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@ U S T . H K
Prof Chen set up a 1,000 cubic meter
sewage demonstration plant that resulted
in significant conclusions: 60%-70%
reduction in biological sludge, 20%
reduction in energy required for
treatment and requiring 40%-50% of the
space for treatment. Optimization is
currently underway to make the process
even more compact and effective at
reducing sludge, and to ultimately achieve
amore energy-saving system.
The revolutionary treatment process
has brought 19 patents and resulted in
over 70 publications and five international
awards, including three from the eminent
International Water Association. The
technology drew interest from the
UNESCO-IHE Institute forWater Education,
leading to a three-year study involving
Prof Chen, the European Union, and a
SANI pilot demonstration plant in Cuba.
The study, completed successfully in June
2017, highlighted ways to mitigate water
scarcity on the island through leading-
edge urban water management systems.
SANI has also attracted attention from
major national and international water
and environmental companies.
Recovery Discovery
Exciting extensions to the fundamental
SANI platform are now moving forward.
Costly materials that normally cannot
be synthesized on an industrial scale
can be recovered from SANI sludge and
two of Prof Chen’s students will set up a
company to take forward their innovative
sludge-to-resource technology that can
help realize production of sulfated
polysaccharides, a high-valued raw
material used in the food and pharmacy
industries. The technology won
the exhibition award at the 7
th
Annual HKUST One Million Dollar
Entrepreneurship Competition in 2017.
Prof Chen and his research team are
also exploring the recovery of phosphorus
from human urine. Phosphorus, which is
rapidly being exhausted, is an important
element for food production through its
use in fertilizers. In ongoing research, the
team has shown the potential for seawater-
catalyzed urine phosphate recovery in a
process that adds seawater to hydrolyzed
urine, leading to the formation of a
valuable phosphorus-containing fertilizer
(struvite precipitates). Related research has
appeared in
Water Research
.
“Now we have SANI, our goal is to
continuously lead the way for space-
saving, energy-efficient wastewater
treatment and resource recovery
through the testing and application of
new technologies,” Prof Chen said.
In 2015, HKUST gained approval from the Ministry of
Science and Technology of China to establish a Hong
Kong Branch of Chinese National Engineering Research
Center (CNERC) for Control and Treatment of Heavy Metal
Pollution. The Center is led by Prof Guanghao Chen and
encourages collaboration between Hong Kong, Mainland
China, and overseas water experts.
Fresh Links
The focus is on optimization of water systems and the
development of new technologies for adoption by industry to
enhance smart urban water and wastewater management,
linking to Prof Mohamed Ghidaoui’s and Prof Joseph Lee’s
work on waves in pipelines and turbulent mixing in rivers
and oceans respectively. “Our main target is the use of
different types of water – saline, brackish water – as
alternative water resources to reduce the use of the
increasingly precious resource of fresh water,” Prof Chen
said. “And to develop smarter urban systems in terms of
quality assurance and monitoring.”
Stage A
Carbon Removal
Anaerobic Reactor
Biological
sulfate reduction
Anoxic Reactor
Autotrophic
denitrification
Aerobic Reactor
Autotrophic
nitrification
Influent
Effluent
No
3
-
/ No
2
-
recycle flow
Stage B
Nitrogen Removal
In the first reactor (anaerobic), sulfate is reduced to sulfide by sulfate-reducing bacteria while organic carbon is oxidized to carbon dioxide
(which dissolves as bicarbonate). In the second reactor (anoxic), sulfide is subsequently oxidized back to sulfate by sulfur-oxidizing bacteria while nitrate is
autotrophically reduced to nitrogen gas. In the third reactor (aerobic), ammonia is oxidized to nitrate by the nitrifiers. All three functional bacteria are
slow growers, i.e. they have very low yields and hence produce minimal sludge.
Sewage treatment area
Biological sludge *
40%-50% reduction of space needed
for sewage treatment
60%-70% reduction in
biological sludge
Conventional
Activated Sludge (CAS)
process using the
two-wheel organic
oxidation and nitrification
biochemical reactions.
Carbon Cycle –
Nitrogen Cycle
Water Research,
100, 496-507 (2016)
*Photo: Sustainable
Sanitation Alliance
C N
CO
2
NO
3
-
NO
2
-
NH
3
O
2
N
2
e
-
Org-C
Sludge
CAS
C S
HCO
3
-
SO
4
2-
SO
3
2-
S
0
S
2-
N
NO
3
-
NO
2
-
NH
3
O
2
N
2
[o]
[o]
Org-C
SANI
Carbon Cycle –
Sulfur Cycle –
Nitrogen Cycle
The novel three-wheel
integrated cycle
proposed by Prof Chen -
anaerobic sulfate
reduction, sulfide
oxidation and
autotrophic
denitrification,
and nitrification
process.
