station
进水
Influent
Coarse
Screen
粗
格
栅
Lift
Pump
进
水
泵
房
Fine
Screen
细
格
栅
Grit
Chamber
Flow meter
Unitank
沉
砂
池
计
量
槽
一反
体应
化池
主体工艺
加
氯
消
毒
Chlorination
Disinfection
出
水
泵
房
排放
Effluent
Grid
Residue
栅渣 栅渣 砂 Sand 剩余污泥 Surplus sludge
栅渣压干机 栅渣压干机 砂水分离器 剩余污泥泵
Presser
栅渣外运
Presser Separator Sludge Pump
至剩余污泥处理段
Landfill To Sludge treatment

Case study: Shidongkou WWTP,Shanghai,China
Reclaimed water
Effluent discharge
Effluent:

Discharged to Yangtze River;
 Reclaimed and reused for road flushing, firefighting, irrigation
Sludge dewatering
Incineration
Sludge treatment

Thickening;

Dewatering;
 incineration;

Landfill

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

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.

Case study: Separation of Algae from Tai Lake

Tai Lake
Shanghai
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

China's famous scenic spot

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

• Algae collection
• Algae separation

2,000 m 3 /d
Designed by
Tongji University
Solid content: 0.5-1%

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

Algae Separation from Tai Lake
(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)

Energy producing and carbon sequestration

Energy producing and carbon sequestration
Table 1. Elementary analysis table of algae sludge element C H N S P content （ % ） 37.63
3.453
3.050
0.94
0.57
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

Algae Separation from Tai Lake
 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

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

Sirte City
Project profile
Grit and insoluble material removal
Biological treatment
((activated sludge))
Sedimentation tank
Sample 2
Sample 1
Return sludge
Sludge to dryers
Sludge digestion
Tertiary treatment
Chemical treatment filtration
Sand filter
To sea
Sample 3
Chlorine injection

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!

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

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