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Study on the Recycling and Reuse of Water Resources for
the Arid and Water-deficient Area in Western China
Key Project of the National Natural Science Foundation of China (NSFC)
(Grant No. 50138020)
Background
In
western
China
especially
the
northwestern region, people have been for
long suffering from chronic water shortage.
This restricts the speed of development
and affects peoples’ living quality. There
are mainly three reasons for this problem:
(1) Dry climate and low rainfall resulting
in an absolute deficiency of total water
quantity;
(2) Water quality pollution due to natural
and artificial reasons, resulting in a
shortage of qualitatively available water
resources;
(3) Shortage of financial sources for
water resource development or appropriate
water treatment.
Consequently many people in this region
cannot be supplied with the minimum
amount of water for drinking and sanitary
purposes, and water shortage becomes
more and more serious with the increase of
population
as
well
as
industrial
development. Continuous development of
exploitable water resources or long distance
water transfer may be one measure to solve
the water shortage problem but this needs
large-scale investment and often causes
new environmental problems. Under such
circumstances, water recycling and reuse is
thought to be a practical way to meet the
needs of sustainable development in
western China.
Study Outputs
Dissolved
< district living w ater>
System dynamic (SD) method was applied
for the development of a mathematic
model for the analysis of a water supply
system which incorporates
reclaimed
water from centralized or decentralized
wastewater treatment as a supplementary
water resource, taking into consideration of
social, economic and environmental
factors.
←80%
←50%
20%→
TN
65%→
50%→
SS
45%→
COD
TP
Combination of enhanced primary
treatment with biodegradation –
Fluidized Pellet Bed Bioreactor
• Development of a hybrid submerged
membrane bioreactor which combines both
suspended growth-activated sludge and
attached growth-biofilm with MF membrane
for wastewater treatment and reuse.
Pilot
study
of
a
decentralized
wastewater treatment and reuse system
8
Raw wastewater
PAC
Legend
2
3
4
4
5
6
Air
10
7
PAM
11 12
9
Recycle
Effluent
1 – raw water tank
2 – raw water pump
3 – static mixer
4 – flow meter
5 – FPB column
6 – agitating blades
7 – sampling tube
8 – motor
9 – outlet
10 – recycling water tank
11 – air dissolving pump
12 – pressure tank
Within a total hydraulic retention time
(HRT) of 33 minutes, the FPB bioreactor
achieved COD, BOD, SS and TP removals
of 90.0%, 93.6%, 95.6% and 94.1%,
respectively from raw domestic sewage.
About 40% removal of TN and 35%
removal of NH3-N were also achieved.
A soft package (SimWin) was developed
for an optimized selection of unit treatment
technology and combination of physical,
physiochemical, biological and chemical
processes for the treatment of domestic
wastewater to meet the requirement of
water reuse for certain purposes according
to raw wastewater quality, scale of
treatment and reuse, and other factors.
This leads to a rational design of a
treatment plant to achieve water
reclamation in China, especially in the dry
and water deficient northwestern regions.
A series of experimental studies were
conducted
for
advanced
wastewater
treatment for water reclamation:
• Development
of
a
dispersed-ozone
floatation (DOF) separator for simultaneous
tertiary treatment and disinfection
Suspended matter takes a large portion of
the contaminants in the raw domestic
wastewater
and
enhanced
primary
treatment was found to be applicable to
achieve a substantial removal of COD,
BOD etc.
1
Modeling and optimization of
treatment for wastewater reuse
60%→
← 35%
Advanced treatment processes
• Application of ultrafiltration (UF) for tertiary
treatment of the secondary effluent
←55%
Increasing rate of
reused
- w ater
ater treatm ent
+
+ < reused w ater
+ Wastew
volum e
+ Wastew ater drainage dem and>
E xpected increasing rate
of reused w ater
volum e
+
R ational size of
+
reused w ater
+ volum e of reused
E xpected
R
eused
w
ater
treatm
ent
size
w ater treatm ent
C hange of reused
w ater price
Pipe m aintaining cost
Investm ent of reused w ater
+
+
+ distributive netw ork
+
+
Financial dem and of
reused w ater running
Financial dem and of
< w ater price>
reuse project
←40%
←60%
40%→
Wastew ater drainage
coefficient
Suspended
0.45m
BOD
30%→
←70%
+
Classification
Organic
-
Enhanced primary treatment
Inorganic
Factors influencing consum ers ’
R eused w ater volum e
acceptable degree
Development
of
applicable
treatment technologies
←30%
70%→
Dynamic analysis and modeling
of centralized and decentralized
wastewater treatment and reuse
systems
A newly developed biofilm supporter
Original surface
Modified surface
Biomass on the
surface
With its surface well modified with pore
size suitable for microorganisms to grow,
the newly developed medium is used as
biofilm supporter in a turbulent bed or
moving bed bioreactor to achieve effective
removal of nitrogen and phosphorus.
A pilot plant was implemented in a village at
the entrance of Xi’an Xiang-yu Forest Park,
using a modified SBR and enhanced filtration
process. The treated water is used for onsite
irrigation.
Risk assessment of water reuse
The risk of using treated wastewater for
various purposes of wastewater reuse was
assessed mainly regarding the pathogenic
microorganisms. PCR assay was applied for
a fast and accurate identification of
microorganisms.
Economic and management aspects
Several models were developed for economic
assessment of water reuse. Life Circle
Assessment was used as a tool for a
comprehensive analysis of both centralized
and decentralized wastewater treatment and
reuse systems.